Dr. Jeff Masters' WunderBlog

Severe Atlantic hurricane season expected; tropical disturbance in the Western Caribbean

By: JeffMasters, 4:09 PM GMT on May 31, 2007

A severe Atlantic hurricane season is on tap for 2007, according to the May 31 seasonal forecast issued by Dr. Bill Gray and Phil Klotzbach of Colorado State University (CSU) today. The Gray/Klotzbach team is calling for 17 named storms, 9 hurricanes, and 5 intense hurricanes--unchanged from their April forecast. An average season has 10-11 named storms, 6 hurricanes, and 2 intense hurricanes. The forecast calls for a much above normal chance of a major hurricane hitting the U.S., both along the East Coast (50% chance, 31% chance is normal) and the Gulf Coast (49% chance, 30% chance is average). The Caribbean is also forecast to have an above normal risk of a major hurricane.

The forecasters cite the expected lack of an El Niño event, the continuation of above average sea surface temperatures in the Atlantic, and slower trade winds (which result in reduced evaporative cooling of the ocean), as the justification for their forecast of a much above average hurricane season.


Figure 1. Top: Tropical Atlantic Ocean temperatures in the Main Development Region for hurricanes (green box) were 0.6 C above average during March and April 2007. This anomalous warmth is expected to persist though hurricane season. Bottom: The 0.6 C above average temperatures are consistent with the exceptionally warm temperatures seen since 2003. Image credit: NOAA.

How good are the CSU forecasts?
The CSU forecast team has been making seasonal hurricane forecasts since 1984. If one grades their late May forecasts based on predictions of a below average, average, or above average season, they have done pretty well over the past eight seasons. Seven of their past eight forecasts have been correct. Their only failure occurred last year, when they called for a very active season, and it was a normal year with 10 named storms, 5 hurricanes, and 2 intense hurricanes. A more rigorous way of determining forecast skill is to compute the mathematical correlation coefficient. A correlation coefficient of 1.0 is a perfect forecast, and 0.0 is a no-skill forecast. The late May CSU forecasts have a respectable correlation coefficient of 0.57 for predicting the number of named storms (1984-2005). This decreases a bit to 0.46 and 0.42 for number of hurricanes and intense hurricanes, respectively. These are respectable correlation coefficients, and the late May CSU forecasts are worth paying attention to. This is in contrast to the December and April CSU forecasts, which have had a correlation coefficient near zero (and thus no skill).

Last year, the CSU team made their first steering current forecast. They predicted that a ridge of high pressure over the Eastern U.S. would steer more storms than average towards the Gulf Coast. However, the opposite happened--a trough of low pressure set up over the Eastern U.S.--and the 2006 steering current forecast was a bust. They've given up on trying to predict what this year's steering currents might be, citing the need to perform more research on this issue. In theory, such a forecast is possible. Gray and Klotzbach published a 2004 paper showing a statistical relationship between variations in Atlantic sea surface temperature and whether hurricanes are more likely to hit the U.S. Gulf Coast or East Coast. These SST variations influence the steering patterns, and help determine whether a persistent trough of low pressure will settle over the East Coast and recurve hurricanes out to sea--as happened in 2006--or whether a ridge of high pressure will settle in, pushing more storms towards the Gulf Coast--as happened in 2004 and 2005. The problem with all of these statistical Atlantic seasonal forecasts is that the atmosphere/ocean system is always changing in new ways that have not occurred in the past. Thus, a statistical scheme that works for forecasting past activity is much worse at predicting the coming year's activity. There is hope that the global dynamical computer models used to forecast the weather will soon be able to surpass the statistical methods used by the CSU team. Indeed, recent papers have shown the the European model (ECMWF) and GFDL model both make seasonal hurricane forecasts that rival the CSU forecasts in skill. No word yet on when these new computer model seasonal forecasts will be available to the public though--more research is needed to develop them.

The bottom line: expect a very active Atlantic hurricane season
The CSU forecast matches up well with the TSR, Inc. forecast (16 named storms, 9 hurricanes, and 4 intense hurricanes) and the NOAA forecast (13-17 named storms, 7-10 hurricanes, and 3-5 major hurricanes). Also, keep in mind that the active hurricane period that began in 1995 has never seen two consecutive years with average or below-average hurricane activity. Given these factors, I am confident that the coming season will be a very active one. The two most recent years that had patterns of El Niño/La Niña events and SSTs similar to what are expected this year were 1995 and 2003. Note that 1995 was the third busiest hurricane season on record, with 19 named storms. However, the great majority of these storms recurved out to sea, since a trough of low pressure settled over the Eastern U.S. I have a similar hope for this season--if the steering currents are your friend, even a top-five hurricane season can have an ordinary number of landfalls. Let's hope the steering currents are our friend this year!

The Tropical Storm Risk, Inc. 2007 Atlantic hurricane season forecast
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issues monthly 2007 Atlantic hurricane season forecasts. Their May 3 forecast has almost the same forecast as the CSU team--16 named storms, 9 hurricanes, and 4 intense hurricanes. I like how they put their skill level right next to their forecast numbers: 30% better than chance skill at forecasting the number of named storms, 34% skill for hurricanes, and 30% skill for intense hurricanes. TSR projects that five named storms will hit the U.S., with 2.3 of these being hurricanes. Their skill in predicting the number of named storms hitting the U.S. is only 8% above a no-skill forecast, but the skill rises to 30% for hurricanes hitting the U.S. In the Lesser Antilles Islands of the Caribbean, TSR projects 2.4 named storms, and 0.7 hurricanes. TSR cites two main factors for their forecast of an active season: above normal Sea Surface Temperatures (SSTs) are expected in August-September 2007 across the tropical Atlantic, as well as slower than normal trade winds. Trade winds are forecast to be 0.78 meters per second (about 1.6 mph) slower than average, which would create greater spin for developing storms, and allow the oceans to heat up due to reduced evaporative cooling. SSTs are forecast to be about 0.2 degrees C above normal. TSR gives an 84% chance that the 2007 Atlantic hurricane season will rank in the top third of active seasons observed since 1957. Their next forecast will be issued June 4.

The NOAA 2007 Atlantic hurricane season forecast
NOAA is also predicting a very active 2007 hurricane season in the Atlantic NOAA's season hurricane forecast issued May 22 predicts a very high (75% chance) of an above-normal hurricane season, a 20% chance of a near-normal season, and only a 5% chance of a below-normal season. They expect 13-17 named storms, 7-10 hurricanes, and 3-5 major hurricanes (a normal season has 10-11 named storm, 6 hurricanes, and 2 intense hurricanes). Most of these storms are expected during the usual August-October peak of hurricane season, but NOAA does not give any breakdown of which portions of the coast are more likely to be affected. They give two reasons for predicting an above-normal hurricane season:

1) A continuation of conditions since 1995 that have put us in an active hurricane period (in particular, the fact that seas surface temperatures in the Atlantic Main Development Region for hurricanes are currently about 0.6 C above normal, Figure 1).

2) The strong likelihood of either neutral or La Niña conditions in the tropical Pacific Ocean.

Tropical disturbance in the Western Caribbean
A large area of disturbed weather developed over the Western Caribbean last night. This disturbance is bringing winds of up to 55 mph over the ocean, according to the 7:07am EDT pass of the QuikSCAT satellite. The NOAA Buoy off the coast of the Yucatan Peninsula recorded winds this morning at 30mph, gusting to 35mph. There is no circulation evident on QuikSCAT or satellite loops, but the disturbance does have the potential to develop into a tropical depression by Saturday as it moves to the northeast over Western Cuba and South Florida. A Hurricane Hunter aircraft is scheduled to investigate the system at 2pm EDT on Friday.

Wind shear is a not-too-unfriendly 10-20 knots, and the shear is expected to remain at these levels through Saturday. Thereafter, most of the models are indicating that the disturbance will get caught up by a strong trough of low pressure with high shear that should stop further development and sweep the system northeastward out to sea. I doubt this system has enough time to get organized into a tropical depression before wind shear rips it up, but the disturbance should bring welcome heavy rains to South Florida over the weekend. Lake Okeechobee recorded its record lowest water level yesterday--8.97 feet (about 4 feet below normal). This was the lowest level since record keeping began in 1931, according to a Miami Herald article this morning. The lake has been dropping about 1/2 inch per rainless day. I expect 1-3 inches of rain over the area this weekend, which should temporarily stabilize the lake water level.

NHC issued this statement at noon today:

Special tropical disturbance statement
1150 am EDT Thu May 31 2007

Showers and thunderstorms in the northwestern Caribbean Sea... southeastern Gulf of Mexico and adjacent land areas are associated with a broad area of low pressure centered about 75 miles southeast of Cozumel Mexico. Although this system has some potential for tropical development over the next day or so...the low is expected to move slowly northward into the southern Gulf of Mexico where environmental conditions would likely favor further development as a non-tropical low. Regardless of development...this system should bring heavy rains across western Cuba and southern Florida over the next couple of days. Please monitor products issued by your local Weather Service office for more details.


Figure 2. Visible satellite image of the Western Caribbean tropical disturbance.

June outlook and the Barometer Bob show
I'll be posting my forecast for the first two weeks of June tomorrow (June 1). I plan to offer 2-week hurricane activity forecasts on the 1st and 16th of each month (except August 1, when I'll be on vacation). These forecasts will have the probability of hurricane formation for the coming two weeks, where the hurricanes will go if they form due to the prevailing steering currents, plus a look at how sea surface temperatures, wind shear, the trade winds, and dry air coming off of Africa are affecting hurricane formation in the Atlantic.

Tonight, I'll be a guest on the Barometer Bob Show, if you want to hear a sneak preview of my outlook for the first two weeks of June and hear about the tropical disturbance in the Western Caribbean. You can listen at barometerbobshow.com, or dial in via their toll-free number 1-866-931-8437 (1-866-WE1THER).

