Category 6™

Hurricane stories

By: JeffMasters, 10:22 AM EDT on May 28, 2005

For those of you who haven't read it, the story of my final flight with the Hurricane Hunters into Hurricane Hugo makes for a great read on just how hairy a pentration into the eye of a ferocious Category 5 hurricane can be. On Tuesday, May 31, at 8pm EDT, I'll be discussing that flight and talking more generally about flying into hurricanes as a guest on the Internet weather talk radio station, They have a weekly show called "Talking Tropics" which features scientists, hurricane experts from the National Hurricane Center, and disaster preparedness officials. They have an audience of several thousand listeners on a typical show. Listeners can email in questions, but cannot speak on-air.

Another more interactive weather talk Internet site during hurricane season is I did several interviews with them last season, and gave away free memberships to callers who correctly called in to answer their hurricane quiz question of the day. Listeners can call in and talk with the featured experts. kicks off hurricane season on Wednesday, June 1, at 8pm EDT.

Have great Memorial Day weekend, everyone, and I hope some of you can tune in Tuesday night!


By: JeffMasters, 3:07 PM GMT on May 26, 2005

The photo below posted today, titled, "Strange clouds" is an example of virga. Virga (also called fallstreaks) are wisps or streaks of rain or ice crystals precipitating out of a cloud, which evaporate before hitting the ground. Virga falling from high clouds made of ice crystals frequently angle back from the parent cloud, as seen in the photo below, "Sunset Virga". This happens because the winds at cloud level (where the jet stream can be) are usually higher than the winds closer to the surface. However, the photo "Wispy downward trend" shows virga falling from a cloud where the winds at cloud level and below are the same.

Atmospheric Phenomena

Record Arctic ozone loss this Spring

By: JeffMasters, 1:18 PM GMT on May 21, 2005

Researchers announced last month that the total ozone levels in the Arctic dropped up to 30% during the annual springtime breakup of the polar vortex, a new record loss in the Arctic. The ozone destruction was caused by human-emitted chlorofluorocarbons (CFCs) present in the stratosphere. Strangely, observations show that levels of CFCs and other ozone depleting gases are at a maximum now and are beginning to decline, thanks to the adoption of the Montreal Protocol in 1987. So why are we seeing record ozone losses?

b>Figure 1. Ozone loss in the Arctic the past 15 years. Source: Nature magazine

The answer is that ozone destruction is critically dependent upon the number of Polar Stratospheric Clouds (PSCs) in the stratosphere, since the chemical reactions that destroy ozone go much faster on cloud particles. Very cold temperatures cause more PSCs, and the temperatures in the stratosphere during the winter of 2005 were the coldest on record (50 years). Indeed, temperatures in the Arctic stratosphere have been declining steadily the past 20 years or more. The main reasons:

1) Lower ozone in the stratosphere due to destruction by CFCs means less UV light is absorbed. Since this absorption heats the air, less heating occurs. This lowers the temperature of the stratosphere, creating more PSCs, which creates ozone destruction, further lowering the temperature in a positive feedback loop.

2) The greenhouse effect acts to cool the stratosphere. Yes, the surface and lower atmosphere are warmed by the greenhouse effect, but this means that the atmosphere must cool somewhere else to compensate. Much of this compensating cooling happens in the stratosphere. This can best be understood by considering that the Earth is in "radiative equilibrium"--the amount of solar energy coming in is balanced by the amount of energy going out. Surface warming must be balanced by upper-atmosphere cooling, since the amount of solar radiation the Earth receives does not change.

Should we be concerned about this loss of ozone in the Arctic? Markus Rex, one of the authors of the Nature study, remarks: "So UV-levels in spring have been higher than in "normal" winters. But they have not been higher than during summer or even in fall. So it is important not to overstate the problem. On the other hand the depletion of the ozone layer in spring certainly can have a significant effect on ecosystems, although so far the ozone layer has not been thinner in spring than later during the year. Plants and animals have adapted to the normal seasonal cycle of total ozone and UV and are not used to high UV-exposure during the part of their life cycle that takes place in spring (e.g. germination, growths of buds, alga blooms in the Arctic ocean, ... ). To my knowledge (which is quite limited in this area) the effect of increased UV-levels during spring on the various ecosystems is subject to ongoing research."

In the Antarctic, where Springtime ozone losses are much more severe (over 70% some years), only modest impacts on ecosystems have yet been found (for example, 6-12% declines in oceanic phytoplankton), so the current observations of record ozone loss in the Arctic should not cause undue alarm. Still, these results from the uncontroled global-scale experiment we humans are performing on our planet should make us all a little nervous. And the ozone destruction isn't going away for at least another 50 years--it will take that long for the atmosphere to flush out the accumulated burden of CFCs we've added.

