Tropical Storm Dorian continues meandering toward the heart of the Caribbean tonight. The National Hurricane Center’s track has shifted only slightly, and if anything is a little less bullish on storm intensity than the day before. A few tropical storm watches and warnings have also popped up in the islands as the storm makes its way through.
As Floridians, it’s only natural to see that big cone pointing vaguely toward the peninsula and default to “It’s comin’ right for us!” Resist the temptation. Never mind the fact that it’s still too early to know exactly what, if anything, this storm is going to do in the U.S. (there’s a reason the NHC only issues tracks for five days even though most forecast models can go out 10+ days). More important to this particular situation is that there are three big obstacles to Dorian’s future development.
1: Dorian is traveling through some pretty darn dry air. Water Vapor Imagery, which distinguishes between dry air (yellows/oranges/reds) and moist air (blues/greens/whites) shows Dorian as an island of moisture in a relatively dry area, including in the area she’ll be travelling through over the coming days.
2: Wind Shear is a big factor in whether a storm sticks together. It’s like trying to move a candle across a room without it going out… which is tough enough… and having a bunch of people blowing on it while you walk by. Dorian will be travelling through some areas of moderate to strong wind shear, as evidenced by this moderately hideous but still useful map from the hurricane folks at University of Wisconsin-Madison(?!).
3: And finally, the islands themselves. Dorian’s track at the moment takes her over several islands on the way. These act as meteorological speed bumps which can hinder the development of storms that flourish over open water. Given that Dorian is a relatively small storm, any islands she comes across will affect a larger surface area of the overall storm, meaning they can pack more of a punch than on a giant storm. It’s the difference between stepping on a pebble or a boulder. Especially of note is Hispaniola, home to Dominican Republic and Haiti. It’s a large island dotted with mountains including Pico Duarte, the highest peak in the Caribbean… topping out at a height of more than 10,000 feet.
All of this is to say that Dorian is not facing the most favorable conditions for long-term development. This is NOT to say that the track won’t change… the wind shear won’t die down… or something else might happen that changes her track, strength, or other intentions. And it’s still too early to know what, if anything, this means for the U.S. It’s even too early to know about Puerto Rico and the U.S. Virgin Islands just yet. So don’t panic… but keep an eye on it as the week goes on.
And by the way, yes, that area in the Atlantic that had been over Florida for a while continues to move away. Current thinking: North Carolina and South Carolina should monitor just in case… but otherwise, Fish Storm.
Official statements on Dorian and the rest from the NHC are below.
Tropical Storm Dorian Advisory Number 7 NWS National Hurricane Center Miami FL AL052019 1100 PM AST Sun Aug 25 2019 ...DORIAN CONTINUES TO HEAD FOR THE WINDWARD ISLANDS... SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...11.7N 55.3W ABOUT 300 MI...485 KM ESE OF BARBADOS ABOUT 410 MI...660 KM ESE OF ST. LUCIA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Barbados Meteorological Service has issued a Tropical Storm Watch for Dominica. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Warning is in effect for... * Barbados * St. Lucia * St. Vincent and the Grenadines A Tropical Storm Watch is in effect for... * Dominica * Martinique * Grenada and its dependencies A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Additional watches or warnings could be issued on Monday for portions of the Windward and Leeward Islands. Elsewhere, interests in Puerto Rico, the Virgin Islands, and Hispaniola should monitor the progress of Dorian. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1100 PM AST (0300 UTC), the center of Tropical Storm Dorian was located near latitude 11.7 North, longitude 55.3 West. Dorian is moving toward the west near 14 mph (22 km/h). A turn toward the west-northwest is expected on Monday, with this motion continuing through Tuesday night. On the forecast track, the center of Dorian is expected to be near the Windward Islands late Monday or early Tuesday and move into the eastern Caribbean Sea on Tuesday. Maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Strengthening is expected during the next few days, and Dorian could be near hurricane strength by Tuesday over the eastern Caribbean Sea. Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1003 mb (29.62 inches). HAZARDS AFFECTING LAND ---------------------- RAINFALL: Dorian is expected to produce total rain accumulations of 2 to 4 inches in portions of the Lesser Antilles, with possible isolated maximum amounts of 6 inches. WIND: Tropical storm conditions are likely in the warning area by late Monday. Tropical storm conditions are possible within the watch area by Monday night or Tuesday. SURF: Swells generated by Dorian will be affecting portions of the Lesser Antilles by late Monday. These swells could cause life- threatening surf and rip current conditions. Please consult products from your local weather office.
Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 PM EDT Sun Aug 25 2019 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on Tropical Storm Dorian, located several hundred miles east-southeast of the Lesser Antilles. 1. An elongated area of low pressure centered about 300 miles south-southwest of Cape Hatteras, North Carolina has changed little in organization this evening. Environmental conditions appear conducive for gradual development, and a tropical or subtropical cyclone is likely to form within the next few days while the system moves slowly northeastward well offshore of the southeastern United States. Interests along the coasts of South and North Carolina should continue to monitor the progress of this system. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system on Monday, if necessary. * Formation chance through 48 hours...high...70 percent. * Formation chance through 5 days...high...80 percent.