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| #875620 (Received by flhurricane at: 4:40 PM 22.Sep.2016) TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 500 PM AST THU SEP 22 2016 Strong vertical shear from an upper-level low near 24N 40W continues to plague Lisa, with the low-level center located to the southwest of the deep convection as seen in a 1749Z SSMIS overpass. The initial intensity remains 45 kt based on the earlier ASCAT data and the latest Dvorak estimate from SAB. UW-CIMSS analysis shows that the shear is already over 40 kt and the SHIPS model shows it near or above this value for the next 36 hours, which should result in weakening. The official forecast follows that trend and is close to the latest SHIPS guidance through 48 hours. After that time, Lisa is expected to remain a 30-kt post-tropical cyclone through 5 days. Even though the shear diminishes in about 72 hours, the mid-level relative humidity remains below 50 percent, and it is assumed that Lisa will be too weak to take advantage of the lower shear. The initial motion estimate is 320/07. Lisa is expected to continue moving northwestward into a break in the subtropical ridge for the next 48 hours. Beyond that time, Lisa or its remnants should recurve ahead of a large mid-latitude trough. The new NHC track forecast is basically an update of the previous one and is along the eastern edge of the latest guidance envelope. There continues to be a fair bit of along-track spread in the guidance late in the period, with the GFS now faster than the other guidance. The NHC forecast has been adjusted a little faster this cycle but is slower than the GFS and close to the latest guidance from the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 20.7N 34.5W 45 KT 50 MPH 12H 23/0600Z 21.8N 35.6W 40 KT 45 MPH 24H 23/1800Z 23.2N 37.0W 35 KT 40 MPH 36H 24/0600Z 24.4N 38.5W 30 KT 35 MPH 48H 24/1800Z 25.6N 40.1W 30 KT 35 MPH 72H 25/1800Z 29.5N 41.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 26/1800Z 34.0N 38.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 27/1800Z 42.5N 30.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan |
