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Tropical Depression Eight Forecast Discussion Number 2

2019-09-04 04:40:37| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 03 2019 000 WTNT43 KNHC 040240 TCDAT3 Tropical Depression Eight Discussion Number 2 NWS National Hurricane Center Miami FL AL082019 1100 PM AST Tue Sep 03 2019 A recent scatterometer pass indicated that the low-level center was farther south than previously thought, and that the strongest winds of 30 kt are within a band of deep convection over the northern semicircle. Based on these data and a blend of the subjective and objective intensity estimates, 30 kt will be the initial intensity for this advisory. The depression will be in a marginally favorable environment of 10 to 15 kt of shear and over SSTs just over 26C for the next few days. Some slight strengthening could occur during this time frame, and it is reflected in the official forecast, bringing the intensity to 50 kt by Thursday night. After that time, the cyclone will begin to move over warmer waters, but into a drier environment with some increase in the wind shear. It is difficult to know at this point in time as to what effect these conflicting conditions may have on the cyclone's intensity. Therefore, beyond 48 hours the intensity is held in a steady state. The official intensity forecast is just a tad higher than the previous one, and is very near the various intensity consensus models. The initial motion is 320/07 kt. A general northwestward motion is expected through the forecast period on the eastern periphery of a subtropical ridge extending from Africa to the eastern Atlantic. An increase in forward motion is expected late this week, as the cyclone gets caught in the southeast flow between the ridge to its east and a developing mid- to upper-level low to the west. The official forecast track is slightly to the left of the previous one through 72 hours due to the adjustment of the initial position. Thereafter the track forecast is little changed and close to the consensus aid TVCX. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 19.1N 32.8W 30 KT 35 MPH 12H 04/1200Z 19.7N 33.6W 35 KT 40 MPH 24H 05/0000Z 20.6N 34.6W 40 KT 45 MPH 36H 05/1200Z 21.6N 35.6W 45 KT 50 MPH 48H 06/0000Z 23.0N 36.6W 50 KT 60 MPH 72H 07/0000Z 27.1N 39.6W 50 KT 60 MPH 96H 08/0000Z 31.7N 43.1W 50 KT 60 MPH 120H 09/0000Z 35.4N 46.1W 50 KT 60 MPH $$ Forecaster Latto

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Hurricane Juliette Forecast Discussion Number 12

2019-09-04 04:34:57| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Tue Sep 03 2019 000 WTPZ41 KNHC 040234 TCDEP1 Hurricane Juliette Discussion Number 12 NWS National Hurricane Center Miami FL EP112019 800 PM PDT Tue Sep 03 2019 A recent AMSR2-GW1 microwave pass showed that Juliette's eyewall had collapsed in the southwestern quadrant. Curved banding features in that portion of the cyclone's cloud pattern have become fragmented as well. Subsequently, it appears that Juliette is on the decline, and both subjective and objective T-numbers support this recent trend. Based on these data, the initial intensity is lowered to 105 kt for this advisory. Cooler oceanic sea surface temperatures, an intruding dry, stable, surrounding environment, and increasing southwesterly shear should cause the cyclone to gradually weaken further, and continue through the entire forecast period. The initial motion estimate is west-northwestward, or 295/6 kt. A mid-tropospheric subtropical ridge extending over the northeastern Pacific from the southwestern United States should steer Juliette west-northwestward through the next several days. Toward the end of the period, a westward motion should commence as Juliette degenerates into a vertically shallow depression, and ultimately, a remnant low, and becomes steered by the low-level easterly flow. The NHC forecast is basically an update of the previous advisory track, and lies between the NOAA HFIP HCCA and TVCE simple multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 19.0N 116.2W 105 KT 120 MPH 12H 04/1200Z 19.3N 117.1W 95 KT 110 MPH 24H 05/0000Z 20.0N 118.7W 85 KT 100 MPH 36H 05/1200Z 20.8N 120.4W 75 KT 85 MPH 48H 06/0000Z 21.6N 122.3W 65 KT 75 MPH 72H 07/0000Z 23.1N 126.5W 45 KT 50 MPH 96H 08/0000Z 23.5N 130.2W 35 KT 40 MPH 120H 09/0000Z 23.5N 134.0W 30 KT 35 MPH $$ Forecaster Roberts

