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Hurricane Teddy Forecast Discussion Number 36

2020-09-21 10:42:46| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 21 2020 000 WTNT45 KNHC 210842 TCDAT5 Hurricane Teddy Discussion Number 36 NWS National Hurricane Center Miami FL AL202020 500 AM AST Mon Sep 21 2020 Where Teddy once had a ragged eye has now become a dry slot, an indication that its eyewall is becoming less defined. Some southwesterly shear and the fact that Teddy is beginning to move over the cold wake of former Hurricane Paulette are probably contributing to the degradation of Teddy's structure. Based on this trend, the intensity estimate is lowered slightly to 85 kt. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Teddy later this morning and will give a better assessment of the hurricane's winds. For now, little change was made to the NHC track or intensity forecasts. Teddy is beginning to interact with a large deep layer trough and frontal system that will play a big role in its evolution during the next couple of days. For the remainder of today, Teddy should remain fairly distinct from the front, moving east and northeast of Bermuda. As it begins to merge with that system on Tuesday, a slight deflection toward the north-northwest is likely, and it is possible Teddy could quickly become post-tropical if it merges with the front at that time. The most recent ECMWF and GFS runs suggest that Teddy will maintain a warm core a little longer than than that as it moves over the Gulf Stream. Regardless of its exact classification, once Teddy moves north of the Gulf Stream and over much cooler waters, it is forecast to weaken below hurricane strength and become extratropical. Even with a decrease in its highest winds, Teddy will likely be producing a large area of tropical-storm-force winds when it approaches Atlantic Canada in a couple of days. After moving over Atlantic Canada, Teddy is expected to accelerate northeastward and ahead of, and then merge with, another mid-latitude trough approaching from the northwest. Teddy's size will likely increase substantially during the next couple of days as it moves northward and interacts with the aforementioned frontal system. Gale force winds are likely along portions of the near shore waters of the northeast U.S. Please see products from your local office for more information about marine hazards. Extremely dangerous surf conditions with 20-ft waves have been reported on the south shore of Bermuda, and officials are encouraging residents to avoid going into or near the water. Key Messages: 1. The center of Teddy is forecast to move east of Bermuda today. Wind gusts near tropical-storm-force have been reported on the island and tropical storm conditions could continue into Monday evening. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada late Tuesday through Thursday, where there is an increasing risk of direct impacts from wind, rain, and storm surge. A Tropical Storm Watch is in effect for portions of Nova Scotia, and heavy rainfall across Atlantic Canada is expected with Teddy between Tuesday and Thursday after it becomes a strong post-tropical cyclone. 3. 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 could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 30.3N 63.2W 85 KT 100 MPH 12H 21/1800Z 32.6N 62.6W 85 KT 100 MPH 24H 22/0600Z 36.7N 62.9W 90 KT 105 MPH 36H 22/1800Z 39.7N 63.8W 80 KT 90 MPH 48H 23/0600Z 42.6N 63.4W 70 KT 80 MPH...POST-TROP/EXTRATROP 60H 23/1800Z 46.2N 61.4W 55 KT 65 MPH...POST-TROP/INLAND 72H 24/0600Z 50.0N 57.5W 40 KT 45 MPH...POST-TROP/INLAND 96H 25/0600Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Beta Forecast Discussion Number 15

2020-09-21 10:42:12| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Mon Sep 21 2020 000 WTNT42 KNHC 210842 TCDAT2 Tropical Storm Beta Discussion Number 15 NWS National Hurricane Center Miami FL AL222020 400 AM CDT Mon Sep 21 2020 Beta is struggling this morning. Satellite images show that much of the deep convection associated with the storm has dissipated, and data from the Air Force Hurricane Hunters indicate that the winds have decreased. Based on a combination of flight-level and SFMR data from the aircraft, the initial intensity is lowered to 45 kt. This estimate is also in agreement with an ASCAT pass from a few hours ago that showed peak winds close to 40 kt. It is also worth noting that the tropical-storm-force winds are largely confined to the northern half of the circulation, and these winds should spread across the Texas coast later this morning. Beta has been moving due westward during the past several hours, with the latest initial motion estimated to be 270/5 kt. In the short term, Beta is expected to resume a west-northwestward motion at a forward speed of about 5 kt, and that motion should take the tropical storm to the Texas coast by tonight. The models differ on how far inland Beta gets over Texas, but the majority of the guidance shows the cyclone stalling just inland on Tuesday in weak steering currents. The combination of an approaching shortwave trough and an amplifying ridge over Florida should cause Beta to turn northeastward along or near the Texas coast late Tuesday and Wednesday, and then farther inland over Louisiana on Thursday. The NHC track forecast is largely an update of the previous one and remains near the various consensus aids. The tropical storm is certainty feeling the effects of dry and stable air that has wrapped into the circulation. The combination of the dry air mass and 15-20 kt of southwesterly wind shear should limit strengthening through landfall tonight. Steady weakening is forecast after that time due to the storm interacting with land and stronger southwesterly shear. The models are in quite good agreement, and the NHC intensity forecast lies near the high end of the guidance envelope. Key Messages: 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southeast Louisiana. Flash, urban, and minor river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and 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. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials. 3. Tropical-storm-force winds will spread westward across the Texas coast later this morning and continue into Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 27.7N 95.1W 45 KT 50 MPH 12H 21/1800Z 28.0N 96.0W 45 KT 50 MPH 24H 22/0600Z 28.4N 96.6W 40 KT 45 MPH...INLAND 36H 22/1800Z 28.7N 96.5W 35 KT 40 MPH...INLAND 48H 23/0600Z 28.9N 95.8W 30 KT 35 MPH...INLAND 60H 23/1800Z 29.4N 94.7W 25 KT 30 MPH...INLAND 72H 24/0600Z 30.2N 93.2W 25 KT 30 MPH...INLAND 96H 25/0600Z 32.8N 90.5W 20 KT 25 MPH...POST-TROP/INLAND 120H 26/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Depression Seventeen-E Forecast Discussion Number 3

