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Tropical Storm Paulette Forecast Discussion Number 13
2020-09-10 04:33:59| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Wed Sep 09 2020 191 WTNT42 KNHC 100233 TCDAT2 Tropical Storm Paulette Discussion Number 13 NWS National Hurricane Center Miami FL AL172020 1100 PM AST Wed Sep 09 2020 Paulette remains a sheared tropical cyclone with the low-level center southwest of a large area of deep convection. Recent scatterometer data showed peak winds of 45-50 kt, so 50 kt is used as the initial wind speed, which happens to be quite similar to a blend of the latest TAFB/SAB Dvorak estimates. Paulette should begin to weaken tomorrow and continue on a downward trend for 2-3 days as strong shear impacts the cyclone. No change has been made to the forecast through Saturday. Thereafter, the storm is likely to move into a lower-shear environment on the northeastern side of a mid/upper-level low, with SSTs rising to about 29C. There is better agreement among the models tonight that Paulette will survive the shear and be able to take advantage of that favorable environment. In fact, almost all of the most reliable guidance, save LGEM/SHIPS, show the storm becoming a hurricane by 120 hours, and the global models are trending in that direction. The new NHC forecast is raised from the previous one, near the model consensus, but isn't quite as high as the regional hurricane models. The storm is moving at about the same motion as before (295/9 kt). Paulette should turn westward tomorrow as it weakens and encounters stronger low/mid-level ridging. A weakness in the ridge develops by the weekend due to the aforementioned mid/upper-level low, which should cause the tropical cyclone to turn and move faster toward the northwest. The new NHC track forecast is very similar to the previous one, lying on the western side of the guidance after placing heavier weight on the global models and corrected-consensus aids than on the regional hurricane guidance. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 20.9N 48.1W 50 KT 60 MPH 12H 10/1200Z 21.3N 49.5W 50 KT 60 MPH 24H 11/0000Z 21.4N 51.5W 45 KT 50 MPH 36H 11/1200Z 21.9N 53.2W 40 KT 45 MPH 48H 12/0000Z 22.8N 54.6W 40 KT 45 MPH 60H 12/1200Z 24.1N 55.9W 40 KT 45 MPH 72H 13/0000Z 25.8N 57.3W 45 KT 50 MPH 96H 14/0000Z 29.0N 62.0W 55 KT 65 MPH 120H 15/0000Z 31.0N 65.0W 65 KT 75 MPH $$ Forecaster Blake
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Tropical Storm Rene Forecast Discussion Number 11
2020-09-09 22:34:28| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Sep 09 2020 000 WTNT43 KNHC 092034 TCDAT3 Tropical Storm Rene Discussion Number 11 NWS National Hurricane Center Miami FL AL182020 500 PM AST Wed Sep 09 2020 Although the cloud pattern of Rene has changed little in overall organization since earlier today, there are some indications that the easterly shear over the storm has diminished somewhat. Cirrus cloud motions show that upper-level outflow is slightly more evident over the eastern portion of the circulation, but it remains limited over that region. The current intensity estimate remains 35 kt in agreement with a Dvorak estimate from TAFB. Vertical shear is predicted to be modest over Rene during the next couple of days, and this should allow for some strengthening. The official intensity forecast is similar to the model consensus and continues to show the system becoming a hurricane, albeit briefly. After day 3, the western portion of a large upper-level trough over the eastern Atlantic is likely to impart increased shear, which should lead to weakening. Conventional satellite and microwave fixes show a continued west-northwestward motion at about 285/11 kt. Rene is currently located on the southwest side of a mid-level ridge over the eastern Atlantic. A weakness in the ridge in the vicinity of 40W-45W longitude should induce a turn toward the northwest and north-northwest in 3-5 days. By the end of the forecast period, Rene's forward progress begins to be blocked by building mid-level heights to its north and northwest, which should cause the cyclone's forward motion to slow down significantly. The official track forecast has been adjusted farther to the left of the previous one, to be closer to the latest model consensus. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 18.0N 32.7W 35 KT 40 MPH 12H 10/0600Z 18.4N 34.3W 40 KT 45 MPH 24H 10/1800Z 18.9N 36.2W 45 KT 50 MPH 36H 11/0600Z 19.5N 38.1W 50 KT 60 MPH 48H 11/1800Z 20.5N 40.0W 60 KT 70 MPH 60H 12/0600Z 21.7N 42.0W 65 KT 75 MPH 72H 12/1800Z 23.5N 43.8W 60 KT 70 MPH 96H 13/1800Z 26.9N 46.0W 50 KT 60 MPH 120H 14/1800Z 28.5N 47.0W 40 KT 45 MPH $$ Forecaster Pasch
