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Tropical Storm LISA Forecast Discussion Number 9
2016-09-21 22:39:17| National Hurricane Center (Atlantic)
Issued at 500 PM AST WED SEP 21 2016 000 WTNT43 KNHC 212039 TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 500 PM AST WED SEP 21 2016 Vertical wind shear of 15-20 kt continues to take a toll on Lisa. The coldest convective tops have moved farther east away from the estimated low-level center position today. Dvorak estimates were T2.5/3.0 from both TAFB and SAB at 18Z, and based on these, the initial intensity has been lowered to 40 kt for this advisory. Given that Lisa has struggled to maintain itself today, and that the SHIPS model shows the shear increasing to 30 kt in the next 18 to 24 hours, there seems to be little opportunity left for the cyclone to strengthen. Given this, the new NHC intensity forecast holds Lisa at 40 kt through 24 hours and then shows gradual weakening to remnant low status in 3 to 4 days as the shear increases to near 40 kt and the mid-level relative humidity drops below 30 percent. This forecast is closest to the SHIPS and LGEM statistical-dynamical models. An AMSR-2 pass from GCOM-W1 from around 1430Z provided some guidance on the center location, but it remains somewhat uncertain given the large spread in the satellite fixes. However, it does appear that the center is located a little to the east of previous estimates, and the initial motion is estimated to be 325/06. The track forecast scenario has not changed, as Lisa is expected to move northwestward into a weakness in the subtropical ridge and then recurve into the mid-latitude flow during the forecast period. Overall, the guidance envelope has shifted eastward this cycle, and given the eastward adjustment in the initial position, the NHC forecast has been shifted eastward by about a degree. The official forecast track is close to a blend of the GFS and ECMWF and lies to the left of multi-model consensus TVCN. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 18.5N 32.5W 40 KT 45 MPH 12H 22/0600Z 19.4N 33.3W 40 KT 45 MPH 24H 22/1800Z 20.8N 34.7W 40 KT 45 MPH 36H 23/0600Z 22.1N 36.0W 35 KT 40 MPH 48H 23/1800Z 23.5N 37.2W 30 KT 35 MPH 72H 24/1800Z 26.0N 40.0W 30 KT 35 MPH 96H 25/1800Z 30.0N 41.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 26/1800Z 36.0N 38.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan
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