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Potential Tropical Cyclone Seven Forecast Discussion Number 1

2019-09-03 11:09:49| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Tue Sep 03 2019 000 WTNT42 KNHC 030909 TCDAT2 Potential Tropical Cyclone Seven Discussion Number 1 NWS National Hurricane Center Miami FL AL072019 400 AM CDT Tue Sep 03 2019 Overnight scatterometer wind data and infrared satellite imagery indicate that the broad low pressure system located over the west-central and southwestern Gulf of Mexico is gradually becoming better defined, but still lacks a well-defined center. However, the scatterometer indicated surface winds of 30-33 kt in the northwestern quadrant and observations from Buoy 42002 north of the center have been indicating wind speeds of 25-27 kt at 4-meter elevation. Based on these data, advisories are being initiated on Potential Cyclone Seven. The initial motion estimate is an uncertain 260/06 kt. The general motion of the broad low is expected to be westward, being steered by a deep-layer ridge located over the southern United States. It is possible, however, that an apparent west-northwestward motion could occur if the low-level center redevelops farther north into the deep convection. The NHC forecast track is similar to, but a little north of, the consensus model TVCN. Some slight strengthening is forecast during then next 36-48 hours before the low moves inland over northeastern Mexico. However, the broad and large circulation should prevent any rapid intensification from occurring. The official intensity forecast is similar to the IVCN consensus model. The primary threat from this system will be heavy rainfall that could produce flooding and mudslides, especially in mountainous areas. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 23.5N 94.3W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 03/1800Z 23.4N 95.2W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 04/0600Z 23.4N 96.3W 35 KT 40 MPH 36H 04/1800Z 23.7N 97.1W 40 KT 45 MPH 48H 05/0600Z 24.3N 98.2W 30 KT 35 MPH...INLAND 72H 06/0600Z...DISSIPATED $$ Forecaster Stewart

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Hurricane Dorian Forecast Discussion Number 40

2019-09-03 10:54:19| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Tue Sep 03 2019 000 WTNT45 KNHC 030854 TCDAT5 Hurricane Dorian Discussion Number 40 NWS National Hurricane Center Miami FL AL052019 500 AM EDT Tue Sep 03 2019 Dorian continues to pound Grand Bahama Island early this morning while moving little. The eyewall has become a little less defined over the past few hours on radar. On infrared satellite images, the eye remains fairly well defined, but the surrounding deep convection is somewhat fragmented. Upper-level outflow is a bit restricted over the western semicircle of the circulation. The initial intensity is held at 105 kt, which is a blend of subjective Dvorak data-T numbers from TAFB and SAB. Dorian is expected to more or less maintain its intensity for about 36 hours. After that time period, increasing vertical shear should cause gradual weakening. However, the system is likely to remain a major hurricane for the next few days. The official forecast is closest to the latest LGEM guidance. Dorian has been nearly stationary for the past 18 hours, as steering currents in its vicinity have collapsed. The global models indicate that a weakness in the subtropical ridge will develop in response to a trough that will amplify along the east coast of the United States within the next day or so. Dorian should respond to these changes by beginning to move north-northwestward toward the weakness in the ridge a little later today. The system should turn northward with a gradual increase in forward speed as it moves through the weakness in around 48 hours. Later in the period, the cyclone should accelerate northeastward on the southern side of the trough. The official track forecast is similar to the previous one, and is fairly close to the model consensus. Although the official forecast does not show Dorian making landfall along the Florida east coast, users are reminded not to forecast on the exact forecast track. A relatively small deviation to the left of this track could bring the core of the hurricane near or over the coastline. Key Messages: 1. Devastating winds and storm surge will continue to affect Grand Bahama Island for several more hours. Everyone there should remain in shelter. 2. Life-threatening storm surge and dangerous hurricane-force winds are expected along portions of the Florida east coast and the coasts of Georgia and South Carolina, regardless of the exact track of Dorian's center. Water levels could begin to rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 3. The risk of life-threatening storm surge and hurricane-force winds continues to increase along the coast of North Carolina. Residents in these areas should follow advice given by local emergency officials. 4. The flash flood threat will increase today and tonight along the Florida peninsula, then spread up the southeast and mid-Atlantic coast during the middle and latter part of the week. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 26.9N 78.4W 105 KT 120 MPH 12H 03/1800Z 27.5N 78.8W 105 KT 120 MPH 24H 04/0600Z 28.5N 79.3W 105 KT 120 MPH 36H 04/1800Z 29.9N 79.7W 105 KT 120 MPH 48H 05/0600Z 31.4N 79.4W 100 KT 115 MPH 72H 06/0600Z 34.3N 76.6W 85 KT 100 MPH 96H 07/0600Z 39.0N 69.3W 75 KT 85 MPH 120H 08/0600Z 46.5N 59.5W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch

