Category 6™

Tornadoes rip Midwest, killing 9; heavy snow hits Upper Midwest

By: JeffMasters, 3:05 PM GMT on February 29, 2012

Strong tornadoes plowed through the Midwest U.S. last night and this morning, killing at least nine people. Six people died in Harrisburg, Illinois when a tornado hit near 5:37 am CST this morning, damaging or destroying 200 buildings. Another person was killed in southwest Missouri near Buffalo when a possible tornado ripped through a mobile home park. Thirteen others were injured in the mobile home park. Two others died in the Cassville and Puxico areas. A tornado also moved through downtown Branson, Missouri early this morning, causing heavy damage to the city's famous theaters, and injuring at least twelve people. A tornado plowed through the small town of Harveyville, Kansas (population 275), twenty miles southwest of Topeka, at 9:03 pm last night. The tornado destroyed 40 - 60% of the structures and injured ten, one critically. NOAA's Storm Prediction Center logged fifteen preliminary tornado reports yesterday and today.

The same storm system also brought the heaviest snows of the winter to portions of the Upper Midwest, which has received scant snowfall this winter. Blizzard warnings are posted in South Dakota this morning, where snowfall amounts of 6 - 10 inches are common. According to NOAA's latest storm summary, five states have experienced snowfall amounts of ten inches or more--Wisconsin, Minnesota, South Dakota, Michigan, and Nebraska. The highest snow amount as of 8 am CST was recorded at Tripoli, Wisconsin, where fourteen inches had fallen.

Figure 1. Radar image of the squall line that passed through Harrisburg, Illinois this morning, spawning a tornado that killed three people. The position of Harisburg is marked by a circle with a "+" symbol.

Figure 2. NOAA's Storm Prediction Center logged thirteen preliminary tornado reports yesterday.

More tornadoes likely today
The powerful late-winter storm system that spawned the deadly tornadoes will move eastwards, bringing snows of 5 - 10 inches to northern Wisconsin, northern Minnesota, Michigan's Upper Peninsula, and northern New England. The storm's cold front is triggering severe thunderstorms over much of Kentucky this morning, and these thunderstorms are expected to grow in severity and spawn more tornadoes this afternoon, once the heat of the day destabilizes the atmosphere. NOAA's Storm Prediction Center has posted tornado watches for portions of Arkansas, Missouri, Tennessee, Kentucky, and Ohio this morning, and has placed much of Tennessee and portions of surrounding states in their "Moderate Risk" area for severe weather today. Consult our Severe Weather Page and Interactive Tornado Page to follow today's severe weather.

Figure 3. NOAA's Storm Prediction Center has placed much of Tennessee and portions of surrounding states in their "Moderate Risk" area for severe weather, one level below the highest level of alert, "High Risk."

Jeff Masters

Tornado Winter Weather

La Niña drawing to a close

By: JeffMasters, 3:39 PM GMT on February 27, 2012

La Niña, the cooling of the equatorial Pacific waters off the coast of South America that has dramatically affected our weather for most of the past two years, is almost done. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", have warmed rapidly over the past two weeks, and were 0.4°C below average on February 27. This is slightly warmer than the -0.5°C threshold to be considered La Niña conditions, and is the first time since early August that La Niña conditions have not been present. It is likely that SSTs will continue to warm during March and April, and NOAA's Climate Prediction Center is predicting that they will declare an official end to La Niña sometime between March and April. A moderate to strong La Niña began in the summer of 2010, weakened briefly during May - July 2011 to neutral status, then re-intensified to a borderline weak/moderate La Niña from August 2011 - January 2012.

Figure 1. Comparison of the sea surface temperature departure from average from January 4 and February 22, 2012, over the tropical Eastern Pacific. During January, a large region of the ocean was more than 0.5°C cooler than average, meaning a La Niña event was present. Beginning in mid-February, waters warmed rapidly from east to west along the Equator, signaling and end to the La Niña event. Image credit: NOAA.

The forecast: neutral or El Niño conditions by fall
The period March - May is the typical time of year that El Niño or La Niña events end, and it is common for the opposite phenomena to take hold by fall. Since 1950, there have been twelve La Niña events that ended during the first half of the year; during six of those years (50%), an El Niño event formed in time for the August - September - October peak of hurricane season. The official forecast from Columbia University's IRI and NOAA's Climate Prediction Center calls for a 31 - 32% chance of an El Niño event during the 2012 Atlantic hurricane season. El Niño conditions tend to suppress Atlantic hurricane activity by creating high levels of wind shear that tends to tear hurricanes apart. Given the relatively high chance of an El Niño event this fall, plus ocean temperatures over the tropical Atlantic that are cooler than we saw in 2011 and 2010, I doubt we'll see an Atlantic hurricane season as active as the ones in 2010 and 2011 (nineteen named storms both years, third busiest seasons on record.) The demise of La Niña also means that global temperatures should begin to approach record warm levels by the end of the year. The cool waters of a La Niña event keep global temperatures cooler than average.

Figure 2. Computer model forecasts of El Niño/La Niña made in mid-February 2012. The forecasts that go above the red line at +0.5°C denote El Niño conditions; -0.5°C to +0.5°C denote neutral conditions, and below -0.5°C denote La Niña conditions. Most of the computer models are predicting neutral or El Niño conditions during the fall peak of the Atlantic hurricane season. Image credit: Columbia University's IRI.

I'll have a new post by Wednesday.

Jeff Masters

Climate Summaries

New product allows you to explore record-setting extreme weather

By: angelafritz , 6:14 PM GMT on February 23, 2012

We've launched a new extreme weather product this week: Record Extremes. Recent, globally record-setting years have demanded a product that combines U.S. and international record extremes into one, easy to use interface. The Record Extremes page will give you the option to see U.S. and international records on a map and table. You can select any combination of record types at once, which, combined with the map, provides a interesting visual way to investigate record-setting events. The product uses data from three sources: (1) NOAA's National Climate Data Center, (2) Wunderground's U.S. records, and (3) Wunderground's International records.

The NCDC records begin in 1850 and include official NOAA record extreme events for ASOS and COOP weather stations in all 50 U.S. states as well as Puerto Rico, the Virgin Islands, and the Pacific Islands. In this database you can find records for maximum high temps, minimum high temps, maximum low temps, minimum high temps, snow, and precipitation on daily, monthly, and all-time scales.

