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Tropical Storm Vicky Forecast Discussion Number 5
2020-09-15 10:35:55| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 15 2020 000 WTNT41 KNHC 150835 TCDAT1 Tropical Storm Vicky Discussion Number 5 NWS National Hurricane Center Miami FL AL212020 500 AM AST Tue Sep 15 2020 Vicky remains sheared this morning with strong upper-level winds causing any deep convection to be located northeast of the center. The low-level circulation has also become distorted as well, with new bursts of convection causing the mean circulation to re-form to the north. The initial wind speed is kept 45 kt since the system isn't appreciably different than the last cycle. Models all weaken the storm during the next couple of days due to rather potent westerly shear (with 200-mb westerly winds as high as 70 kt forecast across Vicky's circulation). These extremely harsh conditions should make the intensity prediction rather simple, and Vicky is likely to decay into a remnant low within a day or two and open up into a trough in a few days. The re-formation of the center leads to an uncertain motion estimate of 325/8 kt. The storm should turn west-northwestward later today and westward on Wednesday as it becomes steered by the low-level subtropical ridge. Little change was made to the previous forecast, except for a small northward adjustment in the first day or so of the prediction due to the initial position. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 20.3N 30.1W 45 KT 50 MPH 12H 15/1800Z 21.0N 31.2W 40 KT 45 MPH 24H 16/0600Z 21.7N 33.1W 35 KT 40 MPH 36H 16/1800Z 22.2N 35.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 17/0600Z 22.5N 37.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 17/1800Z 22.5N 38.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/0600Z 22.5N 40.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0600Z...DISSIPATED $$ Forecaster Blake
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Tropical Storm Karina Forecast Discussion Number 10
2020-09-15 10:32:25| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Tue Sep 15 2020 000 WTPZ41 KNHC 150832 TCDEP1 Tropical Storm Karina Discussion Number 10 NWS National Hurricane Center Miami FL EP162020 200 AM PDT Tue Sep 15 2020 Karina has continued to become a little better organized tonight with a concentrated area of deep convection near and over the estimated low-level center. The latest satellite intensity estimates range from 45 to 55 kt, and the initial wind speed is nudged up to 50 kt based on that data. Karina is approaching the 26 C isotherm, and it should be moving over progressively cooler waters during the next several days. These less favorable oceanic conditions combined with a drier and more stable air mass should promote gradual weakening beginning by tonight, and Karina is forecast to become a post-tropical remnant low in about 60 hours. In addition to the cool waters and dry air, an increase in southerly shear should cause the remnant low to dissipate in 4 to 5 days. The intensity guidance is in good agreement, and the NHC forecast is near the middle of the guidance envelope. The tropical storm is moving northwestward at 10 kt. A continued northwestward motion on the southwestern periphery of a mid-level ridge is expected for the next couple of days. After that time, a turn to the west and a decrease in forward speed are forecast as the weak and shallow system moves in the low-level flow. The initial 34-kt wind radii have been reduced based on partial ASCAT overpasses. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 19.8N 120.6W 50 KT 60 MPH 12H 15/1800Z 20.8N 121.7W 50 KT 60 MPH 24H 16/0600Z 22.0N 123.3W 45 KT 50 MPH 36H 16/1800Z 23.0N 124.8W 40 KT 45 MPH 48H 17/0600Z 23.7N 125.9W 35 KT 40 MPH 60H 17/1800Z 24.0N 126.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 18/0600Z 23.9N 127.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/0600Z 23.1N 129.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 20/0600Z...DISSIPATED $$ Forecaster Cangialosi
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Hurricane Paulette Forecast Discussion Number 34