Climate Change Ozone Layer

Odd Adrian

By: JeffMasters, 6:28 PM EDT on May 18, 2005

Hurricane season is off to an odd start this year--check out Tropical Storm Adrian in the Eastern Pacific. Since 1966, only four tropical cyclones have made landfall in Guatemala or El Salvador in any month, with only one landfalling depression in May. And there is a distinct possibility Adrian could become that rarest of beasts, a multi-ocean tropical cyclone. The storm is currently on track to cross Central America over Honduras, but a wide area of mountains 2000 - 3000 meters high could destroy it before it has a chance to emerge over the Caribbean Sea. However, if Adrian manages to achieve hurricane strength before landfall, the storm should survive the crossing and emerge over the Caribbean Sea as a tropical depression.

Once over the Caribbean, the chances for re-intensification look poor, as water temperatures there are much cooler than over the Eastern Pacific, and the amount of wind shear is high.

Seven tropical cyclones have made the crossing from Atlantic to Pacific, but only two have crossed from the Pacific to the Atlantic since records began:

Northeast Pacific Hurricane Cosme became Atlantic Tropical Storm Allison (June 1989).

A Northeast Pacific tropical storm (September-October 1949) became Atlantic Hurricane Storm #10 and made landfall in Texas.

The first tropical storm in the Atlantic is due to be named Arlene this year, but I've read that Adrian will keep its name. I guess the folks at NHC didn't want all the Arlenes of the world getting hassled about if they really used to be a man named Adrian. The downside for all the Arlenes, though, will be that they'll have to wait until 2011 to have a storm named after them!

Aurora activty and ozone loss

By: JeffMasters, 6:13 PM GMT on May 16, 2005

The sun is only a year or so from the minimum of its 11-year sunspot cycle. This means few solar storms and not many solar charged particles hitting Earth's upper atmosphere triggering auroras. However, the sun has shown an unusual amount of activity the past 2 years, and last night both hemispheres were again treated to spectacular aurora displays (see the great aurora borealis and aurora australialis photos below!)

In a recent discovery published in March 2005 in Geophysical Research Letters, scientists reported that the high-energy particles that trigger auroras can also cause significant destruction of our protective ozone layer. Normally, ozone destruction is associated with human-emitted Chlorofluorocarbons (CFCs) in the lower stratosphere. However, the new discovery shows that natural processes can cause significant ozone destruction in the upper stratosphere.

"The 2003-2004 Arctic winter was unique," said Dr. Gloria Manney, a JPL atmospheric scientist and one of the paper's co-authors. "First, the stratospheric polar vortex, a massive low-pressure system that confines air over the Arctic, broke down in a major stratospheric warming that lasted from January to February 2004. Such midwinter warmings typically last only a few days to a week. Then, in February and March 2004, winds in the upper stratospheric polar vortex sped up to their strongest levels on record. The vortex allowed the nitrogen gases, which are believed to have formed at least 10 kilometers (6 miles) above the stratosphere as a result of chemical reactions triggered by energetic solar particles, to descend more easily than normal into the stratosphere."

What does all this mean in terms of the amount of skin-damaging UV radiation hitting the surface? Should you put on extra sunscreen the day after seeing an aurora? No, the time to put on extra sunscreen is when the polar vortex breaks up in the Spring, when ozone-poor air that was created by CFCs and the energetic solar particles bombarding the upper stratosphere finally gets mixed down to the mid-latitudes where most of us live. This has already happened this year, back in March and April. In another blog entry later this week, I will discuss the record ozone loss--up to 30%--that was seen in the Northern Hemisphere this Spring when the polar vortex broke down. I'll answer the question, "why are we seeing record ozone losses when we've already phased out CFCs?"

Climate Change Ozone Layer

The dreaded bad-i-sad-o-bist-roz

By: JeffMasters, 3:59 PM GMT on May 11, 2005

If you're the owner of a Volkswagen Bora, Sirocco, or Passat, you own a wind. That's right, these are all names of winds. The bora (see photograph below) is a wind that originates high in cold mountain areas. The cold, dense air flows downward under the force of gravity and warms according to the Ideal Gas Law, but is so cold so start with, that it remains much colder than the air at the base of the mountains. The bora is a scourge of the Adriatic Sea, blowing for 40 or more days a year, closing railroads and forcing ships in Trieste, Italy to flee for shelter further south.

The passat is a German term for a trade wind. And the sirocco (Arabic for 'easterly'), a springtime wind that brings hot, dusty air from the Sahara and Arabian Peninsula, has a positively evil repuation, according to Lyall Watson's excellent book, "Heaven's Breath: A Natural History of the Wind". The book quotes a traveler from England who encountered a sirocco in the 1800's: "The sirocco has now blown for these six days without intermission; and has indeed blown away all our gaiety and spirits; and if it continues much longer, I do not know what may be the consequence. It gives a lassitude, both to the body and mind, that renders them absolutely incapable of performing their usual functions." The book goes on to quote extensive medical research on the sirocco's negative effect on people in Israel. More than one third of the Israeli population experience an adverse reaction to the wind.