Jeff Masters

Updated: 4:16 PM GMT on May 31, 2007

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Tropical disturbance forms in Western Caribbean

By: JeffMasters, 1:35 PM GMT on May 31, 2007

A large area of disturbed weather developed over the Western Caribbean last night. This disturbance is bringing winds of up to 55 mph over the ocean, according to the 7:07am EDT pass of the QuikSCAT satellite. The NOAA Buoy off the coast of the Yucatan Peninsula recorded winds this morning at 30mph, gusting to 35mph. There is no circulation evident on QuikSCAT or satellite loops, but the disturbance does have the potential to develop into a tropical depression by Saturday as it moves to the northeast over Western Cuba and South Florida. Wind shear is a not-too-unfriendly 10-20 knots, and the shear is expected to remain at these levels through Saturday. Thereafter, most of the models are indicating that the disturbance will get caught up by a strong trough of low pressure with high shear that should stop further development, and sweep the system northeastward out to sea. I doubt this system has enough time to get organized into a tropical depression before wind shear rips it up, but the disturbance should bring welcome heavy rains to South Florida over the weekend. Lake Okeechobee recorded its record lowest water level yesterday--8.97 feet (about 4 feet below normal). This was the lowest level since record keeping began in 1931, according to a Miami Herald article this morning. The lake has been dropping about 1/2 per rainless day. I expect about an inch of rain over the area this weekend, which should temporarily stabilize the lake water level.


Figure 1. Visible satellite image of the Western Caribbean tropical disturbance.

Dr. Bill Gray/Phil Klotzbach hurricane forecast due later today
I'll be posting an updated blog around noon EDT today, when the latest seasonal Atlantic hurricane forecast by Dr. Bill Gray and company will be out. I'll also post an update on the Western Caribbean disturbance.

June outlook and the Barometer Bob show
I'll be posting my forecast for the first two weeks of June tomorrow (June 1). I plan to offer 2-week hurricane activity forecasts on the 1st and 16th of each month (except August 1, when I'll be on vacation). These forecasts will have the probability of hurricane formation for the coming two weeks, where the hurricanes will go if they form due to the prevailing steering currents, plus a look at how sea surface temperatures, wind shear, the trade winds, and dry air coming off of Africa are affecting hurricane formation in the Atlantic.

Tonight, I'll be a guest on the Barometer Bob Show, if you want to hear a sneak preview of my outlook for the first two weeks of June and hear about the tropical blob in the Western Caribbean. You can listen at barometerbobshow.com, or dial in via their toll-free number 1-866-931-8437 (1-866-WE1THER).

Jeff Masters

Updated: 1:37 PM GMT on May 31, 2007

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Sea life's importance to the climate

By: JeffMasters, 2:45 PM GMT on May 29, 2007

Does the marine biosphere mix the ocean? A group of oceanographers led by W.K. Dewar of Florida State University argue that the swimming action of fish and other marine organisms may play a critical role in driving ocean currents. If true, large-scale over-fishing or the collapse of the marine food chain due to pollution or ocean acidification may cause significant changes in ocean currents--and Earth's climate.


Figure 1. Rainbow made From a sperm whale using his blowhole. Image taken June 17, 2006 in Kaikora, New Zealand by wunderphotographer jhfelder.

The Meridional Overturning Circulation (MOC) or Thermohaline Circulation is a well-known feature of the ocean circulation. In the Atlantic, the Gulf Stream current forms a portion of the MOC. Gulf Stream waters flow to the region near Greenland, where an input of fresh, denser water from melting ice and river run-off creates a downward flow of water that then moves southward along the ocean bottom towards the Equator. This deep water eventually returns to the surface in the mid-Atlantic to complete a cell of the MOC. Scientists have long thought that the energy needed to drive the MOC came from winds and tides--about two terrawatts of energy (Munk and Wunsch, 1998). However, Dewar et al. show that the mechanical energy added to the ocean by the swimming action of whales is about 1% of this total, and the swimming action of other marine organisms (primarily zooplankton) adds up to 50% of this total--one terrawatt of energy. While the authors admit that their calculations may have large errors, this research shows that marine life may have a heretofore unappreciated large impact on Earth's climate. Our climate is intimately connected to the sun, life on land, life in the ocean, and human activities in an incredibly complex web of interconnections. It is our challenge to understand this system, even as we change it and it changes of its own accord.

My next blog will be Thursday afternoon, when the new Dr. Bill Gray/Phil Klotzbach Atlantic hurricane season forecast will be released.

Jeff Masters

Dewar, W.K., R.J. Bingham, R.L. Iverson, D.P. Nowacek, L.C. St. Laurent, and P.H. Wiebe, 2006, "Does the marine biosphere mix the ocean?", Journal of Marine Research, 64, 541-561.

Munk, W., and C. Wunsch, 1998, "Abyssal recipes II: Energetics of tidal and wind mixing", Deep-Sea Res., 45, 1976-2009.

Climate Change

Updated: 8:03 PM GMT on August 16, 2011

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Texas floods kill 5

By: JeffMasters, 3:59 PM GMT on May 26, 2007

Flash flooding triggered by heavy thunderstorm rains of up to seven inches in 24 hours claimed at least five lives in Texas Friday, and large portions of the state remain under flood warnings or flood watches today, as thunderstorms continue across the state. All of those killed were swept away in their vehicles, and police were still looking for a missing man who drove around a barricade blocking a swollen creek.


Figure 1. Precipitation for the 24 hours ending at 8am EDT Saturday May 26, 2007.

Drought last year, floods this year
As I discussed in a March blog last year, grass fires in drought-parched Texas killed seven people on March 12 in the Panhandle, four of them in a car crash on I-40 caused by thick smoke obscuring visibility. More than 1,000 square miles of Texas burned that day--an area about two-thirds the size of Rhode Island. It's amazing what a turnaround has occurred in the past year. Most of Texas and Oklahoma were under drought conditions that reached the extreme level last spring (Figure 2), but this year, the Texas/Oklahoma drought is gone (Figure 3), and instead has moved into the Southeastern U.S. We don't understand very well what causes these shifts in drought patterns, but they do seem to be linked to changes in large-scale sea surface temperature patterns in the Atlantic and Eastern Pacific, plus shifts in the jet stream pattern. Are the floods in Texas this year and drought last year partially due to global warming? Yes, they might be. Global warming theory predicts that both droughts and floods will grow more severe as the climate warms. Floods will increase, since a warmer atmosphere holds more water vapor that can then rain out into heavier floods. Scientists have already documented about a 5% increase in global atmospheric water vapor due to global warming, and this extra moisture is undoubtedly causing heavier rains and more flooding in some regions. Drought will increase in intensity due to global warming, thanks to the hotter temperatures drought-striken areas will receive when jet stream and sea surface temperature patterns conspire to keep rainfall from the drought area.


Figure 2. Drought map for March 7, 2006.


Figure 3. Drought map for May 22, 2007.

Jeff Masters

Climate Change Flood

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Bryan Norcross's Hurricane Almanac: a book review

By: JeffMasters, 1:19 PM GMT on May 24, 2007

Bryan Norcross, Hurricane Analyst for CBS's national news and Director of Meteorology for WFOR-TV in Miami, has just written his second annual Hurricane Almanac: The Essential Guide to Storms Past, Present, and Future. Bryan is famous for his marathon on-air performance during Hurricane Andrew of 1992, when he talked people through the storm as their homes came apart around them. His book is a great addition to the bookshelf of anyone living in Hurricane Alley. Like any almanac, it has information on a variety of topics, and is not meant to be read straight through. My favorite part was his 5-page description of his Hurricane Andrew experience--and the lessons we should have learned from it, but didn't. Some other highlights:

Ready, Set, Hurricane!
The book's greatest strength is the impressive 134-page section that provides checklists and practical information on how to prepare, ride out, evacuate, and recover from a hurricane. There are so many things to think of that having them available in a handy book one can pick up anytime makes Hurricane Almanac a great book to have. When preparing for a hurricane, you'll find tips on what storm shutters and generator to buy, what to do with your pet, computer, boat, pool and car, and how to make a Family Hurricane Plan. Bryan also boosts a web which I also like, onestorm.org. This is a free hurricane preparedness web site that helps you put together a family hurricane plan.

I like how the book emphasizes the most important things it wants you to know. In the case of the Ready, Set, Hurricane! section, Bryan emphasizes this:

IF YOU DON'T DO ANYTHING ELSE, DO THIS!

-Contact a friend or relative out of town and ask him or her to be your family's emergency contact.

-Before the storm, be sure that every member of the family has a piece of paper on them that says, for example:

EMERGENCY CONTACT
AUNT MILLY IN NJ
201-555-5555

-Call Aunt Milly before the wind starts blowing to tell her exactly where you are and what you are planning to do.

-Be sure everybody knows that they should call Aunt Milly if they get lost or anything bad happens.

It's important that your main contact person is out of town, because local calls are more likely to be disrupted after a storm. Both ends of local connections are subject to problems.

Another interesting fact I learned from Hurricane Almanac: You can send an email message to any cell phone able to receive text messages by emailing to XXX-XXX-XXXX@teleflip.com (replace the X's with the phone number of the person's cell phone). The message will be forwarded to any cell phone provider in the U.S.

Hurricane Almanac also details what to do after the storm--how to deal with FEMA and your insurance company, save water-damaged possessions, and purify your drinking water. Additional chapters include an excellent summary of all the various National Hurricane Center advisories and how to interpret them, the basics of hurricane science, and a summary of some of the famous storms in the past. The opening chapter includes a very passionate critique of our emergency management system, building codes, and the politicians who fail to adequately protect us against hurricanes. A sample quote:

That President Bush, DHS Secretary Michael Chertoff, and the head of the U.S. Army Corps of Engineers, General Carl Strock were completely misinformed and saying ridiculous things for days and weeks after the Katrina disaster is frightening. These people know when a pin drops in Afghanistan. How can they not know when a levee breaks in New Orleans? The evidence says that the communications and operational infrastructure of the federal government broke down. We should all be very concerned.

