Wilma: dramatic change in forecast track?

Posted By: JeffMasters at 7:37 PM GMT on October 19, 2005
Updated: 9:15 PM GMT on October 19, 2005

Hurricane Wilma continues across the western Caribbean towards Mexico as a Category 5 hurricane. The Hurricane Hunters reached the storm at 2:06 pm EDT, and reported a pressure of 892 mb, ten mb higher than the Atlantic record lowest pressure of 882 mb set this morning. The 3:56 pm EDT hurricane eye report showed the same pressure, 892 mb. Peak winds measured at flight level were 141 knots in the southern eyewall, compared to 162 knots measured this morning. Infrared satellite imagery shows that the cloud tops have warmed a bit since this morning, and Wilma is a weaker storm–but still a Category 5 capable of catastrophic damage. The eye diameter measured by the hurricane hunters was still a very tiny 5 nm, and an second concentric eyewall with diameter 10 nm has formed. This indicates that Wilma may soon undergo an eyewall replacement cycle, and will weaken to a Category 4 storm.

Figure 1. Computer model tracks for Hurricane Wilma.

Where will Wilma go?
There is now a high degree of uncertainty in the forecast for Wilma. NHC has not adjusted the official forecast much with the 5 pm advisory, other than to slow down Wilma a bit. However, a major shift in the model guidance occurred with the just completed 12Z (8 am) runs, that may force NHC to make major modifications to the official forecast if further model runs continue to show this shift. Three of the top models–the GFS, GFDL, and UKMET models–now show that the trough of low pressure that was expected to pull Wilma sharply northwards and then northeast across Florida is progressing slower than expected, and will not dig as far south. If this forecast verifies, it would be very bad news for Mexico. Wilma may not pass east of Mexico through the Yucatan Channel as originally thought, and may instead make a landfall on the Yucatan Peninsula near Cozumel or Cancun Island on Thursday night or Friday morning, probably as a Category 4 hurricane.

However, this would be very good news for Florida. Any encounter with the Yucatan Peninsula would cause a serious disruption of the hurricane, and make it unlikely that Wilma could affect Florida as a major hurricane. A hit on southwest Florida as a Category 1 or 2 hurricane would be most likely, and the arrival of the hurricane would be delayed until Sunday. It is quite possible that Wilma would not affect Florida as a hurricane at all; the GFDL model forecasts that Wilma will spend three days over Mexico and emerge off the coast as a tropical storm and pass south of Cuba. So, if I lived in Florida and was thinking about evacuating today, I would wait another day and see what the forecast tomorrow brings. Keep in mind, though, that the NOGAPS model, which is one of the top four models for tracking hurricanes, is still showing that Wilma will pass through the Yucatan Channel and a make landfall in southwest Florida as a major hurricane. The Canadian model is showing this as well.