Tropical Storm Bret Discussion Number 12 NWS National Hurricane Center Miami FL AL032023 500 AM AST Thu Jun 22 2023 Bret threw some interesting data at us during the couple of hours after the release of the previous advisory. On the last pass of the Air Force Reserve Hurricane Hunter aircraft through Bret's center, the plane measured SFMR winds as high as 69 kt and a dropsonde surface pressure of 996 mb with 31 kt of wind. Significant mid-level westerly shear is still affecting the system, and a 0539 UTC AMSR2 microwave pass revealed a well-defined mid-level eye feature displaced about a degree to the east of Bret's low-level center. It appears that the strong SFMR winds were measured beneath the strong convection in the western mid-level eyewall feature, so it's possible that they were transient and convectively driven. That said, Bret's initial intensity was raised to 60 kt on the 2 am intermediate advisory out of an abundance of caution, and that remains the current estimate. Another reconnaissance aircraft is scheduled to investigate Bret in a few hours and will hopefully confirm whether or not the storm is still producing winds that strong. Vertical shear is expected to gradually increase over the next couple of days as Bret approaches an upper-level trough located over the eastern Caribbean Sea. The storm could maintain its intensity or fluctuate in intensity through much of today, but it is expected to begin weakening by tonight once it crosses the Lesser Antilles and moves over the eastern Caribbean Sea. Global model fields indicate that Bret should degenerate into a trough over the central Caribbean Sea by day 3, which is shown in the official forecast. There are no changes in the track forecast reasoning. Bret is moving toward the west, or 280/13 kt, steered by a low- to mid-level ridge to its north. An accelerated westward motion is expected during the next few days as Bret weakens, and the NHC track forecast is a little faster than the consensus aids, hedging toward the faster GFS and ECMWF solutions. Users are reminded that NHC's track forecasts have average errors of about 40 n mi at 24 hours, and there is risk of strong winds and heavy rainfall for several islands within the Lesser Antilles regardless of exactly where the center crosses the island chain. KEY MESSAGES: 1. Bret is forecast to approach the Lesser Antilles today and then move across those islands this evening and tonight as a strong tropical storm. 2. A Hurricane Watch and a Tropical Storm Warning are in effect for St. Lucia, and a Tropical Storm Warning is in effect for Martinique and Dominica. There is a risk of flooding from heavy rainfall, strong winds, and dangerous waves along the coast within the warning area. A Tropical Storm Watch remains in effect for Barbados and St. Vincent and the Grenadines. Additional watches or warnings are possible for some islands in the Lesser Antilles later today. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 13.7N 56.6W 60 KT 70 MPH 12H 22/1800Z 13.9N 58.8W 60 KT 70 MPH 24H 23/0600Z 14.1N 61.8W 55 KT 65 MPH 36H 23/1800Z 14.3N 65.2W 50 KT 60 MPH 48H 24/0600Z 14.4N 68.7W 45 KT 50 MPH 60H 24/1800Z 14.6N 72.2W 40 KT 45 MPH 72H 25/0600Z...DISSIPATED $$ Forecaster Berg Almost a hurricane. Recon: https://hurricanecity.com/recon/ As of posting, a mission was nearing the storm, but obs were missing for the first pass from the NW to the SW. So we'll have to see what that mission ends up having to see if Bret has actually strengthened. (see NHC discussion above) The 8am discussion, below, says "The minimum central pressure partially based on data from the Air Force Hurricane Hunters is 996 mb (29.42 inches)", so they might have incomplete data too. (or maybe they had the HDOB pressure data that is extrapolated for the surface and a sonde hasn't reported back actual pressure yet) Tropical Storm Bret Intermediate Advisory Number 12A NWS National Hurricane Center Miami FL AL032023 800 AM AST Thu Jun 22 2023 ...BRET NEAR HURRICANE STRENGTH... ...EXPECTED TO BRING STRONG WINDS AND HEAVY RAIN TO PORTIONS OF THE LEEWARD ISLANDS LATER TODAY AND TONIGHT... SUMMARY OF 800 AM AST...1200 UTC...INFORMATION ---------------------------------------------- LOCATION...13.6N 57.0W ABOUT 170 MI...265 KM E OF BARBADOS MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... * St. Lucia A Tropical Storm Warning in in effect for... * Dominica * St. Lucia * Martinique A Tropical Storm Watch is in effect for... * Barbados * St. Vincent and the Grenadines A Hurricane Watch means that hurricane conditions are possible within the watch area, in this case within the next 24 hours. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within 24 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, in this case within the next 24 hours. Interests elsewhere in the Lesser Antilles should monitor the progress of Bret. Additional watches or warnings may be required later today. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 800 AM AST (1200 UTC), the center of Tropical Storm Bret was located near latitude 13.6 North, longitude 57.0 West. Bret is moving toward the west near 15 mph (24 km/h), and this general motion with an increase in forward speed is expected during the next few days. On the forecast track, the center of Bret is expected to approach the Lesser Antilles today, move across the Lesser Antilles this evening and tonight, and then move westward across the eastern and central Caribbean Sea Friday and Saturday. Maximum sustained winds are near 70 mph (110 km/h) with higher gusts. Little change in strength is forecast today while Bret approaches the Lesser Antilles. Weakening is anticipated to begin tonight or Friday after Bret passes the Lesser Antilles, and the system is likely to dissipate over the central Caribbean Sea by Saturday night. Tropical-storm-force winds extend outward up to 115 miles (185 km) from the center, especially to the north. The minimum central pressure partially based on data from the Air Force Hurricane Hunters is 996 mb (29.42 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Bret can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT3, WMO header WTNT43 KNHC and on the web at hurricanes.gov/text/MIATCDAT3.shtml WIND: Hurricane conditions are possible in the hurricane watch area this evening or tonight. Tropical storm conditions are expected within the tropical storm warning areas and possible within the watch areas later today and tonight. RAINFALL: Storm total rainfall amounts of 3 to 6 inches with maximum amounts of 10 inches are possible across portions of the Lesser Antilles from Guadeloupe south to St. Vincent and the Grenadines, including Barbados. The heavy rainfall could lead to flash flooding, especially across areas of higher terrain. Urban flooding is also possible. SURF: Swells generated by Bret are beginning to affect portions of the Lesser Antilles. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 1100 AM AST. $$ Forecaster Cangialosi |