WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Hurricane Wilma: Category 1 and strengthening
Wilma became a hurricane today, tying the record of 12 hurricanes in a season set in 1969. In that year, the last two hurricanes formed after October 30, so 2005 has a decent chance of breaking that record. I expect 2005 will also break the record of 21 total storms, which it now shares with the 1933 hurricane season.
Wilma continues to intensify as a modest pace. The Hurricane Hunters at 4 pm EDT found a central pressure of 970 mb and flight level winds on the weaker (north) side of the hurricane that correspond to winds of 70 - 75 mph at the surface. Stronger winds probably exist elsewhere in the storm, but all indications are that this is a medium strength Category 1 hurricane. An eye has popped in and out of visible satellite imagery this afternoon, but is not yet evident as a warm spot on infrared satellite imagery. Spiral banding and upper-level outflow continue to improve and cover a larger area.
The upper level environment looks excellent but not perfect for intensification, with low wind shear and two good outflow channels, one on the north side, and one on the southwest side. About five knots of wind shear is degrading the outflow pattern and symmetry on the northwest side, and there is still some dry air there for Wilma to contend with. Continued intensification into a Category 3 hurricane by Wednesday looks reasonable, and I'd give it a 40% chance Wilma makes it to Category 4 status by Friday. The GFDL is calling for a 922 mb Category 4 storm by Friday, but this forecast is probably overdone, as the GFDL has been consistently too aggressive with its intensity forecasts for Wilma. By Saturday, Wilma will be far enough north that wind shear from an upper-level trough of low pressure will reduce Wilma's winds by perhaps 20 mph.
Wilma is currently traversing an area of high oceanic heat content (see Figure 1), and this heat content will not significantly fall unless Wilma passes north of the Florida Keys. I would expect an additional 10 mph reduction in Wilma's winds if she makes landfall in Florida north of the Keys, due to the lower heat content of the water. So, expect landfall as a strong Category 2 hurricane if Wilma moves through the Keys, or as a weak Category 2 hurricane further north. Remember that hurricane intensity forecasts are poor, especially 3 - 5 days out, so Wilma's intensity could easily be a full Category higher or lower than this.
Figure 1. Total heat content of the ocean is high over the northwest Caribbean and the southern Gulf of Mexico south of 25 N latitude. Images credit: NOAA/AOML.
Jamaica continues to take a pounding from Wilma, but this should end tomorrow night as Wilma pulls away. The next area of concern is northern Honduras and Nicaragua, where rains of up to 12 inches are expected. However, the portions of these countries that will receive the heaviest rains are relatively flat, so I do not expect massive loss of life from flooding in the mountains.
Next on Wilma's list will be the Cayman Islands, but flooding is generally not life-threatening in that nation. Mexico and Cuba may escape serious damage if Wilma passes through the Yucatan Channel as forecast.
Figures 1. Computer model forecasts for Wilma.
Wilma started moving WNW at 8 mph today, as all the computer models predicted she would. The models are pretty unified, bringing Wilma through the Yucatan Channel or across the western tip of Cuba, and then northeastward into the Florida Keys or the west coast of Florida by the weekend. Two models (the UKMET and GFS) predict that Wilma will pass just south of the Keys. The furthest north model is the Canadian, which picks Sarasota for its landfall. The GFDL, NOGAPS, and the official NHC forecast are in the middle, with a landfall over the Everglades of Southwest Florida. The NOAA jet is scheduled to makes its first flight tonight, and tomorrow morning we should have a better idea of which part of Florida is at most risk. Climatology favors a more southern track, and I expect that we'll see the models converge on a more southerly track through the Keys in the runs we see Wednesday morning.
Elsewhere in the tropics, there is a large area of disturbed weather midway between Africa and the Leeward Islands. Upper level winds are not favorable for development of this area, which is also too close to the Equator. I'll be back with a update in the morning.
Jeff Masters
Wilma continues to intensify as a modest pace. The Hurricane Hunters at 4 pm EDT found a central pressure of 970 mb and flight level winds on the weaker (north) side of the hurricane that correspond to winds of 70 - 75 mph at the surface. Stronger winds probably exist elsewhere in the storm, but all indications are that this is a medium strength Category 1 hurricane. An eye has popped in and out of visible satellite imagery this afternoon, but is not yet evident as a warm spot on infrared satellite imagery. Spiral banding and upper-level outflow continue to improve and cover a larger area.
The upper level environment looks excellent but not perfect for intensification, with low wind shear and two good outflow channels, one on the north side, and one on the southwest side. About five knots of wind shear is degrading the outflow pattern and symmetry on the northwest side, and there is still some dry air there for Wilma to contend with. Continued intensification into a Category 3 hurricane by Wednesday looks reasonable, and I'd give it a 40% chance Wilma makes it to Category 4 status by Friday. The GFDL is calling for a 922 mb Category 4 storm by Friday, but this forecast is probably overdone, as the GFDL has been consistently too aggressive with its intensity forecasts for Wilma. By Saturday, Wilma will be far enough north that wind shear from an upper-level trough of low pressure will reduce Wilma's winds by perhaps 20 mph.
Wilma is currently traversing an area of high oceanic heat content (see Figure 1), and this heat content will not significantly fall unless Wilma passes north of the Florida Keys. I would expect an additional 10 mph reduction in Wilma's winds if she makes landfall in Florida north of the Keys, due to the lower heat content of the water. So, expect landfall as a strong Category 2 hurricane if Wilma moves through the Keys, or as a weak Category 2 hurricane further north. Remember that hurricane intensity forecasts are poor, especially 3 - 5 days out, so Wilma's intensity could easily be a full Category higher or lower than this.
Figure 1. Total heat content of the ocean is high over the northwest Caribbean and the southern Gulf of Mexico south of 25 N latitude. Images credit: NOAA/AOML.
Jamaica continues to take a pounding from Wilma, but this should end tomorrow night as Wilma pulls away. The next area of concern is northern Honduras and Nicaragua, where rains of up to 12 inches are expected. However, the portions of these countries that will receive the heaviest rains are relatively flat, so I do not expect massive loss of life from flooding in the mountains.
Next on Wilma's list will be the Cayman Islands, but flooding is generally not life-threatening in that nation. Mexico and Cuba may escape serious damage if Wilma passes through the Yucatan Channel as forecast.
Figures 1. Computer model forecasts for Wilma.
Wilma started moving WNW at 8 mph today, as all the computer models predicted she would. The models are pretty unified, bringing Wilma through the Yucatan Channel or across the western tip of Cuba, and then northeastward into the Florida Keys or the west coast of Florida by the weekend. Two models (the UKMET and GFS) predict that Wilma will pass just south of the Keys. The furthest north model is the Canadian, which picks Sarasota for its landfall. The GFDL, NOGAPS, and the official NHC forecast are in the middle, with a landfall over the Everglades of Southwest Florida. The NOAA jet is scheduled to makes its first flight tonight, and tomorrow morning we should have a better idea of which part of Florida is at most risk. Climatology favors a more southern track, and I expect that we'll see the models converge on a more southerly track through the Keys in the runs we see Wednesday morning.
Elsewhere in the tropics, there is a large area of disturbed weather midway between Africa and the Leeward Islands. Upper level winds are not favorable for development of this area, which is also too close to the Equator. I'll be back with a update in the morning.
Jeff Masters
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