Chances of imminent Atlantic tropical cyclone formation increase

June 21, 2010

Since my post yesterday evening, the tropical wave in the eastern Caribbean has progressed west-northwestward.  The National Hurricane Center has increased the probability of a tropical cyclone forming in the next 48 hours from 20% to 50%.  This evening’s Tropical Weather Outlook states that the distrubance shows “signs of increased organization”  and that “upper level winds are conducive for a tropical depression to form during the next couple of days”.  A look at the Caribbean as the sun set this evening:

The presumed center of circulation (and presumption can be an overstatement of certitude when a developing system is being discussed; oftentimes scientific wild-assed guess is the better official term), is at 14.9 North 70.0 W, more or less half way between the Dominican Republic and the north coast of Venezuela.

The global models that I pointed out yesterday have not demonstrated any run-to-run consistency; that is somewhat to be expected when dealing with the tail end of their forecast periods.  At the moment, none of them are showing a strong system forming from this.  However, SHIPS intensity guidance has been consistent in showing that if there were an established circulation at the surface, it would develop into a tropical storm and subsequently a hurricane.  Also, the most recent run of the GFDL shows a storm developing and proceeding through the Yucatan straits into the Gulf of Mexico.  A very disconcerting forecast as it would put the storm in the path of the oil slick in the Gulf and to “the wrong side” of it,  such that it would push the oil towards land.   One clear argument against the scenario it presents is the sharp northwest motion it shows at the beginning of the forecast.  Take that away and it’s more likely the storm would head towards the Yucatan Peninsula and stay clear of the oil.  Between that and the fact that it’s a solitary run, it is not worth heightened concern, yet.

Moving away from the models and towards overall statistical/climatological guidance, the Tropical Cyclone Formation Probability Product wasn’t exactly screaming development though it was indicating the possibility as well as most of its future path as being an area of interest.

It’s been interesting to see both in this instance and last week, how far in front of this product the NHC got regarding the probability of development.  Some of that may be due how climatologically driven the product is combined with how improbable development in the Caribbean/tropical Atlantic is this early in the season.    The climatological argument is against development, but as was often the case in 2005, we may see a storm that defies climatology.

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