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Tropical Storm LISA Forecast Discussion Number 6
2016-09-21 04:41:08| National Hurricane Center (Atlantic)
Issued at 1100 PM AST TUE SEP 20 2016 000 WTNT43 KNHC 210241 TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 1100 PM AST TUE SEP 20 2016 Deep convection has increased in coverage near and to the northeast of the center of Lisa this evening. Although the exact center has been difficult to pinpoint in infrared satellite images, it appears that it is located near the southwestern edge of the convection due to some southwesterly shear. Satellite intensity estimates still support a wind speed of around 40 kt, so the initial intensity is unchanged for this advisory. Lisa has about 24 hours over warm water and in a marginally conducive upper-level wind environment in which to strengthen. After that time, an upper-level low to Lisa's northwest is expected to produce strong southwesterly shear over the cyclone, which should cause weakening. As a result, the NHC intensity forecast calls for peak intensity in about 24 hours, followed by steady weakening thereafter. The official forecast is near the upper-end of the guidance at 24 hours, but is slightly lower than the consensus after that time. The somewhat uncertain initial motion estimate is 315/9 kt. The track forecast appears to be fairly straight forward as Lisa should continue moving northwestward during the next several days toward a break in the subtropical ridge. Late in the forecast period, the cyclone should turn northward ahead of a deepening mid- to upper-level trough over the west-central Atlantic. The dynamical models are in good agreement on this scenario, and the NHC forecast is near a blend of the typically better performing ECMWF and GFS models. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 17.1N 31.7W 40 KT 45 MPH 12H 21/1200Z 17.8N 32.7W 45 KT 50 MPH 24H 22/0000Z 18.6N 34.0W 50 KT 60 MPH 36H 22/1200Z 19.4N 35.2W 45 KT 50 MPH 48H 23/0000Z 20.6N 36.7W 40 KT 45 MPH 72H 24/0000Z 23.6N 39.8W 30 KT 35 MPH 96H 25/0000Z 26.5N 42.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 26/0000Z 31.0N 43.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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