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Tropical Storm Gabrielle Forecast Discussion Number 6

2019-09-05 04:31:48| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Wed Sep 04 2019 000 WTNT43 KNHC 050231 TCDAT3 Tropical Storm Gabrielle Discussion Number 6 NWS National Hurricane Center Miami FL AL082019 1100 PM AST Wed Sep 04 2019 South to southwesterly shear is affecting the overall organization of Gabrielle this evening. A recent scatterometer pass indicated that the low-level center was located on the southern edge of weakening convection, and to the south of a mid-level circulation apparent in infrared satellite imagery. This same scatterometer pass showed an expanded wind field in the northwest quadrant as well as 45-kt peak winds, and this initial intensity is in agreement with the latest subjective satellite intensity estimate from TAFB. The shear is not expected to abate for the next 48 hours, and sea surface temperatures are forecast to remain marginal through 36 hours. Therefore little to no change in intensity is expected from Gabrielle during the next couple of days. After 48 hours, shear is expected to decrease for a few days while the cyclone moves over waters warmer than 28 C. This should allow for some gradual intensification, and Gabrielle is forecast to become a hurricane by Sunday. The official intensity forecast is close to the previous one and very near the intensity from the corrected consensus HCCA. Gabrielle has been moving northwestward or 325/6 kt. This motion should continue for the next day or so as the cyclone is steered by a subtropical ridge to its northeast. After that time, a mid- to upper-level low is forecast to develop to the west of Gabrielle, which will help to increase the forward motion late this week and over the weekend. There was a notable westward shift in the guidance beyond 72 hours possibly due to the interaction of the cyclone with the aforementioned upper low. After 96 hours, an approaching mid-latitude trough will begin to turn Gabrielle to the north then northeast. The official forecast track is very similar to the previous one through 72 hours, and was shifted slightly westward thereafter. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 21.5N 34.4W 45 KT 50 MPH 12H 05/1200Z 22.4N 35.2W 45 KT 50 MPH 24H 06/0000Z 23.7N 36.6W 45 KT 50 MPH 36H 06/1200Z 25.4N 38.3W 45 KT 50 MPH 48H 07/0000Z 27.3N 40.2W 45 KT 50 MPH 72H 08/0000Z 30.8N 44.6W 55 KT 65 MPH 96H 09/0000Z 34.0N 48.0W 65 KT 75 MPH 120H 10/0000Z 37.5N 48.0W 65 KT 75 MPH $$ Forecaster Latto

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Hurricane Dorian Forecast Discussion Number 46

2019-09-04 22:57:12| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Wed Sep 04 2019 000 WTNT45 KNHC 042057 TCDAT5 Hurricane Dorian Discussion Number 46 NWS National Hurricane Center Miami FL AL052019 500 PM EDT Wed Sep 04 2019 Dorian has become a little better organized during the past several hours, with the eye becoming somewhat more distinct and the cold cloud tops in the eyewall becoming more symmetric. An Air Force Reserve Hurricane Hunter aircraft has twice reported 110-kt flight-level winds in the eastern eyewall, and the central pressure has fallen to 961 mb. Based on these data and that of eyewall dropsondes, the initial intensity is increased to 95 kt. The aircraft data show that hurricane-force winds are 50-60 n mi offshore of northeastern coast of Florida, while surface observations show that tropical-storm conditions are affecting portions of the coasts of Georgia and South Carolina. The initial motion is now 345/8. Dorian is moving around the western end of the subtropical ridge, and it should recurve northward and northeastward into the mid-latitude westerlies during the next 12-36 h. This motion should bring the center of Dorian near the coast of South Carolina in about 24 h and near or over the coast of North Carolina during the 36-48 h period. After that time, the cyclone is forecast to accelerate northeastward into the Atlantic toward the Canadian Maritimes, with a quick northeastward motion continuing through 120 h. The track guidance remains very tightly clustered, and the new forecast track is little changed from the previous forecast. It should be noted that the track is close to and almost parallel to the coast of the southeastern United State, and any deviation to the left of the track could bring the center onshore anywhere in the Carolinas. Dorian is expected to remain in an environment of light to moderate vertical wind shear and warm sea surface temperatures during the next 36 h or so. None of the guidance shows significant strengthening during this time, and the official forecast is similar to, but slightly stronger than, the previous forecast. However, based on current trends it is possible that Dorian could briefly regain major hurricane strength during the next 12-24 h. The hurricane is expected to maintain Category 2 intensity as it passes near the southeastern United States coast during the 24-48 h period, followed by a weakening trend due to increasing shear and dry air entrainment. Extratropical transition is now expected to begin between 48-72 h and be complete just after 72 h, with Dorian forecast to become a hurricane-force extratropical low as it moves towards Nova Scotia and Newfoundland. Since the NHC track prediction continues to take Dorian dangerously close to the southeast U.S. coast, all interests from northeast Florida to the Carolinas should remain vigilant to the possibility of experiencing destructive winds, flooding rains, and life- threatening storm surges from this hurricane. Key Messages: 1. Life-threatening storm surge and dangerous winds are expected along portions of the Florida east coast, the coasts of Georgia, South Carolina, and North Carolina, and portions of southeast Virginia and the southern Chesapeake Bay, regardless of the exact track of Dorian's center. Water levels could rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 2. Flash flooding will become increasingly likely across coastal Georgia into the eastern Carolinas tonight into Friday. There is a high risk of flash flooding over coastal sections of the Carolinas, where significant, life-threatening, flash flooding is expected. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 30.6N 79.8W 95 KT 110 MPH 12H 05/0600Z 31.4N 79.8W 95 KT 110 MPH 24H 05/1800Z 32.7N 79.0W 90 KT 105 MPH 36H 06/0600Z 34.0N 77.3W 85 KT 100 MPH 48H 06/1800Z 35.9N 74.4W 85 KT 100 MPH 72H 07/1800Z 42.1N 65.6W 75 KT 85 MPH 96H 08/1800Z 50.5N 56.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 09/1800Z 56.5N 42.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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Hurricane Juliette Forecast Discussion Number 15