Hurricane Almanac (335 pages, softcover) is $10.39 from amazon.com. It's not fancy--all the photos and figures are black and white (if you want a coffee table hurricane book with beautiful color photos and figures, get Dr. Kerry Emanuel's Divine Wind. An added bonus for Hurricane Almanac is a companion web site, hurricanealmanac.com. The web site is not fancy, but does have some useful links and a page that allows you to send Byran emails with suggestions and/or fixes for the 2008 version of his book.

The book also has a provocative chapter titled, "How I'd do it better," that I'll comment on in a future blog.

Jeff Masters

Book and Movie Reviews

Updated: 5:15 PM GMT on July 14, 2011

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Very active Atlantic hurricane season forecast by NOAA

By: JeffMasters, 4:45 PM GMT on May 22, 2007

It's going to be a very active 2007 hurricane season in the Atlantic, according to NOAA's seasonal forecast issued today. The NOAA team predicts a very high (75% chance) of an above-normal hurricane season, a 20% chance of a near-normal season, and only a 5% chance of a below-normal season. They expect 13-17 named storms, 7-10 hurricanes, and 3-5 major hurricanes (a normal season has 10-11 named storm, 6 hurricanes, and 2 intense hurricanes). Most of these storms are expected during the usual August-October peak of hurricane season, but NOAA does not give any breakdown of which portions of the coast are more likely to be affected. They give two reasons for predicting an above-normal hurricane season:

1) A continuation of conditions since 1995 that have put us in an active hurricane period (in particular, the fact that sea surface temperatures in the Atlantic Main Development Region for hurricanes are currently about 0.6 C above normal, Figure 1).

2) The strong likelihood of either neutral or La Niña conditions in the tropical Pacific Ocean.


Figure 1. Top: Tropical Atlantic Ocean temperatures in the Main Development Region for hurricanes (green box) were 0.6 C above average during March and April 2007. This anomalous warmth is expected to persist though hurricane season. Bottom: The 0.6 C above average temperatures are consistent with the exceptionally warm temperatures seen since 2003. Image credit: NOAA.

How good are these forecasts?
NOAA's long lead hurricane outlook team, which consists of scientists from NOAA's Climate Prediction Center (lead: Gerry Bell), National Hurricane center (NHC), and the Hurricane Research Division (HRD), have been making seasonal hurricane forecasts since 1998. If one grades their May forecasts based on predictions of a below average, average, or above average season, NOAA has done pretty well. Seven of their nine forecasts have been correct. Their only failures occurred last year, when they called for a very active season (it was a normal year, with 10 named storms, 5 hurricanes, and 2 intense hurricanes), and 2001, when they called for a normal year (it was a very active year, with 15 named storms, 9 hurricanes, and 4 intense hurricanes).

Steering currents for June
It's now possible to say something about the steering currents for the upcoming Atlantic hurricane season, which officially begins June 1. A hyperactive Atlantic hurricane season is no big deal if the steering currents are your friend! The forecast jet stream pattern for the next two weeks from the GFS model is similar to last year's pattern. I expect we'll see a series of troughs of low pressure marching across the Atlantic Ocean through early June, which is typical for this time of year. The Bermuda High is in its usual location, and there are no signs of the unusual steering pattern of 2005 that brought so many hurricanes over the U.S.. It is still to early to say what the steering patterns will do during peak hurricane season, August through October, though.

The Dr. Bill Gray/Phil Klotzbach's team at Colorado State University issues their updated Atlantic hurricane season forecast on May 31 next week, and I'll be sure to make a post about that forecast.

Jeff Masters

Updated: 2:29 PM GMT on May 23, 2007

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2007 typhoon season forecast

By: JeffMasters, 1:51 PM GMT on May 21, 2007

It's going to be a below-average typhoon season in the Western Pacific, according to the April 23, 2007 forecast issued by Dr. Johnny Chan of the City University of Hong Hong. Dr. Chan is calling for 25 named storms and 14 typhoons in 2007, slightly below the average of 27 named storms and 17 typhoons. The forecast for a below-average typhoon season was based on three main factors:

1) The Western Pacific has been in an inactive period since 1998, and this inactivity is expected to persist.

2) This year should have neutral El Niño conditions, or a La Niña event. These conditions have led to below-average typhoon activity since the current inactive typhoon period began in 1998 (Figure 1).

3) A stronger-than-normal high pressure system has been in place over the subtropics in the Western Pacific in February and March of 2007. Such higher pressures are associated with reduced typhoon activity later in the year.


Figure 1. Time series of the annual number of named tropical storms in the Western Pacific. Red circles and blue squares indicate El Niño and La Niña years, respectively. The green triangle is this year's forecast. An average year has 27 named storms. Image credit: City University of Hong Kong.

How good are these forecasts?
Dr. Chan has been making seasonal typhoon forecasts since 2000, and his forecasts have been skillful. The 2000-2006 forecasts issued in April for number of named storms and typhoons have a Mean Square Skill Score of about 30 and 50, respectively, according to some quick calculations I did. This is considerably higher than the late May seasonal forecasts for Atlantic hurricane activity issued by both Dr. Bill Gray/Phil Klotzbach's team at Colorado State University and Tropical Storm Risk, Inc. However, hurricane activity in the Atlantic has varied much more from year-to-year in the past decade than typhoon activity in the Western Pacific. This makes the Atlantic forecast problem more challenging.

Typhoon Yutu
Typhoon Yutu, the season's first major typhoon, intensified to a Category 4 storm with 145 mph winds yesterday. The typhoon is over open water and weakening, but could pass through the islands near Iwo Jima as a Category 2 typhoon on Tuesday. Yutu is the second named storm of the year in the Western Pacific, which usually sees three named storms by the end of May.

Figure 2. Typhoon Yutu at 00 GMT May 20, 2007. Image credit: Navy/NRL.

Tuesday (tomorrow), I'll report on NOAA's 2007 Atlantic hurricane season forecast, which will be released at 11am EDT.

Jeff Masters

Updated: 1:57 PM GMT on May 21, 2007

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A new name for the National Hurricane Center?

By: JeffMasters, 7:23 PM GMT on May 18, 2007

Administrators at the National Atmospheric and Oceanic Administration (NOAA) are making moves to promote their "Corporate Identity" by renaming the National Hurricane Center and National Weather Service, according to an article published yesterday in the Miami Herald. The new organizations would be called the "NOAA Hurricane Center" and the "NOAA Weather Service". The proposed changes are being vigorously opposed by new NHC director Bill Proenza, who said, "what's happening is scary."

The issue at hand is money. Everyone has heard of the National Hurricane Center (NHC) and the National Weather Service (NWS), but the public is not that familiar with their parent organization, NOAA--part of the U.S. Department of Commerce. By taking over the name of two of the government's most visible, well performing, and trusted organizations, NOAA wants to position themselves to take credit for the fantastic job these organizations do. The result, they hope, will be increased funding for NOAA in the future, thanks to increased name brand recognition. "If NOAA achieves a strong presence in the eyes of the people who use its varied services, the agency will be more successful in budget matters," said Anson Franklin, NOAA's director of communications.

The problem with this is that there are no guarantees that increased funding for NOAA will result in a bump in funding for NHC or NWS. For example, NOAA has an annual budget of over $4 billion, and NHC's budget is just $6.3 million. With NHC losing its identity, its funding may become diluted by NOAA, and will have to fight harder for dollars. Another problem is that the public, who like and trust the NWS and NWS brands, may see the change as an attempt by NOAA bureaucrats to take unwarranted credit for what these organizations do. In addition, it will cost plenty to change the names of these organizations, which may be viewed as a waste of taxpayers' money.

Proenza also complained that NOAA is spending between $1.5 million and $4 million on a "bogus" 200-year NOAA anniversary celebration (NOAA was founded in 1970, although some of its component organizations are 200 years old). I do believe that NOAA has a name recognition problem, and that it needs to spend some public relations money to get their name more recognized by the public. Public relations campaigns are essential for any organization to succeed in today's world. However, I think NOAA is going about their public relations campaign the wrong way. The amount being spent on the 200-year anniversary celebration is excessive, given NOAA's stinginess in funding important hurricane research. Furthermore, NOAA should leave the names of the National Hurricane Center and National Weather Service alone. Departments of NOAA should be named, recognized, and funded based on their individual missions and function, not based on those of their parent organization. NHC and NWS have worked hard to earn their name recognition, and it would be wrong for NOAA to change their names.

NOAA has made a web page available for the public to see the proposed changes to its web pages that would result from its reorganization. You can comment on the proposed changes until June 13.

Jeff Masters

Politics

Updated: 11:04 PM GMT on October 21, 2011

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Warmest January-April on record; new record Arctic sea ice minimum

By: JeffMasters, 2:00 PM GMT on May 17, 2007

April 2007 was the third warmest April for the globe on record, and the first four months of 2007 were the warmest ever, according to statistics released this week by the National Climatic Data Center. The global average temperature for April was 1.19�F/0.66�C above the 20th century mean. Over land, April global temperatures were the warmest ever measured. Ocean temperatures were a bit cooler (seventh warmest on record), thanks to the cooling associated with the disappearance of the winter El Ni�o event.

April temperatures were particularly warm across portions of Europe and Siberia, where readings of 5�C (9�F) above average were common (Figure 1). The UK recorded its warmest and driest April on record. In the U.S., April ranked near normal in temperature, but a record cold snap hit the eastern half of the country April 4-10, setting 900 daily low temperature records. The long duration of the cold outbreak, combined with the large number of hours that remained below freezing, and strong winds that occurred in many areas, contributed to crop losses that could reach into the billions of dollars. The damaging effects of the record cold were made worse by near-record warmth in March that helped induce an earlier spring blossom--in some cases two weeks prior to crop development in 2006. More than 2,500 daily record-high temperatures were set in the contiguous U.S. in March, and it was our second warmest March on record.