Since Volkwagen doesn't seem to have any concerns about naming their vehicles after evil winds, I have a suggestion for their next vehicle name: the Bad-i-sad-o-bist-roz, named after the dreaded Iranian and Afghanistanian 'wind of one hundred and twenty days'. This wind blows constantly for 120 days, June through September, and was described by Lord Curzon as "the most vile and abominable in the universe'. This hot, dry wind, laden with dust and salt, buries entire farms and villages in its relentless march across the desert.

Naturally, the Bad-i-sad-o-bist-roz would have to be one bad SUV. It would come only in black, have dark tinted windows, armor plating to help it take out any economy cars it might meet in a crash, a 500 Watt stereo system, and get about 6 miles per gallon. In short, the most vile and abominable vehicle in the universe.

Jeff Masters

Atmospheric Phenomena

NWS Employee's Union Press release

By: JeffMasters, 9:23 PM GMT on May 09, 2005

From the Wichita, KS Eagle:

The National Weather Service Employee's Union put out a press release outlining their opposition to the bill before Congress to restrict the ability of the NWS to compete with the private sector. I post it here, and invite comments.

Jeff Masters

Santorum bill will cut off weather data and turn the
National Weather Service into an $800 million a year
"corporate welfare" program for large commercial weather
companies, forecasters say.

The professional association and labor organization of
meteorologists and other employees today announced their
opposition to the National Weather Service Duties Act,
introduced on April 14 by Senator Richard Santorum

If enacted, S. 786 would prohibit the National Weather
Service from providing any service, including marine,
public and aviation forecasts (other than severe weather
warnings) to either the public, the media, academia, or
state and local emergency management officials if private
sector weather companies are providing or could provide a
similar service for a fee. Any forecast, severe weather
warning or other service or product that the NWS could
continue to provide under the Act would be disseminated
"through a set of data portals designed for volume access
by commercial providers." The Act also prohibits the NWS
from directly giving interviews or briefings to the news
media, law enforcement or emergency management personnel
during severe weather events, such as the briefings given
by the National Hurricane Center. The public, state and
local governments, and even other Federal agencies would
be required to obtain all their weather information from
private commercial weather companies. These companies
would obtain their information from the National Weather
Service through the "set of data portals" which the Act
would obtain their information from the National Weather
Service through the "set of data portals" which the Act
would require the NWS to maintain solely for the benefit
of and "access by commercial providers" of weather

In a letter sent to Sen. Jim DeMint, Chairman of the
Senate Commerce Committee's Subcommittee on Disaster
Preparedness and Prediction, the organization explained
that "not only would this Act convert the National
Weather Service into an $800 million a year 'corporate
welfare' subsidy to these 'commercial vendors' of weather
information, but it would constitute a tax on state and
local governments who would have to pay middle-men for
repackaged NWS weather information. For example, the NWS
would no longer be able to advise local school districts
and road crews on anticipated snowfall amounts. Such
advice would have to be purchased from a distant
commercial vendor."

According to the union, "the prohibitions contained in S.
786 would benefit only a handful of large commercial
vendors at the expense of smaller firms, and those
seeking to enter the market, who cannot afford the access
fees to the NWS's 'data portals.'" The NWS maintains data
portals, known as the "Family of Services," through which
a very small number of major private vendors currently
obtain volume access to the NWS weather observations,
forecasts and warnings. Some vendors simply resell the
data as received.

"Smaller and new firms that add value to and remarket NWS
products now obtain their weather data from NWS internet
sites which would be shut down under this law. Thus,
rather than increasing competitiveness and bringing new
companies and products into the market place, the NWS
Duties Act would assist a handful of larger, already
capitalized firms in creating a monopoly" on weather
information, explained the NWS forecasters in their
letter to Senator DeMint.

The NWS websites (accessed at could be
shut down under the proposed legislation. These websites
receive over 5 million users each month - 60 million
visitors a year. The annual cost for maintaining the
servers and associated staff to maintain the websites is
only $3,755,000 - a little more than a penny a citizen.

The National Academy of Science's Committee on
Partnerships in Weather and Climate Services recently
concluded that the NWS has an "obligation to make its
information as widely available as possible to those who
have paid for it - the taxpayers."

Although some in the private sector would prefer that the
NWS not issue forecasts, the committee believes that
scientific, legal, and economic arguments overwhelmingly
support the continued dissemination of NWS forecasts and
other weather products. Not only has the infrastructure
supporting the forecast already been paid for, but
other weather products. Not only has the infrastructure
supporting the forecast already been paid for, but
disseminating forecasts provides a measure of visibility
to the NWS, which helps ensure continued support for the
expensive infrastructure needed to generate weather and
climate services.

