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The "Art" of Weather
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Art Horn, Meteorologist
  
 


 
 


 
 

No Hurricane Damage Yet, But Trouble Could Be Brewing
Published by Pajamas Media 9/25/10
By Meteorologist Art Horn

As predicted the Atlantic hurricane season of 2010 has been stormy. To date there has already been 6 hurricanes, 4 of these, Danielle, Earl, Igor and Julia reached massive category 4 status for a time with top sustained winds between 135 and 150 miles per hour. Fortunately these powerhouse hurricanes have not impacted the mainland United States in any major way. This may all be about to change. Conditions are brewing in the Caribbean Sea that may signal the approach of a hurricane somewhere in the southeastern United States sometime around the end of this month. Tropical Storm Matthew is moving into Central America tonight. This storm will likely weaken over Central America this weekend and die.

The volatile mix of atmospheric and oceanic ingredients that existed at the beginning of the hurricane season continue to brew at the current time. A full blown La Nina has blossomed in the Pacific Ocean. La Nina’s cooler waters have muffled the strong high altitude winds over the Atlantic that made last season so quiet when there were only three hurricanes. The Atlantic Ocean continues to be warmer than usual creating more fuel for hurricanes. A steady train of tropical weather disturbances continue to migrate off the coast of Africa and plow to the west. As they steadily traverse the Atlantic they feed on the warm, humid air over the bathtub like temperatures of the tropical Atlantic Ocean and grow stronger.

Hurricanes may have awesome power but oddly they have no control over their own destiny. A hurricane is imbedded in the ocean of air that is our atmosphere. It is this ocean of air that sweeps the hurricane along in its ever changing current that eventually determines where and when a hurricane will or will not strike. The wind currents of the atmosphere are impossible to measure perfectly even with today’s equipment. There are always going to be errors in our readings about how the ocean of air is behaving. It is the small errors in our initial measurements of the atmosphere that in part lead to large errors in forecasts many days into the future.

Computer models are used to simulate the atmospheres behavior. These mathematical weather simulators have limitations. Although ingenious, they do not incorporate all of the subtleties that make the atmosphere work. In addition the model predictions are highly dependent on how well we measure the initial state of the atmosphere. If we don’t measure all the significant atmospheric disturbances to start with, the models are immediately handicapped and will make inaccurate predictions. As a result the models sometimes predict storms that never happen. Large and dangerous hurricanes have been generated by the models as much as 10 to 15 days into the future but turn out to be “computer dreams” or nightmares depending on your point of view!

One element we look for in the models is the persistence of a prediction. If a model predicts a storm over and over again from one forecast to the next the possibility of it actually happening grows. If a hurricane is being forecast from the same model over a number of consecutive days this is significant. It indicates there must be a disturbance in the atmosphere that is repeatedly being captured by our measurement and is significant enough so that the model can predict its future evolution. This persistence of prediction is enough to indicate a degree of credibility.

Since the middle of this month I have been monitoring the computer models. These models have been forecasting the development of a hurricane somewhere in the central Caribbean Sea towards the beginning of next week. The prediction has been very persistent. The GFS (Global Forecasting system) model is run by The National Centers for Environmental Prediction four times a day. Every run of this model since the 15th of September has forecast this hurricane to develop. That is a very long and consistent period of forecasts. This fits the definition of persistence of prediction.

As stated earlier tropical storm Matthew will move into Central America Friday night. This is not the storm I am anticipating. The threat is from another tropical storm that will form in the Caribbean Sea early next week. As this new storm develops into a hurricane the problem then becomes where it will strike. Subtle changes in how well we measure the atmosphere can have dramatic effects on how the computer models resolve the future movement of a storm. With this particular prediction the model forecasts have ranged from a landfall in Texas to Louisiana to Florida. During the last few days the forecasts are focusing on Florida. If this trend continues residence of Florida should start watching the Caribbean Sea very carefully and begin to make preparations. It has been 5 years since Florida has been hit. A degree of complacency may have developed.

A large portion of this stormy hurricane season is ahead of us. The economy has been weathering its own storm for more than two years. With the economic and social damage that’s been inflicted with this great recession we can little afford to have a hurricane blow ashore and cause even more hardship.

There is another five weeks of the most active part of the hurricane season to go. Computer predictions, although speculative has been very consistent in forecasting a hurricane to threaten the southern United States sometime late next week, possibly Florida. Trouble may be just over the horizon, stay tuned.

 

 
   

Christy Sands, Webmaster