Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 11:19 PM GMT on June 06, 2013
Tropical Storm Andrea made landfall near 5:40 pm EDT in the Big Bend region of Florida as a tropical storm with 65 mph winds. Andrea had a busy day Thursday in Florida, dumping heavy rains, spawning ten tornadoes, and bringing a storm surge of up to 4.5' to the coast. While the Hurricane Hunters did measure sustained winds of 65 mph over the ocean shortly before landfall, very few land stations recorded sustained winds in excess of tropical storm force, 39 mph. Here are some of the higher winds measured at coastal stations:
A personal weather station at Bald Point State Park near Apalachicola had sustained winds of 46 mph at 10 am EDT.
Cedar Key had sustained winds of 40 mph, gusting to 50 mph, at 3:43 pm EDT.
Punta Gorda had sustained winds of 37, gusting to 58, at 1:04 pm EDT.
St. Petersburg topped out at 34 mph, gusting to 48 mph, at 10:23 am EDT.
Two sets of tornadic rain bands moved through West Florida on Thursday, one between 2 am and 5 am, and the other between 10 am and 3 pm, spawning a total of five suspected tornadoes. The first band produced two EF-0 tornadoes: one with 75 mph winds that hit Myakka City, damaging 3 homes and 10 other buildings, and one with 80 mph winds that cut throughout the heart of Sun City, causing minor damage. NWS damage surveys will be occurring Friday in Fort Myers, Venice, Clearwater, and Gulfport to check out the damage swaths of the other three suspected tornadoes.
The Florida East Coast was hit by five suspected tornadoes. Only one caused an injury, a tornado that hit The Acreage in Palm Beach County at 6:45 am EDT. Two other tornadoes were reported in Broward and Palm Beach Counties, and two more were reported in coastal areas near the Georgia border.
Here are the highest storm surge values as of 7:00 pm EDT:
3.2' at Tampa (at McKay Bay Entrance)
2.5' at Clearwater Beach (near St. Petersburg)
4.5' at Cedar Key
Figure 1. MODIS satellite image of Tropical Storm Andrea at 1pm EDT Thursday, June 6, 2013. At the time, Andrea had top winds of 60 mph and was 5.7 hours away from landfall in Florida's Big Bend. Image credit: NASA.
Video 1. NASA animation of Andrea satellite images. More cool NASA images of Andrea are here.
The Atlantic hurricane season is getting longer
Andrea's formation in June continues a pattern of an unusually large number of early-season Atlantic named storms we've seen in recent years. Climatologically, June is the second quietest month of the Atlantic hurricane season, behind November. During the period 1870 - 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been fifteen June named storms (if we include 2013's Tropical Storm Andrea.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 - 1994, compared to 6 in the 19-year period 1995 - 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966. However, even during the satellite era, we have seen an increase in both early season (May - June) and late season (November - December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, "Is the North Atlantic hurricane season getting longer?" He concluded that there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high." He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 to 10 days per decade (see my blog post on the paper.)
Figure 2. MODIS satellite image of 92L taken on June 6, 2013. Image credit: NASA.
Invest 92L in the Central Atlantic headed towards the Lesser Antilles
Satellite images show that a large and unusually well-organized tropical wave for so early in the season has developed in the Central Atlantic, midway between Africa and the Lesser Antilles Islands. The wave has a modest degree of spin and heavy thunderstorms. NHC designated this system 92L Thursday afternoon. High wind shear of 20 - 25 knots is ripping up the thunderstorms in 92L as they form, though, and wind shear is predicted to increase to 30 - 40 knots Thursday night through Monday, making development unlikely. The wave will likely bring heavy rain showers and gusty winds to the northern Lesser Antilles Islands beginning on Sunday night.
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