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Tropical Depression Twenty Forecast Discussion Number 7

2020-09-14 10:59:27| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 14 2020 000 WTNT45 KNHC 140859 TCDAT5 Tropical Storm Teddy Discussion Number 7 NWS National Hurricane Center Miami FL AL202020 500 AM AST Mon Sep 14 2020 Earlier ASCAT data indciated peak winds of 33 kt in the northwestern quadrant of the depression. Since then, convection has increased and so have the various satellite intensity estimates. The initial intensity is increased to 35 kt based on the ASCAT data, and satellite estimates of T3.5/35 kt from TAFB and 38 kt from UW-CIMSS SATCON. This makes Tropical Storm Teddy the earliest 19th named storm, besting the unnamed tropical storm on October 4, 2005. The initial motion estimate is 285/12 kt. A deep-layer subtropical ridge positioned over the central Atlantic should keep Teddy moving west-northwestward for the next couple of days. Thereafter, the ridge is expected to shift northward and eastward, and the strengthening cyclone is forecast to turn northwestward around the western periphery of the ridge. The latest NHC track guidance is general agreement on this developing track scenario, and the new official forecast track is similar to the previous one and lies down the middle of the guidance envelope, close to the consensus model tracks. Teddy will have several days to strengthen over very warm ocean temperatures and within a light vertical wind shear regime. The only hindrance to intensification will be intermittent intrusions of dry mid-level air that will briefly disrupt the inner-core convective structure. The NHC intensity forecast remains unchanged and brings Teddy major hurricane strength by the middle of the week. Some of the dynamical hurricane models continue to indicate that Teddy could strengthen faster than that, but I can't bear to make that forecast at this time. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 13.4N 40.4W 35 KT 40 MPH 12H 14/1800Z 13.8N 42.4W 40 KT 45 MPH 24H 15/0600Z 14.3N 44.8W 50 KT 60 MPH 36H 15/1800Z 15.0N 46.7W 65 KT 75 MPH 48H 16/0600Z 15.9N 48.2W 75 KT 85 MPH 60H 16/1800Z 16.9N 49.5W 85 KT 100 MPH 72H 17/0600Z 18.3N 50.8W 95 KT 110 MPH 96H 18/0600Z 21.0N 53.1W 100 KT 115 MPH 120H 19/0600Z 23.9N 55.6W 100 KT 115 MPH $$ Forecaster Stewart

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Tropical Storm Sally Forecast Discussion Number 11

2020-09-14 10:55:57| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Mon Sep 14 2020 000 WTNT44 KNHC 140855 TCDAT4 Tropical Storm Sally Discussion Number 11 NWS National Hurricane Center Miami FL AL192020 400 AM CDT Mon Sep 14 2020 The organization of Sally hasn't changed much during the past several hours. While there was a large burst of convection earlier, it did not translate into any intensification, with flight-level reconnaissance and SFMR surface winds still supporting an initial wind speed of 50 kt. The Air Force Reserve plane did find that the size of tropical-storm-force wind field has notable grown to the north and northwest of the center. The storm still has time to intensify under a seemingly conducive environment during the next 24-36 hours, before a combination of increasing westerly wind shear and land interaction will probably slow the intensification rate. Model guidance has come down slightly from 6 hours ago, but it has been inconsistent from cycle to cycle. The new intensity forecast is similar to the previous one and lies near the top end of the guidance envelope. The reconnaissance plane showed that Sally took a westward turn during the past several hours, but the storm appears to have a resumed a more west-northwestward motion recently. Weak ridging over the southern United States is expected to cause this general motion with a decrease in forward speed today before the storm slowly turns northward sometime on Tuesday due to an approaching trough. Guidance is not in good agreement on exactly when that turn occurs, causing a good deal of spread for a relatively short-range forecast. The track forecast has been shifted to the left in the short-term primarily due to the initial position, showing a track near or over extreme southeastern Louisiana, then is the near the previous one at its final landfall. The bottom line continues to be that Sally is expected to be a dangerous slow-moving hurricane near the coast of southeastern Louisiana, Mississippi and Alabama during the next 2-3 days. KEY MESSAGES: 1. It is 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 48 hours is around 80 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 Alabama/Florida border, 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 by late today within portions of the Hurricane Warning area from Morgan City, Louisiana, to the Mississippi/Alabama border, including Metropolitan New Orleans, with tropical storm conditions likely to begin by late this morning. Preparations should be rushed to completion in those areas. 4. Sally could continue to produce flash flooding across central and northern Florida and prolong existing minor river flooding across west-central Florida through today. Widespread significant flash flooding and minor to isolated major river flooding is likely across southeastern Louisiana, Mississippi, and Alabama through the middle of the week. Flooding impacts are expected to spread farther across the Southeast U.S. through the week. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 28.3N 87.3W 50 KT 60 MPH 12H 14/1800Z 28.6N 88.1W 60 KT 70 MPH 24H 15/0600Z 29.1N 88.9W 70 KT 80 MPH 36H 15/1800Z 29.7N 89.3W 75 KT 85 MPH 48H 16/0600Z 30.6N 89.2W 60 KT 70 MPH...INLAND 60H 16/1800Z 31.6N 88.6W 30 KT 35 MPH...INLAND 72H 17/0600Z 32.5N 87.6W 25 KT 30 MPH...INLAND 96H 18/0600Z 33.5N 85.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 19/0600Z...DISSIPATED $$ Forecaster Blake

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Hurricane Paulette Forecast Discussion Number 30

