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| #984363 (Received by flhurricane at: 5:09 AM 28.Sep.2019) TCDAT3 Hurricane Lorenzo Discussion Number 23 NWS National Hurricane Center Miami FL AL132019 500 AM AST Sat Sep 28 2019 Lorenzo`s tilt has grown this morning. AMSR2 imagery at 0505 UTC showed a 20 n mi displacement between the low- and mid-level centers of the hurricane, a consequence of persistent westerly wind shear. Satellite-based intensity estimates vary greatly, from 77 to 110 kt, so the intensity is set to 100 kt as a compromise of all available data. Despite the decrease in Lorenzo`s maximum winds during the past 24 hours, earlier ASCAT-C data showed that its hurricane-force wind field has expanded, and now reaches up to 45 n mi to the northeast of the center. The lower initial intensity resulted in a slightly lower intensity forecast through most of the period. The wind shear affecting the cyclone is forecast to continue, and a slow decrease in Lorenzo`s peak winds is still expected during the next several days. The official intensity forecast is very near the intensity consensus. Despite the expected decrease in intensity, the hurricane is not forecast to decrease in size, and in fact Lorenzo`s hurricane-force wind field could increase further by next week. Because of that, users are urged to not focus on the exact intensity of Lorenzo since the cyclone will likely remain a powerful storm well into next week. By 120 h, all of the global models indicate that Lorenzo will become post-tropical, and so does the NHC forecast. The aforementioned microwave data was very helpful in identifying Lorenzo`s center location. The hurricane has continued to move left of the forecast track, and the initial motion estimate is 330/9 kt. Despite Lorenzo`s recent tendency to move farther west than anticipated, the hurricane is still forecast to turn northward soon. After continuing northward and north-northeastward for a day or two, Lorenzo should accelerate toward the northeast ahead of a deep mid-latitude trough approaching from the west by mid-week. The NHC track forecast has been shifted slightly left for the first 48 h to account for Lorenzo`s recent motion, but it is very similar to the previous forecast at 72 h and beyond. The models are in excellent agreement for the first 3 days of the forecast but the uncertainty grows by the end of the period, primarily due to differences in the forecast forward speed of the cyclone as it recurves and becomes post-tropical. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 21.4N 44.8W 100 KT 115 MPH 12H 28/1800Z 22.7N 44.8W 95 KT 110 MPH 24H 29/0600Z 24.5N 44.7W 90 KT 105 MPH 36H 29/1800Z 26.0N 44.2W 90 KT 105 MPH 48H 30/0600Z 27.6N 43.5W 85 KT 100 MPH 72H 01/0600Z 31.5N 40.9W 85 KT 100 MPH 96H 02/0600Z 38.0N 32.5W 80 KT 90 MPH 120H 03/0600Z 48.0N 19.0W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky |