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Tropical Storm Paulette Forecast Discussion Number 43
2020-09-22 22:51:08| National Hurricane Center (Atlantic)
Issued at 900 PM GMT Tue Sep 22 2020 000 WTNT41 KNHC 222050 TCDAT1 Tropical Storm Paulette Discussion Number 43 NWS National Hurricane Center Miami FL AL172020 900 PM GMT Tue Sep 22 2020 Although Paulette lacks the typical definition for deep convection, there remains some convection with cloud tops to -20 deg C encircling an eye-like feature noted in the lower cloud layer. Given the low tropopause level across that portion of the Atlantic basin causing the relatively low cloud tops, Paulette is being maintained as a tropical cyclone for at least this cycle. Vertical wind shear near 30 kt along with sea-surface temperatures of 23-22 deg C are expected to result in a gradual weakening and spin down of Paulette's circulation throughout the forecast period. As a result, the small cyclone should become a remnant low on Wednesday and dissipate by Friday or Saturday when the shallow system will be moving westward into westerly mid-level shear. Paulette is moving eastward or 080/10 kt. This general motion is forecast to continue through Wednesday as Paulette remains embedded within deep-layer westerly flow on the east side of mid- to upper-level trough. As Paulette weakens and becomes more vertically shallow, the post-tropical cyclone is expected to slow down in the 36-48 time period and turn southward. Thereafter, Paulette should be steered westward by low-level easterly flow on the south side of the Bermuda-Azores High. The new NHC track forecast is similar to the previous advisory track, and essentially lies down the middle of the NHC track guidance models. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 34.8N 21.2W 35 KT 40 MPH 12H 23/0600Z 35.0N 19.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 23/1800Z 35.4N 17.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 24/0600Z 35.3N 16.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 24/1800Z 34.7N 16.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 25/0600Z 33.6N 19.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 25/1800Z 32.8N 22.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 26/1800Z...DISSIPATED $$ Forecaster Stewart
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Tropical Depression Beta Forecast Discussion Number 21
2020-09-22 22:43:11| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Tue Sep 22 2020 000 WTNT42 KNHC 222043 TCDAT2 Tropical Depression Beta Discussion Number 21 NWS National Hurricane Center Miami FL AL222020 400 PM CDT Tue Sep 22 2020 High-resolution visible satellite imagery, surface observations, and NOAA Doppler weather radar data from San Antonio and Houston, Texas, indicate that Beta has continued to weaken. What convection remains is quite shallow with a few cloud tops only extending up to 25,000- 30,000 ft ASL, mainly near and northeast of the center. However, those low-topped showers are quite prodigious rain-producers with rainfall totals of 13-14 inches having been measured across portions of the Houston metropolitan area thus far. The initial intensity of 25 kt is based on near-shore buoy and surface observing stations. The initial motion estimate is now 065/04 kt. A coastal convergence zone or trough has formed about 20-25 nmi inland from the Texas Gulf coast and, owing to the lack of any significant deep-layer steering flow, Beta is forecast to move slowly along that trough axis and remain inland throughout the forecast period as a result. The ECMWF and UKMET models move Beta rapidly northeastward after 48 hours, but that scenario seems to be overdone given the expected shallow nature of the cyclone. The new NHC official track forecast is similar to the previous advisory track and lies close to a blend of the various consensus models, except that I used the slower forward speed of the GFS model. Since Beta is forecast to remain inland for the next throughout the forecast period, the cyclone is not expected to regain tropical storm status. Beta to degenerate into a remnant low by 36 hours, and dissipate over Mississippi or Alabama in 96 hours, if not sooner. The new intensity forecast is similar to the previous advisory and closely the simple and corrected-consensus models IVCN and HCCA. This is the last NHC advisory on Beta. Future information on this system, including the rainfall threat, can be found in Public Advisories issued by the Weather Prediction Center beginning at 10 PM CDT, under AWIPS header TCPAT2, WMO header WTNT32 KWNH, and on the web at http://www.wpc.ncep.noaa.gov Key Messages: 1. Significant flash and urban flooding is occurring and will continue for the middle and upper Texas coast today. The slow motion of Beta will continue to produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and minor to isolated moderate river flooding is likely. Periods of rainfall will spread east into the Lower Mississippi Valley, portions of the Tennessee Valley, and the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible on smaller rivers. 2. Persistent onshore flow will continue to result in above normal high tides, and coastal flooding over the next few days will be slow to recede. For information on the ongoing coastal flooding, please refer to coastal flood products issued by local National Weather Service offices. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 29.0N 96.3W 25 KT 30 MPH 12H 23/0600Z 29.3N 95.6W 25 KT 30 MPH...INLAND 24H 23/1800Z 30.1N 94.2W 25 KT 30 MPH...INLAND 36H 24/0600Z 31.3N 92.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 24/1800Z 32.5N 90.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 25/0600Z 33.8N 88.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 25/1800Z 35.1N 87.3W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 26/1800Z...DISSIPATED $$ Forecaster Stewart
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Tropical Storm Lowell Forecast Discussion Number 9
2020-09-22 22:35:04| Tropical Depression LIDIA
Issued at 200 PM PDT Tue Sep 22 2020
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Hurricane Teddy Forecast Discussion Number 41