2020-09-14 10:51:23| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 14 2020 005 WTNT42 KNHC 140851 TCDAT2 Hurricane Paulette Discussion Number 30 NWS National Hurricane Center Miami FL AL172020 500 AM AST Mon Sep 14 2020 The large, 35-40-mile-wide eye of Paulette is located over northeastern Bermuda, and nearly the entire island is inside the eye. The last Air Force Reserve hurricane hunter mission measured peak 700-mb flight-level winds of 88 kt in the northeastern quadrant where data from satellites and the Bermuda radar (the radar is still functioning) indicate a large burst of deep convection has developed and persisted in that part of the eyewall, likely bringing down much of those winds to the surface. Using a standard 90-percent adjustment factor yields a surface wind estimate near 80 kt, and that is the intensity used for this advisory. The last reported pressure by the aircraft was 973 mb, which has been confirmed by surface observations from Bermuda. The initial motion estimate is 345/10 kt. The track, intensity, and wind radii forecasts remain essentially unchanged since all of the latest NHC guidance appears to be tightly dialed in on Paulette's future. Additional strengthening appears likely after Paulette moves away from Bermuda and accelerates northeastward over the North Atlantic. Paulette is expected to be at or near major hurricane strength on Tuesday. By the end of the forecast period, weakening is forecast as Paulette interacts with a mid-latitude trough and begins to lose its tropical characteristics. The NHC intensity forecast is remains just above the intensity consensus, but is within the tightly clustered guidance envelope at all times. Confidence in the track forecast also remains high, and the latest track guidance is tightly packed about the previous advisory track. Paulette will move northward away from Bermuda today, followed by a turn toward the northeast by tonight and on Tuesday. A slower eastward to southeastward motion is expected by Friday when a large mid-tropospheric cut-off low over the eastern Atlantic is forecast to begin influencing Paulette's track. Key Messages: 1. The eye of Paulette will gradually move away from Bermuda this morning, with hurricane conditions returning within a couple of hours. A prolonged period of strong winds, storm surge, and very heavy rainfall will likely continue into this afternoon. 2. Swells produced by Paulette are affecting portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 32.3N 64.7W 80 KT 90 MPH 12H 14/1800Z 33.9N 64.4W 85 KT 100 MPH 24H 15/0600Z 36.1N 62.1W 95 KT 110 MPH 36H 15/1800Z 38.4N 57.6W 100 KT 115 MPH 48H 16/0600Z 40.9N 51.8W 95 KT 110 MPH 60H 16/1800Z 43.4N 45.3W 85 KT 100 MPH 72H 17/0600Z 45.3N 40.0W 75 KT 85 MPH 96H 18/0600Z 45.5N 36.3W 55 KT 65 MPH 120H 19/0600Z 41.6N 34.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart

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Tropical Depression Rene Forecast Discussion Number 29

2020-09-14 10:49:52| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 14 2020 727 WTNT43 KNHC 140849 TCDAT3 Tropical Depression Rene Discussion Number 29 NWS National Hurricane Center Miami FL AL182020 500 AM AST Mon Sep 14 2020 Rene continues to produce just enough deep convection to keep it from degenerating to a remnant low. However, it is expected to degenerate later today due to the ongoing impact of strong west-northwesterly vertical shear and dry air entrainment. The initial intensity and the intensity forecast, which call for dissipation by 60 h, are unchanged from the previous advisory. The initial motion is a somewhat uncertain 270/3. The shallow cyclone should accelerate west-southwestward or southwestward in the low-level flow by 12-24 hours and continue on that general motion until dissipation. The new NHC track forecast is an update of the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 27.4N 48.3W 25 KT 30 MPH 12H 14/1800Z 27.2N 49.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 15/0600Z 26.6N 49.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 15/1800Z 25.8N 51.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 16/0600Z 25.0N 52.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 16/1800Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Karina Forecast Discussion Number 6

2020-09-14 10:47:55| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Mon Sep 14 2020 000 WTPZ41 KNHC 140847 TCDEP1 Tropical Storm Karina Discussion Number 6 NWS National Hurricane Center Miami FL EP162020 200 AM PDT Mon Sep 14 2020 Karina continues to be a sheared cyclone with the deep convection displaced to the southwest of the exposed low-level center. Recent scatterometer data showed winds up to 40 kt in the southern semicircle, and thus the initial intensity remains 40 kt. The cyclone has moved more westward during the past several hours, possibly due to reformation of the center closer to the convection. This motion of 280/11 is expected to be short-lived, as all of the available track guidance indicates that Karina should turn northwestward during the next 24 h, with a northwestward to west-northwestward then expected through 96 h. After that, the cyclone or its remnants are expected to turn back to the west. The new forecast track is adjusted to the west of the previous track based on the current position and motion, and it lies a bit to the left of the various consensus models. The 96 h point has been nudged a little to the north of the previous forecast based on a northward shift of the guidance at that time. While Karina is likely to continue to feel the effects of northeasterly vertical shear for the next 36 h or so, the new forecast track gives it a little more time over warmer water. Thus, the intensity forecast keeps the door open for some strengthening for 24 h or so. After that, the center should move over cooler water, which should cause the cyclone to weaken to a remnant low by 96 h and dissipate by 120 h. The new intensity forecast has only minor tweaks from the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 17.9N 118.2W 40 KT 45 MPH 12H 14/1800Z 18.4N 119.3W 45 KT 50 MPH 24H 15/0600Z 19.3N 120.5W 45 KT 50 MPH 36H 15/1800Z 20.2N 121.8W 40 KT 45 MPH 48H 16/0600Z 21.3N 123.2W 35 KT 40 MPH 60H 16/1800Z 22.0N 124.6W 30 KT 35 MPH 72H 17/0600Z 22.6N 125.7W 30 KT 35 MPH 96H 18/0600Z 23.0N 127.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 19/0600Z...DISSIPATED $$ Forecaster Beven

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