2020-09-21 10:32:44| Tropical Depression LIDIA

Issued at 300 AM MDT Mon Sep 21 2020

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Tropical Depression Seventeen-E Forecast Discussion Number 2

2020-09-21 04:59:05| Tropical Depression LIDIA

Issued at 900 PM MDT Sun Sep 20 2020

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Hurricane Teddy Forecast Discussion Number 35

2020-09-21 04:51:38| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sun Sep 20 2020 000 WTNT45 KNHC 210251 TCDAT5 Hurricane Teddy Discussion Number 35 NWS National Hurricane Center Miami FL AL202020 1100 PM AST Sun Sep 20 2020 Teddy's satellite presentation has changed little during the past several hours albeit some warming of the eye. The 53rd Air Force Reserve hurricane hunters recorded a central pressure this evening of 963 mb, unchanged from the previous mission, and the Dvorak subjective intensity estimates haven't changed either. Therefore, the initial intensity is held at 90 kt for this advisory. There is a chance, within the next 24 hours, that Teddy could strengthen a bit due to dynamic forcing as a result of the approaching baroclinic zone moving off of the northeast coast of the United States. In Fact, the HCCA intensity model shows a peak of 95 kt at the 24 hour period. By Tuesday afternoon, however, increasing southwesterly shear associated with the rapidly approaching mid-latitude major shortwave trough, from the northwest, should induce weakening. Because Teddy is a very large and strong tropical cyclone, only gradual weakening is predicted. By mid period, the large-scale models agree that Teddy will merge with the aforementioned trough and associated frontal zone and complete its extratropical cyclone transition south of Nova Scotia Tuesday evening. Teddy is still forecast to be a very large and powerful extratropical cyclone as it approaches, Nova Scotia at that time. Wind, rain, surf and storm surge hazards are expected to spread over an extensive portion of Atlantic Canada mid-week. The forecast wind radii at the 36 hour period and beyond, are based on the RVCN Wind Radii Consensus model that consists of a bias-corrected average of the global and regional models. The initial motion is estimated to be north-northwestward, or 5 kt. The hurricane is likely to turn northward Monday morning and continue in this general motion through Wednesday morning. Around the 60 hour period, a turn north-northeastward is forecast ahead of yet another mid-latitude pulse moving into eastern Canada. No significant adjustments were made to the NHC track forecast and it lies in between the surprisingly tightly clustered model guidance. Extremely dangerous surf conditions with 20-ft waves have been reported on the south shore of Bermuda, and officials are encouraging residents to avoid going into or near the water. Key Messages: 1. The center of Teddy is forecast to move east of Bermuda on Monday. Tropical storm conditions are likely on the island beginning overnight and could continue into Monday evening. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada late Tuesday through Thursday, where there is an increasing risk of direct impacts from wind, rain, and storm surge. A Tropical Storm Watch is in effect for portions of Nova Scotia, and heavy rainfall across Atlantic Canada is expected with Teddy between Tuesday and Thursday after it becomes a strong post-tropical cyclone. 3. 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 could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 29.4N 63.6W 90 KT 105 MPH 12H 21/1200Z 30.9N 63.5W 90 KT 105 MPH 24H 22/0000Z 34.8N 62.9W 95 KT 110 MPH 36H 22/1200Z 38.5N 63.8W 90 KT 105 MPH 48H 23/0000Z 41.3N 64.2W 80 KT 90 MPH...POST-TROP/EXTRATROP 60H 23/1200Z 44.5N 62.8W 65 KT 75 MPH...POST-TROP/INLAND 72H 24/0000Z 48.6N 59.9W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 25/0000Z 57.4N 47.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 26/0000Z...ABSORBED BY A LARGER LOW $$ Forecaster Roberts

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