2020-09-15 10:31:23| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 15 2020 671 WTNT42 KNHC 150831 TCDAT2 Hurricane Paulette Discussion Number 34 NWS National Hurricane Center Miami FL AL172020 500 AM AST Tue Sep 15 2020 Paulette has generally changed little overnight. The hurricane still has a central dense overcast feature with an eye occasionally evident in satellite images. Convective banding remains well organized, especially to the north of the center. The satellite intensity estimates range from 77 to 102 kt and based on that data, the initial intensity is again held at 90 kt. The hurricane could strengthen slightly in the short term due to a combination of baroclinic influences from an approaching trough and relatively warm water beneath the cyclone. However, a steady weakening trend should commence on Wednesday when Paulette moves over much cooler waters and into an environment of strong wind shear. These factors should ultimately lead to extratropical transition, which is forecast to be complete by day 3. However, some of the guidance suggests that this could occur up to a day sooner than that. The NHC intensity forecast is near a blend of the HCCA, IVCN, and GFS models. Paulette continues to pick up speed, and the latest initial motion estimate is northeastward at 17 kt. The hurricane is expected to accelerate northeastward even more during the next couple of days as it becomes more embedded in the mid-latitude westerlies. After a few days, however, Paulette will likely turn southeastward and then southward as it moves in the flow on the west side of a cut off deep-layer low. There are some differences in the models on how sharply Paulette turns southward, but they generally agree on the overall scenario. The NHC track forecast lies roughly between the HCCA and TVCA consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 37.0N 60.5W 90 KT 105 MPH 12H 15/1800Z 38.9N 56.8W 100 KT 115 MPH 24H 16/0600Z 41.3N 50.9W 95 KT 110 MPH 36H 16/1800Z 43.7N 44.2W 75 KT 85 MPH 48H 17/0600Z 45.4N 39.0W 60 KT 70 MPH 60H 17/1800Z 46.0N 35.1W 45 KT 50 MPH 72H 18/0600Z 44.9N 34.2W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 19/0600Z 41.6N 33.3W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 20/0600Z 38.7N 32.7W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi
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Hurricane Sally Forecast Discussion Number 15
2020-09-15 04:46:15| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Mon Sep 14 2020 000 WTNT44 KNHC 150246 TCDAT4 Hurricane Sally Discussion Number 15 NWS National Hurricane Center Miami FL AL192020 1000 PM CDT Mon Sep 14 2020 After rapidly strengthening earlier today, Sally's intensity has plateaued for now. Both the NOAA and Air Force Hurricane Hunters have been investigating Sally this evening and they have found that the minimum pressure and winds have leveled off, and support perhaps a generous initial intensity of 85 kt. Doppler radar images and reports from both aircraft indicate the inner core of the hurricane is quite small and that the eyewall is open on the south side, likely due to some dry air that has wrapped into that portion of the circulation. Aircraft and Doppler radar fixes indicate that Sally is moving very slowly to the west-northwest, with the latest initial motion estimated to be 300/3 kt. Weak high pressure ridging to the north and east of Sally is expected to cause the hurricane to continue to move slowly west-northwestward to northwestward for another 12 hours, bringing the center of the storm very near the northern Gulf coast. By Tuesday afternoon, when the hurricane will likely be just offshore, the models show the steering currents collapsing and Sally is likely to drift northward before finally turning northeastward ahead of a developing mid-level trough over the central U.S. by late Wednesday. There continues to be a significant amount of uncertainty on exactly where and when Sally turns northward and makes landfall, with model solutions ranging from a landfall on the Florida panhandle to a landfall in extreme southeastern Louisiana. It should be emphasized that it is always challenging to forecast the track of hurricanes in weak steering currents, and in Sally's case the weak steering is occurring very near land. The new NHC track forecast is a little to the east of the previous one, trending toward the latest consensus aids. Sally is still in generally favorable environmental conditions consisting of very warm SSTs and low wind shear. Since the hurricane will likely remain in those conditions through Tuesday morning, some strengthening seems likely in the short term. In 12 to 24 hours, when Sally is forecast to be very near the coast, a combination of an increase in westerly shear and cooler upwelled shelf waters should limit additional intensification. After the hurricane makes landfall, rapid weakening is forecast and Sally should become post-tropical in 3 to 4 days over the southeast U.S. The NHC intensity forecast lies at the high end of the model guidance and is quite similar to the previous one. Users are reminded to not focus on the exact forecast track or the specific timing and location of landfall. Hurricane-force winds, dangerous storm surge, and flooding rainfall will affect a large portion of the north-central Gulf Coast during the next few days. KEY MESSAGES: 1. It is still too early to determine where Sally's center will move onshore given the uncertainty in the timing and location of Sally's northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC's average forecast error at 36 hours is around 60 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the center. 