A hurricane warning was in effect from Grand Isle, Louisiana, to the Alabama/Florida border on Friday as Tropical Storm Nate—already a deadly storm in Central America—gathered strength over the warm waters of the Northwest Caribbean. Nate was speeding north-northwest at 21 mph over the Western Caribbean, and the storm is expected to pass very close to the tip of Mexico’s Yucatan Peninsula on Friday evening as a strong tropical storm. Continued strengthening is predicted on Saturday as Nate traverses the Gulf of Mexico, and Nate is likely to be a Category 1 or Category 2 hurricane on Saturday night when it makes landfall on the U.S. Gulf Coast between Southeast Louisiana and the Florida Panhandle.
Dangerous heavy rains from Nate have affected large parts of Central America and the islands of the Western Caribbean. As of midday Friday, Nate had led to a total of 22 deaths in Central America, with another 24 people listed as missing. A personal weather station on the Pacific side of Nicaragua recorded 8.79” of rain from Nate as of 11 am EDT Friday. Satellite rainfall estimates show that Nate has dumped 8+” of rain on the Pacific side of Costa Rica, Nicaragua, and Panama, and also along the northern coast of Honduras and the eastern coast of the Yucatan Peninsula, in both Mexico and Belize.
Figure 1. Rio Baru overflows and destroys a home in Dominical, Puntarenas Province, Costa Rica, as Tropical Storm Nate hits the area on Thursday, October 5, 2017. (Instagram/@tywebbphish)
|Figure 2. Microwave satellite view of Nate taken at 7:58 am EDT Friday, October 6, 2017 (colored areas, showing where the heaviest precipitation is occurring), overlaid on a GOES-13 infrared satellite image from 7:30 am EDT Friday. Nate appeared to be building the southern portion of an eyewall to the south of its center, but the winds measured by the Hurricane Hunters in that area were 40 mph or less. Image credit: Naval Research Laboratory.|
Belize radar and satellite imagery late Friday morning showed an increase in the organization and coverage of Nate’s spiral bands, which were sprawled out over the entire Western Caribbean, from Nicaragua to Cuba. An Air Force and a NOAA hurricane hunter aircraft were in Nate on Friday morning, and found that the pressure was falling and the winds were slowly increasing. Eye penetrations at 7:24 am, 9:03 am, and 10:51 am EDT found the central pressure holding nearly steady at 997 – 998 mb, but the surface winds had risen to 50 mph, mainly in bands well to the east of the center. Though not noted on the center Vortex Data Message, visible and microwave satellite imagery suggest that Nate may be attempting to build an eyewall along the south side of the center.
Conditions were very favorable for development, with low wind shear less than 5 knots, sea surface temperatures (SSTs) a very warm 30°C (86°F), and an unusually moist atmosphere with a mid-level relative humidity of 85%. Nate was traversing an area with exceptionally high ocean heat content in excess of 100 kilojoules per square centimeter, favorable for fueling rapid intensification.