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Tropical Storm Vicky Forecast Discussion Number 11

2020-09-16 22:45:06| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Sep 16 2020 000 WTNT41 KNHC 162044 TCDAT1 Tropical Storm Vicky Discussion Number 11 NWS National Hurricane Center Miami FL AL212020 500 PM AST Wed Sep 16 2020 There's been little change in Vicky's cloud pattern this afternoon. What's left of the deep convection associated with Vicky is displaced well to the east of the center. Cirrus clouds produced by the outflow of Hurricane Teddy, located nearly 1000 miles to the west-southwest of Vicky, are obscuring the sheared surface circulation. The initial intensity is held at 35 kt for this advisory in deference to the earlier scatterometer pass and due to the fact that the cloud pattern has remained unchanged. The UW-CIMSS SAT-Wind/shear products and water vapor imagery reveal an interesting upper wind pattern consisting of an upper low just to the west of Vicky and a narrow upper-tropospheric ridge to the south of the cyclone. These upper-level features are temporarily creating a very diffluent pattern which appears to be offsetting the blistering westerly shear a bit. In any event, Vicky is still forecast to gradually lose strength and degenerate to a remnant low on Friday, which is in best agreement with the global models and the statistical-dynamical intensity aids. The initial motion estimate is more westward, or 270/08. Vicky should continue moving westward for the next day or two before turning west-southwestward in the low-level tradewind flow. The new NHC track forecast is south of the previous one and is close to the HCCA and TCVA multi-model consensus guidance. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 21.5N 35.7W 35 KT 40 MPH 12H 17/0600Z 21.6N 37.0W 35 KT 40 MPH 24H 17/1800Z 21.3N 38.9W 30 KT 35 MPH 36H 18/0600Z 20.6N 40.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 18/1800Z 19.8N 42.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 19/0600Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Sally Forecast Discussion Number 23

2020-09-16 22:42:29| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Wed Sep 16 2020 410 WTNT44 KNHC 162042 TCDAT4 Tropical Storm Sally Discussion Number 23 NWS National Hurricane Center Miami FL AL192020 400 PM CDT Wed Sep 16 2020 The center of Sally continued its slow trek inland across the far western Florida Panhandle early this afternoon, and it is now located over southeastern Alabama. The satellite and radar presentation of the storm has continued to degrade, and surface observations and Doppler radar data show that winds have continued to gradually decrease. The initial intensity has been reduced to 50 kt, and rapidly weakening should continue as the circulation moves farther inland. Sally is forecast to become a tropical depression tonight or early Thursday, and degenerate into a remnant low in 36-48 hours. The system is expected to be absorbed by a frontal boundary near the southeast U.S. coast on Friday. Sally is moving north-northeastward at a slightly faster forward speed of 6 kt. The cyclone should turn northeastward and move at a slightly faster forward speed as it become embedded within the southern extent of the mid-latitude westerlies, and this general motion should continue until dissipation occurs. The dynamical models are tightly clustered and the NHC track is near the center of envelope. Although the winds and storm surge from Sally are expected to continue to subside this evening, heavy rainfall and flooding will continue to spread inland over southeastern Alabama, central Georgia, and western South Carolina over the next day or so. KEY MESSAGES: 1. Historic and catastrophic flooding, including widespread moderate to major river flooding, is unfolding along and just inland from west of Tallahassee, Florida to Mobile Bay, Alabama. Significant and widespread flooding is expected across inland portions of Alabama, central Georgia and upstate South Carolina, and widespread flooding is possible across western/central North Carolina, and far southeast Virginia. 2. Life-threatening storm surge is occurring along portions of the coastline of the western Florida Panhandle, including Pensacola Bay. 3. Tropical storm conditions are expected to continue this evening within portions of the Tropical Storm warning area in southern Alabama, and the western Florida panhandle. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 31.2N 86.8W 50 KT 60 MPH 12H 17/0600Z 31.9N 86.0W 30 KT 35 MPH...INLAND 24H 17/1800Z 33.2N 84.0W 25 KT 30 MPH...INLAND 36H 18/0600Z 34.2N 81.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 18/1800Z...DISSIPATED $$ Forecaster Brown

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Tropical Depression Karina Forecast Discussion Number 16

2020-09-16 22:39:32| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Wed Sep 16 2020 000 WTPZ41 KNHC 162039 TCDEP1 Tropical Depression Karina Discussion Number 16 NWS National Hurricane Center Miami FL EP162020 Issued by NWS Central Pacific Hurricane Center Honolulu HI 200 PM PDT Wed Sep 16 2020 Karina has significantly devolved over the past day or so as it has moved into an increasingly hostile environment characterized by cool waters, dry mid-level air and increasing southerly vertical wind shear. While latest visible satellite images show a well-developed low-cloud swirl, infrared imagery shows a lack of deep convection, and the initial intensity is estimated to be 30 kt for this advisory, supported by a 1730Z ASCAT-C pass. The system is moving toward the northwest at about 7 kt, steered by a mid-level ridge to its east. With significant deep convection not expected to redevelop, Karina is expected to degenerate to a remnant low by tonight, and the increasingly shallow remnant will be steered by a low-level high centered to the northwest. This will cause a turn toward the west, and then southwest, before dissipation occurs in a couple of days. The new official forecast closely follows the previous and is supported by global model guidance. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 23.0N 124.6W 30 KT 35 MPH 12H 17/0600Z 23.5N 125.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 17/1800Z 23.9N 126.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 18/0600Z 24.0N 127.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 18/1800Z 23.7N 129.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 19/0600Z 23.3N 130.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 19/1800Z...DISSIPATED $$ Forecaster Birchard

