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Dean now a major hurricane

UPDATE 11:45pm, Friday: The 11pm Advisory holds Dean at 145mph and 937mb central pressure.

UPDATE 9:45pm, Friday: The latest USAF Hurricane Hunter report from Hurricane Dean reports his maximum sustained windspeed at 145mph and a central pressure of 937mb. This represents a 24mb drop in just under 5 hours.

UPDATE 8:35pm, Friday: The NHC has raised the windspeed on Dean to 135 mph. This makes Dean a Category FOUR Hurricane. In addition, they have dropped his central pressure to 946mb. This represents a 15mb drop in the three hours between the 5pm and 8pm advisories. Wow. This is a big drop, and some further strengthening is still forecast.

The latest advisory from the National Hurricane Center updates Hurricane Dean to Category THREE with winds of 125 mph and notes a continued pressure drop to 961 mb. Dean is maintaining a solid eye and and very healthy outflow in all quadrants. Interestingly, the visible imagery is showing a larger eye than infrared. I suspect that we may be seeing a reorganization into a structure with a larger eye. Such a reorganization could result in a drop in wind speed due to conservation of angular momentum, but allow Dean to grow in size and power... remember to keep an eye on the central pressure!

20070817.2015.goes12.x.vis1km_high.04LDEAN.110kts-961mb-148N-636W.100pc.jpg
Visible Satellite
20070817.1945.goes12.x.ir1km.04LDEAN.110kts-961mb-148N-636W.100pc.jpg
Infrared Satellite

Hurricane Dean had been stalling his intensification for almost 24 hours, hovering between 970mb and 979mb of central pressure but has now broken away from the dry air that was inhibiting his growth. While the latest advisory is holding Dean's intensity steady, we are still waiting for another hurricane hunter to arrive around 8pm EDT for an updated report.

Moving into the warmer Caribbean waters with less dry air around him have done promising things for further intensification as the models have been indicating for several days. In particular, the warmer and deep warm water in the western Caribbean should allow dean to steadily intensify

The latest model runs continue to show astounding congruity between the models, tracking Dean almost on top of each other WNW directly over Jamaica until just south of the Caymans where they begin to diverge with some models bringing Dean over the Yucatan and some bringing him in a more Wilma/Ivan track between Cuba and the Yucatan and into the central Gulf of Mexico. Our ability to predict beyond 3 days (beyond just past Jamaica) is very suspect though, as there are many variables that we just cannot control. All interests in the Gulf of Mexico from Texas to Florida should keep a close watch on Hurricane Dean.

If, as currently indicated, Dean tracks directly over Jamaica, we will have to reevaluate everything. Jamaica has quite large mountains in the center of the island and Hurricanes do very poorly when passing over high elevations. Jamaica could do quite a number on our storm and knock his strength down significantly with the right conditions. Not only will the elevation condense out a lot of water from Dean's circulation, unstable flow and wave breaking over mountains can cause a redistribution of potential vorticity, which can create several type of lateral instability in the flow.


Posted by Bryan Woods | Permalink