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Tropical Storm Lorenzo Forecast Discussion Number 8
2019-09-24 22:48:40| National Hurricane Center (Atlantic)
Issued at 500 PM AST Tue Sep 24 2019 000 WTNT43 KNHC 242048 TCDAT3 Tropical Storm Lorenzo Discussion Number 8 NWS National Hurricane Center Miami FL AL132019 500 PM AST Tue Sep 24 2019 Based on recent microwave imagery and visible satellite loops, it appears that there's been just enough westerly shear over Lorenzo to disrupt the inner core and keep the storm from strengthening through the day. The CDO is slightly offset from the low-level center, and prominent convective banding is mostly within the southeastern semicircle. Subjective intensity estimates remain T3.5/55 kt from TAFB and SAB, and objective numbers have come up slightly to around 60 kt. However, since the morning scatterometer data was running about 10 kt lower than the satellite estimates, and the overall structure has not changed appreciably, the initial intensity will remain 55 kt. A mid-level high centered west of Madeira and the Canary Islands continues to drive Lorenzo quickly westward, or 285/15 kt. There has been no change to the track forecast thinking. A break in the ridge over the central Atlantic is expected to cause Lorenzo to begin recurving in about 48 hours, with the system ultimately moving northward by the end of the foreast period. The updated NHC forecast has only been nudged westward, but this is mainly due to the slightly faster initial forward motion. Otherwise, the spread in the guidance is still bounded by the GFS on the right and the ECMWF on the left, which is mirrored by those models' respective ensemble members. The official forecast hedges toward the western side of the guidance, roughly between the HCCA model and the other consensus aids. Global model guidance suggests that the westerly shear over Lorenzo should abate during the next 24 hours, allowing another intensification phase to begin. Whether or not rapid intensification occurs is difficult to know at this point until it becomes clearer if the cyclone can develop a well-defined inner core. The intensity guidance has decreased further on this cycle, but this is largely due to the hiatus in the strengthening trend during the day. There's still plenty of time for more strengthening to occur, so out of an abundance of caution, I did not lower the forecast peak intensities that have been shown in the previous few advisories. As such, the official forecast lies above nearly all the guidance during the first 2-3 days, and then is close to the HWRF and HCCA on days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 12.8N 31.0W 55 KT 65 MPH 12H 25/0600Z 13.2N 33.0W 65 KT 75 MPH 24H 25/1800Z 13.8N 35.6W 75 KT 85 MPH 36H 26/0600Z 14.5N 38.1W 85 KT 100 MPH 48H 26/1800Z 15.6N 40.0W 90 KT 105 MPH 72H 27/1800Z 18.8N 42.9W 100 KT 115 MPH 96H 28/1800Z 21.9N 45.1W 105 KT 120 MPH 120H 29/1800Z 24.9N 45.3W 100 KT 115 MPH $$ Forecaster Berg
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