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Subtropical Storm Rebekah Forecast Discussion Number 5

2019-10-31 21:32:54| National Hurricane Center (Atlantic)

Issued at 500 PM AST Thu Oct 31 2019 000 WTNT44 KNHC 312032 TCDAT4 Subtropical Storm Rebekah Discussion Number 5 NWS National Hurricane Center Miami FL AL192019 500 PM AST Thu Oct 31 2019 Rebekah continues to have a small band of moderate-to-deep convection around the center, although the overall cloud pattern is becoming stretched from northeast to southwest. The initial wind speed is kept at 40 kt. All of the models keep stretching Rebekah out overnight and show it degenerating into a trough within 24 h while it moves eastward. A convergent environment and the cyclone's movement over cool waters are expected to offset any cooling aloft which would promote convection. Since Rebekah is not expected to be a tropical or subtropical cyclone near the Azores, hazard information can be found in regular products issued by the Portuguese Institute for the Sea and Atmosphere (IPMA) for those islands at https://www.ipma.pt/pt/index.html. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 41.1N 33.5W 40 KT 45 MPH 12H 01/0600Z 41.2N 29.9W 35 KT 40 MPH...POST-TROP/EXTRATROP 24H 01/1800Z...DISSIPATED $$ Forecaster Blake

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Subtropical Storm Rebekah Forecast Discussion Number 4

2019-10-31 15:34:49| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Thu Oct 31 2019 000 WTNT44 KNHC 311434 TCDAT4 Subtropical Storm Rebekah Discussion Number 4 NWS National Hurricane Center Miami FL AL192019 1100 AM AST Thu Oct 31 2019 The storm has lost organization since yesterday with only a skeletal curved band west and north of the center. However, ASCAT just came in with 35-40 kt winds, so the initial wind speed will stay 40 kt. Weakening is anticipated today as the low moves over cool waters and into a convergent environment aloft. All of the guidance shows any remaining convection dissipating by this evening, so the storm will likely be in the graveyard in about 12 h. A general eastward track is forecast until Rebekah decomposes into a trough sometime tomorrow, at best becoming a wave along an approaching cold front. Since Rebekah is not expected to be a tropical or subtropical cyclone near the Azores, hazard information can be found in regular products issued by the Portuguese Institute for the Sea and Atmosphere (IPMA) for those islands at https://www.ipma.pt/pt/index.html. FORECAST POSITIONS AND MAX WINDS INIT 31/1500Z 40.7N 35.3W 40 KT 45 MPH 12H 01/0000Z 41.1N 32.1W 35 KT 40 MPH...POST-TROPICAL 24H 01/1200Z 41.0N 27.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 36H 02/0000Z...DISSIPATED $$ Forecaster Blake

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Subtropical Storm Rebekah Forecast Discussion Number 3

2019-10-31 09:33:46| National Hurricane Center (Atlantic)

Issued at 500 AM AST Thu Oct 31 2019 000 WTNT44 KNHC 310833 TCDAT4 Subtropical Storm Rebekah Discussion Number 3 NWS National Hurricane Center Miami FL AL192019 500 AM AST Thu Oct 31 2019 Rebekah's cloud pattern has eroded significantly since the previous advisory and only a narrow band of fragmented convection remains in the northeastern quadrant. There are no signs of any upper-level anticyclonic outflow, so the cyclone will retain subtropical status. Earlier ASCAT-A/B/C overpasses indicated several 38-39 kt surface wind vectors in the southern semicircle and given that Rebekah is now moving at a faster forward speed, the intensity remains at 40 kt despite the degraded convective pattern. The initial motion estimate is 065/18 kt. Rebekah is forecast to move east-northeastward to eastward around the southeastern periphery of a larger non-tropical low pressure system for the next day or two before dissipating by 48 hours. The model guidance has shifted northward significantly and the official forecast has been moved in that direction as well, but not as far north nor as fast as the model consensus, lying closer to a blend of the GFS and ECMWF model solutions. Rebekah will be moving over cooler waters that are less than 20 deg C and into a stronger vertical wind shear regime by 12 h and beyond. This combination of unfavorable dynamic and thermodynamic conditions should cause the cyclone to steady weaken and become a post-tropical cyclone in 24 h or less, with dissipation expected by 48 h. Although the center of Rebekah is expected to pass north of the Azores, those islands could still receive gusty winds and locally heavy rainfall, especially on the southward-facing slopes of elevated terrain. Since Rebekah is not expected to be a tropical or subtropical cyclone when it nears the Azores, hazard information can be found in regular products issued by the Portuguese Institute for the Sea and Atmosphere (IPMA) for those islands at https://www.ipma.pt/pt/index.html. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 39.7N 36.7W 40 KT 45 MPH...SUBTROPICAL STORM 12H 31/1800Z 40.6N 33.7W 40 KT 45 MPH...SUBTROPICAL STORM 24H 01/0600Z 40.6N 29.4W 35 KT 40 MPH...POST-TROP/EXTRATROP 36H 01/1800Z 40.3N 25.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 48H 02/0600Z...DISSIPATED $$ Forecaster Stewart

