Wilma devastating Cancun; TD 25 a major threat to Haiti

The eye of very dangerous Category 2 Hurricane Wilma remains onshore the Yucatan mainland near Cancun. The most extreme winds of the eyewall have now been battering Cozumel and the mainland Yucatan Peninsula for over 24 hours. Sustained winds of 100 - 140 mph affecting a built-up resort area like Cozumel/Cancun for so long must have done extreme damage. Wilma has weakened to a Category 2 hurricane with 110 mph winds, and may further weaken to a Category 1 hurricane with 90 mph winds today as its center remains over land. Still, the damage to Mexico may double today as structures already weakened by 24 hours of relentless winds continue to receive another 12 hours of stress, and as new areas along the north coast of the Yucatan receive the eyewall's worst pounding.

Cancun radar, which is miraculously still functioning, shows the the eyewall of Wilma is degrading and starting to have gaps. The eye is now filled with clouds, and the cloud top temperatures of her eyewall clouds continue to warm as Wilma steadily weakens. When Wilma finally moves back over the ocean late tonight, she will probably be a weak Category 2 hurricane with 95 mph winds.

Conditions in Cancun
Wunderblogger LizinCancun reported yesterday on conditions in Cancun:

"We evacuated our home in Cancun yesterday and came 200 miles west to Merida. Our home sits about 100 feet away from the beach. The waves were crashing over our 6 foot tall sea wall yesterday before we left and destroyed the palapa that sits about 10 feet out in the water. We fully expect our home and all our belongings to be gone. We lost contact with all of our friends that stayed, cell and land lines are down of course as is power. We just talked with a friend that says the power is out, phones only working when the generators are running to pump out all the water. He said the hotel is blowing apart (not in the hotel zone) and all you can see when looking outside is a wall of water blowing sideways and pieces of things being shredded by the high winds, some huge."


Figure 1. Total rainfall for the week. Image generated by NASA's TRMM rainfall measuring satellite.

A deluge of rain
Rainfall amounts in Mexico from Wilma have been extreme. Isla Mujeres, just offshore from Cancun, has reported almost 35" of rain over the past 1 1/2 days, and at one point reported 4" of rain in one hour between 2 and 3 am EDT today. Rainfall amounts in Cuba have not been nearly so extreme--at least in the areas of western Cuba that are still reporting data. San Juan y Martinez measured 10.7 cm (4.2 inches) of rain the past 24 hours, and storm total rainfall amounts of up to 18 cm (7 inches) have been measured in Cuba's westernmost province. Grand Cayman received five inches, Jamaica's Kingston airport eight inches, and Belize four inches. The north coast of Honduras has had numerous locations receive ten inches of rain, with one unofficial report of 20 inches. Rainfall in Haiti reached 8 - 10 inches, and, triggered flash floods that killed 11 people.

How will Wilma affect Florida?
The latest 2 am EDT (06Z) model runs are in, and continue to agree on the basic scenario that Wilma will move offshore the Yucatan late tonight as a weak Category 2 hurricane. On Sunday, the storm will move slowly north and then northeast as westerly winds from a strong trough of low pressure start affecting the storm. There is about an 18-hour window of opportunity for Wilma to re-intensify to a Category 3 hurricane on Sunday. By Sunday night, Wilma will begin to accelerate, and wind shear will begin to substantially weaken the storm. By Monday morning, Wilma will cross the west coast of Florida between Fort Myers and the Keys as a Category 1 or 2 hurricane. My best guess is that Wilma will be a 100-mph Category 2 hurricane hitting near Marco. Storm surges tend to be worse with large and faster moving hurricanes, so I would expect a storm surge characteristic of a Category 3 hurricane, 10 to 16 feet, in and south of Marco, causing very heavy damage in that city. Fortunately, the area south of Marco is primarily uninhabited--the Everglades swamp. However, if Wilma comes ashore north of Naples--or further south near the Keys--storm surge flood damage in those areas could easily reach billions of dollars. Storm surge flooding should be only 2 - 4 feet on the east coast of Florida, where wind damage is the primary threat.


Figure 2. Storm surge map for southwest Florida.

Wilma's winds and rain
Wilma will be moving too fast to dump more than 5 - 10 inches of rain. The rain will be concentrated on the north side of the hurricane, since there will be a cold front there that will trigger more condensation. Areas to the north of the eye's passage will see winds a full Category--25 to 30 mph--lower than those on the south. This is because the storm's high rate of forward motion, near 25 - 30 mph, will add to the windspeeds seen on the south side of the Wilma's counterclockwise rotation, and subtract on the north side. Since the storm will be moving so fast, the duration of hurricane force winds will be just a few hours.

After Florida, then what?
After crossing Florida, Wilma should bring tropical storm force winds to the northern Bahama Islands, but not hurricane force winds. Wilma should pass close enough to North Carolina's Outer Banks to bring 40 mph winds there. Wilma is not expected to bring high winds to New England, but could bring 50 mph winds to Nova Scotia five days from now.

TD 25
Tropical Depression 25 has formed 200 miles southwest of Puerto Rico, and looks like a good bet to develop into a tropical storm later today. Long range radar from San Juan, Puerto Rico shows some increasing spiral banding and echo intensity, and satellite imagery shows a good outflow channel developing to the southeast. Wind shear of about 10 knots is eroding the northwest portion of the storm.

Since we are all out of names this year, TD 25 will be given the name Alpha should it develop into a tropical storm. Given the storm's expected track over Haiti, the 8 - 12 inches of rain expected may cause heavy loss of life in that country due to the inability of the deforested hillsides to handle flood waters.

I'll be back in the morning with the latest, or later today, if events warrant.

Jeff Masters