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Tropical Storm Paulette Forecast Discussion Number 12
2020-09-09 22:31:58| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Sep 09 2020 000 WTNT42 KNHC 092031 TCDAT2 Tropical Storm Paulette Discussion Number 12 NWS National Hurricane Center Miami FL AL172020 500 PM AST Wed Sep 09 2020 Paulette's satellite presentation has not changed since this morning, with the center exposed just to the south of the deepest convection. Between this morning's ASCAT pass and the most recent satellite classifications from TAFB and SAB, which are unchanged at T3.0 and T3.5, respectively, the maximum wind estimate remains 50 kt. Paulette continues to move into an area of stronger southwesterly shear, which is now estimated to be 25-30 kt, and this shear is likely to increase further to 30-35 kt within the next 24 hours. As a result, Paulette is expected to begin weakening by Thursday, and the NHC forecast is embedded among the tightly clustered intensity guidance during the first 2-3 days. The shear is expected to relax gradually from 48 hours and beyond and turn out of the southeast, which should allow for some restrengthening on days 3 through 5 when shear magnitudes could go as low as 10 kt. The HWRF and COAMPS-TC models in particular take full advantage of this environment and bring Paulette to hurricane intensity by day 4. The updated NHC intensity forecast is not nearly this aggressive, but it does indicate a little more strengthening at the end of the forecast period than has been shown in previous forecasts, lying closest to the statistical-dynamical guidance. Model environmental trends will be monitored, and additional intensity adjustments at the end of the forecast period will be made accordingly in subsequent forecasts. Paulette remains on a west-northwestward course (295/9 kt), located to the south of low- to mid-level ridging which extends across the central and western Atlantic. The track models suggest that when the cyclone weakens in a day or two, lower-level winds could steer the cyclone westward for a short time. However, a combination of the ridge weakening and Paulette's expected re-strengthening should cause the cyclone to turn northwestward in 2-3 days and maintain that trajectory through the end of the forecast period. The only significant change from the previous forecast is that the 5-day forecast point has been shifted westward, with the GFS, ECMWF, HWRF, and HCCA models all lying on the left side of the guidance envelope by that time. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 20.5N 47.4W 50 KT 60 MPH 12H 10/0600Z 20.9N 48.9W 50 KT 60 MPH 24H 10/1800Z 21.4N 50.9W 45 KT 50 MPH 36H 11/0600Z 21.6N 52.7W 40 KT 45 MPH 48H 11/1800Z 22.3N 54.1W 40 KT 45 MPH 60H 12/0600Z 23.3N 55.4W 40 KT 45 MPH 72H 12/1800Z 24.8N 56.6W 45 KT 50 MPH 96H 13/1800Z 28.0N 60.5W 50 KT 60 MPH 120H 14/1800Z 30.5N 64.5W 55 KT 65 MPH $$ Forecaster Berg
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Tropical Storm Paulette Forecast Discussion Number 11