The Wunderground extremes were compiled by our weather historian Christopher C. Burt. Chris monitors 300 stations across the U.S. for Record Extremes in maximum and minimum temperature, precipitation, and snow events. Most of these U.S. records go back to the end of the 19th century, though the oldest site in this database is Charleston, SC, where precipitation records started in 1737! Internationally, Chris monitors 150 countries worldwide for all-time record high temperatures and all-time record low temperatures. If you're interested in diving deeper into extreme weather in the U.S. and abroad, Chris's book Extreme Weather is an excellent resource.

Figure 1. All-time snow records broken during the Groundhog Day Blizzard of 2011. These records were found by selecting NCDC as the source, a start date of 2011-01-31, an end date of 2011-02-02, "maximum snowfall," and "all-time."

We built the Record Extremes product to make it easy to find specific records you're looking for, or just browse the records in general.

Check records that were set on a specific date
You can check on records that were set yesterday, for example, by setting the calendar to yesterday's date, and selecting all the record variables and types that you're interested in.

Explore all records set in a certain time range
2011 was a record-setting year for the U.S., and most of the records were high maximum temp and high minimum temps. To see all of these warm records that were set last year, select "NCDC" as the source, 2011-01-01 as the start date and 2011-12-31 as the end date. Select Maximum High Temp and Maximum Low Temp in weather variables, and select all-time in the record type.

View current standing international records in the Wunderground database
Select either the Wunderground International records, and instead of choosing a date range, select "Show current standing records." This will bring up all standing records in the database for whatever record variable and type you select. Whereas we've collected every record ever set or broken from NCDC, the Wunderground records are always the current, standing record, whenever it was set. As you move your map around the globe, you'll see each country's all-time maximum high temp and all-time maximum low temp.

Filter your table results
Looking for a specific location or record within your search results? Use the "Filter Results" option in the table to narrow down your search.

Let us know what you think!


Extreme Weather

4 out of 5 Americans affected by weather-related disasters since 2006, study finds

By: JeffMasters, 5:55 PM GMT on February 20, 2012

Since 2006 , federally declared weather-related disasters in the United States have affected counties housing 242 million people--or roughly four out of five Americans. That's the remarkable finding of Environment America, who last week released a detailed report on extreme weather events in the U.S. The report analyzed FEMA data to study the number of federally declared weather-related disasters. More than 15 million Americans live in counties that have averaged one or more weather-related disasters per year since the beginning of 2006. Ten U.S. counties--six in Oklahoma, two in Nebraska, and one each in Missouri and South Dakota--have each experienced ten or more declared weather-related disasters since 2006. South Carolina was the only state without a weather-related disaster since 2006. The report did a nice job explaining the linkages between extreme weather events and climate change, and concluded, "The increasing evidence linking global warming to certain types of extreme weather events--underscored by the degree to which those events are already both a common and an extremely disruptive fact of life in the United States--suggests that the nation should take the steps needed now to prevent the worst impacts of global warming and to prepare for the changes that are inevitably coming down the road."

Figure 1. County-level map of federally-declared weather-related disasters between 2006 - 2011. Tornadoes and severe thunderstorms in the Midwest, and heavy rains and snows from Nor'easters, hurricanes, and other storms in the Northeast gave those two regions the most disaster declarations. An interactive version of this map that allows one to click and see the individual disasters by county is on the Environment America website.

Jeff Masters

Extreme Weather Politics

Heartland Institute documents reveal strategy of attacks against climate science

By: JeffMasters, 3:15 PM GMT on February 17, 2012

Documents illegally leaked from the Heartland Institute, one of the most active groups engaged in attacking the science of climate change, provide an unprecedented look into how these groups operate. The story was broken Tuesday by DeSmogBlog, a website dedicated to exposing false claims about climate change science. The documents reveal that donors to Heartland included oil billionaire Charles Koch, and Heartland has spent several million dollars over the past five years to undermine climate science. Tens of thousands of dollars are slated to go this year to well-known climate contrarians S.Fred Singer, Craig Idso, and Anthony Watts of the Watts Up With That? website. Naturally, the leaked documents have lit up the blogosphere, but none of the revelations are particularly surprising. The U.S. has a very successful and well-funded climate change denial industry, primarily funded by fossil fuel companies, that has spent hundreds of millions of dollars over the past few decades on a PR campaign against climate change science. I made a lengthy post on the subject in 2009 called, The Manufactured Doubt industry and the hacked email controversy. I won't say more here, but has compiled a long list of blogs that have interesting posts on the Heartland Institute affair for those interested in following this story.

Eight books challenging the Manufactured Doubt industry
Important scientific findings should always be challenged with the goal of finding flaws and improving our scientific understanding. But there's nothing a scientist hates more than to see good science attacked and the reputations of good scientists smeared in name of protecting corporate profits or ideology. A number of scientists have fought back against the recent unfounded assaults on climate change science by publishing books calling attention to the Manufactured Doubt industry's tactics and goals. Anyone priding themselves on being a open-minded skeptic of human-caused global warming should challenge their skepticism by reading one of these works. I thought so highly of Unscientific America, Merchants of Doubt, and Climate Coverup, that I donated 50 copies of these books to undergraduates at the University of Michigan last year. Here's a short synopsis of eight books published in the past three years defending climate change science against the attacks of the Manufactured Doubt industry:

Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming, by Naomi Oreskes and Erik Conway. If you're going to read one book on the attacks on climate science, this should probably be the one--Dr. Oreskes, a history professor at UC San Diego, was voted climate change communicator of the year in 2011. A review of Merchants of Doubt and a video of her defending her book against skeptics is at, my favorite website for staying current on the politics of climate change. From the review: "Make the journey with them, and you’ll see renowned scientists abandon science, you’ll see environmentalism equated with communism, and you’ll discover the connection between the Cold War and climate denial. And for the most part, you’ll be entertained along the way."

Climate Cover-up: The Crusade to Deny Global Warming, by co-founders James Hoggan and Richard Littlemore. The main author, James Hoggan, owns a Canadian public relations firm, and is intimately familiar with how public relations campaigns work. It's another fascinating and very readable book.

Unscientific America: How Scientific Illiteracy Threatens our Future, by science writer Chris Mooney. He writes a blog focusing on science communication called the intersection. This is a fantastic book, and should be required reading for all college science majors.

