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Tropical Storm Lorenzo Forecast Discussion Number 9
2019-09-25 04:36:48| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Tue Sep 24 2019 000 WTNT43 KNHC 250236 TCDAT3 Tropical Storm Lorenzo Discussion Number 9 NWS National Hurricane Center Miami FL AL132019 1100 PM AST Tue Sep 24 2019 Over the past several hours, deep convection has increased in coverage and intensity near Lorenzo's center, with cloud tops now as cold as -85 degrees Celsius. Some modest northwesterly shear impacted the cyclone starting early today and lasted through this evening, but now Lorenzo seems to be overcoming the shear. The initial intensity has been increased to 60 kt and this is a blend of the latest subjective Dvorak estimates from TAFB and SAB. Recent scatterometer passes show that the wind radii have continued to expand, with tropical storm force winds now reaching up to 180 n mi from the center. Lorenzo is moving west-northwestward at 14 kt to the south of a mid-level ridge. A break in the ridge is forecast to develop between 40-50W in a few days, which should cause the cyclone to turn to the northwest. By late in the forecast period, Lorenzo will turn to the north as it rounds the western periphery of the ridge. This forecast track scenario is in very good agreement with the numerical models, and little change was made from the previous official forecast. The shear that has been occurring over Lorenzo is expected to decrease through Wednesday, and based on the current convective trend, strengthening appears likely over the next couple of days. Dynamical and statistical models are in good agreement on bringing Lorenzo to hurricane intensity by Wednesday morning, and then continuing some gradual strengthening through 72 hours. After that time, the dynamical model intensity forecasts diverge from the statistical model forecasts. SHIPS and LGEM suggest that Lorenzo will reach its peak intensity in about 3 or 4 days, and weakening is possible by day 5. The dynamical models disagree with this scenario, and the consensus of those models makes Lorenzo a major hurricane in about 72 hours, with additional strengthening possible through the end of the forecast period. The official forecast is more in line with the dynamical guidance, although it is not as high as some of those solutions late in the period. Due to the divergence in model intensity forecasts beyond 72 hours, the confidence in the official forecast at that time is not high. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 13.2N 32.4W 60 KT 70 MPH 12H 25/1200Z 13.6N 34.4W 70 KT 80 MPH 24H 26/0000Z 14.2N 37.0W 80 KT 90 MPH 36H 26/1200Z 15.1N 39.1W 90 KT 105 MPH 48H 27/0000Z 16.4N 40.9W 95 KT 110 MPH 72H 28/0000Z 19.9N 43.6W 100 KT 115 MPH 96H 29/0000Z 23.0N 45.5W 105 KT 120 MPH 120H 30/0000Z 26.0N 45.0W 105 KT 120 MPH $$ Forecaster Latto
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