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Tropical Storm Fernand Forecast Discussion Number 4

2019-09-04 04:33:31| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Tue Sep 03 2019 000 WTNT42 KNHC 040233 TCDAT2 Tropical Storm Fernand Discussion Number 4 NWS National Hurricane Center Miami FL AL072019 1000 PM CDT Tue Sep 03 2019 A NOAA Hurricane Hunter plane investigated Fernand this evening and found that the circulation of the cyclone was better organized with a central pressure of 1000 mb. The plane also measured a peak flight level wind of 51 kt, and numerous SFMR observations of around 45 kt. This is the intensity assigned to Fernand in this advisory. These strong winds were confined to the western semicircle of the storm and very close to the coast of Mexico. The satellite presentation has also improved during the past few hours, but due to shear, the center is still located on the southeastern edge of an area of very deep convection. Fernand does not have to much room for strengthening since its circulation will soon be interacting with the high terrain of eastern Mexico. However, in the next 12 to 18 hours before the center moves inland, some intensification could occur as indicated in the official NHC forecast. Once Fernand moves inland, it will weaken rapidly. The cyclone is moving slowly westward or 270 degrees at 3 kt. Fernand is trapped south of a strong mid-level ridge over the southwestern United States, and this pattern should slowly steer the cyclone on a west-to west-northwest track for the next day or so. This track is consistent with the previous one, and it is consistent with the solution of the global models. The primary threat from this system will be heavy rainfall that could produce flooding and mudslides, especially in the mountainous areas of Mexico. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 23.2N 96.4W 45 KT 50 MPH 12H 04/1200Z 23.5N 97.5W 55 KT 65 MPH 24H 05/0000Z 24.0N 98.5W 30 KT 35 MPH...INLAND 36H 05/1200Z 24.5N 100.0W 20 KT 25 MPH...INLAND 48H 06/0000Z...DISSIPATED $$ Forecaster Avila

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Hurricane Dorian Forecast Discussion Number 42

2019-09-03 22:49:55| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Tue Sep 03 2019 000 WTNT45 KNHC 032049 TCDAT5 Hurricane Dorian Discussion Number 42 NWS National Hurricane Center Miami FL AL052019 500 PM EDT Tue Sep 03 2019 Dorian has finally begun a more definitive northwestward motion this afternoon. The satellite presentation of the hurricane is slightly better in one-minute GOES 16 imagery with the large eye becoming a little more apparent. The eye has also become better defined in NWS Doppler radar from Melbourne, Florida. Reconnaissance aircraft data continue to show an expansion of the tropical-storm and 50-kt wind radii, and it is likely that the area of hurricane-force winds will also increase somewhat during the next 24-36 hours. The initial intensity remains 95 kt, and is a blend of the earlier reconnaissance data and the latest satellite estimates. Dorian will be moving northwestward over untapped waters east of the Florida peninsula, which may lead to some structural re-organization, but little overall change in intensity is expected during the next couple of days. After that time, a gradual decrease in the peak wind speed and an increase in storm size are predicted while the vertical shear increases and the storm moves farther north. An approaching mid-latitude trough and front will begin interacting with the hurricane on Saturday and Dorian is forecast to become a powerful extratropical low by 120 hours. Dorian is now moving northwestward or 325/5 kt. The deep-layer trough along the east coast of the United States is expected to amplify on Wednesday, which should cause Dorian to move at a slightly faster north-northwestward motion tonight and Wednesday. After that time, Dorian should turn northward, and then north- northeastward ahead of a shortwave trough moving into the eastern United States. Once Dorian is offshore of eastern North Carolina, it should accelerate northeastward within the mid-latitude westerlies. The track envelope has edged closer to the coasts of South Carolina and North Carolina and the NHC track has been adjusted in that direction. A track that close to the coast, even if landfall does not occur, is likely to bring dangerous winds, life-threatening storm surge, and flooding rains across the eastern portions of the Carolinas. Key Messages: 1. Life-threatening storm surge and dangerous winds are expected along portions of the Florida east coast and the coasts of Georgia, South Carolina, and North Carolina, 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. The risk of wind and rain impacts along portions of the Virginia coast and the southern Chesapeake Bay are increasing. Residents in these areas should continue to monitor the progress of Dorian. 3. The flash flood threat will increase tonight along the Florida east coast and then spread up the southeast and mid-Atlantic coast during the middle and latter part of the week. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 27.7N 78.7W 95 KT 110 MPH 12H 04/0600Z 28.7N 79.4W 95 KT 110 MPH 24H 04/1800Z 30.0N 80.0W 95 KT 110 MPH 36H 05/0600Z 31.4N 80.0W 95 KT 110 MPH 48H 05/1800Z 32.6N 79.2W 90 KT 105 MPH 72H 06/1800Z 36.1N 74.0W 80 KT 90 MPH 96H 07/1800Z 42.0N 65.0W 75 KT 85 MPH 120H 08/1800Z 50.0N 55.0W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Tropical Depression Eight Forecast Discussion Number 1