April's cold snap in the U.S. shows that although the globe as a whole may be warming, there is still plenty of natural variability capable of bringing very cold weather to local regions.


Figure 1. Temperature departure from average for April 2007. Image credit: National Climatic Data Center.

Arctio sea ice extent
After three months of not recording a record monthly minimum, sea ice extent in the Arctic recorded a new record low extent in April. The record warmth of the first four months of 2007, combined with the 8th lowest snow cover on record observed in winter 2006/2007, combined to produce the record low ice extent (Figure 2).


Figure 2. Arctic sea ice extent for April, for the years 1979-2007. April 2007 set a new record for the lowest Arctic sea ice extent measured. April sea ice coverage has declined about 9% since 1979. Image credit: National Snow and Ice Data Center.

Atlantic storms
The computer models have been forecasting development of several low pressure systems along the East Coast over the next few days. All of these lows will be non-tropical in nature, due to the high levels of wind shear. The models are beginning to hint that wind shear could relax over the ocean waters north of Panama next week, and we may have to watch that area for tropical development if the shear does indeed relax as forecast.

Jeff Masters

Climate Change Climate Summaries

Updated: 8:03 PM GMT on August 16, 2011

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East Coast storm on Friday; Eastern Pacific hurricane season begins today

By: JeffMasters, 1:58 PM GMT on May 15, 2007

All of the major computer models are forecasting the development of a extratropical low pressure system late this week over the Bahama Islands, about 300 miles east of Florida. This low is forecast to develop Thursday night or Friday morning, then move north-northeastward along the East Coast. The models have a wide range of solutions for the intensity and track of this storm, but it appears unlikely that it will have enough time over warm water to become Subtropical Storm Barry. Several of the models predict that the storm will become quite intense and hit New England on Saturday, bringing gale force winds and heavy rain. It's too early to judge the likelihood of this, though.


Figure 1. Hurricane Daniel on July 21, 2006, as seen by NASA's Terra satellite. Daniel was the strongest hurricane to affect the Eastern Pacific in 2006 (Category 4, top winds of 150 mph).

Eastern Pacific hurricane season begins today
Today marks the official start to the hurricane season in the Eastern Pacific. Starting today, NHC will issue their Tropical Weather Outlook for the Eastern Pacific four times daily. The 2-week forecast from the GFS model is not predicting that Tropical Storm Alvin will form in the coming week, but hints that the last week of May could see some development. The International Research Institute for Climate and Society at Columbia University is the only group that I am aware of that issues long-range seasonal forecasts for the Eastern Pacific. Their May 2007 forecast calls for a 40% chance of below normal activity (nine or fewer named storms), a 35% chance of normal activity (10-15 named storms), and a 25% chance of an above normal season (more than 15 named storms). The forecast of a less active than usual season is primarily based on their prediction that sea surface temperatures will be below normal in the Eastern Pacific during hurricane season. Unfortunately, they don't provide an easy way to determine how reliable their long-range forecasts are.

I'll have an update on Thursday.
Jeff Masters

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Andrea's remains head out to sea

By: JeffMasters, 4:10 PM GMT on May 13, 2007

After lingering by the coast of Florida and almost reaching tropical depression status the past two days, Andrea has finally gotten caught up in a west-to-east moving trough of low pressure, and gotten swept out to sea. Andrea's remains could bring tropical storm force winds to Bermuda Monday morning. Here is the latest thing NHC had to say about the storm:

SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1000 AM EDT SUN MAY 13 2007

AN AREA OF LOW PRESSURE...THE REMNANT OF SUBTROPICAL STORM ANDREA...IS CENTERED ABOUT 445 MILES EAST-NORTHEAST OF DAYTONA BEACH FLORIDA AND ABOUT 550 MILES WEST OF BERMUDA. THE SYSTEM IS NOW MOVING EAST-NORTHEASTWARD AT 10 TO 15 MPH...AND A GENERAL MOTION TOWARD THE EAST AT A FASTER FORWARD SPEED IS EXPECTED DURING THE NEXT 24 HOURS. THERE HAS BEEN LITTLE CHANGE IN ORGANIZATION DURING THE NIGHT...AND THE LOW IS NOW MOVING OVER COLDER SEA SURFACE TEMPERATURES. THUS...THE POTENTIAL FOR DEVELOPMENT INTO A TROPICAL DEPRESSION IS DECREASING. THIS SYSTEM IS EXPECTED TO MERGE WITH AN APPROACHING COLD FRONT AS IT PASSES NEAR BERMUDA ON MONDAY.


Figure 1. Visible satellite image from May 13, 2007, showing the remains of Andrea moving out to sea (upper right corner), and some residual smoke over the Gulf of Mexico from Florida's Bugaboo fire.

Andrea's departure is welcome news to most of Florida, as winds over the Bugaboo fire region have calmed down considerably with the storm's departure. Lighter winds have kept the smoke from the fire near its source, forcing the closure of a 35-mile stretch of I-75 and a portion of I-10 in northern Florida. Air pollution levels are still dangerous to vulnerable people in much of Florida, but have improved greatly over Friday's record-breaking levels.

Have a great Mother's Day, all you moms!
Jeff Masters

Updated: 4:16 PM GMT on May 13, 2007

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Andrea's smoke a major hazard

By: JeffMasters, 1:43 PM GMT on May 12, 2007

Andrea refuses to totally die. Thunderstorm activity associated with the remnant low continues to flare up, and wind shear remains low enough (10 knots) to permit redevelopment of this system. Current radar out of Melbourne, Florida shows some disorganized rainbands surrounding the center of the storm, and infrared satellite loops show intermittent bursts of thunderstorms, particularly to the east of the center. The activity as seen on radar and satellite is not very organized, and any redevelopment of Andrea should be slow to occur. However, the remains of Andrea have some tropical storm force winds of 45-55 mph a few hundred miles east of the center, as seen in this morning's 7:29am EDT QuikSCAT pass. Water vapor loops show some very dry air around the remnants of Andrea, and sea surface temperatures are still a rather cool 24-26 C. By Sunday, wind shear will increase to near 20 knots, and a trough of low pressure is expected to finally move Andrea's remains out to sea.

NHC put out this special advisory at 9pm today:

SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
900 PM EDT SAT MAY 12 2007

AN AREA OF LOW PRESSURE...THE REMNANT OF SUBTROPICAL STORM ANDREA...IS CENTERED ABOUT 250 MILES EAST OF DAYTONA BEACH FLORIDA. THIS SYSTEM HAS NOT BECOME ANY BETTER ORGANIZED SINCE THIS MORNING...AND IS CURRENTLY ACCOMPANIED BY ONLY A SMALL AREA OF THUNDERSTORMS TO THE EAST OF THE CENTER. ALTHOUGH NO SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS EXPECTED...ONLY A SMALL INCREASE IN ORGANIZATION WOULD
RESULT IN THE FORMATION OF A TROPICAL DEPRESSION. THE LOW IS MOVING EAST-NORTHEASTWARD AT 5 TO 10 MPH AND A CONTINUED MOTION AWAY FROM THE SOUTHEASTERN UNITED STATES IS EXPECTED DURING THE NEXT 24 HOURS.


Figure 1. True color image from NASA's Terra satellite of the remains of Andrea off the coast of Florida at 12:30 pm EDT Friday May 11, 2007. The counter-clockwise circulation around the storm fanned fires (red dots near the Florida/Georiga border) and drew the smoke all the way along the length of Florida, and into the center of the storm. Note the huge area of smoke covering the Gulf Of Mexico, blown there on previous days. Image credit:NASA.

Andrea and the Florida/Georgia fires
The strong winds of Andrea fanned the huge fires burning in the Florida/Georgia border region, and the counterclockwise flow of air around the low drew the smoke over the entire length of Florida yesterday. The Air Quality Index (AQI) for particle pollution reached the "Very Unhealthy" level between 10am and 5pm yesterday in both Tampa and St. Petersburg. "Very Unhealthy" values trigger a health alert, meaning everyone may experience more serious health effects. For several hours the AQI exceeded 300 in both cities. An AQI of 300 is the threshold for "Hazardous" air pollution, which the EPA defines as "Health warnings of emergency conditions. The entire population is more likely to be affected". Air quality in the Tampa Bay area was among the worst ever measured there; at the USMC Reserve Center monitoring site in Hillborough County, particulate matter pollution reached 753 micrograms per cubic meter, and the 24 hour average was 198--nearly six times the federal standard of 35 micrograms per cubic meter.

Fortunately, residents seem to be paying attention to the air pollution advisories. "Area hospitals reported just a handful of patients complaining about breathing problems, which was an encouraging sign for health officials who say people with poor health seem to be heeding warnings to stay inside", according to the St. Petersburg Times. But there's no doubt that the pollution is very dangerous. Take a look at this comment posted on the Tampa Bay Tribune web site yesterday:


After my mile walk this evening at 11pm, I felt tired and weak at the knees later about midnight my heart pounded fast and hard. I have slight chest pain, anxiety comes in waves, lying down is worse, my throat feels opened up and there.s too much cold air, my throat is scratchy and my lungs are sore. I might need to call 911 It.s now 2:45am sometimes I feel like I might die. like my heart may explode. I was OK yesterday. An hour later I was feeling better thank God! I've wondered if it was the smoke in the air from the brush fires. I checked my resting heart rate before and it was 100 beats a minute. Now it's 56 beats a minute. I went to bed at 4:00am however I woke up 3 hours later 7am I started getting mild symptoms again. I found a face mask. It does help.