2020-09-09 16:59:55| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Sep 09 2020 000 WTNT42 KNHC 091459 TCDAT2 Tropical Storm Paulette Discussion Number 11 NWS National Hurricane Center Miami FL AL172020 1100 AM AST Wed Sep 09 2020 Morning visible satellite images show that Paulette's center is located beneath a thin veil of cirrus and displaced to the south of the deep convection. Based on a blend of Dvorak estimates from TAFB and SAB, and a recent ASCAT pass which showed an area of 45-50 kt winds northwest of the center, the initial intensity remains 50 kt. A large upper-level trough is located to the northwest of Paulette, and this feature is producing 20-30 kt of south-southwesterly shear over the cyclone. The shear is forecast to increase well over 30 kt during the next day or two as Paulette gets closer to the upper-level disturbance, which should cause the cyclone's maximum winds to gradually decrease through day 3. The shear is forecast to abate somewhat and back around from the southeast by days 4 and 5, which could allow Paulette to restrengthen a little bit over the subtropical Atlantic at that time. The new NHC intensity forecast is identical to the previous one and is generally close to the IVCN intensity consensus and the HCCA corrected consensus. Although Paulette has been hopscotching around a bit, likely being influenced by the sheared convection, the 12-hour motion is now toward the west-northwest (290/8 kt). Subtropical ridging to the north of Paulette is forecast to keep the cyclone on a westward or west-northwestward trajectory for the next 48 hours. After that time, the ridge is likely to weaken a bit, which should allow Paulette to move toward the northwest with some increase in forward speed on days 3 though 5. There is a typical amount of spread among the track models for this forecast, and while they all agree on the general future trajectory, there are some speed differences. In particular, the UKMET and HWRF start out much slower than the other models, and the ECWMF is much faster than the rest of the guidance by days 4 and 5. Relying on continuity and the model consensus aids, the updated NHC track forecast has been shifted very little from the previous prediction. The initial and forecast tropical-storm-force wind radii have been expanded based on the recent scatterometer data. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 20.0N 46.5W 50 KT 60 MPH 12H 10/0000Z 20.3N 48.0W 50 KT 60 MPH 24H 10/1200Z 20.7N 49.9W 45 KT 50 MPH 36H 11/0000Z 20.9N 51.6W 45 KT 50 MPH 48H 11/1200Z 21.3N 53.1W 40 KT 45 MPH 60H 12/0000Z 22.2N 54.3W 40 KT 45 MPH 72H 12/1200Z 23.5N 55.6W 40 KT 45 MPH 96H 13/1200Z 27.0N 59.0W 45 KT 50 MPH 120H 14/1200Z 30.0N 62.5W 50 KT 60 MPH $$ Forecaster Berg
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Tropical Storm Rene Forecast Discussion Number 10
2020-09-09 16:31:53| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Sep 09 2020 000 WTNT43 KNHC 091431 TCDAT3 Tropical Storm Rene Discussion Number 10 NWS National Hurricane Center Miami FL AL182020 1100 AM AST Wed Sep 09 2020 Although easterly shear has been affecting the system, Rene is producing vigorous deep convection, along with a broad convective band, over its western semicircle. Scatterometer data indicate winds to 35 knots over the northwestern quadrant, and therefore the system is again being designated as a tropical storm. The cyclone should be within an environment of moderate vertical shear, on the western side of an upper-level anticyclone, for the next couple of days. Therefore, gradual strengthening is forecast, and Rene is expected to become a hurricane late this week. By the weekend, increasing westerly shear should cause weakening. The official intensity forecast is a little above the model consensus. Rene is currently moving west-northwestward, or 285/11 kt, on the southern side of a mid-level ridge. A weakness in the ridge near 40W longitude is likely to cause the storm to turn toward the northwest in 2 to 3 days, followed by a turn toward the north-northwest. By the end of the forecast period, Rene's forward progress should slow as it encounters a block in the mid-level flow. As anticipated, the official track forecast is shifted to the left of the previous one, but not as far to the left as the latest corrected multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 17.6N 31.5W 35 KT 40 MPH 12H 10/0000Z 18.1N 33.1W 40 KT 45 MPH 24H 10/1200Z 18.8N 35.1W 45 KT 50 MPH 36H 11/0000Z 19.5N 37.0W 50 KT 60 MPH 48H 11/1200Z 20.4N 39.0W 60 KT 70 MPH 60H 12/0000Z 21.7N 40.9W 65 KT 75 MPH 72H 12/1200Z 23.5N 42.7W 60 KT 70 MPH 96H 13/1200Z 27.0N 44.5W 50 KT 60 MPH 120H 14/1200Z 28.7N 45.0W 40 KT 45 MPH $$ Forecaster Pasch
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