A large low pressure system off the Florida Gulf Coast, Invest 95L, is bringing heavy rains to Southwest Florida. Rainfall amounts in excess of 3 inches have been common across South Florida since Saturday; Miami has picked up 3.80″ as of 9 am EDT this morning, and Key West Naval Air Facilityhas recorded 14.41″. Key West has experienced other rain events with far more precipitation; their all-time 24-hour rainfall is 23.28″, set on November 11, 1980. Interestingly, this is more rain than fell in the entire year of 1974, when Key West received only 19.99″.Rains of 5 – 10 inches have fallen over much of the Florida Keys and Central Cuba since Sunday, according to radar rainfall estimates from the Key West Radar. Long-range radar out of Key West shows that the rain has now pushed north of the Keys, and the region between Naples and Fort Myers is getting the heaviest rains. Satellite loops show that 95L has a respectable amount of heavy thunderstorm activity, but the system is disorganized and has been stretched by wind shear. With wind shear now a high 20 – 30 knots over 95L, development is unlikely, and NHC has dropped their odds of it developing into a tropical depression to 10%. 95L will bring heavy rains of 2 – 3 inches to Southwest Florida today, and NOAA’s Storm Prediction Center has placed much of Florida in their “slight risk” area for severe weather, including the possibility of isolated tornadoes.

Figure 1. True-color MODIS image of an interesting 50 km-wide vortex near the north coast of Mexico’s Yucatan Peninsula that became the center of 95L late yesterday afternoon. Image taken at 1:45 pm EDT October 17, 2011. Image credit: NASA.

Heavy rains kill 84 in Central America
A week of torrential rains across Central America have triggered extreme floods and landslides that have killed 84 people, with 9 missing, according to media reports. El Salvador and Guatemala have seen the worst flooding, with 32 and 31 people killed, respectively. Another 13 have died in Honduras, and 8 in Nicaragua. The rains were due to a large area of low pressure that was moistened by the landfall of Tropical Depression 12-E near the Mexico/Guatemala border last week. Since the beginning of October, the region near the coast on the Guatemala/El Salvador border has received over 800 mm (31.50″) of rain, according to Norman Avila of climaya.com, a Guatemalan weather web site.

Figure 2. Visible satellite animation of the Texas South Plains dust storm of October 17, 2011. Image credit: NWS Lubbock.

Massive dust storm sweeps through the Texas Panhandle
It was a very bad afternoon rush hour yesterday in the Texas Panhandle. A powerful cold front pushed through the state during the afternoon, and damaging north winds behind the front whipped up a dangerous dust storm that cut visibility to near-zero during the afternoon rush hour. Lubbock recorded sustained winds of 48 mph, gusting to 63 mph, with a visibility of 0.2 miles in heavy dust at 5:36 pm CDT. The dust storm was reminiscent of the great dust storms of the 1930s dust bowl era, and was due to the ongoing exceptional drought. Unfortunately, the front brought no rain to the area, and Lubbock has received just 3.16″ of rain so far in 2011–more than 13.50″ below average. In his Climate Abyss blog, Texas’s state climatologist, John Nielsen-Gammon, gives a 25% that the current drought will last five more years. He has an interesting post on how global warming may have affected the drought. He concludes:

Precipitation: The balance of evidence does not support the assertion that the rainfall deficit since October 2010 was made larger or more likely by global warming.

Temperature: Compared to long-term averages of summer temperature, the rainfall deficit accounted for about 4°F of excess heat and global warming accounted for about 1°F of excess heat. Warmer temperatures lead to greater water demand, faster evaporation, and greater drying-out of potential fuels for fire. Thus, the impacts of the drought were enhanced by global warming, much of which has been caused by man.

Jeff Masters