Climate Change Denial: Heads in the Sand, by Haydn Washington and John Cook. John Cook writes for one of my favorite climate science blogs,, which focuses on debunking false skeptic claims about climate science. The book does a great job debunking all the classic climate change denial arguments.

Doubt is Their Product: How Industry's Assault on Science Threatens Your Health, by George Washington University epidemiologist David Michaels, who now heads the Occupational Health and Safety Administration (OSHA). This meticulously-researched book has just one chapter on climate change, and focuses more on tobacco and hazardous chemicals. About the the tobacco industry's Manufactured Doubt campaigns, Michaels wrote: "the industry understood that the public is in no position to distinguish good science from bad. Create doubt, uncertainty, and confusion. Throw mud at the anti-smoking research under the assumption that some of it is bound to stick. And buy time, lots of it, in the bargain". The title of Michaels' book comes from a 1969 memo from a tobacco company executive: "Doubt is our product since it is the best means of competing with the 'body of fact' that exists in the minds of the general public. It is also the means of establishing a controversy".

The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, by climate scientist Dr. Michael Mann. Dr. Mann is the originator of the much-debated "hockey stick" graph of global temperatures over the past 1,000 years, which looks like a hockey stick due to the sharp increase in temperatures in recent decades. This book just came out last week, and I hope to write a review on it this spring. Dr. Mann is one of the main contributors to my favorite web site for staying current on climate change research, John Cook of wrote a review, calling it "an eye-opening account of the lengths the opponents of climate science will go to in their campaign to slander climate scientists and distract the public from the realities of human caused global warming."

Fool Me Twice: Fighting the Assault on Science in America by Shawn Lawrence Otto. I haven't had a chance to read this one yet, but it looks interesting. A review by Katherine O’Konski of Climate Science Watch called the book "a fascinating look at the status of science in American society."

The Inquisition of Climate Science, by Dr. James Lawrence Powell, a geochemist with a distinguished career as a college teacher, college president, museum director, and author of books on earth science for general audiences. I haven't read it, but John Cook of wrote a review, calling it "a must-read for anyone who wishes to understand the full scope of the denial industry and their modern day persecution of climate science."

Have a great weekend, everyone! I'll be taking a few vacation days next week, and wunderground meteorologist Angela Fritz will probably be doing most of the blogging for me during the coming week.

Jeff Masters

Climate Change Politics

January 2012 the globe's 19th warmest

By: JeffMasters, 3:18 PM GMT on February 16, 2012

January 2012 was the globe's 19th warmest January since record keeping began in 1880, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC) and NASA. January 2012 global land temperatures were the 26th warmest on record, and ocean temperatures were the 17th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were colder than average, the 9th or 14th coldest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). Eurasia had its ninth largest snow cover extent in the 46-year period of record. Cold and snowy conditions dominated across central and Eastern Europe, as well as much of China. North America had its third smallest January snow cover extent, since much of the United States and southern Canada were warmer and drier than average, limiting snow cover. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of January in his January 2012 Global Weather Extremes Summary.

Figure 1. Departure of temperature from average for January 2012. Image credit: National Climatic Data Center (NCDC) .

La Niña conditions continue
A borderline weak/moderate La Niña event continues in the equatorial Pacific, where sea surface temperatures were approximately 1.0°C below average during January and the the first half of February. The majority of the El Niño computer models predict that La Niña will weaken this spring, and will likely be gone by summer.

Arctic sea ice extent fourth lowest on record
Arctic sea ice extent was at its fourth lowest on record in January, according to the National Snow and Ice Data Center. The growth rate for Arctic sea ice in January was the slowest in the satellite record. Satellite sea ice records date back to 1979.

No billion-dollar weather disasters in January
The globe had no billion-dollar weather disasters in January 2012, reported insurance broker Aon Benfield. The most expensive weather disaster of the month was winter storm Ulli in the UK and Scandanavia, which did $306 million in damage and killed three people. Severe winter weather in Japan killed at least 56 people in January, but damage estimates are not available yet. The most expensive U.S. disaster in January was the winter storm that hit Oregon and Washington January 17 - 22, causing major flooding on several Oregon rivers. The only month during the two-year period 2010 - 2011 without a billion-dollar weather disaster was March 2011, so last month's relatively quiet weather comes as a welcome relief.

Next post
The Tuesday release of leaked documents from a non-profit group active in attacking climate change science is creating a ruckus in the blogosphere, as reported by the New York Times. I'll have more to say on this Friday. Also, I'll have an update on a possible Saturday severe weather outbreak over the Southeast U.S.

Jeff Masters

Climate Summaries

Wunderground launches BestForecast; Giovanna kills ten in Madagascar

By: JeffMasters, 4:41 PM GMT on February 15, 2012

Weather Underground's meteorologists have spent over five years developing and testing a powerful forecasting system called BestForecast, which has been used to provide all of our forecasts for non-U.S. locations for the past several years. After some final improvements made in the past year, the forecasts from BestForecast have become competitive with forecasts from the National Weather Service (NWS) over much of the U.S. As of today, BestForecast forecasts are the default on the site. What's cool about BestForecast is that we can make its forecasts specific for any site that collects weather data. We gather several years of weather data from a site and optimize the forecast to suit the unique microclimate of a particular station. Thus, "backyard meteorologists" that own and maintain one of the more than 22,000 personal weather stations that record and send live weather conditions to Weather Underground will now have a forecast specifically generated for their own backyard. BestForecast also gives the expected precipitation amounts (in inches), and provides ten days of forecast information, instead of the seven days provided by the National Weather Service.

Users can evaluate the reliability of these forecasts themselves and get a second opinion by switching back to the National Weather Service forecasts that were previously published. In some areas, the National Weather Service will out-perform BestForecast, so play around with using both, and see what works the best for your location. Web site visitors can switch between best forecast and NWS forecasts using the switch "BestForecast" ON|OFF at the top of the forecast page. To create transparency in our forecasts, will publish the recent accuracy of its temperature forecasts over the past 20 days for every location, alongside the accuracy of the NWS. The accuracy is given in terms of the Root Mean Square Error (RMSE), in degrees Centigrade. A lower RMSE is better. The "MaxT" number is the verification of the daily high temperature forecasts, while the "Average" number is for the hour-by-hour forecasts.

A video demonstration of BestForecast is available on the About Our Data page.

