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Tropical Storm Paulette Forecast Discussion Number 15
2020-09-10 16:38:10| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 10 2020 000 WTNT42 KNHC 101438 TCDAT2 Tropical Storm Paulette Discussion Number 15 NWS National Hurricane Center Miami FL AL172020 1100 AM AST Thu Sep 10 2020 The highest winds in a recent scatterometer pass have decreased a little since last evening, and they remain embedded within deep convection which is displaced to the north of the center of circulation. Paulette's intensity is estimated to have decreased to 45 kt based on this ASCAT pass and Dvorak CI numbers of 3.0/45 kt from both TAFB and SAB. The sheared convection has been tugging Paulette's center northward at times, causing wobbles in the estimated longer-term west-northwestward motion of 295/9 kt. For the next 4 days or so, fluctuations in the strength of the subtropical ridge to the north of Paulette will cause the cyclone's trajectory to vary between west-northwest and northwest, with a peak in forward speed around day 3. At the end of the forecast period, a mid-latitude trough is expected to move across the northeastern United States, with a mid-tropospheric high becoming established over the central Atlantic. This should allow Paulette to begin to recurve over the western Atlantic, turning northward by day 5. The only notable change in the track guidance on this cycle was a slight westward shift among some of the models on days 4 and 5, and the NHC track forecast follows suit, lying close to the HFIP Corrected Consensus (HCCA) aid. Southwesterly shear has increased over the cyclone as expected, with the latest UW-CIMSS analysis now between 35 and 40 kt. SHIPS diagnoses suggest that the shear over Paulette should peak in about 12 hours, thus a little more weakening is anticipated over the next day or so. The shear is then forecast to gradually abate, and both the GFS and ECMWF versions of the SHIPS guidance show the shear magnitudes decreasing to 10 kt or less in 3-4 days. This more favorable environment, combined with a more unstable air mass and sea surface temperatures exceeding 29 degrees Celsius, are expected to allow Paulette to restrengthen and become a hurricane as it moves in the vicinity of Bermuda. The new NHC intensity forecast has been raised a bit between days 2 and 4 compared to the previous prediction, although it still lies below the intensity consensus, IVCN, and the HCCA solutions. Therefore, additional upward adjustments to the forecast intensity may be required later today. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 21.5N 49.1W 45 KT 50 MPH 12H 11/0000Z 21.8N 50.7W 45 KT 50 MPH 24H 11/1200Z 22.6N 52.6W 40 KT 45 MPH 36H 12/0000Z 23.8N 54.4W 40 KT 45 MPH 48H 12/1200Z 25.4N 56.3W 45 KT 50 MPH 60H 13/0000Z 26.9N 58.4W 50 KT 60 MPH 72H 13/1200Z 28.0N 61.0W 60 KT 70 MPH 96H 14/1200Z 30.0N 65.0W 70 KT 80 MPH 120H 15/1200Z 32.5N 65.0W 75 KT 85 MPH $$ Forecaster Berg
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