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Tropical Storm Paulette Forecast Discussion Number 42

2020-09-22 16:49:36| National Hurricane Center (Atlantic)

Issued at 300 PM GMT Tue Sep 22 2020 000 WTNT41 KNHC 221449 TCDAT1 Tropical Storm Paulette Discussion Number 42 NWS National Hurricane Center Miami FL AL172020 300 PM GMT Tue Sep 22 2020 The last of the deep convection near the center of Paulette dissipated early this morning, and the circulation now consists of low-topped shower activity with the cloud tops warmer than -30 degrees C. The nearest shower activity that could qualify as deep convection is nearly 100 n mi from the cyclone's center and appears to be associated with a frontal boundary. A pair of recent ASCAT overpasses sampled peak winds of 33 kt, and therefore the initial advisory intensity is being lowered to 35 kt. Moderate-to-strong vertical wind shear and cool sea surface temperatures are expected to continue to weaken Paulette, and the cyclone is forecast to become a remnant low within 36 h. If the deep convection does not return to Paulette soon, then the cyclone could be declared a remnant low by as early as this evening. Paulette is moving eastward at 12 kt, and this general motion is expected to continue through Wednesday as the cyclone remains embedded in the flow around a mid-latitude trough to its north. The trough is expected to lift out of the region in about 36 h, and a ridge is forecast to build in its place in a couple of days. This evolution should cause Paulette, or its remnants, to slow down and make a 180 degree right turn over the course of a couple of days. By late week, whatever is left of the cyclone should be moving west-southwestward. An alternate scenario depicted by a couple of the models is that Paulette never escapes the flow around the trough and continues to move east-northeast until it dissipates. The latest NHC track forecast is in good agreement with the previous one, but is somewhat uncertain after 36 h due to the diverging model solutions. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 35.0N 22.3W 35 KT 40 MPH 12H 23/0000Z 35.2N 20.3W 35 KT 40 MPH 24H 23/1200Z 35.6N 18.1W 30 KT 35 MPH 36H 24/0000Z 35.9N 16.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 24/1200Z 35.6N 15.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 25/0000Z 34.9N 15.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 25/1200Z 33.9N 18.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 26/1200Z...DISSIPATED $$ Forecaster Latto

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Tropical Storm Lowell Forecast Discussion Number 8

2020-09-22 16:44:03| Tropical Depression LIDIA

Issued at 800 AM PDT Tue Sep 22 2020

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Tropical Storm Paulette Forecast Discussion Number 41

2020-09-22 11:00:34| National Hurricane Center (Atlantic)

Issued at 900 AM GMT Tue Sep 22 2020 000 WTNT41 KNHC 220900 TCDAT1 Tropical Storm Paulette Discussion Number 41 NWS National Hurricane Center Miami FL AL172020 900 AM GMT Tue Sep 22 2020 The tops of Paulette's convective clouds have been warming since the previous advisory, and first-light visible images show that a swirl of low- to mid-level clouds is about all that is left. The estimated maximum winds remain 50 kt based on last evening's ASCAT pass, but that value could be generous given the degraded convective structure. New scatterometer passes this morning should give us a better idea of how the winds have changed. Moderate to strong vertical wind shear and cool sea surface temperatures are expected to induce weakening over the next couple of days, and Paulette is expected to become post-tropical by 48 hours. If convection does not redevelop later today, the transition to a post-tropical cyclone would likely occur before 48 hours. The remnant low is expected to dissipate by day 5. Paulette is moving toward the east-northeast, or 065/15 kt. This motion is expected to continue for the next 36 hours. After that time, there is significant model divergence, with several models (such as the GFS) taking Paulette to the Iberian Peninsula while others (such as the ECMWF) stop it on a dime and turn it westward. The latter solution appears more realistic since a shallow convection-less low would be steered toward the west by ridging to the north. The NHC forecast is a blend of the previous interpolated official forecast and the HCCA consensus aid. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 34.7N 23.7W 50 KT 60 MPH 12H 22/1800Z 35.1N 21.5W 45 KT 50 MPH 24H 23/0600Z 35.4N 19.0W 45 KT 50 MPH 36H 23/1800Z 35.8N 17.0W 40 KT 45 MPH 48H 24/0600Z 35.6N 16.3W 35 KT 40 MPH...POST-TROPICAL 60H 24/1800Z 34.9N 16.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 25/0600Z 34.3N 17.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 26/0600Z 33.3N 21.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 27/0600Z...DISSIPATED $$ Forecaster Berg

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Tropical Storm Lowell Forecast Discussion Number 7

2020-09-22 10:59:56| Tropical Depression LIDIA

Issued at 200 AM PDT Tue Sep 22 2020

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Tropical Storm Beta Forecast Discussion Number 19

2020-09-22 10:57:56| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Tue Sep 22 2020 949 WTNT42 KNHC 220857 TCDAT2 Tropical Storm Beta Discussion Number 19 NWS National Hurricane Center Miami FL AL222020 400 AM CDT Tue Sep 22 2020 Beta's center has continued to move farther inland since making landfall on the southern end of the Matagorda Peninsula around 10 PM CDT last evening. There have not been any surface observations of sustained tropical-storm-force winds, and an earlier ASCAT pass indicated that winds over the water had decreased to near 35 kt. That is Beta's estimated intensity at the moment, with the assumption that those winds are still occurring somewhere over water or within the deep convection near the center. Beta has been moving northwestward, or 315/3 kt. Steering currents around the storm are now collapsing, and Beta is expected to meander during the next 12-24 hours. By this time tomorrow, however, a mid-level trough over west Texas is forecast to begin moving eastward and should scoop Beta up, causing the storm to move toward the east-northeast near or just inland of the upper Texas coast through 36 hours. After that time, Beta is expected to turn northeastward, moving farther inland across Louisiana and Mississippi before dissipating in about 4 days. Because Beta has moved a little farther inland than expected, much of the model trackers have shifted northward, and now only the UKMET and its ensemble mean show Beta's center re-emerging over the extreme northwestern Gulf of Mexico. The new NHC track forecast has been adjusted northward accordingly and generally lies between the HCCA aid and the TVCN multi-model consensus. Now that Beta's center may not move back out over the Gulf, the intensity guidance indicates that the cyclone will gradually weaken during the next few days. However, since a part of the circulation will remain over water and the system could still produce deep convection, the NHC forecast shows Beta maintaining tropical storm status for another 12 hours or so (a scenario which is above all of the guidance). Beta should weaken to a tropical depression in about 24 hours, and it is expected to become a remnant low in 2-3 days when vertical shear is expected to be well over 30 kt. 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 river flooding is likely. Periods of rainfall will continue into the ArkLaTex region and 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. 2. Storm surge flooding will continue throughout the morning, around the times of high tide along portions of the Texas coast within the storm surge warning areas. Residents in these areas should continue to follow advice of local officials. 3. Tropical-storm-force winds will continue near portions of the Texas coast within the warning area today. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 28.8N 96.7W 35 KT 40 MPH...INLAND 12H 22/1800Z 28.8N 96.5W 35 KT 40 MPH...INLAND 24H 23/0600Z 29.1N 95.6W 30 KT 35 MPH...INLAND 36H 23/1800Z 29.8N 94.3W 30 KT 35 MPH...INLAND 48H 24/0600Z 30.8N 92.8W 25 KT 30 MPH...INLAND 60H 24/1800Z 32.1N 90.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 25/0600Z 33.6N 89.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 26/0600Z...DISSIPATED $$ Forecaster Berg

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