Track: http://www.nhc.noaa.gov/refresh/graphics_at5+shtml/?cone#contents Floater: http://www.ssd.noaa.gov/PS/TROP/floaters/15L/15L_floater.html Wider Atlantic views: http://www.ssd.noaa.gov/PS/TROP/trop-atl.html Tropical Storm Maria Discussion Number 2 NWS National Hurricane Center Miami FL AL152017 500 PM AST Sat Sep 16 2017 Satellite images indicate that the system located several hundred miles east of the Lesser Antilles has become much better organized throughout the day. The low-level center of circulation is now well defined, and banding features have become better established in all quadrants. The initial wind speed is increased to 45 kt, in agreement with a Dvorak classification from TAFB. This makes the system a tropical storm, Maria becomes the thirteenth named storm in the Atlantic basin this season. Maria is moving quickly westward at 17 kt on the south side of a mid-level ridge. This ridge is expected to remain in place but weaken some, which should cause Maria to move west-northwestward at a progressively slower pace through the forecast period. The models are in fair agreement, and the NHC official track forecast is closest to the HCCA model. This forecast takes the core of Maria near the Leeward Islands in 48 to 72 hours, and close to the Virgin Islands and Puerto Rico in about 4 days. The tropical storm is located within conducive environmental conditions of low wind shear, high amounts of moisture, and over warm 29 deg C SSTs. Since these conditions are not expected to change much, steady or even rapid strengthening is likely during the next 3 to 4 days. Slight weakening is predicted by the end of the forecast period due to some land interaction and a slight increase in wind shear. The NHC intensity forecast is raised significantly from the previous one to come into better agreement with the latest guidance. KEY MESSAGES: 1. Maria is expected to strengthen and affect portions of the Leeward Islands as a hurricane early next week, bringing dangerous wind, storm surge and rainfall hazards. Hurricane and tropical storm watches have been issued for portions of the Lesser Antilles, and additional watches will likely be issued tonight and Sunday. 2. Maria could also affect the British and U.S. Virgin Islands and Puerto Rico by mid week as a dangerous major hurricane, and hurricane watches could be issued for these islands as early as Sunday. Interests in these areas should monitor the progress of Maria and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 12.3N 52.6W 45 KT 50 MPH 12H 17/0600Z 13.0N 54.5W 55 KT 65 MPH 24H 17/1800Z 13.9N 56.6W 65 KT 75 MPH 36H 18/0600Z 14.6N 58.3W 70 KT 80 MPH 48H 18/1800Z 15.2N 59.8W 80 KT 90 MPH 72H 19/1800Z 16.5N 62.7W 95 KT 110 MPH 96H 20/1800Z 17.9N 65.5W 105 KT 120 MPH 120H 21/1800Z 19.5N 68.6W 95 KT 110 MPH $$ Forecaster Cangialosi Tropical Storm Maria Advisory Number 2 NWS National Hurricane Center Miami FL AL152017 500 PM AST Sat Sep 16 2017 ...DEPRESSION BECOMES TROPICAL STORM MARIA... ...ADDITIONAL STRENGTHENING IS FORECAST... SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...12.3N 52.6W ABOUT 620 MI...1000 KM ESE OF THE LESSER ANTILLES MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 20 MPH...31 KM/H MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Antigua has issued a Hurricane Watch for Antigua, Barbuda, St. Kitts, Nevis, and Montserrat. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... * Antigua, Barbuda, St. Kitts, Nevis, and Montserrat A Tropical Storm Watch is in effect for... * St. Lucia * Martinique and Guadeloupe * Dominica * Barbados * St. Vincent and the Grenadines A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Interests elsewhere in the Lesser Antilles should monitor the progress of this system. Additional Tropical Storm or Hurricane Watches will likely be issued tonight or early Sunday. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 500 PM AST (2100 UTC), the center of Tropical Storm Maria was located near latitude 12.3 North, longitude 52.6 West. Maria is moving toward the west near 20 mph (31 km/h). A slower west-northwest motion is expected during the next couple of days. On the forecast track, Maria is expected to approach the Leeward Islands on Monday. Maximum sustained winds have increased to near 50 mph (85 km/h) with higher gusts. Additional strengthening is expected during the next 48 hours, and Maria is forecast to be a hurricane when it approaches the Leeward Islands early next week. Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1002 mb (29.59 inches). HAZARDS AFFECTING LAND ---------------------- WIND: Hurricane conditions are possible within the hurricane watch area by Monday night or Tuesday, with tropical storm conditions possible on Monday. Tropical storm conditions are possible in the tropical storm watch area on Monday. STORM SURGE: A dangerous storm surge accompanied by large and destructive waves will raise water levels by as much as 3 to 5 feet above normal tide levels within the hurricane watch area. RAINFALL: Maria is expected to produce total rain accumulations of 6 to 12 inches with isolated maximum amounts of 20 inches across portions of the central and southern Leeward Islands through Tuesday night. Rainfall amounts of 2 to 4 inches with isolated maximum amounts of 8 inches will be possible for portions of the northern Leeward Islands through Tuesday night. These rains could cause life-threatening flash floods and mudslides. SURF: Swells generated by Maria are expected to begin affecting the Lesser Antilles by Sunday night. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 800 PM AST. Next complete advisory at 1100 PM AST. $$ Forecaster Cangialosi |