Tropical Storm Dolly Forms in the Gulf of Mexico

Say hello to the Atlantic's fourth named storm of 2014--Tropical Storm Dolly, which formed Tuesday morning in the Gulf of Mexico's Bay of Campeche. Radar loops out of Altamira, Mexico show Dolly's heavy thunderstorms were already beginning to move ashore over the coast of Mexico a few hundred miles south of the Texas border Tuesday morning, though the heaviest activity was still well offshore. Satellite loops on Tuesday morning showed the classic appearance of a tropical storm struggling with wind shear--a low level circulation center partially exposed to view, with the heavy thunderstorms limited to one side (the south side) by strong upper-level winds. Sea Surface Temperatures (SSTs) were very warm, near 30°C (86°F), but dry air to the north of Dolly was being driven into the center of the storm's circulation by strong upper-level winds from the north-northwest, keeping development slow. Dolly doesn't have long over water before it makes landfall on Wednesday morning, and likely will not have time to intensify into a hurricane, given the dry air to its north and continued moderate levels of wind shear expected to affect the storm. None of the Tuesday morning runs of the reliable hurricane intensity models showed Dolly becoming a hurricane. Heavy rain is the main threat of the storm, and Dolly's rains will be capable of generating dangerous flash floods and mudslides over the mountainous terrain of Mexico near and to the south of the landfall location. The heavy rain threat will be less to the north of the landfall location, due to the presence of dry air.


Figure 1. Latest satellite image of Dolly.

Say Hello, Dolly--again!
Dolly's formation on September 2 comes more than a week later than the usual formation date of the Atlantic's fourth named storm, August 23. The 2014 version of Tropical Storm Dolly is the eighth appearance of a storm named Dolly in the Atlantic. Dolly made its first appearance in 1953 as hurricane that weakened before passing over Bermuda. Dolly's most recent appearance, as a 2008 Category 2 hurricane that hit near the Texas/Mexico border, was its most damaging--$1.5 billion in losses were recorded. This was not enough to get the name Dolly retired, though, and I expect we will see the name Dolly get recycled again in 2020. (The record number of appearances of a storm name for the Atlantic is ten, held by Arlene.)

New African tropical wave this weekend may develop
A tropical wave is expected to come off the coast of Africa on Thursday and move to the west at about 15 mph. This wave will be capable of bringing heavy rain and strong winds to the Cape Verde Islands on Friday and Saturday. Our three reliable computer models for predicting tropical storm formation all show development by Saturday of the wave, and in their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 0% and 30%, respectively. The Tuesday morning runs of the GFS and European ensemble models favored the storm taking a more west-northwesterly track into the open ocean next week, with no long-range threat to the Lesser Antilles Islands indicated.

Tropical Storm Norbert a potential threat to Baja Mexico
In the Eastern Pacific, Tropical Storm Norbert is gathering strength a few hundred miles south of the southwestern coast of Mexico. Though Mexico's Baja Peninsula was not in NHC's cone of uncertainty for Friday, the 00Z Tuesday run of the reliable European model did show Norbert coming very close to Baja on Friday, and residents there should be alert to a possible shift in the predicted track of Norbert towards them in future NHC advisories. Satellite loops show that Norbert has plenty of heavy thunderstorms, but this activity was just offshore of Southwest Mexico on Tuesday morning. Norbert's formation on September 2 comes more than 5 weeks before the typical October 11 formation date of the season's fourteenth storm in the Eastern Pacific.

Jeff Masters