Wednesday, October 5, 2011

Tropical/Subtropical Development Possible This Weekend

For the third straight day, several of our reliable computer models are indicating the potential for tropical or subtropical storm development over the weekend into early next week. The area to watch is along an old front extending from the Yucatan Peninsula across Cuba and into the Bahamas.

The models differ on the exact location of development, but there's a growing consensus that something will begin to form by this weekend. The European model shows a broad low pressure center developing near western Cuba this weekend and then moving north or north-northwest toward the Florida panhandle. The map below shows the European model's forecast location of the low for 7 a.m. on Monday.

The GFS model (what some are now calling the "American" model) shows the low developing over the northern Bahamas this weekend and then moving northwest over the Florida peninsula into the southeastern states early next week. The map below shows the GFS model's forecast location of the low for 7 a.m. on Monday.

So, the bottom line for us is that while there's a growing consensus that we'll see either a tropical or subtropical system develop this weekend or early next week, nothing indicates at this point it will be a threat to Louisiana. Additionally, it appears as though this system could be somewhat lopsided, with most of the bad weather confined to its eastern side, further reducing the threat locally.

While this system doesn't appear to be much of a threat to us, it serves as reminder that we are still in Hurricane Season and should remain vigilant for the next few weeks. October impacts aren't terribly common, but the map below from NOAA's Coastal Services Center shows that 22 tropical storms or hurricanes have passed within 50 miles of Louisiana's coastline since 1842. That equates to 1 impact about every 7 or 8 years.

Our last October impact was Tropical Storm Matthew which made landfall near Cocodrie as a minimal tropical storm on October 10, 2004. Notable October 'hits' along the Louisiana coastline include Lili (2002), Juan (1985), and Hilda (1964).

Wondering what the difference is between a tropical storm and a subtropical storm? There are many, but most importantly, subtropical systems tend to have a broader wind field, with the strongest winds well-removed from the center of circulation. Tropical systems have their strongest winds right around the center and in general tend to be more symmetric than subtropical systems.