2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to the Okaloosa/Walton County Line in the Florida Panhandle, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are expected early Tuesday within the Hurricane Warning area in southeastern Louisiana and are expected by late Tuesday and Tuesday night within the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. Tropical storm conditions are already occurring in some of these areas. 4. Life-threatening flash flooding is likely with Sally, as well as widespread minor to isolated major flooding on area rivers, along and just inland of the Central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across inland portions of Mississippi and Alabama and into northern Georgia, southeastern Tennessee and the western Carolinas through the week. Sally may continue to produce flash flooding across the Florida peninsula and prolong existing minor river flooding across west-central Florida through tonight. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 28.9N 87.6W 85 KT 100 MPH 12H 15/1200Z 29.1N 88.1W 95 KT 110 MPH 24H 16/0000Z 29.6N 88.4W 90 KT 105 MPH 36H 16/1200Z 30.4N 88.3W 85 KT 100 MPH...INLAND 48H 17/0000Z 31.3N 87.4W 50 KT 60 MPH...INLAND 60H 17/1200Z 32.0N 86.3W 30 KT 35 MPH...INLAND 72H 18/0000Z 32.7N 84.9W 25 KT 30 MPH...INLAND 96H 19/0000Z 33.1N 82.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/0000Z...DISSIPATED $$ Forecaster Cangialosi
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Tropical Storm Karina Forecast Discussion Number 9
2020-09-15 04:39:21| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Mon Sep 14 2020 000 WTPZ41 KNHC 150239 TCDEP1 Tropical Storm Karina Discussion Number 9 NWS National Hurricane Center Miami FL EP162020 Issued by NWS Central Pacific Hurricane Center Honolulu HI 800 PM PDT Mon Sep 14 2020 Karina may not have reached its peak after all. The northeasterly vertical wind shear appears to have eased a bit, allowing the dense cirrus overcast from the central convection to fully obscure the low level cloud center. The cyclone also appears to be better organized than 24 hours ago. As a result, most of the Dvorak intensity estimates have increased, with ADT up to 39 kt, and PHFO and TAFB indicating 55 kt. SAB was unchanged from the 6 hours ago at 35 kt. Based on a blend of the estimates, the initial intensity for this advisory has been increased to 45 kt. The 12 ft seas radii have also been adjusted based on guidance from TAFB. Moderate shear should continue to affect Karina for another 12 to 24 hours. The shear is forecast to weaken after that, but by then the cyclone is expected to be over sub-26 degree C sea surface temperatures. There is still a narrow window for additional intensification, but most of the guidance holds the intensity for another 12 to 24 hours, with gradual weakening occurring afterward. The forecast holds Karina at 45 kt for 24 hours, followed by weakening to post-tropical remnant low status by 72 hours. This is close to the HCCA guidance. The initial motion for this advisory is 310/10 kt. Karina is forecast to continue moving northwestward to the southwest of a mid-level anticyclone. This motion is expected to continue through 60 to 72 hours. Karina should turn toward the southwest as deep convection ceases and the cyclone becomes steered by the low level flow. The objective guidance is tightly packed through around 60 hours, with variations occurring thereafter regarding when the southwestward turn will occur. The forecast track is close to the previous forecast and closely follows the consensus guidance. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 19.1N 119.8W 45 KT 50 MPH 12H 15/1200Z 20.0N 120.7W 45 KT 50 MPH 24H 16/0000Z 21.3N 122.2W 45 KT 50 MPH 36H 16/1200Z 22.4N 123.7W 40 KT 45 MPH 48H 17/0000Z 23.3N 124.9W 35 KT 40 MPH 60H 17/1200Z 23.8N 125.8W 25 KT 30 MPH 72H 18/0000Z 23.9N 126.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/0000Z 23.5N 128.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/0000Z...DISSIPATED $$ Forecaster Kodama
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