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Tropical Storm Debby Forecast Discussion Number 6

2018-08-08 22:33:15| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Aug 08 2018 581 WTNT44 KNHC 082033 TCDAT4 Tropical Storm Debby Discussion Number 6 NWS National Hurricane Center Miami FL AL042018 500 PM AST Wed Aug 08 2018 Satellite images indicate that Debby's circulation is becoming elongated and the low-level center is on the northeastern edge of an area of moderate convection. A blend of the satellite intensity estimates, and data from an earlier ASCAT pass yields an intensity of 35 kt at this time. Debby is already moving over cooler waters, so additional weakening is anticipated, and the circulation should should open up into a trough on Thursday. In fact, this is the solution of the GFS and the ECMWF models. Satellite fixes indicate that Debby is moving toward the northeast or 040 degrees at 13 knots. The cyclone is well embedded within the southwesterly flow ahead of a mid-latitude trough, and this pattern should continue to steer Debby northeastward with some increase in forward speed. The track models continue to be in pretty good agreement. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 42.0N 47.2W 35 KT 40 MPH 12H 09/0600Z 43.5N 45.4W 30 KT 35 MPH 24H 09/1800Z 45.5N 41.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 36H 10/0600Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm Kristy Forecast Discussion Number 8

2018-08-08 22:31:44| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Wed Aug 08 2018 500 WTPZ43 KNHC 082031 TCDEP3 Tropical Storm Kristy Discussion Number 8 NWS National Hurricane Center Miami FL EP132018 200 PM PDT Wed Aug 08 2018 Kristy's overall structure hasn't changed much over the past few hours, but cloud tops associated with the deepest convection have noticeably warmed. The intensity estimates from all agencies have also not changed, so the initial intensity has been held at 40 kt. Unfortunately, the various intensity models have not changed, either and the spread remains high. While the HWRF continues to show Kristy quickly strengthening to hurricane intensity, all of the statistical-dynamical guidance keeps the tropical storm very weak throughout the forecast period. The NHC forecast therefore continues to split the difference between these scenarios and shows slow strengthening for a couple of days while the cyclone remains in a low-shear environment. By days 4 and 5, Kristy is forecast to be moving over much cooler SSTs and through a more stable environment, which should cause it to weaken and become a remnant low. The track forecast is also still low confidence. Although Kristy is currently moving west-northwestward with an initial motion of 300/5 kt, the models are in good agreement that Kristy will turn northward overnight and tomorrow due to a weakness in the subtropical ridge created by Hurricane John. The uncertainty grows substantially beyond 24 h. The GFS continues to insist on a steering flow that will cause Kristy to become wrapped up in the larger circulation of John, while the UKMET and ECMWF show only a slow northward motion, followed by a turn back toward the west or northwest once the cyclone becomes a remnant low. The NHC forecast has been favoring the western solution, and I don't see an obvious reason to change that reasoning at this time. Therefore, little change has been made to the track forecast, which lies near a consensus of those two models, a little west of the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 14.7N 129.6W 40 KT 45 MPH 12H 09/0600Z 15.3N 130.0W 40 KT 45 MPH 24H 09/1800Z 16.2N 130.3W 45 KT 50 MPH 36H 10/0600Z 17.2N 130.3W 50 KT 60 MPH 48H 10/1800Z 18.2N 130.0W 50 KT 60 MPH 72H 11/1800Z 20.2N 130.0W 45 KT 50 MPH 96H 12/1800Z 21.3N 130.7W 35 KT 40 MPH 120H 13/1800Z 22.0N 132.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Zelinsky

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Hurricane John Forecast Discussion Number 12

2018-08-08 16:36:14| Tropical Depression LIDIA

Issued at 900 AM MDT Wed Aug 08 2018

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Tropical Storm Debby Forecast Discussion Number 5

2018-08-08 16:36:14| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Aug 08 2018 013 WTNT44 KNHC 081436 TCDAT4 Tropical Storm Debby Discussion Number 5 NWS National Hurricane Center Miami FL AL042018 1100 AM AST Wed Aug 08 2018 The cloud pattern of Debby this morning is definitely typical of a tropical cyclone instead of a subtropical system with moderate convection wrapping around the center, and a well defined upper-level outflow in the eastern semicircle. A blend of the satellite intensity estimates from TAFB and CIMMS SATCON still support an initial intensity of 40 kt. A recent ASCAT pass suggest that this estimate could be generous. Debby is already moving over cooler waters, so a gradual weakening is anticipated before the system becomes extratropical and then gets absorbed by a larger trough. In fact, most of the reliable global models degenerate Debby into a trough of low pressure on Thursday. The initial motion is toward the northeast or 035 degrees at 10 kt. The cyclone is embedded within a mid-latitude trough, and will continue to move on this general northeastward track with some increase in forward speed in tandem with the trough until dissipation. The track models are in pretty good agreement on this solution. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 41.2N 48.3W 40 KT 45 MPH 12H 09/0000Z 42.4N 47.2W 35 KT 40 MPH 24H 09/1200Z 44.2N 44.0W 35 KT 40 MPH 36H 10/0000Z 46.5N 39.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 48H 10/1200Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm Kristy Forecast Discussion Number 7

2018-08-08 16:33:41| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Wed Aug 08 2018 359 WTPZ43 KNHC 081433 TCDEP3 Tropical Storm Kristy Discussion Number 7 NWS National Hurricane Center Miami FL EP132018 800 AM PDT Wed Aug 08 2018 Kristy has continues to have the structure of a strongly sheared tropical cyclone. The low-level center has been difficult to identify overnight, but recent microwave data indicates that it is displaced to the northwest of the primary convective mass. The initial intensity has been held at 40 kt based on a blend of Dvorak Final-T numbers from TAFB and SAB. Although the low-level center has been somewhat difficult to track, it appears that Kristy has begun to turn west-northwestward, and the initial motion estimate is 290/7 kt. Little change has been made to the official track forecast, but confidence remains very low. A break in the subtropical ridge created by Hurricane John should allow Kristy to continue turning, resulting in a northward motion by Thursday. Beyond that time, the model spread remains high, fueled by a combination of uncertainty as to how much John and Kristy will directly interact, and how much Kristy will respond to an upper-level trough to the northwest. The GFS is a notable outlier on the east side of the guidance envelope, and is the only model showing Kristy wrapping around the circulation of John. For now, the NHC forecast continues to downplay this possibility, and is a little to the west of the multi-model consensus. The intensity guidance spread is also high, ranging from the HWRF which makes Kristy a hurricane, to the SHIPS and LGEM which forecast only gradual weakening. Since the shear is forecast to decrease over the next 12 to 24 hours, and Kristy will be moving away from the cold wake of Hector and over warmer waters, at least some strengthening seems likely. By the second half of the forecast period, the cyclone will be passing over much colder SSTs and through a drier environment, which should cause the cyclone to steadily weaken and become a remnant low. The NHC forecast is now close to the model consensus IVCN, which is higher this cycle. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 14.4N 129.3W 40 KT 45 MPH 12H 09/0000Z 15.0N 130.0W 40 KT 45 MPH 24H 09/1200Z 15.9N 130.5W 45 KT 50 MPH 36H 10/0000Z 16.8N 130.6W 45 KT 50 MPH 48H 10/1200Z 17.7N 130.4W 50 KT 60 MPH 72H 11/1200Z 19.8N 130.2W 45 KT 50 MPH 96H 12/1200Z 21.5N 131.5W 35 KT 40 MPH 120H 13/1200Z 22.0N 133.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Zelinsky

Tags: number discussion storm tropical

 

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