People with heart or lung disease, older adults, and children should avoid all physical activity outdoors during the heavy smoke conditions. Everyone else should avoid prolonged or heavy exertion. Pay attention to the air pollution advisories issued for your area. This air pollution episode has the potential to be far more deadly than any hurricane that has affected Florida over the past 79 years!

Jeff Masters

Updated: 2:16 AM GMT on May 13, 2007

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Andrea not dead yet

By: JeffMasters, 1:53 PM GMT on May 11, 2007

NHC declared Andrea dead last night, but thunderstorm activity has flared up again on the storm's southeast side this morning, and Andrea may be making a comeback. Wind shear has dropped to about 10 knots, and is forecast to remain low until Sunday. Current radar out of Melbourne, Florida shows a marked increase in rainbands along the southeast side of the low, and recent infrared satellite loops show a burst of thunderstorms with cloud tops developing there. Buoy 41009 23 miles east of Cape Canaveral has not shown much change in winds today, which have been running 23-28 mph. This morning's 7:29am EDT QuikSCAT pass showed top winds in the 30-35 mph range--tropical depression strength. If the storm had had its current presentation at 11pm last night, NHC would have kept it as a subtropical depression. However, the more organized appearance may just be a transitory burst, and the storm will have to continue to improve in appearance until late this afternoon in order to regain her name. That's not going to be easy, given that water vapor loops show some very dry air around the remnants of Andrea, and sea surface temperatures are still a rather cool 24-26 C. I give Andrea a 30% chance of regaining her name over the next 24 hours.

Andrea's remains continue to drift south at about 5 mph, but most of the models show it stalling by Saturday, then getting swept out to sea on Sunday. So it appears now that even if Andrea does make a comeback, it will not bring Florida much in the way of needed rainfall. Bermuda may encounter some gale force winds early next week when the remnants of Andrea interact with an extratropical low pressure system that is expected to develop between Bermuda and the U.S. coast.

NHC had this to say about Andrea's remnants at 3pm today:

A SMALL AREA OF LOW PRESSURE...THE REMNANT OF SUBTROPICAL STORM ANDREA...IS CENTERED ABOUT 75 MILES OFF THE EAST COAST OF CENTRAL FLORIDA. THIS SYSTEM HAS BEEN PRODUCING SPORADIC THUNDERSTORM ACTIVITY TODAY...BUT IT LACKS SUFFICIENT ORGANIZATION TO QUALIFY AS A TROPICAL CYCLONE. WHILE SIGNIFICANT DEVELOPMENT IS NOT ANTICIPATED...THIS SYSTEM WILL BE MONITORED FOR SIGNS OF TROPICAL CYCLONE FORMATION. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WILL BE AVAILABLE TO INVESTIGATE THIS SYSTEM TOMORROW...IF NECESSARY.

INTERESTS NEAR THE SOUTHEAST COAST OF THE UNITED STATES SHOULD CONSULT PRODUCTS ISSUED BY LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICES. ADDITIONAL INFORMATION ON THIS SYSTEM CAN ALSO BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...


Figure 1. Infrared satellite image at 7:15 GMT Friday May 11 2007.

Interesting infrared satellite image
This morning's 7:15 GMT infrared satellite image of Florida (Figure 1) shows an interesting feature--the fires burning along the Georgia/Florida border. These fires are so hot that they are visible on the infrared satellite image. Infrared satellite images are a map of heat energy emitted, and where the hot fires are burning, we see black pixels. The high, cold cloud tops of the thunderstorms surrounding the remnants of Subtropical Depression Andrea show up white.

Other blogs
The View From the Surface blog shows a nice satellite animation of yesterday's Florida/Georgia fires, and Mike Theiss has posted more photos of his chases in Tornado Alley during last week's incredible severe weather outbreak.

My next update will depend on the weather--
Jeff Masters

Updated: 6:59 PM GMT on May 11, 2007

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Andrea slowly weakening

By: JeffMasters, 1:44 PM GMT on May 10, 2007

Subtropical Storm Andrea has weakened this morning, and currently poses little threat to land--other than some minor beach erosion along the Georgia and northern Florida coasts. Storm tides are running about one foot above normal in these areas, with 2-4 foot surf. Andrea's satellite presentation shows a classic example of a weak storm experiencing significant wind shear. Most of the heavy thunderstorm activity is displaced to the east side of the storm, pushed there by strong upper level winds from the northwest and west. Wind shear is about 20 knots, and is expected to remain this high for another day, then decrease by Saturday. The organization of the spiral bands of rainfall visible on the Jacksonville, FL long range radar is poor. The top winds found by the Hurricane Hunters this morning at their flight level of 1000 feet were 41 mph, as of 9:20am EDT. The central pressure had risen to 1003 mb, according to their 9:20am center fix, and Andrea may get downgraded to a tropical depression later today. The GFS model is calling for Andrea to dissipate by Saturday, and given the marginal Sea Surface Temperatures (24-25 C), significant dry air surrounding the system, and strong wind shear, NHC is also calling for dissipation. However, there is a good possibility that Andrea could hang on and eventually get swept out to sea, as the GFDL model is calling for. In this scenario, Andrea could intensify early next week and threaten Bermuda as a strong subtropical storm.


Figure 1. Forecast smoke levels at 11am EDT Thursday, May 10 from NOAA's air quality computer model. Note the ring of smoke encircling Jacksonville, due to the counterclockwise flow of air around Andrea. Image credit: NOAA.


Figure 2. Observed levels of fine particulate matter pollution (PM2.5) over Florida. Orange circles mark cities where the air is "Unhealthy for Sensitive Groups", and people with heart or lung disease, older adults, and children should reduce prolonged or heavy exertion in these areas. Image credit: EPA.

Andrea and the Florida/Georgia fires
The counter-clockwise circulation of air around Andrea's center of low pressure can be seen in the forecast movement of smoke from the fires burning in northern Florida and Southeastern Georgia (Figure 1). The Hurricane Hunters reported that dense smoke was obscuring visibility over the ocean waters near Jacksonville during their mission into Andrea this morning--the first time I've ever seen that observation during a hurricane hunter mission. This smoke is expected to form a ring encircling Jacksonville, and an air pollution alert for unhealthy levels of particulate matter pollution has been posted today for that city. Particulate matter pollution advisories have also been posted along a swath from Orlando to Miami. People with heart or lung disease, older adults, and children should reduce prolonged or heavy exertion in these areas. A map of current particulate matter pollution levels is posted in Figure 2. Wunderblogger aquak9 has a Floriga/Georgia fire blog for those interested in conversing about the fires.

Rainfall from Andrea has been less than 0.3 inches across the fires zones, which is not enough to douse them. Andrea is a very dry storm; peak rainfall rates are only about 0.25 inches per hour, in the storm's southeastern rainbands. These rainbands are not expected to hit the coast in the next two days. Maximum total rainfall observed by the Jacksonville radar has been less than 1.5 inches.

I'll have an update Friday morning, unless some significant change in Andrea occurs today. The 8am QuikSCAT pass missed Andrea; the next pass is at about 8pm. The next Hurricane Hunter mission is not until 8am Friday.

Jeff Masters

Updated: 1:54 PM GMT on May 10, 2007

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Andrea no help for Florida's fires

By: JeffMasters, 11:26 PM GMT on May 09, 2007

Subtropical Storm Andrea has changed little since it was named at 11am today. The amount of thunderstorm activity has decreased on the storm's west side, but become a little more concentrated on the east side. The organization of the spiral bands of rainfall visible on the Jacksonville, FL long range radar has remained about the same, and winds at some of the offshore buoys have remained fairly constant. Andrea remains a sloppy, disorganized storm. The main threat from the storm is coastal erosion due to the pounding surf it is generating--plus a possible fanning of the fires burning in Florida and Georgia (see below).

Wind shear has increased from 10 knots this morning to about 25 knots this evening. Shear is expected to increase to over 30 knots late tonight. Given the unfavorable wind shear, and the fact that the storm is over waters of 24-25 degrees C, I don't expect any significant intensification of Andrea. A slow decay as forecast by NHC seems reasonable.

Andrea and the Florida/Georgia fires
As Andrea began to form on Tuesday off the Carolina coast, the counter-clockwise circulation of air around the center of low pressure brought northerly winds over northern Florida and southern Georgia, where significant fires are burning. These north winds blew the smoke from the fires into the Tampa/St. Petersburg area, where unhealthy levels of particulate matter air pollution were recorded (Figure 1). The storm moved far enough west and south today that a more westerly flow of air has been carrying the smoke out over the Atlantic. Rainfall from Andrea has been less than 0.3 inches across the fires zones, which is not enough to douse them; in fact, the storm's high winds have served to fan the flames.

Andrea is a very dry storm; peak rainfall rates are only about 0.25 inches per hour, in the storm's southeastern rainbands. These rainbands are not expected to hit the coast in the next two days. Maximum total rainfall observed by the Jacksonville radar has been less than 1.5 inches.


Figure 1. NASA MODIS image of fires burning over Florida on May 8, 2007. Image credit: NASA Earth Observatory.

Early storms
The last time a named storm formed so early in the year was on April 18 2003, when Tropical Storm Ana formed near Bermuda. An unnamed subtropical storm also formed on April 21, 1992.

Longest period with a tropical cyclone ends
Andrea's formation brings to a close the longest period on record globally without a tropical cyclone. The last advisory issued on a tropical cyclone this year was at 06 GMT on April 6th, for Tropical Cyclone Cliff in the Southern Hemisphere. Today's 15 GMT advisory on Subtropical Storm Andrea ends the record longest period without a tropical cyclone at 33.4 days, besting the old record of 31.5 days set mid-April to mid-May in 1984. Reliable records of global tropical cyclone numbers go back to the beginning of the satellite era, about 1970.

I'll have an update in the morning. The next Quikscat pass is at about 8pm. The next Hurricane Hunter mission is not until 8am Thursday.

