| Track: http://www.nhc.noaa.gov/refresh/graphics_at1+shtml/?cone#contents Hurricane Irma Discussion Number 10 NWS National Hurricane Center Miami FL AL112017 500 PM AST Fri Sep 01 2017 Well, that eyewall replacement cycle didn't last long. Satellite images indicate that the cycle is now complete, with Irma displaying a larger warm eye. The initial wind speed has been set to 105 kt, in agreement with the CIMSS ADT. Since the eyewall cycle is finished, some strengthening is possible, although SSTs are currently pretty marginal. Although no increase in winds is shown in the short term, this could be conservative. During the next few days, water temperatures along the track will warm significantly, but there could be some higher shear, and of course more eyewall replacements. The forecast is a compromise between the statistical/dynamical models, which bring the intensity down then up again, versus the global models and hurricane models, which show a rather strong cyclone. The westward turn of Irma has begun, and the current motion is 275/12. A building mid-level high should cause the hurricane to turn west-southwestward tomorrow and continue through early next week. Later on, Irma should reach the southern periphery of the ridge, and begin to move west-northwestward. The biggest change since the last forecast is that the GFS and its ensemble has trended southwestward, toward the unwavering ECMWF model on the track forecast. Given the trend in guidance, little change is made to the official track prediction, although the corrected consensus models and the HWRF are now southwest of the latest forecast. KEY MESSAGES: 1. Irma is expected to be a major hurricane when it approaches the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials. 2. It is much too early to determine what direct impacts Irma will have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 18.8N 39.1W 105 KT 120 MPH 12H 02/0600Z 18.9N 40.9W 105 KT 120 MPH 24H 02/1800Z 18.5N 43.4W 105 KT 120 MPH 36H 03/0600Z 17.9N 45.7W 105 KT 120 MPH 48H 03/1800Z 17.2N 47.9W 105 KT 120 MPH 72H 04/1800Z 16.4N 52.2W 110 KT 125 MPH 96H 05/1800Z 17.0N 56.5W 110 KT 125 MPH 120H 06/1800Z 19.0N 61.0W 115 KT 130 MPH $$ Forecaster Blake Hurricane Irma Advisory Number 10 NWS National Hurricane Center Miami FL AL112017 500 PM AST Fri Sep 01 2017 ...IRMA TURNS WESTWARD WITH 120-MPH WINDS... SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...18.8N 39.1W ABOUT 1495 MI...2405 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 13 MPH...20 KM/H MINIMUM CENTRAL PRESSURE...964 MB...28.47 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. Interests in the northern Leeward Islands should monitor the progress of this system. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 500 PM AST (2100 UTC), the center of Hurricane Irma was located near latitude 18.8 North, longitude 39.1 West. Irma is moving toward the west near 13 mph (20 km/h). A turn toward the west-southwest is expected tomorrow. Maximum sustained winds are near 120 mph (195 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Fluctuations in strength, up or down, are possible during the next few days, but Irma is expected to remain a powerful hurricane through the weekend. Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km). The estimated minimum central pressure is 964 mb (28.47 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- Next complete advisory at 1100 PM AST. $$ Forecaster Blake |