...ERIKA A LITTLE STRONGER...CENTER PASSING BETWEEN GUADELOUPE AND ANTIGUA... 000 WTNT35 KNHC 270850 TCPAT5 BULLETIN TROPICAL STORM ERIKA ADVISORY NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 500 AM AST THU AUG 27 2015 ...ERIKA A LITTLE STRONGER...CENTER PASSING BETWEEN GUADELOUPE AND ANTIGUA... SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...16.8N 61.5W ABOUT 35 MI...55 KM N OF GUADELOUPE ABOUT 30 MI...45 KM SE OF ANTIGUA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Warning is in effect for... * Anguilla * Saba and St. Eustatius * St. Maarten * St. Martin * St. Barthelemy * Montserrat * Antigua and Barbuda * St. Kitts and Nevisis * Puerto Rico * Vieques * Culebra * U.S. Virgin Islands * British Virgin Islands A Tropical Storm Watch is in effect for... * Guadeloupe * North coast of the Dominican Republic from Cabo Engano to Cabo Frances Viejo * Southeastern Bahamas * Turks and Caicos Islands A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Interests elsewhere in the Dominican Republic should monitor the progress of Erika. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside the United States, please monitor products issued by your national meteorological service. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 500 AM AST (0900 UTC), the center of Tropical Storm Erika was located near latitude 16.8 North, longitude 61.5 West. Erika is moving toward the west near 16 mph (26 km/h). A turn toward the west-northwest is forecast later today, and this general motion should continue for the next 48 hours. On the forecast track, the center of Erika will move near or over portions of the Leeward Islands this morning, move near the Virgin Islands later today, move near or north of Puerto Rico tonight, and pass north of the north coast of the Dominican Republic on Friday. Maximum sustained winds have increased to near 50 mph (85 km/h) with higher gusts. Little change in strength is forecast during the next 48 hours. Tropical storm force winds extend outward up to 105 miles (165 km), mainly to the north and east of the center. The latest minimum central pressure based on data from a NOAA Hurricane Hunter aircraft is 1003 mb (29.62 inches). HAZARDS AFFECTING LAND ---------------------- WIND: Tropical storm conditions are expected to spread across the warning area in the Leeward Islands this morning, and reach the Virgin Islands later today and Puerto Rico tonight. Tropical storm conditions are possible in the watch area in the Leeward Islands this morning. Tropical storm conditions could reach portions of the watch area in the Dominican Republic on Friday and the southeastern Bahamas, and Turks and the Caicos Islands late Friday and Friday night. RAINFALL: Erika is expected to produce total rain accumulations of 3 to 5 inches with maximum amounts of 8 inches across portions of the Leeward Islands, the Virgin Islands, Puerto Rico, the Dominican Republic, the Turk and Caicos Islands and the southeast Bahamas through Saturday. NEXT ADVISORY ------------- Next intermediate advisory at 800 AM AST. Next complete advisory at 1100 AM AST. $$ Forecaster Brennan 000 WTNT45 KNHC 270856 TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 500 AM AST THU AUG 27 2015 Data from a NOAA Hurricane Hunter aircraft indicate that Erika has strengthened overnight, although it is not clear as to how much. The central pressure dropped to around 1001 mb around 0540Z, but was up to 1003 mb on the next fix about an hour later. The highest 850-mb flight-level winds sampled by the aircraft were 48 kt, which would correspond to an intensity of around 40 kt. However, the aircraft found SFMR winds of 45 to 55 kt near the center. Based on a blend of these data, the initial intensity has been conservatively raised to 45 kt for this advisory. An Air Force Hurricane Hunter aircraft will be investigating Erika again later this morning. Aircraft data and satellite imagery show that Erika is still a sheared tropical cyclone, with the deepest convection found east and southeast of the center due to about 20 kt of westerly shear. The models show the environment remaining unfavorable for significant strengthening in the first 48 hours, with shear associated with an upper-level trough west of Erika expected to increase to 25 to 30 kt. Given this, most of the intensity guidance shows little change during the first couple of days and so does the NHC forecast. After that time, the upper trough weakens and Erika should encounter a more favorable upper-level pattern and warmer SSTs, which should support intensification assuming that the cyclone survives the next 48 hours. The HWRF and GFDL are much stronger than the statistical models this cycle, but the GFS and ECMWF now keep Erika weaker than they did previously. The NHC forecast has been adjusted upward slightly late in the period, but is well below the intensity consensus given the large uncertainty and spread in the guidance. Aircraft fixes and radar data from Guadeloupe were helpful in finding the low-level center and determining an initial motion of 280/14. The steering flow from the subtropical ridge to the north should result in a west-northwestward heading for the next 2 to 3 days. After that time, the spread in the guidance increases as the cyclone moves between the southwestern edge of the ridge and a mid/upper-level trough over the southeastern U.S. and Gulf of Mexico. The models are in poor agreement on the eventual structure and track of Erika late in the period. The ECMWF is weaker this cycle and is on the left side of the dynamical model envelope. The GFS, HWRF, and UKMET are all farther east but have trended west this cycle. Given the large spread and the continued run-to-run variability, little change was made to the NHC track forecast. The new NHC forecast is closest to the latest GFS model prediction at day 3 and beyond. One should remember to not focus on the exact forecast track, especially at the long range where the average NHC track errors during the past 5 years are about 180 miles at day 4 and 240 miles at day 5. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 16.8N 61.5W 45 KT 50 MPH 12H 27/1800Z 17.6N 63.5W 50 KT 60 MPH 24H 28/0600Z 19.0N 66.2W 50 KT 60 MPH 36H 28/1800Z 20.3N 69.0W 50 KT 60 MPH 48H 29/0600Z 21.5N 71.6W 50 KT 60 MPH 72H 30/0600Z 24.0N 76.0W 55 KT 65 MPH 96H 31/0600Z 26.5N 78.5W 65 KT 75 MPH 120H 01/0600Z 29.0N 79.5W 75 KT 85 MPH $$ Forecaster Brennan |