Figure 1. Visible image from NASA's Terra satellite of Tropical Cyclone Giovanna over Madagascar, taken at 10:45 UTC Wednesday February 15, 2012. At the time, Giovanna was a tropical storm with 45 mph winds. Note the extensive plume of runoff and sediment stirred up by the storm flowing southwards along the east coast of Madagascar. Image credit: NASA.

Tropical Cyclone Giovanna kills ten in Madagascar
At least ten people were killed by Tropical Cyclone Giovanna in Madagascar, which hit the island nation as a powerful Category 3 storm with 125 - 130 mph winds at 22 UTC Monday night. An estimated 600,000 people lived in areas that received hurricane-force winds, but the eyewall of the storm missed the capital of Antananarivo, which received peak winds of 38 mph, gusting to 55 mph. Many remote areas that were affected by the storm have not been heard from yet, so the full extent of Giovanna's damage is not yet known. Giovanna is currently in the Mozambique Channel between Madagascar and Mozambique as a tropical storm with 50 mph winds, and is slowly intensifying. Latest computer model forecasts from the GFS and ECMWF models conflict, with the ECMWF model predicting the storm will swing around and pass very close to the southern tip of Madagascar next week, and the GFS model predicting landfall in Mozambique this weekend. Meanwhile, Madagascar must also keep an eye on Tropical Cyclone Thirteen, which is gathering strength over the waters to the east of the island, and is on a course that will bring it close to Madagascar next week.

Jeff Masters


Giovanna hits Madagascar; major damage likely

By: JeffMasters, 1:07 PM GMT on February 14, 2012

Tropical Cyclone Giovanna powered ashore along the east coast of Madagascar as a destructive Category 3 storm with 125 - 130 mph winds at 22 UTC last night. Winds at the coastal city of Tamatave, 70 miles north-northeast of where the center came ashore, peaked at 52 mph, gusting to 71 mph. Giovanna is moving west across the island at 17 mph, and passed just south of the capital of Antananarivo as a Category 1 storm at 8 am local time Tuesday morning. The eyewall missed Antananarivo , and the peak winds in the city were 38 mph, gusting to 55 mph. Microwave satellite imagery from the Navy Research Lab in Monterrey showed that Giovanna had rainfall rates of up to one inch per hour at landfall, and it is likely that the storm dumped 5 - 10 inches of rain along much of its path. The heaviest rains fell on deforested mountain slopes that drain into some of the most densely populated regions on the island, so major flood damage is likely. Heavy wind and storm surge damage undoubtedly occurred where the core of the storm hit the island, as well.

Figure 1. Visible image from NASA's Terra satellite of Tropical Cyclone Giovanna over Madagascar, taken at 7:15 UTC Tuesday February 14, 2012. Seven hours previous to this time, Giovanna was a Category 2 storm with 110 mph winds, but had probably weakened to a Category 1 storm by the time this picture was taken. Image credit: NASA.

The forecast
Passage over the rugged terrain of Madagascar has significantly weaken Giovanna, and the cyclone will move into the Mozambique Channel between Madagascar and Mozambique as a tropical storm later today. Latest computer model forecasts from the GFS and ECMWF models suggest Giovanna may reintensify over water, and swing around and pass very close to the south tip of Madagascar early next week. Meanwhile, Madagascar must also keep an eye on Tropical Cyclone Thirteen, which is gathering strength over the waters to the east of the island, and is on a course that will bring it close to Madagascar this weekend.

Figure 2. Microwave satellite image of Tropical Cyclone Giovanna taken at 02:44 UTC Tuesday, February 14, 2012. The cyclone was still a well-organized Category 2 storm at this time, five hours after landfall. Image credit: Navy Research Lab, Monterrey.

Jeff Masters


Category 4 Giovanna battering Madagascar

By: JeffMasters, 2:45 PM GMT on February 13, 2012

Earth's most dangerous storm of 2012 is Tropical Cyclone Giovanna, which is bearing down on Madagascar as a powerful Category 4 storm with 145 mph winds. Giovanna is predicted to hit a heavily populated portion of the east coast of the island near 22 GMT tonight as a Category 3 storm, then move inland, passing near the capital of Antananarivo as a Category 1 storm on Tuesday morning. The outer spiral bands of the storm have already moved over the island, bringing heavy rains and gusty winds.

Figure 1. Visible image from NASA's Terra satellite of Tropical Cyclone Giovanna approaching Madagascar, taken at 6:35 UTC Monday February 13, 2012. At the time, Giovanna was a Category 4 storm with 145 mph winds. Image credit: NASA.

Figure 2. Webcam view of the skies over the Andila Beach Hotel in northwest Madagascar, taken at 6:15pm local time on Monday February 13, 2012. Image credit: Andilana Beach Hotel.

The forecast: not good
Recent microwave satellite imagery (Figure 3) shows that Giovanna has concentric eyewalls, and it likely that the inner eyewall will collapse today as the storm undergoes an eyewall replacement cycle. This process should gradually weaken the storm, and I expect Giovanna will weaken slightly to a still very dangerous Category 3 storm with 125 - 130 mph winds at landfall. However, the eyewall replacement cycle will spread out the storm's hurricane-force winds over a larger area, increasing the storm surge. A 70-mile long swath of the coast that is heavily populated will receive sustained hurricane-force winds tonight. Rainfall amounts in excess of eight inches in a 24-hour period are expected along the center of Giovanna's path. These rains will cause extensive flooding and major damage to the country, and the storm is likely to be one of the top three most expensive disasters in Malagasy history. The damage potential is higher than for previous storms of similar intensity, due to the considerable deforestation Madagascar has experienced over the past 30 years. Madagascar lost 8.3% of its forest cover between 1990 and 2010 and is now just 22% forested, according to Flood waters run off quicker from deforested land, reach higher heights, and cause greater damage.

Figure 3. Microwave satellite image of Tropical Cyclone Giovanna taken at 12:30 UTC (7:30 am EST) Monday, February 13, 2012. The echo-free eye is surrounded by two concentric eyewalls, the sign of a storm undergoing an eyewall replacement cycle. Image credit: Navy Research Lab, Monterrey.

Madagascar's tropical cyclone history
The strongest and deadliest tropical cyclone ever recorded in Madagascar was Tropical Cyclone Gafilo, which hit the northern end of the island on March 7, 2004, as a Category 5 storm with 160 mph winds. Galfilo dumped up to 20 inches of rain on the island, and its winds and flooding rains killed 363 people and did $250 million in damage, making it the deadliest and second most expensive storm in Madagascar's history. Gafilo's central pressure of 895 mb made it the second strongest tropical cyclone ever recorded in the Southern Hemisphere, behind the 890 mb central pressure of Tropical Cyclone Zoe of December 2002, which affected Fiji and the Solomon Islands. With a central pressure of 937 mb, Giovanna is a much less intense storm than Gafilo was.

