| Track: https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/?cone#contents Satellite floater: https://www.star.nesdis.noaa.gov/GOES/floater.php?stormid=AL092021 Mesoscale floaters: https://www.star.nesdis.noaa.gov/GOES/meso_index.php More satellite data: http://hurricanecity.com/models/models.cgi?basin=al&year=2021&storm=09#satellite Cayman Islands radar: http://www.weather.gov.ky/portal/page/portal/nwshome/forecasthome/radar Cuba radars: http://www.insmet.cu/asp/genesis.asp?TB0=PLANTILLAS&TB1=RADARES My model system called this a tropical storm a little earlier. That was because the best track data from the NHC earlier had this as a 35 knot tropical storm, but did not assign a name at the time. (Ida, Julian and Kate are next names on the list) They have since updated the best track to make it a tropical depression again. Only advisory data should be considered official. Best track data is sometimes an indication of what they might do, but sometimes they change their mind too. In this case it looks like they want to see what the plane finds in the rest of the storm. Tropical Depression Nine Discussion Number 2 NWS National Hurricane Center Miami FL AL092021 500 PM EDT Thu Aug 26 2021 The overall satellite presentation of the tropical cyclone has continued to gradually improve today. Visible imagery and very recent observations from an Air Force Reserve reconnaissance aircraft indicate that the circulation has continued to become better defined. In addition, the convective activity has become a little better organized in a band around the northeastern and eastern portions of the circulation, and the system is likely near tropical storm strength. However, the initial intensity remains 30 kt pending the aircraft fully sampling the eastern portion of the circulation. The initial motion estimate is northwestward or 325/12 kt. The 1200 UTC dynamical model guidance continues to take the system northwestward around the southwestern side of well-established deep-layer ridge over the western Atlantic. On the forecast track, the system is expected to move over portions of western Cuba late Friday, over the southeastern and central Gulf of Mexico on Saturday, and approach the northern Gulf coast on Sunday. Although the track guidance envelope has tightened this cycle, increasing confidence in the overall forecast scenario, some shifts in the track are still likely until the system consolidates and becomes better defined. Users are reminded to not focus on the exact forecast track as storm surge, wind, and rainfall hazards will extend far from the center, and the average NHC track forecast error at day 3 is around 120 miles. The lastest NHC track forecast is close to the previous official forecast, and lies between the TCVA and HCCA consensus aids. There is some evidence of some light to moderate southerly shear over the system, but with the cyclone moving over the high ocean heat content waters of the northwestern Caribbean Sea the shear should not hinder intensification, with steady strengthening anticipated during the next 12 to 24 hours. Once the system moves over the Gulf of Mexico, it will be traversing a warm eddy, and this feature, combined with a favorable upper-level wind pattern and a moist atmosphere, is likely to result in steady to rapid strengthening on Saturday and Saturday night. The NHC intensity forecast again brings the system to near major hurricane strength when it approaches the northern Gulf coast on Sunday. This is supported by the HWRF and CTCI models, and the global model guidance that has consistently showed significant deepening of the system over the Gulf of Mexico over the past several model cycles. Therefore, as mentioned this morning, there is higher-than-normal confidence that a strengthening tropical cyclone will be moving over the Gulf of Mexico this weekend. Key Messages: 1. Tropical storm conditions are expected in portions of the Cayman Islands tonight and in portions of western Cuba and the Isle of Youth Friday. Dangerous storm surge is possible Friday in portions of western Cuba, including the Isle of Youth, in areas of onshore flow. 2. Life-threatening heavy rains, flash flooding and mudslides are expected across Jamaica, the Cayman Islands, and western Cuba, including the Isle of Youth. 