National Research Council, Fair Weather: Effective
Partnerships in Weather and Climate Services, 5 (National
Academies Press, 2003).

NWSEO represents over 3,700 forecasters and other
employees of the National Weather Service located at 122
Forecast Offices, 13 River Forecast Centers, and various
specialized forecast offices (such as the National
Hurricane Center) across the country.



By: JeffMasters, 2:46 PM GMT on May 03, 2005

The name haboob comes from the Arabic word "habb", meaning wind, and refers to a sudden dust storm triggered by the cold-air outflow from a decaying thunderstorm. Cold air from the mid-troposphere is dragged down by falling rain inside the thunderstorm. When the cold air hits the ground, it spreads out in all directions. If there is a dusty desert area below, the strong gusty winds of this cold air outflow will pick up the dust and mix it up to great heights. The edge of this cold air (called a "gust front") will then appear as a wall of dust up to 3000 feet high, moving across the desert at speeds of up to 50 mph. Haboobs are commonly seen in the Sahara desert, Iraq, Australia, and the Southwestern United States.

Atmospheric Phenomena

Follow-up on NWS Duties Act of 2005 discussion

By: JeffMasters, 6:56 PM GMT on May 01, 2005

Thanks to all who joined our discussion on this important issue! (for those new to this thread, I am referring to the fact that it may soon be illegal for the National Weather Service (NWS) to issue non-severe weather forecasts under the provisions of the National Weather Service Duties Act of 2005, Senate Bill S.786, introduced April 14 by Sen. Rick Santorum, R-Pa.)I think we have all learned and benefited from this discussion, and I believe a few points of clarification are needed:

1) The bill is difficult to interpret and confusing. I asked Dave Moran, Professor of Law at Wayne State University, to comment on the bill. He remarked that the bill was "incredibly poorly drafted" and criticized it for leaving key terms undefined, such as "hydrometeorological guidance" and "core forecast information." (To this list, I would add "severe weather"). This confusion alone makes the bill unworthy of passage.

2) The only NWS functions completely protected are listed in Section 2(a)(1): "preparation and issuance of severe weather forecasts and warnings designed for the protection of life and property of the general public" because section 2(b) says: "The Secretary of Commerce shall not provide, or assist other entities in providing, a product or service
(other than a product or service described in subsection (a)(1)) that is or could be provided by the private sector." The only exceptions given are aviation forecasts and things the private sector cannot provide.

What this means is that while the NWS may continue to make its own "sunny and warm" public forecasts and marine forecasts (which is not certain under the vague conditions of the bill, but lets assume it might be so), it cannot give these out to the public if a private meteorology company complains. Sen. Santorum seems to think that no one will make such a challenge, remarking in a recent interview, "the NWS will not cease dissemination of regular daily forecasts, weather information and climate data." However, the comments of Barry Myers of AccuWeather indicate that his company does plan to have these type of forecasts eliminated under the new law:

"The National Weather Service has not focused on what its core mission should be, which is protecting other people's lives and property," said Myers, whose company is based in State College, Pa. Instead, he said, "It spends hundreds of millions of dollars a year, every day, producing forecasts of 'warm and sunny.'"

Who are you going to believe? And when Sen. Santorum says the NWS will continue to issue "regular forecasts", does this mean "sunny and warm" forecasts, or just regular "severe forecasts"? It's not clear.

3) I did not mean to criticize private forecasters when I commented that "I believe the expertise of the NWS forecasters is unmatched anywhere in the world." There are many excellent forecasters in the private sector, and
private weather forecasters do better forecasting than the NWS in many cases, particulary for specialized applications that the more general NWS forecasts do not focus on. How else could private companies get their business clients to pay for their services, when free NWS forecasts are available?

4) It would be interesting to see some forecast verifications of NWS vs. AccuWeather vs. Weather Channel forecasts. If anyone has some links, please post them. However, general judgements on which forecasts are the best will be difficult to draw, since one could easily pick a few cities or use a statistical technique that favors one forecast provider over another.

The Weather Underground is preparing a packet arguing against adoption of the Santorum bill. This packet will go to all the members of the Senate Commerce Committe later this week. We plan to use the comments posted in this blog as part of our argument. Thanks to everyone who wrote in, both pro and con!

Jeff Masters
How to oppose The National Weather Service Duties Act of 2005. The National Weather Service Duties Act of 2005 is currently before the Senate Commerce Committee, and will have to make it out of there before the full Senate votes on it. The time to kill this bill is now! If you're interested, you can sign a petition opposing the National Weather Service Duties Act of 2005, or write your Senator if he or she is on the Senate Commerce Committee:


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