Jeff Masters


My worst global warming fear: buckeyes in Ann Arbor

By: JeffMasters, 2:53 PM GMT on February 10, 2012

Last week, I blogged about how wintertime minimum temperatures in the U.S. have risen so much in recent decades, that the United States Department of Agriculture (USDA) had to update their Plant Hardiness Zone Map for gardeners for the first time since 1990. The Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. I got to looking at the new zone map for Ann Arbor, Michigan, where I live, and saw how we've shifted one 5-degree Fahrenheit half-zone warmer. Ann Arbor used to be in Zone 5, but is now solidly in the warmer Zone 6. This got me to wondering, what sort of plants in Zone 6, until now rare or unknown in Ann Arbor, might migrate northwards in coming decades into the city? Then, with a sudden chill, I contemplated a truly awful possibility: The Ohio Buckeye Tree.

Figure 1. Comparison of the 1990 and 2012 USDA Plant Hardiness Zone Maps. Image credit: USDA and Arbor Day Foundation.

Buckeyes in Ann Arbor? The Horror!
For those of you unfamiliar the the buckeye tree, it is the emblem of Ohio State University. The Buckeyes of Ohio State have one of the most fierce rivalries in sports with that "school up north", the University of Michigan. As someone who spent twelve years of my life as a student at the University of Michigan, the thought of Buckeye trees in Ann Arbor is not one I care to contemplate. But the USDA Forest Service has published a Climate Change Tree Atlas which predicts that the most favorable habitat for the Ohio Buckeye Tree can be expected to move northwards with a warming climate. While they give their model for the Buckeye Tree a rating of "low reliability", it is nonetheless chilling to contemplate the potential infestation of Ann Arbor with this loathsome invader. I can only sadly predict that to stem the invasion, non-ecologically-minded University of Michigan students will unleash genetically engineered wolverines that eat buckeye seeds.

Figure 2. Potential changes in the mean center of distribution of the Ohio Buckeye tree. The green oval shows the current center of the range of the Buckeye Tree, well to the south of Ann Arbor. In a scenario where humans emit relatively low amounts of heat-trapping gases like carbon dioxide (light blue oval), the most favorable climate for the Buckeye Tree edges into Southern Michigan, and marches into Ann Arbor under the medium and high scenarios for emissions (other ovals.) Image credit: USDA Forest Service Climate Change Tree Atlas.

Libyan snowstorm triggered major Saharan dust storm
On February 6, a rare snow storm hit North Africa, bringing 2 - 3 inches of snow to Tripoli, Libya. It was the first snow in Tripoli since at least 2005, and may be the heaviest snow the Libyan capital has seen since February 6, 1956. The storm responsible for the North African snow also had strong winds that kicked up a tremendous amount of dust over Algeria during the week. This dust became suspended in a flow of air moving to the southwest, and is now over the Atlantic Ocean.

Figure 3. Dust storm on February 7, 2012, off the coast of West Africa, spawned by a storm that brought snow to North Africa on February 6. Note the beautiful vorticies shed by the Cape Verde Islands, showing that the air is flowing northeast to southwest. The red squares mark where fires are burning in West Africa. Image credit: NASA.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Humor Climate Change

Fourth warmest January on record for the U.S.

By: JeffMasters, 2:25 PM GMT on February 08, 2012

It wasn't the warmest January in U.S. history, but it sure didn't seem like winter last month--the contiguous U.S. experienced its fourth warmest January on record, and the winter period December 2011 - January 2012 was also the fourth warmest in the 117-year record, reported NOAA's National Climatic Data Center yesterday. The percent area of the U.S. experiencing extremes in warm maximum temperatures was 56 percent--the second highest value on record. Twelve of the 550 major U.S. cities with automated airport weather stations broke or tied all-time records for their hottest January temperature:

Craig, CO 82°F
Bakersfield, CA 82°F
Duluth, MN 48°F
Minot, ND 61°F
Mitchell, SD 68°F
Fargo, ND 55°F
Jamestown, ND 56°F
Huron, SD 65°F
Aberdeen, SD 63°F
Iron Mountain, MI 52°F
Alma, GA 83°F
Omaha, NE 69°F

However, extremely cold air settled in over Alaska in January, and several cities in Alaska had their coldest average January temperatures on record: Nome (-16.6 degrees F), Bethel (-17.3 degrees F), McGrath (-28.5 degrees F), and Bettles (-35.6 degrees F).

Figure 1. State-by-state rankings of temperatures for January 2012. Nine states had top-ten warmest Januarys on record, while no states had below-average temperatures in January. Records go back to 1895. Image credit: NOAA's National Climatic Data Center.

28th driest January for the contiguous U.S.
The first week of January was almost precipitation-free across the entire contiguous U.S., but a series of storms over Texas, the Ohio Valley, and the Pacific Northwest later in the month boosted precipitation totals enough to make January 2012 the 28th driest in the 118-year period of record. Remarkably, Texas had its 30th wettest January on record, and was the 2nd wettest state during the month. Texas also had a very wet December, their 19th wettest December. It is very rare for Texas to receive so much precipitation during a La Niña winter. Texas had not experienced two consecutive months with above-average precipitation since January - February 2010, during the last El Niño event.

Figure 2. State-by-state rankings of precipitation for January 2012. Three states had top-ten driest Januarys on record, while no states had a top-ten wettest January. Records go back to 1895. Image credit: NOAA's National Climatic Data Center.

3rd least-snowy January
According to the Rutgers Global Snow Lab, the average U.S. snow extent during January was the 3rd smallest January snow cover extent in the 46-year period of record. The National Weather Service sends out a daily "Weather and Almanac" product for several hundred major U.S. cities that we make available on underground. The February 6 statistics for those cities that reported measurable snow this winter show that only fifteen cities in the lower 48 states reported above-average snowfall as of February 6, and 155 had received below-average snowfall.

