Gabrielle Dissipates; the Atlantic Quiets Down

After a brief 12-hour stint as a tropical storm, Gabrielle was torn apart Thursday night by a strong tropical disturbance to its east, and interaction with the rough terrain of Puerto Rico and the Dominican Republic. The remnants of Gabrielle and the tropical disturbance to its east are generating heavy thunderstorms over Puerto Rico, the Eastern Dominican Republic, and the Virgin Islands, as seen on satellite loops. The tropical disturbance that helped pull Gabrielle apart is a threat to become a tropical depression on its own--NHC put its 5-day odds of development at 30% in their 8 am EDT Friday Tropical Weather Outlook. The disturbance is headed to the northwest at 10 - 15 mph, and may merge with Gabrielle's remnants early next week. Heavy thunderstorms from Gabrielle dumped 5.37" of rain on St. Thomas in the Virgin Islands and Southeast Puerto Rico, but the storm did not generate any sustained winds of tropical storm force (39 mph) at any land stations.


Figure 1. Total rainfall from Gabrielle, as compiled by NOAA.

Gabrielle's place in history
Gabrielle's formation date of September 5 (UTC time) comes eleven days earlier than the usual formation date of the season's 7th storm, September 16. However, by this point in the season, we should already have had two hurricanes, one being an intense hurricane, and 2013 has not yet had a hurricane. Gabrielle is the 7th consecutive named storm in the Atlantic that has not reached hurricane strength. Only one season since record keeping began in 1851 has had a longer string of consecutive storms that did not reach hurricane strength--2011, when the season began with eight such storms. It is possible such an event occurred before the advent of reliable satellite data in 1966, when we were first able to identify weak tropical storms that stayed out to sea. Several seasons have had six consecutive tropical storms without a hurricane, most recently in 2002. The air over the Tropical Atlantic has been more stable and drier than usual (and was so in 2011), making it difficult for storms to attain hurricane strength. Wunderblogger Lee Grenci's latest post, "The Lack of Atlantic Hurricanes: The Saga of Low Relative Humidity Continues", looks at how dry the Tropical Atlantic has been this hurricane season. Part of the unusual dryness, he maintains, is due to dry air coming off the coast of Brazil, which is in severe to extreme drought, according to the global drought monitor. Aon Benfield puts the cost of the Brazilian drought at $8.3 billion so far this year, making it Brazil's most expensive natural disaster in its history.

Elsewhere in the Atlantic
A tropical wave over the Western Gulf of Mexico's Bay of Campeche (Invest 99L) will move ashore on the Mexican coast near Tampico by early afternoon. Satellite images show that 99L has a moderate area of heavy thunderstorms that are slowly increasing in size and intensity, and the storm may have a closed circulation, as evidenced by northwest winds observed at Tampico, Mexico at 8 am CDT on Friday. In their 8 am EDT Friday Tropical Weather Outlook, NHC put the 5-day and 2-day odds of development at 20%.

A tropical wave in the Eastern Atlantic about 600 miles west of the Cape Verde Islands (Invest 98L) is headed west-northwest at about 10 mph. Satellite images show that 98L has a decent amount of spin, but a very limited amount of heavy thunderstorms. The system has encountered an area of dry, stable air, and in their 8 am EDT Friday Tropical Weather Outlook, NHC put the 5-day and 2-day odds of development at 0%.

A strong tropical wave is predicted to emerge from the coast of Africa on Saturday, and all of the models develop this wave into a tropical depression just west of the Cape Verde Islands by Tuesday. The storm is expected to track to the northwest into a region of ocean where very few tropical cyclones ever make the long crossing of the Atlantic Ocean to threaten North America. In their 8 am EDT Friday Tropical Weather Outlook, NHC put the 5-day odds of development at 50%.

Jeff Masters