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Hurricane Juliette Forecast Discussion Number 9

2019-09-03 10:31:18| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Tue Sep 03 2019 000 WTPZ41 KNHC 030831 TCDEP1 Hurricane Juliette Discussion Number 9 NWS National Hurricane Center Miami FL EP112019 300 AM MDT Tue Sep 03 2019 Juliette has rapidly intensified 50 kt since this time last night, and the recent satellite signature has continued to improve. The initial intensity of 105 kt is based on satellite intensity estimates of T5.5/102 kt from TAFB, SAB, and UW-CIMSS ADT, and also the recently improved eye pattern. The initial motion estimate is 310/08 kt. A large subtropical ridge located to the north and northeast of Juliette should keep the hurricane moving northwestward today, followed by a turn toward the west-northwest on Wednesday, which should continue into Friday. By day 5, a westward motion is expected to begin as Juliette weakens considerably and becomes steered by the easterly trade wind flow. The new official forecast is a little north or to the right of the previous advisory track, and lies between the consensus models HCCA and TVCE to the north, and FSSE to the south. Some additional strengthening is forecast with Juliette possibly reaching category 4 status later today or tonight. Thereafter, cold upwelling is expected to begin, which will induce a slow weakening trend on Wednesday. The weakening rate is expected to be tempered by low vertical shear conditions and a very favorable upper-level outflow regime. By day 3 and beyond, however, more significant upwelling is expected to enhance the weakening process, with rapid weakening becoming a distinct possibility on days 4 and 5. The new NHC intensity forecast is similar to the previous advisory, and lies slightly above all of the guidance for the next 24 hours, and then closely follows the IVCN and HCCA consensus models on days 2-5. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 18.2N 114.5W 105 KT 120 MPH 12H 03/1800Z 18.7N 115.6W 115 KT 130 MPH 24H 04/0600Z 19.2N 116.9W 105 KT 120 MPH 36H 04/1800Z 19.7N 118.4W 100 KT 115 MPH 48H 05/0600Z 20.4N 120.1W 85 KT 100 MPH 72H 06/0600Z 22.0N 124.0W 60 KT 70 MPH 96H 07/0600Z 23.4N 128.3W 45 KT 50 MPH 120H 08/0600Z 24.0N 132.0W 35 KT 40 MPH $$ Forecaster Stewart

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Hurricane Dorian Forecast Discussion Number 39

