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Posted at 02:00 PM ET, 10/06/2011

Potential Florida subtropical system could be East Coast rainmaker next week

System could break D.C.’s dry streak

Several weather models are predicting the development of a low pressure system near Florida and the Southeast U.S. late in the weekend or early next week. It could become a sub-tropical storm, essentially a hybrid between a mid-latitude storm and a tropical system, and then move up the eastern seaboard next week. Sub-tropical storms do get names, and if this one materializes, it would be Rina.


Model simulation showing possible development of low pressure over Florida in 4-5 days. (NOAA)
Although this low pressure system does not yet exist in real time observations, it is forecast to form as a result of the interaction between an upper-level low (outlined by the orange line to the right) and a small low-level disturbance along a stalled front in the region. More akin to a rain storm or a nor’easter, a development like this will not likely possess, or acquire, truly tropical characteristics.

The upper low will impart windy (highly sheared) conditions aloft, while the flow of dry low-level air from the northeast (depicted in black) will impede the organization of the type of thunderstorm complexes required for tropical system formation.


4-8” of rain is predicted over the East Coast of Florida between now and early next week (NOAA’s Hydrometeorological Prediction Center)
Even before this system potentially forms, rainy, windy, and wavy conditions are likely over the Florida peninsula this weekend from the combination of the stalled front and strong, moist flow from the northeast. The National Weather Service Office in Miami Florida is predicting impressive rain amounts:

IT LOOKS LIKE RAINFALL TOTALS FROM THIS EVENT WILL RANGE FROM 2 TO 4 INCHES WITH LOCALLY HIGHER AMOUNTS OF 4 TO 6 INCHES OVER SOUTH FLORIDA WHICH COULD LEAD TO SOME LOW LYING AND STREET FLOODING

In addition, the NWS is highlighting a high rip current risk and the possibility of beach erosion due to seas exceeding 7 feet.

The subtropical low may form in the Sunday into Monday timeframe and then lift north Tuesday. NOAA’s Hydrometeorological Prediction Center is advertising a “rainy/windy period for Florida and much fo the Eastern Seaboard” Monday through Thursday. But it cautions:

THERE REMAINS A GOOD DEAL OF UNCERTAINTY PINNING DOWN THE LOCATION OF THE EXPECTED SURFACE LOW.

What this means is that it’s difficult to say exactly where the heaviest rain will fall, and there are also questions about the timing of the rain in different locations. And there’s even the possibility this low pressure center never really gets organized, resulting in little if any rain up the coast.


GFS simulation showing some moderate to heavy rain having accumulated over north central Virginia Tuesday night ( StormVistaWxModels.com )
The latest GFS model produces a rain shield that moves into northern and central Virginia Tuesday night and into Wednesday. Last night’s European model was a little slower in carrying the moisture north, not reaching Virginia and Maryland until Wednesday into Thursday.

Based on the projected intensity of the low shown in forecast simulations, while winds may be a bit gusty, damaging winds are very unlikely.

As next week draws closer, we’ll provide additional details about the development of this system, and the timing/coverage/amount of any rain that might come north.

In the meantime, everyone north of Florida should enjoy the sunshine!

By and  |  02:00 PM ET, 10/06/2011

Categories:  U.S. Weather, Tropical Weather, Latest

 
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