| Track: https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/?cone#contents Tropical Storm Dorian Discussion Number 8 NWS National Hurricane Center Miami FL AL052019 500 AM AST Mon Aug 26 2019 Satellite images indicate that deep convection associated with Dorian continues to fluctuate curtailing significant strengthening likely due to intrusions of dry air. The overall trend, however, suggests that Dorian is gradually getting better organized with its cloud pattern consisting of a compact central dense overcast and some broken outer bands. The initial intensity is nudged up to 50 kt based on a blend of the satellite intensity estimates. Dorian remains a small storm with its tropical-storm-force winds estimated to extend no more than 40 n mi from the center. During the next couple of days, as Dorian moves through the Windward Islands and across the eastern Caribbean, slow strengthening seems likely due to low wind shear conditions and high SSTs. However, the surrounding dry air around the cyclone should continue to limit the rate of intensification. When Dorian approaches Hispaniola in about 3 days, the models show an increase in shear and those stronger environmental winds and the potential interaction with the rugged terrain of Hispaniola suggest that significant weakening is likely. The NHC intensity forecast remains between the dynamical models that show little or no strengthening and the statistical DSHP and LGEM that show significant intensification. It should be noted that the GFS and ECMWF have been very consistent in showing Dorian dissipating over the Caribbean Sea. Due to the wide range of the model solutions, the NHC intensity forecast remains of low confidence. It should be noted that compact tropical cyclones like Dorian are often challenging to predict. Dorian is moving westward at 12 kt steered by a subtropical ridge to its north. The storm should turn west-northwestward today and then northwestward on Wednesday when the cyclone gets closer to the eastern end of the mid- to upper-level low. The track models have shifted slightly to the right or north this cycle, and the NHC track forecast has been nudged in that direction. Key Messages: 1. Dorian is expected to bring tropical storm conditions to portions of the Lesser Antilles, where tropical storm watches and warnings are in effect. Residents in these areas should refer to advice from local government officials and products from their local meteorological service for additional information. 2. Dorian is expected to produce 2 to 4 inches of rain in Barbados, the Windward Islands, and Dominica, with isolated amounts as high as 6 inches. 3. While it is too soon to determine the specific time or magnitude of possible direct impacts in Puerto Rico, the Virgin Islands, or Hispaniola, interests in those areas should monitor the progress of Dorian and watches could be required later today. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 11.9N 56.4W 50 KT 60 MPH 12H 26/1800Z 12.4N 58.2W 50 KT 60 MPH 24H 27/0600Z 13.2N 60.3W 55 KT 65 MPH 36H 27/1800Z 14.4N 62.4W 55 KT 65 MPH 48H 28/0600Z 15.5N 64.5W 60 KT 70 MPH 72H 29/0600Z 18.0N 68.4W 65 KT 75 MPH 96H 30/0600Z 20.8N 71.6W 30 KT 35 MPH 120H 31/0600Z 23.0N 75.0W 30 KT 35 MPH $$ Forecaster Cangialosi Tropical Storm Dorian Advisory Number 8 NWS National Hurricane Center Miami FL AL052019 500 AM AST Mon Aug 26 2019 ...COMPACT DORIAN STRENGTHENS A LITTLE... ...EXPECTED TO BRING TROPICAL STORM CONDITIONS TO THE WINDWARD ISLANDS LATER TODAY... SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...11.9N 56.4W ABOUT 225 MI...365 KM ESE OF BARBADOS ABOUT 335 MI...540 KM ESE OF ST. LUCIA MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. 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. Interests in Puerto Rico, the Virgin Islands, and Hispaniola should monitor the progress of Dorian as watches could be required as early as later today. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 500 AM AST (0900 UTC), the center of Tropical Storm Dorian was located near latitude 11.9 North, longitude 56.4 West. Dorian is moving toward the west near 14 mph (22 km/h). A turn toward the west-northwest is expected later today, with this motion continuing through Tuesday night. On the forecast track, the center of Dorian is expected to be near the Windward Islands late today and tonight and move into the eastern Caribbean Sea on Tuesday. Maximum sustained winds have increased to near 60 mph (95 km/h) with higher gusts. Slow strengthening is forecast during the next few days, and Dorian could be near hurricane strength on Tuesday and and Wednesday while it is over the eastern Caribbean Sea. Dorian is a small tropical cyclone. 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 ---------------------- RAINFALL: Dorian is expected to produce total rain accumulations of 2 to 4 inches in Barbados, the Windward Islands, and Dominica through Tuesday. Isolated maximum amounts of 6 inches are possible in Barbados and the Windward Islands. WIND: Tropical storm conditions are likely in the warning area by late today. Tropical storm conditions are possible within the watch area by tonight or Tuesday. SURF: Swells generated by Dorian will be affecting portions of the Lesser Antilles by late today. These swells could cause life- threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 800 AM AST. Next complete advisory at 1100 AM AST. $$ Forecaster Cangialosi Below is the SHIPS output from 2am EDT Monday. The NHC mentions it when they talk about DSHP and LGEM. The track in the SHIPS output is listed as OFCI and here is that path: http://hurricanecity.com/models/models.cgi?basin=al&year=2019&storm=05&display=google_map&latestrun=1&models=OFCI In the models, these are the model identifiers that are represented in the SHIPS output: V (KT) NO LAND ... SHIP V (KT) LAND ... DSHP V (KT) LGEM ... LGEM DSHP takes land into account. After 72 hours the storm is going over Hispaniola in the points below. SHIP basically pretends Hispaniola isn't there. If it did miss Hispaniola, then it could be something that is actually useful. DSHP peaks it at 90mph. (78 knots). LGEM peaks it at 100mph. (87 knots) The chance of rapid intensification is also high. But again, with a storm as small as this it is susceptible of going either way, rapidly strengthening or even weakening. For purely informative purposes relating to how the output works, this is what the current SHIPS output has: 43% chance of a 121mph (105 knots; current 50 knots + 55 knots) storm in 48 hours. 39% chance of a 132mph (115 knots; current 50 knots + 65 knots) storm in 72 hours. Dry air is a very big wild card. GFS and Euro as they mention are not showing anything like that right now, which is why the NHC is still at 75mph. GFS and Euro would have a handle on the environment than the statistical SHIPS, so the upper amounts of some of the SHIPS rapid intensification output don't seem reasonable.
From: https://ftp.nhc.noaa.gov/atcf/stext/?C=M;O=D Recon will be important tonight to see what the core actually looks like. I think it's hard for satellites to get a good handle on intensity for a storm this small. GFS: https://www.tropicaltidbits.com/analysis/models/?model=gfs®ion=watl&pkg=mslp_uv850 Euro: https://www.tropicaltidbits.com/analysis/models/?model=ecmwf®ion=watl&pkg=mslp_uv850 |