Jeff Masters

Fire

Updated: 9:36 PM GMT on August 16, 2011

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Subtropical Storm Andrea not changing much

By: JeffMasters, 6:02 PM GMT on May 09, 2007

Subtropical Storm Andrea has changed little since it was named at 11am today. The amount of thunderstorm activity in the rainbands surrounding the center has decreased, and the cloud tops have warmed some, indicating weakening. However, the organization of the spiral bands of rainfall visible on the Jacksonville, FL long range radar has improved some, and winds at some of the offshore buoys have remained fairly constant the past few hours. Tropical storm-force winds cover a wide swath of ocean surrounding the center. Winds from the 6:44am EDT pass of the QuikSCAT satellite (Figure 1) were as high as 50 knots (57 mph) in the heaviest thunderstorms on the southeast side. Winds at Gray's Reef 45 miles southeast of Savannah, Georgia, have been just below tropical storm force this afternoon--33 mph, gusting to 38 mph.


Figure 1. QuikSCAT image of the surface winds at 6:44am EDT Wed May 10. Image credit: NOAA/NESDIS.

Wind shear has increased from 10 knots this morning to about 20 knots this afternoon. Shear is expected to increase to over 30 knots late tonight. Given the unfavorable wind shear, and the fact that the storm is over waters of 24-26 degrees C, I don't expect any significant intensification of Andrea. A slow decay as forecast by NHC seems reasonable.

Early storms
The last time a named storm formed so early in the year was on April 18 2003, when Tropical Storm Ana formed near Bermuda. An unnamed subtropical storm also formed on April 21, 1992.

Longest period without a tropical cyclone ends
Andrea's formation brings to a close the longest period on record globally without a tropical cyclone. The last advisory issued on a tropical cyclone this year was at 06 GMT on April 6th, for Tropical Cyclone Cliff in the Southern Hemisphere. Today's 15 GMT advisory on Subtropical Storm Andrea ends the record longest period without a tropical cyclone at 33.4 days, besting the old record of 31.5 days set mid-April to mid-May in 1984. Reliable records of global tropical cyclone numbers go back to the beginning of the satellite era, about 1970.

I'll have an update early this evening. The next Quikscat pass is at about 8pm. The next Hurricane Hunter mission is not until 8am Thursday.

Jeff Masters

Updated: 8:12 PM GMT on May 09, 2007

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Subtropical Storm Andrea forms

By: JeffMasters, 1:34 PM GMT on May 09, 2007

Throw away the calendar, hurricane season is here! The Hurricane Hunters are in the air, and found that the intensifying storm of the Georgia coast had acquired enough organization to be called Subtropical Storm Andrea. Here's the special advisory put out by NHC at 9am:


Special tropical disturbance statement
905 am EDT Wed May 9 2007

Satellite imagery and preliminary reports from an Air Force Reserve reconnaissance aircraft this morning indicate that the area of low pressure centered about 150 miles east of Jacksonville is acquiring the characteristics of a subtropical cyclone. The system continues moving generally westward at about 5 mph. If present trends continue... advisories on subtropical storm Andrea would be
initiated later this morning.

Dangerous surf conditions continue along the coasts of the
Carolinas... Georgia... and northeastern Florida. Interests in these areas should continue to monitor products issued by local National Weather Service forecast offices.


Andrea has developed several bands of intense thunderstorm activity, well removed from the center. Tropical storm-force winds cover a wide swath of ocean surrounding the center. Winds from the 6:44am EDT pass of the QuikSCAT satellite (Figure 2) were as high as 50 knots (57 mph) in the heaviest thunderstorms on the southeast side. Winds overnight at buoy SKMG1 located about 60 miles off the Georgia coast were as high as 50 mph, gusting to 56 mph. These strong winds will continue to bring coastal flooding and significant beach erosion from North Carolina to northern Florida today.


Figure 1. Visible satellite image of Subtropical Storm Andrea shortly before it was named on May 9, 2007.


Figure 2. QuikSCAT image of the surface winds at 6:44am EDT Wed May 9. Image credit: NOAA/NESDIS.

Andrea is currently under about 10 knots of wind shear, but this shear is expected to increase to over 30 knots late tonight, so only a small window of time exists for the storm to intensify. Andrea is very unlikely to grow to hurricane strength, due to the combined effects of increased wind shear and cooler waters it will find near the coast. Landfall should occur Thursday morning over the region between northern Florida and southern South Carolina.

I'll have another update on Andrea this afternoon.
Jeff Masters

Updated: 5:58 PM GMT on January 30, 2008

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Hybrid coastal storm pounds Southeast coast

By: JeffMasters, 2:42 PM GMT on May 08, 2007

A powerful coastal storm centered about 300 miles east of the Georgia coast continues to bring coastal flooding and significant beach erosion from North Carolina to southern Florida. Flood waters driven ashore by winds approaching tropical storm force closed the only road connecting North Carolina's Outer Banks to the mainland on Monday. The water over U.S. 12 just north of Rodanthe cut off a Warner Brothers movie crew filming "Nights in Rodanthe," which stars Richard Gere and Diane Lane. A lifeguard office and garage slid into the ocean at Jupiter Inlet, Florida, and about 100 feet of coastal road were underwater at 1:30 am Tuesday. A coastal flood warning remains in effect for much of the North Carolina coast, where a storm surge of 3-5 feet is expected today. High surf advisories are posted for the entire coast from Maryland to Miami. Winds of minimal tropical storm force (35 knots, or 39 mph) are occurring over a large stretch of ocean surrounding the storm, according to the latest QuikSCAT satellite wind estimates. The South Carolina buoy 41004 had 15 foot seas and sustained winds of 39 mph at 9am EDT this morning.


Figure 1. Model tracks for the Southeast coastal storm, now dubbed "Invest 90L" by NHC.


Figure 1. Visible satellite image of the May 8, 2007 coastal storm.

The coastal low moved over the core of the Gulf Stream (dark orange colors of Figure 3) last night, the warm waters it encountered helped intensify the storm to a central pressure of 1000 mb--which was not forecasted well by the computer models. The low is now a hybrid between a cold-cored Nor'easter and a warm-cored tropical storm, but does not have the characteristics needed to be called a subtropical storm. A subtropical storm has much heavier rains and more organized thunderstorm activity, which typically form a solid band of rainfall 100 miles or more from the center. Today's storm shows no evidence of bands of precipitation forming; the thunderstorm activity is disorganized. If a major organized band of thunderstorms does develop over the next day or two, the NHC could designate this storm as Subtropical Storm Andrea. I am not expecting that to happen, given the marginal SSTs (24-26 C), and significant amount of dry continental air surrounding the storm.


Figure 3. Sea Surface Temperatures on May 7, 2007, as measured by the AVHRR satellite. The dark orange colors mark the position of the Gulf Stream current. Image credit: Ocean Remote Sensing Group, Johns Hopkins university Applied Physics Laboratory.

Cyclone Phase Space diagrams available at the Florida State University web site maintained by Dr. Bob Hart show that the storm has neither a cold nor a warm core, but is a hybrid. The model forecasts call for the storm to remain in this hybrid state until it makes landfall by Thursday morning, somewhere between the Georgia and South Carolina coasts. The storm should gradually decrease in strength, and winds have already dropped considerably from yesterday. Unfortunately, the storm has not acquired enough tropical moisture to be a big rain maker, and its winds are serving to fan fires in southern Georgia and northern Florida. I expect the storm will bring 1-2 inches of rain to South Carolina on Thursday, and lesser amounts to Georgia and northern Florida.

NHC issued this special advisory this afternoon:

SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
400 PM EDT TUE MAY 8 2007

A NON-TROPICAL LOW PRESSURE SYSTEM...CENTERED ABOUT 200 MILES SOUTHEAST OF THE GEORGIA AND SOUTH CAROLINA COASTS...HAS BEEN MOVING SLOWLY WESTWARD AT 5 TO 10 MPH. THE LOW IS PRODUCING GALE-FORCE WINDS NEAR THE COASTS OF NORTH CAROLINA...SOUTH CAROLINA...AND GEORGIA. THIS SYSTEM HAS CHANGED LITTLE SINCE THIS MORNING...AND NO SIGNIFICANT STRENGTHENING IS EXPECTED. THE LOW IS BEING MONITORED FOR SIGNS OF TROPICAL OR SUBTROPICAL CYCLONE DEVELOPMENT...AND AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WILL BE AVAILABLE TO INVESTIGATE THE SYSTEM TOMORROW MORNING...IF
NECESSARY.

INTERESTS ALONG THE COAST OF THE SOUTHEASTERN UNITED STATES SHOULD MONITOR PRODUCTS ISSUED BY LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICES.

Severe weather in the Plains finally abates
The severe storm action finally quieted down yesterday in the Midwest, where no tornadoes were reported for the first time since Thursday. The severe weather action should stay at a slow simmer through Thursday over the Plains; the Storm Prediction Center (SPC) has portions of the region under its "Slight Risk" area for severe weather. Flooding continues to be a major concern over most of eastern Kansas, plus large portions of Oklahoma, Missouri, and Iowa. Although the heaviest rains are now over, river levels are still expected to rise in many regions through Thursday.

Global tropical cyclone record set
Today marks the 31st straight day without a tropical cyclone anywhere in the world, breaking the record for the longest such streak on record. Margie Kieper's View From the Surface blog has more details on this unusual event.

I'll have an update on Wednesday morning.
Jeff Masters

Updated: 10:08 PM GMT on May 08, 2007

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Greensburg tornado an EF-5; coastal storm will bring 3-5' storm surge to Carolinas

By: JeffMasters, 2:42 PM GMT on May 07, 2007

The huge, 1.4 mile-wide tornado that devastated Greensburg, KS on Friday night, May 4, was an EF-5 tornado on the Enhanced Fujita Scale. A preliminary damage survey by the National Weather Service found that the storm likely had 205 mph winds, putting it just above the 200 mph wind threshold for an EF5 rating. This is the first tornado ever rated as an EF5 using the new scale, adopted in February of 2007, and the first tornado to receive a "5" rating since the May 3, 1999 Moore-Bridge Creek tornado that devastated the southern suburbs of Oklahoma City. Had the Greensburg tornado hit downtown Chicago, the death toll could have easily been in the thousands, as I discussed last month in my blog, "Big Wind in the Windy City".

