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Models coming to an agreement on Ernesto

Before I talk about tonight's weather developments, we at The StormTrack would like to pass along our sincere appreciation to Max Mayfield at the National Hurricane Center. The last couple of years have worn down Max and today he announced that he will be retiring after this hurricane season. We would all like to thank him for his decades of dedicated service and again thank him for saving countless lives with his comforting, timely, and accurate forecasts. Thank you Max!

With the latest advisory, NHC has increased Ernesto's wind speed slightly to 45 mph with a central pressure of 1003 mb. However, Ernesto remains a weak tropical storm, a status that is likely to soon change. The official forecast calls for Ernesto to enter the Gulf of Mexico as a hurricane early next week. Tropical storm watches and warnings are now active for Jamaica and parts of Hispanola. Given a recent strengthening trend, a hurricane hunter will investigate the storm tonight. I personally believe that Ernesto may be stronger than NHC is giving it credit for.

Ernesto's minimal strength is due to moderate wind shear displacing the convection from the center of circulation. This wind shear should be lessening tomorrow and allow for strengthening to begin at that time. While the current convective pattern is hardly impressive, tomorrow could hold a different story. As I will explain later, the Western Caribbean holds much deeper warm water that can allow for rapid intensification.

The models are in an even more clear consensus agreeing on a track over the western tip of Cuba. By early next week, Ernesto could be roaming the Gulf of Mexico as a hurricane. The GFDL model is no longer an outlier and has joined the main back. Of the models forecasting a strike on the Yucatan, 3 of them are variations on the Beta-drift and Advection Model, which is not true forecast model. Instead, it just predicts what would happen if the storm were simply blown along. The AEMN is also in that area, but it represents the average of an ensemble of the Aviation model. However, three of those ensemble members also lie directly in the main pack to the north. It seems clear now that the models are in a complete consensus. Something similar to Hurricane Dennis is a definitely possibility. However, New Orleans is also in the middle of the target area.

Most of my trusted models are also calling for Ernesto to strengthen into a hurricane. The GFDL and DSHP models are the ones I would trust the most in this case, and they both quickly bring Ernesto to hurricane strength. The LGEM even forecasts Ernesto to become a major hurricane in 4 days.

The ocean is ripe for Ernesto when he reaches the western Caribbean and Gulf of Mexico. Let's take these one at a time though. Below is a map of Tropical Cyclone Heat Potential (TCHP) in the Caribbean. TCHP is basically the amount of energy in the water that is available to a tropical system. Technically it is the thermal energy above 26 degrees C in the surface layer, but for our purposes just consider it the amount of fuel available to support a hurricane.

Taking a quick look at sea surface temperatures (SSTs) in the Gulf of Mexico does not provide much insight. During the summer the Gulf becomes covered in a thin film of very warm water which hides the true nature of the water underneath. Right now you can see that very warm water across the entire Gulf of Mexico.

Knowing that warm water expands provides a powerful tool in examining the surface of the ocean. By using radar altimeters aboard satellites, we can actually see an expansion of the ocean and higher sea levels where there are deep layers of warm water. One such deep layer is positioned just south of Louisiana at this time. Oceanographers call these features "warm core rings" and they are nothing more than warm parcels of water that break off of the Loop Current near the Florida Keys and drift northward towards Louisiana and eventually westward towards Texas. This particular warm core ring is extremely strong and would provide and incredible amount of energy to any hurricane that would pass over it. Warm core rings weaker than this one were responsible of the very rapid strengthening observed in hurricanes Opal, Katrina, and Rita among others. If Ernesto were to drift over this warm tongue of water with favorable atmospheric conditions, as are currently being forecast at that time, Ernesto could undergo a very rapid strengthening. It is worth noting that a similar feature is noticeable to the south of Cuba in the previous map.

P.S. Some of you may notice some inconsistencies on the page this weekend. We are working to roll out a new format that has been in the works for a while now. Some features such as the taglines may not be on the new format right away, but rest assured they will be brought back online. Additionally, the roll out may be staggered as we institute the changes throughout the various sections of the site. Keep an eye out over the next week because changes are coming!


Posted by Bryan Woods | Permalink