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Tropical Storm Beta Forecast Discussion Number 7
2020-09-19 10:54:01| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Sat Sep 19 2020 000 WTNT42 KNHC 190853 TCDAT2 Tropical Storm Beta Discussion Number 7 NWS National Hurricane Center Miami FL AL222020 400 AM CDT Sat Sep 19 2020 Beta has generally changed little overnight. The storm is still quite asymmetric due to southwesterly wind shear with the low-level center located near the southwestern edge of the main area of deep convection. An ASCAT pass from a few hours ago showed peak winds in the 40-45 kt range, with most of the tropical-storm-force winds on the north side of the circulation. In addition, the latest Dvorak classifications are 3.0/45 kt from TAFB and SAB. The initial intensity of 50 kt, based on the earlier aircraft data, is a little above the satellite estimates. The Air Force Hurricane Hunters are scheduled to investigate Beta again later this morning, and the data they collect will provide a better estimate of the intensity and structure of the storm. Beta is moving northward, with the latest initial motion estimated to be 360/7 kt. The shortwave trough that has been causing the north to northeastward motion during the past day or so is moving away and a weak mid-level ridge is expected to build to the north of the storm soon. This change in the steering pattern should cause Beta to turn westward and slow down later today and then move generally westward to northwestward through the remainder of the weekend and into early next week. This motion should take Beta toward the Texas coast by Monday. Around the time Beta is forecast to be near the Texas coastline, the ridge is expected to retreat as another shortwave trough approaches, which should cause the storm to slow down even more and gradually turn to the northeast near the Texas coast by the middle of next week. The models are in fair agreement, and the NHC track forecast lies close to the various consensus aids. As mentioned above, the tropical storm is still feeling some effects of southwesterly wind shear, but the upper-level pattern is expected to become more favorable for strengthening later today. Although the shear is expected to lessen, water vapor images show a swath of dry air approaching the storm from the west. Based on these mixed environmental conditions, slow strengthening is forecast during the next couple of days and Beta is forecast to reach hurricane intensity in about 36 hours. Beyond a few days, the models suggest that there could be another increase in southwesterly shear, which in combination with land interaction should cause some weakening. Of course, the rate of weakening will depend on whether Beta is inland or offshore. The NHC intensity forecast is largely an update of the previous one and lies at the high end of the model guidance. 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 19/0900Z 26.0N 92.5W 50 KT 60 MPH 12H 19/1800Z 26.6N 92.6W 55 KT 65 MPH 24H 20/0600Z 26.9N 93.4W 60 KT 70 MPH 36H 20/1800Z 27.1N 94.3W 65 KT 75 MPH 48H 21/0600Z 27.4N 95.2W 70 KT 80 MPH 60H 21/1800Z 27.7N 95.9W 70 KT 80 MPH 72H 22/0600Z 28.1N 96.3W 65 KT 75 MPH 96H 23/0600Z 28.7N 95.4W 60 KT 70 MPH 120H 24/0600Z 29.7N 93.3W 50 KT 60 MPH $$ Forecaster Cangialosi
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Tropical Storm Wilfred Forecast Discussion Number 4
2020-09-19 10:32:59| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sat Sep 19 2020 000 WTNT43 KNHC 190832 TCDAT3 Tropical Storm Wilfred Discussion Number 4 NWS National Hurricane Center Miami FL AL232020 500 AM AST Sat Sep 19 2020 Helpful AMSR microwave imagery from near 4Z revealed that Wilfred consists of a small low embedded within a broader elongated area of low pressure. A skinny, ragged band of convection wraps around the western and southern portions of the tropical storm, but Wilfred is only producing a small amount of convection near its center. Objective and subjective satellite intensity estimates are generally near 35 kt, and the intensity is held at that value. No noteworthy changes were made to the NHC track or intensity forecasts. Wilfred should continue to move generally west-northwestward for the next few days, steered by a subtropical ridge to the north. Small fluctuations in intensity are possible for the next day or two, but Wilfred should be on the overall decline by the end of the weekend due to increasing wind shear and an expected influx of dry, stable air. The dynamical guidance consensus is that Wilfred will open into a trough and dissipate in about 72 h, and this is reflected in the NHC forecast. Both the NHC track and intensity forecasts are based on the multi-model consensus throughout the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 13.1N 36.9W 35 KT 40 MPH 12H 19/1800Z 13.8N 39.0W 40 KT 45 MPH 24H 20/0600Z 14.8N 41.7W 35 KT 40 MPH 36H 20/1800Z 15.8N 44.4W 35 KT 40 MPH 48H 21/0600Z 16.5N 46.8W 30 KT 35 MPH 60H 21/1800Z 16.8N 48.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 22/0600Z...DISSIPATED $$ Forecaster Zelinsky
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Hurricane Teddy Forecast Discussion Number 27