2019-09-03 04:52:16| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Mon Sep 02 2019 000 WTNT45 KNHC 030252 TCDAT5 Hurricane Dorian Discussion Number 39 NWS National Hurricane Center Miami FL AL052019 1100 PM EDT Mon Sep 02 2019 Dorian continues to pummel Grand Bahama Island this evening. The hurricane still has an impressive presentation in satellite and radar images, however, there have been occasional dry slots observed in the western part of the eyewall. Both the NOAA and Air Force Hurricane Hunters provided excellent data in Dorian this evening, and based primarily on the flight-level wind data from the aircraft, the initial intensity of Dorian is set to 115 kt. The westernmost outer rain bands are reaching the east coast of south Florida and producing gusty winds. The major hurricane has been stationary much of the day. The reason the cyclone has moved very little is because it is caught in weak steering currents between high pressure ridges to its east and northwest and a trough to its north. This weak flow should result in a very slow and likely erratic northwest drift through at least early Tuesday. After that time, the models are in general agreement that the ridge to the east and trough to the north will amplify. This change in the steering pattern should cause Dorian to move a little faster to the north on Wednesday and to the northeast on Thursday and Friday. The NHC track forecast remains consistent and continues to show the core of Dorian offshore, but dangerously close to the east coast of the U.S. from Florida to North Carolina during the next 3 days or so. This track forecast is largely an update of the previous one and it is in good agreement with the various consensus models. Users are reminded that the hurricane is not a point, and that life-threatening storm surge and hurricane-force winds extend far from the center. Regardless of the exact forecast track, Dorian is likely to produce strong winds and a life-threatening storm surge along a portion of the U.S. east coast from Florida through the Carolinas. The intensity models are in agreement that Dorian should slowly lose strength during the next several days due to a gradual increase in wind shear and perhaps drier air. Regardless of the details of the intensity forecast, the bottom line is that Dorian is expected to remain a powerful hurricane as it tracks very near the east coast of the U.S. from Florida to North Carolina during the next few days. The NHC intensity forecast is the same as the previous one and close to the HCCA and IVCN guidance. Key Messages: 1. Devastating winds and storm surge will continue to affect Grand Bahama Island for several more hours. Everyone there should remain in shelter. 2. Life-threatening storm surge and dangerous hurricane-force winds are expected along portions of the Florida east coast and the coasts of Georgia and South Carolina, regardless of the exact track of Dorian's center. Water levels could begin to rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 3. The risk of life-threatening storm surge and hurricane-force winds continues to increase along the coast of North Carolina. Residents in these areas should follow advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the southeast and lower mid-Atlantic regions of the United States through Friday. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 26.9N 78.5W 115 KT 130 MPH 12H 03/1200Z 27.1N 78.7W 115 KT 130 MPH 24H 04/0000Z 27.9N 79.1W 110 KT 125 MPH 36H 04/1200Z 29.2N 79.7W 110 KT 125 MPH 48H 05/0000Z 30.6N 79.7W 105 KT 120 MPH 72H 06/0000Z 33.7N 77.3W 90 KT 105 MPH 96H 07/0000Z 38.0N 71.0W 80 KT 90 MPH 120H 08/0000Z 45.4N 61.5W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi

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Hurricane Juliette Forecast Discussion Number 8

2019-09-03 04:33:46| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Mon Sep 02 2019 000 WTPZ41 KNHC 030233 TCDEP1 Hurricane Juliette Discussion Number 8 NWS National Hurricane Center Miami FL EP112019 900 PM MDT Mon Sep 02 2019 Enhanced BD-curve infrared GOES-17 imagery shows that Juliette is undergoing a rapid intensification evolution. An earlier GMI microwave pass revealed that the eyewall has completed closed off, and this is also visible in the infrared images as a -70C black ring. A blend of the subjective and objective satellite intensity estimates yield 80 kt, but since that time, due to the much improved inner core now depicted in imagery, the initial intensity is raised to 100 kt. Rapid strengthening should continue during the next 12 hours or so. Beyond the short term intensification trend, Juliette is forecast to continue to move within a favorable atmosphere consisting of low deep-layer shear, a diffluent upper wind pattern, and warm oceanic temperatures which should allow Juliette to strengthen a bit further. Afterward, a steady weakening trend is forecast as Juliette traverses cooler water and moves into a more stable, drier marine layer air mass. Juliette's initial motion is estimated to be northwestward, or 310/9 kt. The cyclone should continue moving generally northwestward, or west-northwestward within the mid-tropospheric steering flow produced by a subtropical ridge to the north of Juliette, and an upper-level low just to the west-southwest. There's still quite a bit of across-track model spread beyond the 48 hour period in response to continued large-scale synoptic dissimilarities in the strength of the subtropical ridge. The NHC track forecast is similar to the previous one, and is close to the TVCE consensus model. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 17.8N 114.0W 100 KT 115 MPH 12H 03/1200Z 18.4N 115.1W 115 KT 130 MPH 24H 04/0000Z 18.9N 116.4W 115 KT 130 MPH 36H 04/1200Z 19.4N 117.8W 100 KT 115 MPH 48H 05/0000Z 19.9N 119.4W 85 KT 100 MPH 72H 06/0000Z 21.4N 123.2W 65 KT 75 MPH 96H 07/0000Z 23.0N 127.8W 45 KT 50 MPH 120H 08/0000Z 24.1N 131.3W 35 KT 40 MPH $$ Forecaster Roberts

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