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Post-Tropical Cyclone Paulette Forecast Discussion Number 39

2020-09-16 16:41:05| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Sep 16 2020 000 WTNT42 KNHC 161440 TCDAT2 Post-Tropical Cyclone Paulette Discussion Number 39 NWS National Hurricane Center Miami FL AL172020 1100 AM AST Wed Sep 16 2020 Conventional GOES-16 visible and enhanced BD-curve satellite imagery show that Paulette has merged with the large baroclinic zone extending over the north-central Atlantic. Deep convection just to the north of the surface center that was noted on earlier microwave images has dissipated. Therefore, the system is now classified as extratropical cyclone and this is the last NHC advisory. The initial intensity is conservatively lowered to 75 kt based on 1221 UTC scatterometer data, earlier Dvorak intensity estimates and a SATCON analysis of 64 kt. The NHC intensity forecast is based on a blend of the global models and is just above the HCCA multi-model consensus. Although not specified in the NHC forecast, there is some chance that Paulette could reacquire tropical or subtropical characteristics later this week or over the weekend when it turns southward back over warmer oceanic temperatures. This possibility will be monitored for inclusion in future Tropical Weather Outlooks, if necessary. The post-tropical cyclone's initial motion is east-northeastward, or 060/30 kt. The low is expected to continue quickly in this general motion through Thursday morning within the deep-layer mid-latitude flow. By mid-period, Post-Tropical Paulette is expected to slow down and turn southeastward to southward as it moves on the west side of mid- to upper-level low to the east of the cyclone. The new track forecast is based primarily on the HCCA and TVCA consensus aids. Paulette is producing a large area of high seas. The maximum seas estimated by the Ocean Prediction Center near the core of the hurricane are up to 50 feet. Swells from Post-Tropical Cyclone Paulette have spread far away from the center and continue to affect Atlantic Canada, Bermuda, and portions of the U.S. east coast. This is the last NHC advisory on Paulette. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 43.3N 45.2W 75 KT 85 MPH...POST-TROP/EXTRATROP 12H 17/0000Z 45.0N 39.9W 60 KT 70 MPH...POST-TROP/EXTRATROP 24H 17/1200Z 46.2N 35.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 18/0000Z 45.1N 33.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 18/1200Z 42.5N 32.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 60H 19/0000Z 39.5N 32.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 19/1200Z 37.0N 32.7W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 20/1200Z 35.0N 32.9W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 21/1200Z 34.0N 32.4W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Roberts

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Hurricane Sally Forecast Discussion Number 22

2020-09-16 16:41:02| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Wed Sep 16 2020 000 WTNT44 KNHC 161440 TCDAT4 Hurricane Sally Discussion Number 22 NWS National Hurricane Center Miami FL AL192020 1000 AM CDT Wed Sep 16 2020 NWS Doppler Radar and fixes from an Air Force Reserve Hurricane Hunter aircraft indicate that Sally made landfall near Gulf Shores, Alabama, around 0945 UTC with an intensity of 90 kt and a minimum central pressure of 965 mb. Since that time, the center has been inching its way inland over southeastern Alabama and the extreme western portion of the Florida panhandle. The eye has degraded in radar imagery, and Doppler velocities are gradually decreasing. The intensity has therefore been reduced to 70 kt for this advisory. Sally should continue to rapidly weaken today, and once the majority of the circulation is onshore by Thursday morning, it should weaken to a tropical depression. The remnant low is forecast to be absorbed by a frontal boundary near the southeastern United States coastline in a couple of days. Radar and the earlier aircraft fixes show that the longer-term motion is 030/4 kt. Sally should continue to move north- northeastward to northeastward with a gradual increase in forward speed as it enters the southern extent of the mid-latitude westerlies over the next 24-36 hours. A faster east-northeastward motion is expected by 36-48 hours before Sally or its remnants merge with the aforementioned frontal zone. The updated NHC track forecast is close to the HFIP corrected consensus, which is slightly north of the previous advisory. As Sally moves inland, ongoing heavy rainfall and flooding will spread northeastward across southeastern Alabama and portions of Georgia and western South Carolina during the next day or two. KEY MESSAGES: 1. Historic and catastrophic flooding, including widespread moderate to major river flooding, is unfolding along and just inland from west of Tallahassee, Florida, to Mobile Bay, Alabama. Significant and widespread flooding is likely across inland portions of Alabama into central Georgia, and possible across western South Carolina, western and central North Carolina, and far southeast Virginia. 2. Life-threatening storm surge is occurring along portions of the coastline from Alabama to the western Florida Panhandle, including Pensacola Bay. 3. Hurricane conditions are expected to continue this afternoon within portions of the Hurricane Warning area in southern Alabama and the western Florida panhandle. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 30.6N 87.4W 70 KT 80 MPH...INLAND 12H 17/0000Z 31.3N 86.7W 45 KT 50 MPH...INLAND 24H 17/1200Z 32.4N 85.4W 30 KT 35 MPH...INLAND 36H 18/0000Z 33.6N 83.1W 25 KT 30 MPH...INLAND 48H 18/1200Z 34.6N 80.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 19/0000Z...DISSIPATED $$ Forecaster Brown

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