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Tropical Storm Beta Forecast Discussion Number 6
2020-09-19 04:58:25| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Fri Sep 18 2020 000 WTNT42 KNHC 190258 TCDAT2 Tropical Storm Beta Discussion Number 6 NWS National Hurricane Center Miami FL AL222020 1000 PM CDT Fri Sep 18 2020 An Air Force Reserve Hurricane Hunter aircraft investigating Beta this evening found that the center has re-formed or been tugged northeastward by bursts of strong convection. While flying through that convection, the plane measured a peak flight-level wind of 57 kt at 10,000 feet before descending to 2500 feet. To the northwest of the center, the SFMR instrument on the plane measured a solid area of 46-48 kt, and there have been multiple ship reports in the region of 40-45 kt. Based on all these data, Beta's initial intensity is estimated to be 50 kt. The plane reported an extrapolated minimum pressure of 996 mb on the last pass through the center, which also corresponds to a typical 50-kt tropical storm. The aircraft fixes indicate that Beta is moving north-northeastward, or 030/10 kt. This motion is expected to continue for the next 12 hours or so, but as mid-level ridging develops over the Southern Plains on Saturday, Beta should begin to slow down and turn westward. A slow motion in the direction of the Texas coast should continue through day 3, with a shortwave trough possibly causing the cyclone to recurve and move northeastward near or along the Texas coast on days 4 and 5. While there remains a large amount of spread among the track models, they all agree on this general scenario and indicate that Beta is likely to move very slowly as it makes its closest approach to the Texas coast. The initial position fixed by the plane necessitated a northward shift in the NHC official forecast compared to the previous forecast for the first 3 days, but it comes back in line with the previous prediction on days 4 and 5. Beta has been able to strengthen despite being affected by strong southwesterly shear. The shear could begin to relax over the next few days, particularly by day 2 and 3, which could allow for some further strengthening. The SHIPS guidance remains the most aggressive of the intensity models, and the NHC intensity forecast leans heavily toward those solutions given Beta's recent intensification trend (which SHIPS seemed to handle better). Beta is forecast to steadily strengthen and become a hurricane in a couple of days as it approaches the Texas coast. Some weakening is forecast on days 4 and 5 due to another increase in southwesterly shear and possible land interaction. Key Messages: 1. There is an increasing risk of heavy rainfall and flooding along the northwest Gulf Coast Sunday through at least the middle of next week as Beta is forecast to move slowly toward and along or offshore of the coast through that time. For additional information, see products from your local National Weather Service office. 2. Life-threatening storm surge and hurricane-force winds are possible along portions of the Texas coast early next week, with tropical storm conditions possible by late this weekend. Storm Surge and Hurricane watches are in effect, and residents in these areas should ensure they have their hurricane plan in place and follow advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 25.5N 92.3W 50 KT 60 MPH 12H 19/1200Z 26.3N 92.2W 55 KT 65 MPH 24H 20/0000Z 26.8N 92.8W 60 KT 70 MPH 36H 20/1200Z 26.8N 93.7W 65 KT 75 MPH 48H 21/0000Z 27.0N 94.6W 70 KT 80 MPH 60H 21/1200Z 27.4N 95.5W 70 KT 80 MPH 72H 22/0000Z 27.8N 96.0W 70 KT 80 MPH 96H 23/0000Z 28.4N 95.8W 65 KT 75 MPH 120H 24/0000Z 29.4N 94.1W 55 KT 65 MPH $$ Forecaster Berg
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