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 , 2:11 PM GMT on September 07, 2006
Florence continues to struggle with 10-15 knots of wind shear today, and doesn't appear any stronger than yesterday. QuikSCAT satellite data from this morning at 5:26am showed only a few patches of 50 mph winds. Compounding Florence's troubles has been the presence of some dry air at mid levels, which Dr. Jason Dunion of NOAA's Hurricane Research Division pointed out in a blog yesterday.
The big questions with Florence are, will she intensify, and how close will she pass to Bermuda? Well, the intensity forecast remains the same, with the upper level low to the west forecast to move off and allow a lower shear environment for Florence to intensify in. The GFDL model intensifies Florence to a strong Category 2 hurricane at her closest approach to Bermuda on Monday. However, Florence has thus far resisted intensification, so a more conservative intensity forecast may be in order.
Figure 1. QuikSCAT satellite winds estimates for Thursday morning, September 8, 2006. Image credit: NOAA/NESDIS.
All the computer models are unanimous in bringing Florence close to Bermuda, then out to sea, missing both the U.S. and Canada (although a sideswipe of Newfoundland is possible). It would be a major surprise if Florence hit the U.S. We can, however, expect plenty of heavy surf and minor beach erosion along the East Coast next week if Florence does intensify into a Category 2 hurricane. Bermuda is a small target in a big ocean, and I expect that island will escape a direct hit from Florence. Florence is a very large storm, though, and tropical storm force winds will probably affect the island Sunday through Tuesday. The Hurricane Hunters are scheduled to make their first flight into Florence Friday afternoon.
Florence strangles her little brother
Tropical disturbance 91L, about 800 miles east-southeast of Florence, is no longer a threat to develop. The disturbance's close proximity to its big sister has proved too much for the disturbance, which now has very little spin and just a few thunderstorms. There is a small chance 91L could separate from Florence on Sunday and make a comeback, just northeast of the northernmost Lesser Antilles Islands.
A stalled cold front off the Carolina coast spawned a low-pressure area yesterday that moved quickly northeast and is now northeast of Cape Hatteras, North Carolina. This low is under 30 knots of wind shear and is transitioning into an extratropical storm, and is not a threat to become a tropical storm. This morning's 7:07am EDT QuikSCAT pass (Figure 1) does show one orange 30 knot (34 mph) wind barb, so this low is of tropical depression strength. Another area of low pressure off the South Carolina coast this morning is poised to repeat what yesterday's system did. This area of disturbed weather had winds up to 40-50 mph in some heavy squalls in the QuikSCAT satellite pass at 7:13am EDT today. The system does have some potential to develop into a tropical depression today as it scoots northeast just offshore the North Carolina coast. However, it will probably not have enough time to develop, and will become extratropical by Friday afternoon over the waters to the northeast of Cape Hatteras.
Huge extratropical storm hits Brazil
Perhaps the most damaging storm in the world this September was not Ernesto in the Atlantic, John in Baja, nor Ioke on Wake Island. Brazil had an usually intense wintertime extratropical cyclone bring wind gusts to hurricane force along the coast of Brazil's southernmost state, Rio Grande do Sul, on September 2. Winds of 101 km/h in that state's capital city of Porto Alegre tore roofs of of houses, downed trees and powerlines, and caused power outages to half a million people. Luiz Fernando Nachtigall, Chief Meteorologist for MetSul Meteorologia Weather Center, sent me a link to some damage photos from the event. After the wind event, the storm brought the most widespread snow event in Southern Brazil since 1994. It snowed in 62 cities.
Figure 1. Visible satellite image of the September 2, 2006 extratropical cyclone that affected Brazil. The storm had a minimum pressure of 980 mb, similar to what one finds in a Category 1 hurricane! Extratropical cyclones that move over warm ocean currents can start to exhibit characteristics of hurricanes, as I described in my February blog, Flying into a record Nor'easter. Extratropical storms of this intensity happen fairly regularly off the Northeast U.S. coast, but are extremely rare along the Brazilian coast. Image credit: MetSul Meteorologia Weather Center.
I'll have an update this afternoon or Friday morning.
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