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Posted at 02:15 PM ET, 10/25/2010

Richard's troublesome tropical journey

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After battering Belize with heavy rains and strong winds (measured to around 60 mph), Richard - now a tropical depression - is winding down, with little deep convection remaining. Although Richard's remnants may re-emerge in the Gulf of Mexico after crossing the Yucatan Peninsula, strong upper level winds are likely to impede any redevelopment.

Richard's life as a tropical cyclone has been a difficult one. After an extremely slow intensification process, it finally reached hurricane strength Sunday morning (see this cool radar loop of Richard making landfall). Fueled by 85-degree ocean water, amidst weakening vertical wind shear (changing of the wind with height) and a progressively humidifying environment, Richard's maximum sustained winds peaked at 90 mph just prior to its landfall roughly 20 miles south of Belize City late Sunday.

Since its inception late on the October 20, Richard battled a very dry and windy environment. Data from aircraft observing the storm late last week revealed exceedingly low dew points -more typical of fall-like conditions in the Northeast- throughout thick layers of the atmosphere working their way toward the core of the circulation. Only in the final few hours before landfall was it able to conquer these formidable obstacles, enough so to attain hurricane status.

Yet formidable is not a strong enough adjective to describe the conditions Richard had to overcome.

Dry and windy environments can be lethal barriers to a tropical cyclone's maturation. Once dry air gets inside a storm, as it apparently did to some degree with Richard for much of its lifetime, large-scale downdrafts begin to develop in the same region that requires upward motion and nearly saturated conditions to survive. These relatively cool sinking motions, similar to the gust fronts we observe with the passage of thunderstorms in our area, act to reverse the counter-clockwise hurricane swirl as they spread outward upon nearing the surface.

Even in the absence of the destructive forces of wind shear, which can dismantle and tear apart the plume of heat in the core that powers the circulation, dry air intrusions can assassinate a hurricane.

Tropical cyclones, and in particular hurricanes, are markedly unlike the thunderstorm complexes we experience in the mid-latitudes. Their existence largely requires weak wind patterns (instead of highly sheared flows), humid conditions, and little if any of the kind of "instability" (cool temperatures aloft) that our neighborhood storms thrive on.

By  |  02:15 PM ET, 10/25/2010

Categories:  Tropical Weather

 
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