3. The system is forecast to approach the northern Gulf coast at or near major hurricane intensity on Sunday, where there is an increasing risk of life-threatening storm surge, damaging hurricane-force winds, and heavy rainfall Sunday and Monday, especially along the coast of Louisiana. Storm Surge and Hurricane watches will likely be issued for a portion of this area later tonight or Friday morning. Interests in these areas should closely monitor the progress of this system and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 18.0N 79.8W 30 KT 35 MPH 12H 27/0600Z 19.7N 81.0W 45 KT 50 MPH 24H 27/1800Z 21.7N 82.8W 55 KT 65 MPH...INLAND 36H 28/0600Z 23.7N 84.8W 60 KT 70 MPH...OVER WATER 48H 28/1800Z 25.6N 87.0W 70 KT 80 MPH 60H 29/0600Z 27.2N 88.8W 85 KT 100 MPH 72H 29/1800Z 28.9N 90.4W 95 KT 110 MPH 96H 30/1800Z 31.9N 91.4W 50 KT 60 MPH...INLAND 120H 31/1800Z 34.6N 90.0W 25 KT 30 MPH...INLAND $$ Forecaster Brown Tropical Depression Nine Advisory Number 2 NWS National Hurricane Center Miami FL AL092021 500 PM EDT Thu Aug 26 2021 ...DEPRESSION EXPECTED TO STRENGTHEN INTO A TROPICAL STORM SOON... ...AIR FORCE HURRICANE HUNTER AIRCRAFT CURRENTLY INVESTIGATING THE SYSTEM... SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...18.0N 79.8W ABOUT 100 MI...160 KM WSW OF NEGRIL JAMAICA ABOUT 130 MI...205 KM SE OF GRAND CAYMAN MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H PRESENT MOVEMENT...NW OR 325 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Warning is in effect for... * Cayman Islands * Cuban provinces of Matanzas, Mayabeque, Havana, Artemisa, Pinar del Rio, and the Isle of Youth A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. Interests elsewhere in central and western Cuba, in the northern Yucatan Peninsula, and along the northern U.S. Gulf coast should monitor the progress of this system. Watches may be required for a portion of the northern Gulf coast later tonight or Friday morning. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 500 PM EDT (2100 UTC), the center of Tropical Depression Nine was located near latitude 18.0 North, longitude 79.8 West. The depression is moving toward the northwest near 14 mph (22 km/h), and this general motion should continue over the next few days. On the forecast track, the center of the depression will pass near or over the Cayman Islands tonight, the Isle of Youth and western Cuba Friday, and over the southeastern and central Gulf of Mexico Friday night and Saturday. The system is forecast to approach the U.S. northern Gulf coast on Sunday. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Steady strengthening is forecast during the next few days. The depression is expected to become a tropical storm tonight, and become a hurricane when it is near western Cuba or over the southeastern Gulf of Mexico. Additional strengthening is likely over the Gulf of Mexico, and the system could be near major hurricane strength when it approaches the northern Gulf coast. The estimated minimum central pressure from Air Force Reserve reconnaissance data is 1006 mb (29.71 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Tropical Depression Nine can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC, and on the web at hurricanes.gov/graphics_at4.shtml?key_messages. STORM SURGE: A dangerous storm surge will raise water levels by as much as 2 to 4 feet above normal tide levels in areas of onshore winds along the immediate coast of the Isle of Youth and near and to the east of where the center crosses the coast of western Cuba. Near the coast, the surge will be accompanied by large and destructive waves. WIND: Tropical storm conditions are expected in the Cayman Islands tonight, and are expected to reach the Isle of Youth and portions of western Cuba in the warning area on Friday. RAINFALL: The depression is expected to produce total rainfall accumulations of 6 to 10 inches with maximum totals of 15 inches across Jamaica. Rainfall totals of 8 to 12 inches with isolated maximum amounts of 20 inches are expected across the Cayman Islands and western Cuba, including the Isle of Youth. These rainfall amounts may produce life-threatening flash floods and mudslides. The depression may begin to bring rainfall and potential flooding impacts to the central Gulf Coast by early Sunday. SURF: Swells generated by this system will begin affect Jamaica, the Cayman Islands and Cuba tonight and Friday. 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 EDT. Next complete advisory at 1100 PM EDT. $$ Forecaster Brown |