Figure 3. The new "Blue Marble" image of Earth on January 4, 2012, as seen by the VIIRS instrument on the new Suomi NPP satellite. The U.S. and Canada are virtually snow-free and cloud-free, which is extremely rare for a January day. The lack of snow in the mountains of the Western U.S. is particularly unusual. I doubt one could find a January day this cloud-free with so little snow on the ground throughout the entire satellite record, going back to the early 1960s. NOAA's Advanced Hydrologic Prediction Service shows that only one state--Washington--had areas where precipitation accumulated more than 0.25" on January 4, 2012, which is an extraordinary occurrence for a January day. Image credit: NASA.

Drought expands in January
According to the U.S. Drought Monitor, as of January 31st, 2012, about 3.3 percent of the contiguous U.S. was experiencing the worst category of drought--called D4 or exceptional drought--about the same as the beginning of the month. However, the percent area of the U.S. experiencing drought of any severity increased from 32 percent at the beginning of January to 38 percent at the end of the month. Most of the drought expansion occurred across the Upper Midwest and the western states.

2nd most January tornadoes on record
With 95 preliminary tornado reports, January 2012 is likely to end up with the 2nd most January tornadoes since 1950 (the record is 218, set in January 1999.)

I'll have a new post on Friday.

Jeff Masters

Climate Summaries

Harsh winter weather continues in Europe; rare snowstorm hits Libya

By: JeffMasters, 2:57 PM GMT on February 07, 2012

Europe's winter onslaught continues unabated this week, with very cold temperatures and heavy snows over much of the continent. Yesterday, a rare snow storm hit North Africa, bringing 2 - 3 inches of snow to Tripoli, Libya. It was the first snow in Tripoli since at least 2005, and may be the heaviest snow the Libyan capital has seen since February 6, 1956. Across Europe, at least 250 deaths have been blamed on the winter weather since the cold spell began on January 26. Hardest hit has been Ukraine, with 135 deaths--mostly of homeless people. According to weather records researcher Maximiliano Herrera, the current cold snap is the most severe for Europe since February 1991.

Figure 1. The scene in Tripoli, Libya, on February 6, 2012, after a rare snowstorm. Image credit:

Unusual jet stream kink causing Europe's harsh winter weather
The reason for the exceptionally cold and snowy winter weather in Europe lies in the behavior of the jet stream. The jet stream--the band of strong west-to-east blowing upper-level winds that circles the globe at mid-latitudes--acts as the dividing line between cold, polar air to the north, and warmer subtropical air to the south. On average, the jet blows straight west to east. But this winter, the jet has had a highly convoluted shape, with unusually large excursions to the north and south. When the jet bulges southwards, it allows cold air to spill in behind it, and that is what has happened to Europe over the past two weeks. The jet often gets "stuck" in one of these highly convoluted shapes, allowing a persistent period of extreme weather to occur. The latest predictions from the GFS and ECMWF models show the unusual jet stream pattern over Europe persisting for at least another week.

Figure 2. The jet stream pattern over Europe shows that the jet is taking a major dive southwards across France and into North Africa, keeping almost all of Europe on the cold (north) side of the jet.

The AO and NAO
A good measure of the tendency of the jet to form major bulges in winter is the Arctic Oscillation (AO) Index, which has ranged between -1 and -3 over the past two weeks. A strongly negative AO Index like this means the winds of the jet are relatively weak, allowing it to sag southwards over Europe and allow cold air to plunge southwards behind it. Usually, a negative AO also means cold winter weather over North America, but not this winter. In North America, we're better off paying attention to the North Atlantic Oscillation (NAO) Index, which we can think of as the Northern Atlantic portion of the AO. Ordinarily, the AO and NAO are in phase during winter (about 80 - 90% of the time), meaning that Europe and North America experience similar winter weather. However, over the past two weeks, the NAO has been positive while the AO has been negative. The positive NAO means that jet stream winds have been strong over North America and the North Atlantic, keeping cold air bottled up to the north over Canada and the Arctic. This pattern is predicted to persist for at least another week. We've seen many record extremes of both the positive and negative phase of the AO since 2006; see that latest post by Andrew Freedman of to learn more.

Jeff Masters

Winter Weather

Rare February tropical disturbance drenching the Florida Keys

By: JeffMasters, 1:51 PM GMT on February 06, 2012

Our calendars may say it's February, but Mother Nature's calendar says it's more like May in the waters of South Florida, where the year's first significant tropical disturbance is drenching the Keys. The disturbance, designated Invest 90L by NHC late Sunday morning, has dumped 1 - 3 inches of rain over much of the Florida Keys this morning, with Key West receiving 4.34" of rain on Sunday, a record for the date. The storm was close to developing a surface circulation last night, thanks to wind shear values to fell to 20 - 25 knots, and NHC gave 90L a 30% chance of developing into a subtropical depression in a special Tropical Weather Outlook issued last night. However, wind shear has increased to a prohibitive 30 - 40 knots this morning, and 90L is looking much less organized. In their 7 am EST outlook this morning, NHC gave 90L a 0% chance of developing. The system will continue to grow less organized today as it moves over Nassau in the Bahamas and heads out to sea.

Figure 1. Radar-estimated rainfall from Invest 90L.

What's going on?
Obviously, strong tropical disturbances capable of developing into named storms are very rare in February, and I've never seen one in my 30 years as a meteorologist. However, ocean temperatures are warm enough year-round to support a tropical storm in the waters of the Western Caribbean. Water temperatures today in the region were 26 - 26.5°C (79 - 80°F), which is near average for this time of year. If an unusual configuration of the jet stream allows wind shear to drop below about 25 knots in the Western Caribbean, there is the opportunity for a rare off-season tropical storm to form in February. I discussed in an appearance on NPR's All Things Considered on Friday just how unusual the atmospheric flow patterns have been this winter, and today's rare tropical disturbance over South Florida is symptomatic of how whacked-out our 2012 atmosphere has been. In isolation, the strange winter weather of 2011 - 2012 could be a natural rare occurrence, but there have been way too many strange atmospheric events in the past two years for them all to be simply an unusually long run of natural extremes. Something is definitely up with the weather, and it is clear to me that over the past two years, the climate has shifted to a new state capable of delivering rare and unprecedented weather events. Human emissions of heat-trapping gases like carbon dioxide are the most likely cause of such a shift in the climate, as I discussed in my post last week, Where is the climate headed?