2019-09-04 22:38:41| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Wed Sep 04 2019 000 WTPZ41 KNHC 042038 TCDEP1 Hurricane Juliette Discussion Number 15 NWS National Hurricane Center Miami FL EP112019 200 PM PDT Wed Sep 04 2019 Juliette continues to exhibit a large, ragged eye in both visible and infrared satellite imagery, but there are some breaks in the convective banding. Warming of the cloud tops over the southeastern portion of the circulation has also been observed. Recent microwave data show that the low-level eye remains fairly well defined, and that the center was located a little south of the previous estimates. The initial intensity remains 85 kt, which is a blend of the various objective and subjective satellite intensity estimates. Although the vertical shear is forecast to remain quite low during the next several days, the hurricane will be moving over decreasing SSTs and into less favorable thermodynamic conditions. This should result in gradual weakening during the next several days, and Juliette is now forecast to become a remnant low by the end of the forecast period. The hurricane is moving west-northwestward or 295/6 kt. A mid-level ridge extending from the southwestern United States over the eastern Pacific should continue to steer Juliette west- northwestward at a slightly faster forward speed during the next 2 to 3 days. After that time, the cyclone is predicted to turn westward as it weakens and is steered by the easterly trade wind flow. The farther south initial position required a slight southward adjustment of the early portion of the track forecast, but the latter portion remains similar to the previous official forecast. The track guidance is tightly clustered and the NHC forecast is near middle of the envelope. The wind radii were adjusted slightly based on recent scatterometer data. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 19.4N 117.8W 85 KT 100 MPH 12H 05/0600Z 20.0N 118.9W 75 KT 85 MPH 24H 05/1800Z 21.1N 120.5W 70 KT 80 MPH 36H 06/0600Z 22.1N 122.4W 60 KT 70 MPH 48H 06/1800Z 23.0N 124.4W 50 KT 60 MPH 72H 07/1800Z 23.6N 128.1W 35 KT 40 MPH 96H 08/1800Z 23.2N 131.5W 30 KT 35 MPH 120H 09/1800Z 22.8N 135.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Depression Fernand Forecast Discussion Number 7

2019-09-04 22:33:43| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Wed Sep 04 2019 000 WTNT42 KNHC 042033 TCDAT2 Tropical Depression Fernand Discussion Number 7 NWS National Hurricane Center Miami FL AL072019 400 PM CDT Wed Sep 04 2019 Fernand moved inland a few hours ago, and the surface center is already showing signs of becoming poorly defined. The intensity is now estimated at 30 kt, assuming weakening has occurred since the cyclone moved inland. This makes Fernand a Tropical Depression. The depression should move westward or west-northwestward for the next 12 h or so while it continues to weaken, and it could dissipate as soon as tonight. Although the winds have decreased and the depression will likely dissipate soon, Fernand is still producing substantial convection and continues to pose a significant rain threat to northeast Mexico. Life-threatening flash floods and mudslides will be possible through Thursday, even after Fernand dissipates. Please consult products from you local weather service for more information on the potential rainfall hazard. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 24.4N 98.3W 30 KT 35 MPH 12H 05/0600Z 25.0N 100.0W 25 KT 30 MPH 24H 05/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Gabrielle Forecast Discussion Number 5

2019-09-04 22:31:41| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Sep 04 2019 000 WTNT43 KNHC 042031 TCDAT3 Tropical Storm Gabrielle Discussion Number 5 NWS National Hurricane Center Miami FL AL082019 500 PM AST Wed Sep 04 2019 Recent microwave data suggest that Gabrielle continues to gradually become better organized, and the last few GOES-16 images show a convective burst forming over the center. The initial intensity is estimated at 45 kt based on the Dvorak number from TAFB and an earlier ASCAT pass from this morning, but it's possible that this intensity estimate may be conservative. The storm could intensify a little more in the short-term, but overall it is expected to remain in a marginal environment during the next couple of days, characterized by moderate southerly to southwesterly wind shear, low values of mid-level relative humidity and SSTs near 26-27C. Little overall change in strength is predicted during the next two days. Thereafter, some strengthening is likely as Gabrielle moves on the northeastern side of an upper-level low into a lower shear region, at the same time the cyclone moves over warmer water. The new NHC intensity forecast shows Gabrielle reaching hurricane strength in about 5 days, which is consistent with the latest HWRF, NOAA corrected-consensus and COAMPS-TC models. The initial motion is estimated at 325/8. For the next 5 days, Gabrielle is forecast to move generally northwestward toward a break in the Bermuda-Azores high pressure ridge. An increase in forward speed is expected due to the gradient between an upper-level low to the west and the ridge to the northeast. The latest models have shifted a little to the west for the point of recurvature in about 5 days, and the official forecast splits the difference between the previous NHC forecast and the latest various consensus models in the day 4 to 5 time period. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 21.0N 34.0W 45 KT 50 MPH 12H 05/0600Z 21.7N 34.6W 50 KT 60 MPH 24H 05/1800Z 22.8N 35.8W 50 KT 60 MPH 36H 06/0600Z 24.2N 37.4W 45 KT 50 MPH 48H 06/1800Z 26.1N 39.1W 45 KT 50 MPH 72H 07/1800Z 30.0N 43.2W 50 KT 60 MPH 96H 08/1800Z 33.0N 47.5W 55 KT 65 MPH 120H 09/1800Z 36.5N 48.5W 65 KT 75 MPH $$ Forecaster Blake/Hagen

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