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Hurricane Gonzalo Leaves the Lesser Antilles; Hawaii at Risk From Tropical Storm Ana

By: Dr. Jeff Masters, 1:23 PM GMT on October 14, 2014

Intensifying Category 2 Hurricane Gonzalo is heading northwest at 13 mph away from Puerto Rico and the Virgin Islands after plowing through the northernmost Lesser Antilles Islands overnight, bringing Category 1 hurricane conditions. The storm passed over Antigua Island between 10 am - 11 am AST on Monday, and Antigua recorded sustained winds of 67 mph gusting to 88 mph late Monday morning. Winds at nearby Barbuda were sustained at 60 mph, gusting to 70 mph, at 1:54 pm AST. St. Martin had sustained winds of 39 mph, gusting to 64 mph, at 7 pm AST, before the station stopped reporting. St. Maartin recorded sustained winds of 63 mph, gusting to 75 mph Monday evening. A Personal Weather Station (PWS) on St. Barthelemy recorded sustained winds of 82 mph, gusting to 108 mph, between 3 - 5 pm AST Monday. Gonzalo became the sixth hurricane of the 2014 Atlantic hurricane season at 5 pm Monday. Although Gonzalo's formation into a tropical storm on October 12 came nearly a month later than the typical September 16 date for formation of the season's seventh named storm, we are now ahead of schedule for hurricanes--a typical hurricane season has only six hurricanes, with the last one usually occurring in November.

Figure 1. Long range Puerto Rico radar image of Hurricane Gonzalo taken at 8:23 am EDT October 14, 2014. Gonzalo's outermost rain bands were still affecting the Virgin Islands.

Figure 2. MODIS satellite image of Hurricane Gonzalo taken at approximately 10:30 am EDT October 14, 2014, as the storm was pulling away from the Virgin Islands. At the time, Gonzalo had top winds of 110 mph. Image credit: NASA.

Forecast for Gonzalo
Satellite loops showed on Tuesday morning that Gonzalo was well-organized, with plenty of low-level spiral bands and heavy thunderstorm activity, and an eye that was growing more prominent. With wind shear a moderate 10 - 15 knots and warm Sea Surface Temperatures (SSTs) near 29°C (84°F), Gonzalo should continue to intensify on Tuesday. The 8 am Tuesday run of the SHIPS model predicted that conditions would remain favorable for development through Thursday, with light to moderate wind shear and SSTs remaining near 29°C (84°F). By Wednesday, Gonzalo has a good chance of becoming the Atlantic's first Category 4 hurricane since October 2, 2011, when Hurricane Ophelia reached 140 mph winds. By Thursday night and Friday morning, Gonzalo will encounter high wind shear, cooler SSTs of 28°C (81°F), and dryer air, which should drive steady weakening. During Gonzalo's closest pass by Bermuda on Friday, the hurricane could be anywhere between a Category 1 and Category 3 storm. Our two top models for predicting hurricane track, the GFS and European, differed considerably with their 00Z Tuesday runs on how fast Gonzalo would accelerate towards Bermuda on Friday. The European model predicted that Gonzalo would pass within 80 miles of the island near midnight EDT Friday night, while the GFS model had Gonzalo passing within 30 miles at 11 am EDT Friday.

Brian McNoldy of the Univ. of Miami, Rosenstiel School, has put together some great radar loops of Gonzalo, Hudhud, and Vongfong here.

Figure 3. Latest satellite image of Tropical Storm Ana.

Hawaii needs to pay attention to Tropical Storm Ana
In the Central Pacific, Tropical Storm Ana has formed, and was located about 900 miles east-southeast of the Big Island of Hawaii on Tuesday morning. Ana is headed northwest at 7 mph towards Hawaii. Satellite loops show that Ana has developed a Central Dense Overcast (CDO) of high cirrus clouds, characteristic of an intensifying tropical storm on its way to reaching hurricane status. The 8 am EDT Tuesday run of the SHIPS model predicted that wind shear would be light to moderate, 5 - 15 knots, and ocean temperature would be warm, 27 - 28.5°C (81 - 83°F) for the next five days along Ana's path, with some modest drying of the atmosphere. These conditions favor development, and I expect Ana will be able to reach Category 2 hurricane strength by Thursday. Our top two models for predicting hurricane tracks, the GFS and European models, both show Ana passing very close to the Big Island of Hawaii this weekend, and it is possible that the island could experience tropical storm conditions for the second time this year.

Hurricane expert Steve Gregory has more on the tropics in a Tuesday afternoon post.

Jeff Masters


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