2019-09-03 22:40:36| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 03 2019 000 WTNT43 KNHC 032040 TCDAT3 Tropical Depression Eight Discussion Number 1 NWS National Hurricane Center Miami FL AL082019 500 PM AST Tue Sep 03 2019 Satellite images indicate that the broad area of low pressure over the eastern Atlantic has become better defined during day, with rainbands forming on the eastern side of the circulation. This structure is good enough for a tropical depression, and the initial wind speed is set to 30 kt, which agrees with earlier ASCAT passes that showed 25-30 kt. The initial motion estimate is 310/7 kt. A general northwestward motion is anticipated during the next several days, faster by the weekend, as the system is steered by a strengthening eastern Atlantic ridge. One source of uncertainty in the future track is how much the cyclone is affected by a developing mid-level low around 25N45W in a few days. This feature could briefly induce a north-northwestward motion on Friday, and later west-northwestward on day 5 depending on exactly how close the new tropical cyclone gets to the mid-level low. For now it is best not to bite off on any particular model solution, since the intensity and depth of the cyclone isn't certain at this range. Thus, the forecast is close to the Atlantic model consensus TVCA, shaded a bit on the fast side assuming the system keeps some vertical depth. Although the depression is forecast to be in a low-shear environment during the next couple of days, marginal water temperatures should keep the strengthening rate modest. The intensity forecast is complicated beyond that point due to the system's interaction with the mid-level low, drier air in the mid-levels, and increasing waters temperatures. This mixed bag of factors makes the forecast rather murky, with any intensity changes at longer range having low predictability at this point. Therefore, the forecast is leveled off at long range, similar to the NOAA corrected-consensus model HCCA, but this uncertain forecast could require a great deal of revision later tonight or tomorrow. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 19.0N 32.3W 30 KT 35 MPH 12H 04/0600Z 19.7N 33.2W 35 KT 40 MPH 24H 04/1800Z 20.4N 34.0W 40 KT 45 MPH 36H 05/0600Z 21.4N 34.9W 45 KT 50 MPH 48H 05/1800Z 22.4N 35.8W 45 KT 50 MPH 72H 06/1800Z 26.2N 38.5W 45 KT 50 MPH 96H 07/1800Z 30.0N 41.5W 45 KT 50 MPH 120H 08/1800Z 34.0N 45.5W 45 KT 50 MPH $$ Forecaster Blake

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