The severe storm action finally quieted down yesterday in Kansas and the Plains; only 11 reports of tornadoes were received, compared to 93 on Saturday and 33 on Friday. The severe weather action should stay at a slow simmer through Wednesday over the Plains; the Storm Prediction Center (SPC) has portions of the region under its "Slight Risk" area for severe weather through Wednesday. Flooding is a major concern now; most of eastern Kansas, plus large portions of Oklahoma, Texas, Missouri, Iowa, Nebraska, and South Dakota are under flood warnings. More heavy thunderstorm rains during the week are expected to add to the problem.

We've saved some extraordinary 1 Mb animations of the radar reflectivity and Doppler velocities of the tornado. I asked wunderground meteorologist and tornado expert Rob Carver to comment on what's going on in the animations, and here was his analysis:

This was likely an example of cyclic mesocyclogenesis. In a nutshell, the rear-flank downdraft surges out, wraps around and occludes the mesocyclone (Meso A for short). Meso A then veers to the left and dies, this is why tornado family members curve to the left as they dissipate. While Meso A is dying, a new meso spins up and becomes the dominant meso. Now, while I've seen plenty of simulated cyclic cases where the hook retreats when Meso A occludes, I don't think I've seen anything as dramatic.


Wunderblogger Mike Theiss was out chasing the weekend storms; be sure to tune into his blog over the next few days to read his chase accounts.


Figure 1. Visible satellite image of the May 7, 2007 coastal storm.

Coastal Carolina storm
A powerful non-tropical low pressure system formed off the coast of North Carolina last night, and is bringing tropical storm-force winds as high as 55 mph to the waters offshore the Carolina coast, according to the latest QuikSCAT satellite wind estimates. The North Carolina Diamond Shoals buoy had 17 foot seas and sustained winds of 43 mph at 9am EDT this morning, and buoy 41001 about 175 miles east of Cape Hatteras recorded sustained winds of 62 mph gusting to 80 mph at 1am this morning. Seas were 41 feet at this buoy this morning! The strong winds will bring 10-20 foot seas and significant beach erosion to the shores of North Carolina, South Carolina, and northeast Florida through Wednesday. A 3-5 foot storm surge is expected along portions of the North Carolina coast through Tuesday morning. The latest set of computer model runs have the storm drifting slowly southwest, and bring it ashore between the South Carolina and northern Florida coast on Wednesday. The storm will start to develop thunderstorm activity and a warm core, but will probably not have time to become fully subtropical and become Subtropical Storm Andrea. However, the storm is only expected to weaken slowly, and will have an impact similar to a tropical storm in regards to offshore winds and coastal flooding today and Tuesday. If the storm does indeed make landfall on Wednesday as expected, it will most likely be of tropical depression strength, with top sustained winds around 30-35 mph. Heavy rains of 1-3 inches can be expected to the north of where the center makes landfall, but rains will not be as significant as what a tropical storm would bring.

I'll have an update on this storm Tuesday morning.
Jeff Masters

Tornado

Updated: 10:08 PM GMT on October 24, 2011

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Another wild night in Tornado Alley

By: JeffMasters, 11:40 AM GMT on May 06, 2007

The sirens sounded two more times in tornado-ravaged Greensburg, Kansas last night, as two more twisters tore through the county. However, both tornadoes missed populated areas, as did most of the approximately 75 tornadoes that touched down yesterday. The action should quiet down considerably today; the Storm Prediction Center (SPC) has placed most of Kansas and Nebraska under its "Slight Risk" area for severe weather. Sweetwater, Oklahoma received significant damage from a tornado last night, and we've saved 300 Kb animations of the radar reflectivity and Doppler velocities of the tornado.

It will take a long time for Greensburg to recover from Friday's tornado. To get an idea of the scale of devastation, see the aerial photos posted by the Wichita Eagle. Damage surveys are not yet complete on the tornado, but photos I've seen of the destruction show damage consistent with EF4 winds(168-199 mph). It is possible the storm was an EF5 (winds more than 200 mph). The nine deaths from the tornado bring the U.S. tornado death toll to 68 so far this year, two more than the toll for all of last year.

We've saved some extraordinary 1 Mb animations of the radar reflectivity and Doppler velocities of the tornado. I asked wunderground meteorologist and tornado expert Rob Carver to comment on what's going on in the animations, and here was his analysis:

This was likely an example of cyclic mesocyclogenesis. In a nutshell, the rear-flank downdraft surges out, wraps around and occludes the mesocyclone (Meso A for short). Meso A then veers to the left and dies, this is why tornado family members curve to the left as they dissipate. While Meso A is dying, a new meso spins up and becomes the dominant meso. Now, while I've seen plenty of simulated cyclic cases where the hook retreats when Meso A occludes, I don't think I've seen anything as dramatic.



Figure 1. Radar image of the storm that spawned the Greensburg, KS tornado of May 4, 2007, showing the clearly defined hook echo associated with the twister.

Coastal Carolina storm
The latest (8pm EDT) computer forecast models continue to show a moderately strong coastal storm developing several hundred miles southeast of Cape Hatteras, North Carolina, on Monday. The storm will be extratropical in nature when it forms. We'll have a lot of time to watch the storm, as it is expected to meander offshore for five days and gradually weaken. Water temperatures are 22-23 C off of the coast, which may be warm enough to allow the low to acquire some subtropical characteristics and become the season's first named storm. The models are hinting that the storm could remain over water long enough for this to happen, and I put the odds of a Subtropical Storm Andrea forming late this week at about 20%.

Wunderblogger Mike Theiss was out chasing yesterday and caught some of the storms; be sure to tune into his blog over the next few days to read his chase accounts. Stormchaser Dan Robinson posted some video stills of the Greensburg tornado.

Jeff Masters

Tornado

Updated: 10:08 PM GMT on October 24, 2011

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Tornado smashes small Kansas town; major tornado outbreak today

By: JeffMasters, 6:30 PM GMT on May 05, 2007

A terrible scene--played out all too often in 2007--happened again last night in Greensburg, Kansas. The sirens sounded, warning of an advancing tornado, but the black of night hid the 3/4-mile wide monster twister approaching from the southwest. The residents of this small town of 1600 had time to find safe shelter, but the tornado was so powerful, that even sturdy buildings could not protect the residents. The tornado destroyed or heavily damaged 90% of the town, destroying the central business district, city hall, and the high school. Eight people died, plus one more person 30 miles away. Damage surveys are not yet complete on the tornado, but photos I've seen of the destruction show damage consistent with EF4 winds(168-199 mph). It is possible the storm was an EF5 (winds more than 200 mph). The ten deaths yesterday bring the U.S. tornado death toll to 69 so far this year, three more than the toll for all of last year. For those interested, I've saved a 1 Mb animation of the radar reflectivity and Doppler velocities of the tornado (thanks to Wunderblogger redefined for saving these!) The animations show some very strong rotation and odd swirling behavior that I don't recall ever seeing in a tornado radar animation before.

Wunderblogger Mike Theiss was out chasing yesterday and caught some of the storms; be sure to tune into his blog over the next few days to read his chase accounts.


Figure 1. Radar image of the strom that spawned the Greensburg, KS tornado of May 4, 2007.

Major severe weather outbreak today expected
More strong (EF2 and EF3) or violent (EF4 and EF5) tornadoes are possible again tonight, and the Storm Prediction Center (SPC) has put a large area of Kansas and Nebraska under its highest risk level, "High Risk". This is the fourth time this year that SPC has issued its "High Risk" forecast. The last time it did so, on April 24, an EF3 tornado struck the Mexico/Texas border near Eagle Pass, killing ten (the "High Risk" area defined by SPC was actually a bit north of where the tornado struck). Tornadoes have already been reported in Colorado and Nebraska today, so tune into our severe weather page and radar page to follow the outbreak.

Coastal Carolina storm
The latest (8am EDT) computer forecast models continue to show a moderately strong coastal storm developing several hundred miles southeast of Cape Hatteras, North Carolina, on Monday. The storm will be extratropical in nature when it forms. It will bring strong winds and high surf to the Carolina coast for several days early next week, as it meanders offshore. Water temperatures are 22-23 C off of the coast, which may be warm enough to allow the low to acquire some subtropical characteristics and become the season's first named storm. However, none of the models are showing this, and I put the odds of a Subtropical Storm Andrea forming next week at about 10%.

Jeff Masters

Tornado

Updated: 10:09 PM GMT on October 24, 2011

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Pick your poison

By: JeffMasters, 7:41 PM GMT on May 03, 2007

A huge, destructive hurricane takes aim at a major U.S. city. The media creates a riveting drama, followed by millions of people, who watch in awe as the massive storm smashes ashore. Grimly, wind-blown reporters and concerned news anchors document the mounting death toll and billions in damage wrought, bemoaning nature's deadliest and most destructive weather phenomena--the hurricane.

We've got it all wrong. The hurricane is not nature's deadliest and most destructive weather phenomena. Yes, hurricanes have taken a terrible toll in the U.S. over the past 20 years. They've killed an average of 150 people and caused $15 billion in damage per year--mostly thanks to Katrina. But the nation's deadliest weather events are not destructive storms that shred cities. Nature's most innocent weather--high pressure systems that bring sunny skies and light winds--are our deadliest weather events, thanks to the witch's brew of pollution we pour into our atmosphere.