2020-09-22 17:00:06| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Tue Sep 22 2020 000 WTNT45 KNHC 221459 TCDAT5 Hurricane Teddy Discussion Number 41 NWS National Hurricane Center Miami FL AL202020 1100 AM AST Tue Sep 22 2020 Teddy is in the late stages of extratropical transition. The hurricane has taken on a large comma shape in satellite images, with a huge dry-air intrusion aloft near the center and a cold front on the western side of the cyclone. While it is tempting to call it an extratropical now, temperature data from a NOAA Hurricane Hunter aircraft indicate that Teddy has maintained a significant warm core, and the strongest winds on the southwestern side appear to be more related to the cyclone and not the front. Lastly, deep convection is trying to re-develop near the center, another indication that the transition is not yet done. Thus Teddy will remain a hurricane on this advisory. The initial wind speed is set to 90 kt, a blend of the 122-kt flight-level winds, 75-kt SFMR values, and global model analyses since much of this large hurricane is not being sampled. Teddy should transition into a post-tropical cyclone by the time it reaches Nova Scotia and steadily weaken as it moves over the cooler waters north of the Gulf Stream. The cyclone should turn northward today and north-northeastward tomorrow ahead of the next trough in the mid-latitudes. This will take Post-Tropical Teddy over Nova Scotia and near Newfoundland during the next couple of days, with the cyclone likely being absorbed into a larger extratropical cyclone west of Greenland in 2-3 days. There are no significant changes to report, except to show a sooner dissipation, which is consistent with the latest global models solutions. The hurricane-force and tropical-storm-force winds fields, plus 12-ft seas area, from Teddy have just about doubled overnight, so it is important to note that hazards will extend much farther than normal from the center of this hurricane. The NOAA Hurricane Hunter reported hurricane-force surface winds 120 n mi northwest of the center, and Canadian buoy 44150 has recently reported 34-ft significant wave heights, with the buoy still about 180 n mi from the center. Key Messages: 1. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada late today through Thursday. The most significant hazard expected from Teddy is large destructive waves forecast along the southern coast of Nova Scotia through Wednesday. 2. Very large swells produced by Teddy are expected to affect portions of Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, the east coast of the United States, and Atlantic Canada during the next few days. These swells are expected to cause life-threatening surf and rip current conditions. 3. Tropical Storm Watches and Warnings are in effect for portions of Nova Scotia, Prince Edward Island and Newfoundland, and heavy rainfall across Atlantic Canada is expected with Teddy through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 39.6N 63.7W 90 KT 105 MPH 12H 23/0000Z 41.8N 64.1W 75 KT 85 MPH 24H 23/1200Z 44.8N 62.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 24/0000Z 48.8N 59.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 24/1200Z 54.0N 54.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 25/0000Z...DISSIPATED $$ Forecaster Blake
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Tropical Depression Beta Forecast Discussion Number 20
2020-09-22 16:59:06| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Tue Sep 22 2020 000 WTNT42 KNHC 221458 TCDAT2 Tropical Depression Beta Discussion Number 20 NWS National Hurricane Center Miami FL AL222020 1000 AM CDT Tue Sep 22 2020 High-resolution visible satellite imagery, surface observations, and NOAA Doppler weather radar data from San Antonio, Corpus Christi, and Houston, Texas, indicate that Beta has moved a little farther inland and has weakened to a tropical depression. The same data also show that Beta has started a slow drift toward the northeast. Deep convection has waned considerably since the previous advisory, especially during the past few hours, with cloud tops now warmer than -30 deg C, which no longer meets the Dvorak satellite classification criterion. The initial intensity is 30 kt is based on average Doppler velocities of 35-40 kt between 1500-2500 ft ASL just to the southeast and south of Galveston. The initial motion estimate is now 045/02 kt. Steering currents around Beta remain weak. However, water vapor imagery indicates that a broad mid- to upper-level trough over western Texas is moving slowly eastward, and that feature should gradually force Beta east-northeastward later today and tonight, followed by a faster motion toward the northeast on Wednesday and Thursday across Louisiana and Mississippi before dissipating in about 4 days. The new NHC forecast track is similar to the previous advisory track, which keeps Beta just inland from the Gulf coast, and lies near a blend of the simple consensus models TVCA and GFEX, and the NOAA corrected-consensus model HCCA. Since Beta's center is forecast to remain just inland for the next 36-48 hours, chances of the cyclone regaining tropical storm status are becoming less likely. As a result, the new official intensity forecast shows Beta remaining a 25-30 kt depression during that time, followed by weakening to a remnant low by 48 hours, and dissipation over Mississippi or Alabama by 96 hours. This is consistent with the various simple and corrected-consensus models. Although Beta is now an inland tropical depression, the National Hurricane Center will continue to issue advisories on the cyclone due to its proximity to the Gulf of Mexico and until it becomes clear that re-strengthening into a tropical storm is unlikely. Key Messages: 1. Significant flash and urban flooding is occurring and will continue for the middle and upper Texas coast today. The slow motion of Beta will continue to produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and minor to isolated moderate river flooding is likely. Periods of rainfall will spread east into the Lower Mississippi Valley and portions of the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible on smaller rivers. 2. Persistent onshore flow will continue to result in above normal high tides, and coastal flooding over the next few days will be slow to recede. For information on the ongoing coastal flooding, please refer to coastal flood products issued by local National Weather Service offices. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 28.9N 96.7W 30 KT 35 MPH...INLAND 12H 23/0000Z 29.0N 96.3W 30 KT 35 MPH...INLAND 24H 23/1200Z 29.6N 95.1W 30 KT 35 MPH...INLAND 36H 24/0000Z 30.4N 93.7W 25 KT 30 MPH...INLAND 48H 24/1200Z 31.7N 92.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 25/0000Z 33.1N 90.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 25/1200Z 34.4N 88.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 26/1200Z...DISSIPATED INLAND $$ Forecaster Stewart
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