A historical precedent: the 1952 Groundhog's Day tropical storm
There is a historical precedent for a tropical storm this time of year--the 1952 Groundhog's Day tropical storm that hit Southwest Florida. According to Wikipedia,

The 1952 Groundhog Day Storm was the only Atlantic tropical cyclone on record in the month of February. First observed in the western Caribbean Sea on February 2, it moved rapidly throughout its duration and struck southwestern Florida within 24 hours of forming. In the state, the winds damaged some crops and power lines, but no serious damage was reported.

Meteorologist Andrew Hagen performed a re-analysis of all the tropical storms between 1944 - 1953 for his Ph.D. thesis, and looked in detail at the 1952 Groundhog Day's storm. He noted that it didn't look like a classic tropical storm, but it didn't look like an extratropical storm, either, and should stay in the database as the first named storm of 1952. In the old teletype files for February 1952, he found a February 2 message from the Cuban Weather Service that expressed some concern about possible tropical development between Cuba and Florida. NHC responded: "TROPICAL STORMS DO NOT FORM IN FEBRUARY."

Figure 2. February 2, 1952 teletype message from the Hurricane Center to the Cuban Weather Service, explaining that there couldn't possibly be a tropical storm in February. Image credit: Andrew Hagen.

Jeff Masters


Super Sunday tropical disturbance forms in Yucatan Channel

By: JeffMasters, 8:17 PM GMT on February 05, 2012

OK, this is officially nuts. The first Super Sunday Invest in history formed this morning in the Yucatan Channel between Mexico and Cuba, and is slowly becoming more organized as it moves northeast towards Southwest Florida. The new disturbance, dubbed Invest 90L by NHC late this morning, has a modest but growing area of heavy thunderstorms near its center. Visible satellite imagery shows a pronounced spin at middle levels of the atmosphere, and 90L may be able to close off a surface circulation if it can find 24 more hours of marginally favorable conditions. Radar loops out of La Bajada on the western tip of Cuba show heavy thunderstorms over Western Cuba, but there is no organization of the echoes into low-level spiral bands. Wind shear is a high 20 - 25 knots, which is marginal for tropical storm formation. Ocean temperatures in the Yucatan Channel are 26 - 26.5°C (79 - 80°F), which is also marginal. 90L is suffering from ingestion of dry air along its western flanks, courtesy of an upper-level trough over the Gulf of Mexico, as seen on water vapor satellite imagery.

Figure 1. Is this football season or baseball season? The Super Sunday Invest 90L looks more characteristic of something we'd expect to see in May.

Forecast for 90L
Both the GFS and ECMWF models predict that the shear will remain below 25 knots through Monday, so there is some potential for continued development of 90L as it moves northeast towards South Florida. On Monday afternoon or evening, the storm will merge with a cold front and move over South Florida, bringing heavy rains of 1 - 3 inches and sustained winds of 20 - 25 mph. If it develops into a tropical depression or tropical storm, which I put at a 20% chance, the winds and rains will be higher. I doubt 90L has enough time or favorable enough conditions to become a tropical or subtropical depression, especially considering the disturbance's small size. There is a historical precedent for a tropical storm this time of year in this location--the 1952 Groundhog's Day tropical storm that hit Southwest Florida. According to Wikipedia,

The 1952 Groundhog Day Storm was the only Atlantic tropical cyclone on record in the month of February. First observed in the western Caribbean Sea on February 2, it moved rapidly throughout its duration and struck southwestern Florida within 24 hours of forming. In the state, the winds damaged some crops and power lines, but no serious damage was reported.

Jeff Masters


Europe cold wave deaths hit 200; low-snow winter for the U.S.

By: JeffMasters, 4:06 PM GMT on February 03, 2012

Brutal winter cold continues over most of Europe, where at least 200 people have died in a cold wave that began January 26. Hardest hit has been Ukraine, where the temperature bottomed out at -17°F (-27°C) at the capital of Kyiv this morning. It was the second coldest day of the cold wave, behind the -28°C reading of February 2. These temperatures are the coldest winter weather in six years in Ukraine, and at least 101 deaths are being blamed on the cold there. Also hard-hit has been Poland, where 37 people, most of them homeless, have died from the cold. Rome, Italy experienced a rare snowfall today, only its second day with snow during the past fifteen years. Very cold temperatures 10 - 20°C below average will continue for another seven days in Europe before gradually moderating late next week.

Figure 1. Departure of temperature from average as analyzed by the GFS model, for February 2, 2012. Remarkably cold air was present over Europe and western Alaska, while very warm air was over central North America and Siberia. This image is being generated experimentally by wunderground, and will be regularly available on our web site in the future.

Meanwhile, a snow drought for the U.S.
In the U.S., it's been the opposite story, with temperatures 10 - 15°F above average continuing this week over much of the nation. January 2012 is in the weather record books as the 3rd least-snowy January for the contiguous U.S. since snow records began in 1966, and December 2011 ranked as the 11th least snowy December on record. With no major snow storms in the offing over at least the next ten days, it's looking probable that the non-winter of 2011 - 2012 will set numerous record-low seasonal snowfall totals. The National Weather Service sends out a daily "Weather and Almanac" product for several hundred major U.S. cities that we make available on wunderground. I went through yesterday's statistics for those cities that reported measurable snow this winter. Only nine cities out of 166 major U.S. cities in the lower 48 states reported above-average snowfall as of February 1; 157 cities received below-average snowfall. The big winner in the snow sweepstakes has been Alaska, which is boasting 8 of the top 10 locations for heaviest snowfall this winter. While the 27.75 feet of snow that has fallen on Valdez has gotten a lot of attention, more remarkable is the 18.8 feet of snow Yakutat has received. That's more than 12.5 feet above what they usually have by this time of year.

The big losers in the snow stats for this winter are the cities along the lake effect snow belts on the Great Lakes. Most notably, Syracuse, New York is nearly four feet of snow below average for this time of year. Perhaps more exceptional is Williston, North Dakota, which has received just 1.8" of snow this winter--more than two feet below their average for February 1.

Have a super weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Winter Weather

Six more weeks of non-winter

By: JeffMasters, 3:35 PM GMT on February 02, 2012

Here Ye! Here Ye! Here Ye!

On Gobbler's Knob on this magnificent Groundhog Day, February 2nd, 2012
Punxsutawney Phil, the Seer of Seers, the Prognosticator of all Prognosticators,
was summoned from his burrow in the old oak stump
by the tap of President Bill Deedly.

He greeted his handlers, John Griffiths and Ron Ploucha.

