Thursday, September 05, 2013

Gabrielle Forms In Caribbean, Not Threat To Mainland US

Tropical Storm Gabrielle developed from the complex of thunderstorms that existed across the Leeward and Windward Islands for the past couple of days. Gabrielle's center coalesced around one part of a large, disorganized batch of thunderstorms and was able to develop a low level center of circulation.  Gabrielle has since strengthened to tropical storm strength, moving slowly northwest towards Puerto Rico as of this morning.

The storm is still disorganized as far as a surface low is concerned -- the mid level center on radar looks pretty solid to identify based on early morning radar to the southeast of Puerto Rico. As Gabrielle lifts northwest, I would expect some struggles over the next couple of days with organization thanks to the proximity with the hilly terrain of Puerto Rico and eventually Hispaniola.  Additionally, stronger wind shear is projected to develop once Gabrielle gets north of Puerto Rico...wind shear being another enemy of tropical storms in terms of getting them to strengthen.  The Euro is one model that suggests Gabrielle's future is bleak thanks to that wind shear, likely to weaken if not dissipate altogether.

In the interim, heavy rains will fall over Puerto Rico and the Dominican Republic today, with the prospect of ten inches of rain falling in some of mountainous areas. Wind is likely not a factor with this storm system given its relatively disorganized state at this point.

The good news is that the vast, vast majority of tropical cyclone and traditional modeling suggests Gabrielle, should it survive any projected wind shear development, will track to the east of the US mainland. Bermuda may need to keep an eye out for this system -- or at least a rainy remnant of it -- this weekend; however, modeling suggests the US should avoid this storm system thanks to the cool front that's pushing off the coast today to provide a roadblock for this storm system.

For those keeping score, this is the season's seventh storm. Last season's seventh storm organized on August 15th. And, yes, as of now we're still hurricaneless, which only three other years since the satellite era (1960ish) can out-do.