2020-09-19 04:59:51| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Sep 18 2020 000 WTNT45 KNHC 190259 TCDAT5 Hurricane Teddy Discussion Number 27 NWS National Hurricane Center Miami FL AL202020 1100 PM AST Fri Sep 18 2020 Teddy continues to have an impressive appearance on satellite images with a fairly symmetrical Central Dense Overcast, although recent images show some warming of the cloud tops over the southeastern part of the circulation. Upper-level outflow is well-defined over the northern semicircle of the hurricane and not as strong to the south. Earlier microwave images showed a concentric eyewall structure and it appears that the hurricane has re-intensified slightly over the past several hours. The current intensity estimate is set at 115 kt which is a blend of subjective and objective Dvorak estimates. Some additional fluctuations in strength as a result of eyewall replacements could occur through Saturday. On Sunday and beyond, a less conducive oceanic and atmospheric environment should lead to slow weakening. However, Teddy should remain a powerful hurricane for the next several days. The numerical guidance shows that the circulation will become even larger during the forecast period due to Teddy combined with a high pressure area coming behind a cold front over the eastern United States. Teddy is expected to make the transition to an extratropical cyclone when it moves into Atlantic Canada. The hurricane continues its northwestward trek and is moving around 325/11 kt. Teddy should move around the western side of a subtropical high pressure system for the next day or so. Then, the cyclone should turn northward with an increase in forward speed as it approaches a strong mid-latitude trough cutting off into a low as it moves off the northeast U.S. coast in 2-3 days. The track of the system could bend a bit the left as it interacts with the trough/low while approaching Nova Scotia. Around the end of the forecast period, the post-tropical cyclone should turn northeastward as it moves along the eastern side of a mid-level trough. The official track forecast is close to the corrected model consensus. Teddy is producing seas to 48 feet and an extensive area of large waves and swells which are impacting much of the western Atlantic basin. See the Key Messages below. Key Messages: 1. While the center of Teddy is forecast to move east of Bermuda late Sunday or Monday, there is still a risk of strong winds, storm surge, and heavy rainfall on the island, and a Tropical Storm Watch is in effect. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada early next week, where there is an increasing risk of direct impacts from wind, rain, and storm surge. Residents there should closely monitor the progress of Teddy and updates to the forecast through the weekend. 3. Large swells produced by Teddy are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the east coast of the United States, and Atlantic Canada during the next few days. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 24.0N 57.4W 115 KT 130 MPH 12H 19/1200Z 25.5N 58.6W 115 KT 130 MPH 24H 20/0000Z 27.3N 60.4W 110 KT 125 MPH 36H 20/1200Z 29.0N 61.8W 105 KT 120 MPH 48H 21/0000Z 30.8N 62.3W 100 KT 115 MPH 60H 21/1200Z 33.5N 61.4W 95 KT 110 MPH 72H 22/0000Z 37.7N 61.1W 85 KT 100 MPH 96H 23/0000Z 45.5N 62.5W 70 KT 80 MPH...POST-TROP/EXTRATROP 120H 24/0000Z 50.5N 56.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch
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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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Tropical Storm Wilfred Forecast Discussion Number 3
2020-09-19 04:46:22| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Sep 18 2020 241 WTNT43 KNHC 190246 TCDAT3 Tropical Storm Wilfred Discussion Number 3 NWS National Hurricane Center Miami FL AL232020 1100 PM AST Fri Sep 18 2020 Conventional satellite imagery shows that Wilfred's surface circulation has lost quite a bit of definition during the last several hours, and it has been difficult to pinpoint the center. Additionally, deep convection has become less organized and the cloud tops just to the east of the estimated center position have warmed considerably. The initial intensity is generously held at 35 kt for this advisory and is in best agreement with blend of the subjective and objective satellite intensity estimates. The GFS and ECMWF global model soundings indicate 30-35 kt of northeasterly shear at about 300 mb, and it's apparently undercutting the much lighter, diffluent southeasterly flow above. Statistical-dynamical guidance, however, still show an outside chance of some strengthening Saturday, and the NHC forecast follows suit. Afterward, a combination of Teddy's massive outflow and increasing northwesterly shear produced by an mid- to upper-level trough to the north of the cyclone, should induce slow weakening on Sunday and this trend should continue through the forecast period. The initial motion is estimated to be west-northwestward, or 285/16 kt, and the cyclone is being steered by a low to mid-tropospheric subtropical ridge to the north. A few of the global models are hinting at a slow turn toward the north-northwest prior to dissipation as the steering pattern becomes very meridional with developing high amplitude high pressure over the eastern Atlantic, and Hurricane Teddy well to the northwest creating a large weakness over the western Atlantic. For now, the NHC forecast shows some reduction in forward speed at day 3, before dissipation, and lies close to the consensus aids, HCCA and TVCA. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 12.8N 36.0W 35 KT 40 MPH 12H 19/1200Z 13.5N 38.3W 40 KT 45 MPH 24H 20/0000Z 14.5N 40.9W 40 KT 45 MPH 36H 20/1200Z 15.8N 43.8W 35 KT 40 MPH 48H 21/0000Z 16.7N 46.3W 35 KT 40 MPH 60H 21/1200Z 17.3N 48.3W 30 KT 35 MPH 72H 22/0000Z 17.9N 50.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 23/0000Z...DISSIPATED $$ Forecaster Roberts
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