After casting an appreciative glance towards thousands of his faithful followers,
Phil proclaimed
As I look at the crowd on Gobbler's Knob
Many shadows do I see
So six more weeks of winter it must be!

That's the official word posted at from Punxsutawney Pennsylvania's famous prognosticating rodent, Punxsutawney Phil, who saw his shadow this morning. According to tradition, this means that a solid six more weeks of winter can be expected across the U.S. When the sun rises in San Francisco, this morning, wunderground's Alan T. Groundhog can give us an additional shadow-based forecast for the coming winter (video here.)

Figure 1. Wunderground's prognosticating groundhog, Alan T. Groundhog, prepares to go in front of the blue screen with wunderground meteorologist Jessica Parker.

How did this this crazy tradition start?
It all started in Europe, centuries ago, when February 2 was a holiday called Candlemas. On Candlemas, people prayed for mild weather for the remainder of winter. The superstition arose that if a hibernating badger woke up and saw its shadow on Candlemas, there would be six more weeks of severe winter weather. When Europeans settled the New World, they didn't find any badgers. So, they decided to use native groundhogs (aka the woodchuck, land beaver, or whistlepig) as their prognosticating rodent.

What winter? The non-winter of 2011 - 2012
Considering winter hasn't really arrived in the lower 48 states yet, I'm not sure how much validity we can give to fearless Phil's forecast. Here in Michigan, like in most of the U.S., we've basically had three straight months of November weather. There have been no major snowstorms, and frequent sunny days with highs in the 50s--twenty five degrees above average. January 2012 is in the weather record books as the 3rd least-snowy January for the contiguous U.S. since snow records began in 1966, the Rutgers Snow Lab reported yesterday, and December 2011 ranked as the 11th least snowy December on record. With the latest 2-week forecast from the GFS model showing a huge ridge of high pressure dominating the Western U.S. and no major snowstorms over the U.S. through mid-February, the winter of 2011 - 2012 has a chance to end up as the second least snowy winter in U.S. history. Temperature statistics for January will not be available until next week, but I expect the month will end up being a top-five warmest January, with temperatures about 4 - 5°F above average. We won't be able to beat the 8.7°F above-average temperature posted during the warmest January in U.S. history, which occurred in 2006. If U.S. temperatures remain 4 - 5°F above average during February, the winter of 2011 - 2012 will be the warmest in U.S. history. The five warmest U.S. winters since record keeping began in 1895 have all occurred since 1992, with the winter of 1999 - 2000 holding the record for warmest winter. Winter average temperature in the contiguous U.S. has been increasing by about 1.6°F per century since 1895 (Figure 2.)

Figure 2. Winter temperatures in the contiguous U.S. during the period 1895 - 2011 increased at a rate of about 1.6°F per century. The warmest winter was 1999 - 2000, and the coldest was 1978 - 1979. Image credit: NOAA/NCDC.

What's going on?
This January's remarkable warmth and lack of snow contrasts starkly with what happened during the previous two winters. January 2011 was the 5th snowiest and 35th coldest in U.S. history, and January 2010 was the 7th snowiest and 55th coldest. Wunderground meteorologist Angela Fritz had this to say in her blog post yesterday about what's been going on this winter: In December, we were reporting that the lower-48's unseasonably warm weather and lack of snow was due to a particularly positive Arctic Oscillation (AO) index. The Arctic Oscillation is a measure of the jet stream's strength. A positive AO is a stronger than average jet stream, and it tends to keep cold air bottled up in the Arctic. During a positive AO, the Arctic is colder than average, and the mid-latitudes are warmer than average. In December and early January, the AO was positive. In mid-January, the AO went negative, which we expect to have the opposite impact. A weak jet steam means cold, Arctic air can escape to the south, and that's what we've been seeing in Europe this week. This cold air has yet to spill southwards into the Eastern U.S. like it usually does during a negative-AO period, since the North Atlantic Oscillation (NAO)--the component of the AO over the North Atlantic--has not gone negative, and is close to normal right now. However, the long-range GFS model is predicting a modest cold air outbreak will occur over the Eastern U.S. around February 15.

Jeff Masters

Winter Weather

New USDA Plant Hardiness Zone Map for gardeners shows a warming climate

By: JeffMasters, 2:17 PM GMT on February 01, 2012

Wintertime minimum temperatures in the U.S. have risen so much in recent decades that the United States Department of Agriculture decided last week to update their Plant Hardiness Zone Map for gardeners for the first time since 1990. The Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones. Compared to the 1990 version, zone boundaries in the new 2012 edition of the map have generally shifted one 5-degree Fahrenheit half-zone warmer than the previous map throughout much of the United States. This is mostly a result of using temperature data from a longer and more recent time period. The old 1990 map was based on temperature data from only a 13-year period of 1974-1986, while the new map uses data from the 30-year period 1976-2005.

Figure 1. Comparison of the 1990 and 2012 USDA Plant Hardiness Zone Maps. Image credit: USDA and Arbor Day Foundation

Northwards, ho!
While humans are generally not attuned enough to nature's rhythms to tell if the climate is changing, plants and animals know the climate is changing. Many species of animals, insects, and plants have shifted their ranges poleward and to higher elevations in recent decades because of global warming. The 2007 IPCC report stated that "numerous studies document a progressively earlier spring by about 2.3 to 5.2 days per decade in the last 30 years in response to climate warming. That report also documented over 400 species that have moved their ranges poleward or to higher elevations because of climate change. For example, conifer trees expanded northwards into former tundra areas at a rate of 12 km per year between 1982 - 2000 in portions of Canada (Fillol and Royer, 2003.) Holly plants moved northwards by several hundred kilometers in recent decades into coastal Norway, Northeast Germany, Denmark, and coastal Sweden in response to warming temperatures (Walther et al., 2005.) As the climate continues to warm, plant and animal species previously unknown in many regions will appear, and will disappear from places they used to inhabit.

Figure 2. Change in the boundary line between conifer forest (taiga) and tundra between 1982 (grey line) and 2000 (white line) over Canada. In the grey box marked "Transect", the rate of northwards migration was 12 km per year, or 228 km (142 miles) in nineteen years. Image credit: Fillol and Royer, 2003, "Variability analysis of the transitory climate regime as defined by the NDVI/Ts relationship derived from NOAA-AVHRR over Canada", Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International.

Jeff Masters

Climate Change

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Category 6™


Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather