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Tropical Storm Isaac Forecast Discussion Number 3
2024-09-26 16:37:24| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 26 2024 000 WTNT45 KNHC 261437 TCDAT5 Tropical Storm Isaac Discussion Number 3 NWS National Hurricane Center Miami FL AL102024 1100 AM AST Thu Sep 26 2024 Isaac's structure has remained mostly steady state during the past 6 hours. Cloud tops associated with the tropical storm are still not particularly cold, but as noted in previous discussions, this is not unexpected for its synoptic environment. A blend of subjective Dvorak estimates from TAFB and SAB plus objective estimates from UW-CIMSS still supports an intensity of 45 kt for this advisory. For the next 48-60 h, the track forecast appears to be mostly straightforward. All reliable guidance indicates that Isaac will continue moving eastward to east-northeastward with a mid-latitude trough during that period. However, there is a significant bifurcation in the dynamical models after that. A majority of the guidance, including most of the ECMWF ensemble, indicate that Isaac will turn back eastward, continuing with the mid-latitude flow associated with another deep-layer trough. However, a few members of the global ensembles, plus the deterministic GFS, indicate Isaac could move slightly slower, which could cause the tropical storm to interact with a different trough, currently located over eastern Canada. This may cause the tropical cyclone to move northward after 60 h, on a very different track. The NHC forecast treats the GFS as an outlier, and is instead near the consensus of the remaining guidance. It is therefore very similar to the previous forecast. However, confidence in this forecast is particularly low, and we can't rule out needing to make an unusually large change to later forecasts. Isaac appears to be in an environment that should be generally conducive for some strengthening, especially during the next day or two. After that, unusually cold upper-tropospheric temperatures could help sustain the tropical cyclone for a while, even as it moves over colder SSTs in the 24-25 deg C. By the end of the forecast period, much colder SSTs and a dramatic increase in shear should cause Isaac to become post-tropical. No changes of note were made to the NHC forecast, which still shows Isaac reaching hurricane strength during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 37.3N 51.7W 45 KT 50 MPH 12H 27/0000Z 37.4N 49.8W 50 KT 60 MPH 24H 27/1200Z 37.9N 46.9W 55 KT 65 MPH 36H 28/0000Z 38.7N 43.5W 60 KT 70 MPH 48H 28/1200Z 39.9N 39.9W 65 KT 75 MPH 60H 29/0000Z 41.2N 36.7W 65 KT 75 MPH 72H 29/1200Z 42.3N 33.3W 60 KT 70 MPH 96H 30/1200Z 43.5N 25.5W 55 KT 65 MPH 120H 01/1200Z 43.5N 18.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster D. Zelinsky
Category:Transportation and Logistics
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Summary for Tropical Storm Isaac (AT5/AL102024)
2024-09-26 16:36:54| National Hurricane Center (Atlantic)
...ISAAC FORECAST TO STRENGTHEN OVER THE NORTH ATLANTIC DURING THE NEXT COUPLE OF DAYS... As of 11:00 AM AST Thu Sep 26 the center of Isaac was located near 37.3, -51.7 with movement E at 12 mph. The minimum central pressure was 997 mb with maximum sustained winds of about 50 mph.
Category: Transportation and Logistics
Tropical Storm Isaac Public Advisory Number 3
2024-09-26 16:36:54| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 26 2024 000 WTNT35 KNHC 261436 TCPAT5 BULLETIN Tropical Storm Isaac Advisory Number 3 NWS National Hurricane Center Miami FL AL102024 1100 AM AST Thu Sep 26 2024 ...ISAAC FORECAST TO STRENGTHEN OVER THE NORTH ATLANTIC DURING THE NEXT COUPLE OF DAYS... SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...37.3N 51.7W ABOUT 1345 MI...2170 KM W OF THE AZORES ABOUT 820 MI...1315 KM ENE OF BERMUDA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...E OR 80 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM AST (1500 UTC), the center of Tropical Storm Isaac was located near latitude 37.3 North, longitude 51.7 West. Isaac is moving toward the east near 12 mph (19 km/h). A turn toward the east-northeast or northeast is expected by the weekend, along with a slight increase in forward speed. Maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Strengthening is forecast, and Isaac is expected reach or be near hurricane strength by late Friday or early Saturday. Tropical-storm-force winds extend outward up to 70 miles (110 km) from the center. The estimated minimum central pressure is 997 mb (29.44 inches). HAZARDS AFFECTING LAND ---------------------- SURF: Swells generated by Isaac and a large wind fetch from a deep-layer trough are affecting portions of the coast of Bermuda and could spread into the Azores by this weekend. 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 500 PM AST. $$ Forecaster D. Zelinsky
Category: Transportation and Logistics