Monday, August 1, 2005

Not So Doggy Day

After finishing July with 13 90-degree days (season total so far: 20), temperatures at mid afternoon were mainly in the upper 80s in the Washington metro area with sunny skies and light and variable winds. Even Leesburg was in line with other locations at 88. Humidities were marginally comfortable with readings from the mid 60s to a bit over 70. The only showers on radar within a couple of hundred miles were tiny isolated spots in the mountains of West Virginia.


Low temperatures tonight under mostly clear skies should be near 70. Tomorrow will be a little warmer and more humid, highs in the low 90s.

Tropical Topics

Here is something we haven't seen much lately from the National Hurricane Center: "There are no tropical cyclones in the Atlantic at this time." There are a couple of tropical waves each in the Caribbean and Atlantic, but none of them are showing signs of development in the near future.

Meanwhile, in the Indian Ocean region, heavy monsoon rains are continuing. The death toll is near 1000 in the Mumbai (Bombay) region, and more heavy rain is expected. The Indian Meteorological Department publishes a daily monsoon report along with rainfall data.

Hurricanes and Global Warming

Meteorology Professor Kerry Emanuel of MIT published an interesting study of hurricane intensity in the online edition of the journal Nature yesterday. The article, titled "Increasing destructiveness of tropical cyclones over the past 30 years", defines an "index of the potential destructiveness of hurricanes based on the total dissipation of power, integrated over the lifetime of the cyclone." The study finds that the index has "increased markedly since the mid-1970s." The increase results from both increased storm lifetimes and greater storm intensities. As measured by the index, the total destructiveness has roughly doubled over the 30-year period. The author concludes that "net hurricane power dissipation is highly correlated with tropical sea surface temperature." In other words, the observed increases in sea-surface temperatures appear to be related to increased total power of tropical storms.

These results are particularly significant because Prof. Emanuel, who is an expert in modeling hurricane intensity, has long been skeptical of alleged relationships between global warming and hurricanes. He is listed as the third author of a joint article titled "Hurricanes and Global Warming" which was accepted in June for publication in the Bulletin of the AMS. This article concludes that "claims of linkages between global warming and hurricanes are
misguided." Prof. Emanuel also wrote a favorable review in the May 2005 BAMS of Michael Crichton's scientifically dubious "State of Fear".

On the other hand, there are some serious caveats to the latest results. Improvements in airplane reconnaissance and satellite technology mean that recent storm data are more likely to be accurate than older data. This means that there is a relatively short time span available for comparison, even after making corrections for changes in methods of data analysis. A graph from the paper which is available online shows the wide scatter in the data points for the relationship between minimum air pressure and maximum winds. Hurricane-frequency forecaster Prof. William Gray of Colorado State University is quoted as saying, ''It's a terrible paper, one of the worst I've ever looked at." (C'mon, Dr. Gray, tell us what you really think!)

The full text of the article is only available by subscription, but it is being widely covered in the press:
Reflecting its continuing neglect of science and environmental issues, the Paper of Watergate and Don't Ever Forget It has the Associated Press article online and a 187-word blurb buried under "Ornithologists have discovered a male bird in South America that attracts mates by rubbing its wings together to generate 'songs.'" in the "Science Notebook" of the dead-tree edition.

Prof. Emanuel has published widely on the subjects of hurricanes and convection. He has a new book called Divine Wind on the history and science of hurricanes which is about to be published by Oxford University Press.

Prof. Gray is scheduled to release his updated hurricane season forecast on Friday.

Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.