Figure 1. Pick your poison--a Category 5 hurricane, or a sunny high pressure system with light winds? If you're an asthmatic, or have heart or lung disease, you'd probably be better off picking the Cat 5 hurricane. Photo of Los Angeles smog courtesy of wunderphotographer boytonbeachboy.

How high pressure systems trap pollution
High pressure systems are regions where the air gradually sinks, warming as it approaches the surface. This warming, sinking air creates a layer of air aloft (typically near 3000 feet in altitude) that is warmer than the air beneath it. This "upper air inversion" acts as a lid on the atmosphere, keeping pollutants trapped near the surface. Updrafts carrying surface air into the inversion suddenly encounter air that is warmer and less dense, so the updraft dies and the pollutants that they were trying to carry aloft settle back down towards the surface. If the high pressure region is large, an extensive area of light winds at the surface will exist, keeping the pollutants trapped under the inversion from being blown away horizontally. If the high pressure system stays in place for several days, pollutants will accumulate day by day, reaching levels harmful to human health and triggering a sharp rise in the death rate. "Particulate matter," also known as particle pollution or PM, is the pollutant that causes the largest rise in the death rate. Particulate matter pollution can occur any time of year, when winds are light and an inversion exists. In summertime, a double-whammy dose of ozone pollution can also hit, if temperatures are warm enough to drive the chemical reactions that form ozone.

How many people does pollution kill?
Why is it that air pollution episodes that kill thousands of Americans don't receive the media attention that hurricanes get? It's because it is not obvious when someone dies from air pollution, and there is very large uncertainty in the numbers. The only way to see air pollution deaths is to analyze death rate statistics for multiple years, carefully filtering out other influences such as weather extremes. Over two thousand studies have been published in the scientific literature documenting the link between air pollution and higher death and hospitalization rates. Most of these studies concern fine particulate matter (less than 2.5 microns in diameter), which can get deep into a person's lungs and be passed into the blood stream. Recent studies have also documented higher death rates from ozone pollution. For example, in a 2004 study published in the Journal of the American Medical Association, Dr. Michelle Bell, an air quality and health expert at Yale University, found that an ozone increase of 10 parts per billion increased the death rate by an average of .52% in 95 U.S. cities (containing 40% of the U.S. population) during the period 1987-2000. Bell's research implies that a change in the ozone standard from the current 80 ppb (parts per billion) to the newly proposed standard of 60 ppb could prevent nearly 8,000 premature deaths per year in those 95 cities. About half of the people who died prematurely in Bell's study were over age 75, but the death rate increased the same amount for both young and old. In some cases, the people who died were victims of strokes or heart attacks that had other contributing causes, such as high blood pressure or sedentary lifestyles. Thus, the "premature deaths" caused by air pollution are only partly attributable to breathing bad air, while drowning in a hurricane's storm surge is entirely due to the hurricane. Nevertheless, a great many children die of pollution-induced asthma attacks who would not have died otherwise, and the mortality due to air pollution in the general population is in the thousands or ten of thousands each year. Outdoor air pollution in the U.S. due to particulate pollution alone was estimated by the EPA in 1997 to cause at least 20,000 premature deaths each year. A 2005 study by EPA scientists (Particulate Matter Health Risk Assessment for Selected Urban Areas) estimated that over 4,700 premature deaths occur each year in just nine cities (Detroit, Los Angeles, Philadelphia, Pittsburgh, St. Louis, Boston, Phoenix, Seattle, and San Jose)--even if those cities all met the current federal standards for particulate matter pollution. Extrapolating these data to the entire nation puts the annual death toll in the tens of thousands--but the EPA has not calculated that total. Some studies have placed the annual pollution death toll in the U.S. at 50,000 to 100,000 (Dockery, D.W., and C.A Pope III. Acute Respiratory Effects of Particulate Air Pollution. Annual Review Public Health, 1994, vol. 15,107-32.) The death toll is much higher in other parts of the world, where air pollution standards are not as stringent (see the photos below of pollution in Cairo and Hong Hong!) Globally, about 800,000 people per year die prematurely due to outdoor air pollution, according to a 2005 study published in the Journal of Toxicology and Environmental Health. This represents about 1.2 percent of total annual global deaths.



Figure 2. Trends in fine particulate air pollution in the U.S. Since 1999, fine particles (less than 2.5 micrometers in diameter) have decreased 15%. Image credit: U.S. EPA.

Progress is being made
Significant progress has been made in recent years in cleaning the nation's air. Between 1970 and 2004, total emissions of the six major air pollutants regulated by the Environmental Protection Agency (EPA) dropped by 54 percent. This is particularly impressive when noting that the gross domestic product increased 187 percent, energy consumption increased 47 percent, and U.S. population grew by 40 percent during the same time. Fine particulate matter pollution, which causes the most deaths due to pollution, has dropped 15% since 1999 (Figure 2), although it did increase in some Eastern U.S. cities in 2006. In March 2005, the EPA instituted the Clean Air Interstate Rule (CAIR). This new rule will cost $3 billion per year to implement, but the EPA estimates annual savings of nearly $100 billion in health costs, plus the prevention of over 17,000 premature deaths, by the year 2015.

How you can avoid a premature death due to air pollution
- Pay attention to forecasts for high air pollution days to know when to take precautions
- Avoid exercising near high-traffic areas
- Avoid exercising outdoors when pollution levels are high, or substitute an activity that requires less exertion
- Eliminate indoor smoking
- Reduce the use of fireplaces and wood burning stoves

How you can help others avoid a premature death due to air pollution
- Support national, state and local efforts to clean up sources of pollution. When one hears talk about the high cost of cutting fossil fuels use to reduce global warming, keep in mind that any lessening of fossil fuel use will also reduce air pollution and all of its costs.
- Conserve electricity and set your air conditioner at a higher temperature.
- Choose a cleaner commute--share a ride to work or use public transportation. Combine errands and reduce trips.
- Bicycle or walk to errands when possible.
- Refuel cars and trucks after dusk.
- Limit engine idling.
- Get regular engine tune ups and car maintenance checks (especially for the spark plugs).
- Avoid spilling gas and don't "top off" the tank. Replace gas tank cap tightly.
- Properly dispose of household paints, solvents and pesticides. Store these materials in airtight containers.
- Paint with a brush, not a sprayer.
- Buy low VOC paints for indoor and outdoor painting jobs.
- Reduce or eliminate fireplace and wood stove use.
- Avoid using gas-powered lawn and garden equipment.
- Avoid burning leaves, trash and other materials.
- Use household, workshop, and garden chemicals in ways that keep evaporation to a minimum, or try to delay using them when poor air quality is forecast.
- Replace your car's air filter and oil regularly

For more information
The U.S. Environmental Protection Agency (EPA) has designated this week as Air Pollution Awareness Week. Check out their Air Pollution Awareness Week web site to learn more.

My next blog will be Monday.
Jeff Masters

Air and Water Pollution

Updated: 9:24 PM GMT on July 13, 2011

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Ozone pollution improving in the U.S.

By: JeffMasters, 7:03 PM GMT on May 01, 2007

Air pollution season is here, and the good news is that ozone pollution in 2006 was considerably better than in previous years. Along with pollution due to small particles (particulate matter), ground-level ozone is the most serious pollutant in the U.S. Ozone levels in 2006 showed improvement in 23 out of 35 of the major cities in the U.S. (Figure 1) compared to 2005, and was at or below the 10-year average in all but five cities. Atlanta, Georgia, showed the greatest jump in the number of unhealthy days, from 17 in 2005 to 30 days in 2006; however, this number was still below the 10-year average. Many western cities reached levels at or above the 10-year average, including San Diego, Sacramento, Denver, and Las Vegas. This was in part due to much above average summertime temperatures in the western U.S. (Figure 2). Los Angeles had the worst ozone pollution in the U.S., with 46 unhealthy days. Los Angeles also was the most polluted city overall in 2006, according to the American Lung Association. However, Los Angeles' bad ozone days declined by 16% in 2006 compared to 2005.


Figure 1. The number of days in May through September of 2005 and 2006 in which ground-level ozone reached Unhealthy for Sensitive Groups--an Air Quality Index (AQI) above 100. Corresponding 10-year averages are also shown. Image credit: EPA.

Ozone pollution has improved
Is the improvement seen in ozone levels in 2006 merely due to a lack of meteorological conditions that favor air pollution? To check, I've plotted the difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005 (Figure 2). The chemical reactions that form ozone are most efficient at high temperatures, so if the summer of 2006 was cooler than usual, we'd expect a drop in ozone levels. However, the summer of 2006 was the second warmest in U.S. history--but ozone levels still dropped. All of the cities where ozone increased significantly in 2006 over 2005 levels were areas where temperatures were above average. Los Angeles had summer temperatures more than 1 degree C above normal, yet still recorded a drop in ozone, suggesting that strategies to control ozone pollution there are paying dividends. In fact, new rules to limit nitrogen oxide emissions from power plants have been enacted nation-wide in the past few years, and the ozone pollution statistics from 2006 are evidence that these emissions rules are working. Ozone pollution since 1980 has dropped 21% (Figure 3), despite the fact that the average summer temperatures have generally been increasing.


Figure 2. The difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005. Temperatures were above the 10-year average across most of the country, except for New Mexico, and portions of the Ohio Valley surrounding Kentucky. Image credit: NCAR/NCEP.


Figure 3. Trends in ozone air pollution in the U.S. (white line) and uncertainty (blue areas, marking the standard deviation). The federal standard of 0.08 ppm is indicated by the dashed line. Since 1980, maximum ozone levels have declined 21%. Since 1990, the decline has been 9%. Note that the lowest ozone levels were recorded in 2004, which was an exceptionally cool summer across most of the U.S. Image credit: U.S. EPA.

Next blog (Thursday): Pollution costs and deaths exceed the impact of a new Hurricane Katrina hitting the U.S. each year.

Jeff Masters

Air and Water Pollution

Updated: 9:36 PM GMT on July 13, 2011

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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