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Tropical Storm FIONA Forecast Discussion Number 15
2016-08-20 16:52:05| National Hurricane Center (Atlantic)
Issued at 1100 AM AST SAT AUG 20 2016 000 WTNT41 KNHC 201451 TCDAT1 TROPICAL STORM FIONA DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 1100 AM AST SAT AUG 20 2016 Fiona is fighting off southwesterly shear this morning as the center has become embedded under the southwestern side of an area of deep convection. The Dvorak estimates from TAFB and SAB have held steady, so the initial intensity is held at 35 kt. Although a recent ASCAT overpass missed the center of Fiona, the pass did show 30-kt winds more than 50 n mi east of the center, suggesting that tropical-storm-force winds could be occurring closer to the center of circulation. Strong southwesterly shear of 25 to 30 kt is forecast to persist during the next few days. These unfavorable conditions combined with dry air along the path of the cyclone should induce a gradual weakening trend, and Fiona is expected to weaken to a tropical depression by tonight or early Sunday morning. The ECMWF and UKMET models continue to open this system into a trough within 3 days, whereas, the other model guidance lessens the shear slightly toward the end of the 5-day period and allows Fiona to survive for the next several days. The official forecast is similar to the previous one, and leans toward the ECMWF and UKMET model solutions. The initial position of Fiona is located slightly to the north of the previous forecast track, based on recent microwave data. The track forecast reasoning remains unchanged, as the low- to mid-level subtropical ridge over the central Atlantic should keep Fiona moving west-northwestward for the next several days. There remains a fair amount of spread in the guidance, which appears largely dependent on the future strength and status of the cyclone. The NHC track forecast lies on the western side of guidance, except for the short term forecast positions where a slight adjustment to the north was made due to the initial position and motion. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 20.3N 47.8W 35 KT 40 MPH 12H 21/0000Z 21.2N 49.5W 35 KT 40 MPH 24H 21/1200Z 22.3N 52.1W 30 KT 35 MPH 36H 22/0000Z 23.3N 54.8W 30 KT 35 MPH 48H 22/1200Z 24.2N 57.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 23/1200Z 26.2N 61.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 24/1200Z 28.2N 63.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 25/1200Z...DISSIPATED $$ Forecaster Cangialosi/Latto
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