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Subtropical Storm Rebekah Forecast Discussion Number 2

2019-10-31 03:38:15| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Wed Oct 30 2019 000 WTNT44 KNHC 310238 TCDAT4 Subtropical Storm Rebekah Discussion Number 2 NWS National Hurricane Center Miami FL AL192019 1100 PM AST Wed Oct 30 2019 The cloud pattern has not changed very much during the past few hours and still consists primarily of a convective band that wraps around the center of circulation of the cyclone. Recent ASCAT data reveal that the cyclone has a well-defined circulation with 40-kt winds, but these strong winds are confined to the southern semicircle. Most of the guidance indicates that Rebekah will change very little in intensity during the next 24 hours, and after that time, the combination of cold waters and strong upper-level winds should result in the cyclone becoming extratropical while weakening. Most of the global models dissipate the cyclone in 48 hours or sooner, and so does the NHC forecast. As indicated in the previous advisory, Rebekah is rotating around a larger non-tropical low pressure system, and the best estimate of the initial motion is toward the east or 080 degrees at 15 kt. However, a turn to the east-northeast is possible tonight and early Thursday, before Rebekah becomes even more embedded within the flow behind a mid-level trough. The cyclone should then turn toward the east-southeast until it dissipates later this week. Since the track guidance is better agreement tonight, the confidence in the track prediction is a little higher. The NHC forecast is in the middle of the guidance envelope and is not very different from the previous one. Since Rebekah is not currently forecast to be a tropical or subtropical cyclone when it nears the Azores, hazard information can be found in regular products issued by the Portuguese Institute for the Sea and Atmosphere (IPMA) for those islands. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 38.5N 38.8W 40 KT 45 MPH 12H 31/1200Z 39.5N 36.0W 40 KT 45 MPH 24H 01/0000Z 40.0N 32.5W 40 KT 45 MPH 36H 01/1200Z 39.5N 28.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 02/0000Z 38.0N 22.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 03/0000Z...DISSIPATED $$ Forecaster Avila

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Subtropical Storm Rebekah Forecast Discussion Number 1

2019-10-30 21:39:06| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Oct 30 2019 000 WTNT44 KNHC 302039 TCDAT4 Subtropical Storm Rebekah Discussion Number 1 NWS National Hurricane Center Miami FL AL192019 500 PM AST Wed Oct 30 2019 Cloudiness and showers associated with a small low pressure system embedded within a larger non-tropical low over the north-central Atlantic have become better organized during the day. The cyclone has a broken convective band that wraps about halfway around its eastern semicircle, with a small area of central convection near its center. The cloud tops within the convection are not particularly cold and the system is co-located with a large upper-level low, so it is initially designated as a subtropical cyclone. The intensity is assessed as 40 kt based primarily on earlier ASCAT data. It is worth mentioning that the system also has some characteristics of a tropical cyclone, since the radius of maximum winds is not very large and the system has some moderate central convection. Much like Pablo just a few days ago, Rebekah is currently rotating around a larger non-tropical low pressure system. The initial motion estimate is 080/11 kt, but an east-northeastward motion is expected later tonight. The track model spread is larger than normal and confidence in the track forecast is low, though most of the models generally show Rebekah turning back toward the east by early Friday, followed by a turn toward the east-southeast until it dissipates later this week. On the forecast track, the center of Rebekah is forecast to approach the western-most Azores early Friday as a post-tropical/extratropical cyclone. The intensity guidance unanimously forecasts that Rebekah will change little in strength during the next 24 h, though given the small size of the cyclone, some short-term fluctuations are possible tonight. Most of the dynamical models then forecast that Rebekah's convection will decrease substantially by early Friday, likely due to a combination of colder SSTs and unfavorable upper-level winds. The cyclone is therefore forecast to become post-tropical around that time, and gradual weakening is expected. Rebekah will likely dissipate by the weekend, if not sooner. Since Rebekah is not currently forecast to be a tropical or subtropical cyclone when it nears the Azores, hazard information can be found in regular products issued by the Portuguese Institute for the Sea and Atmosphere (IPMA) for those islands. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 38.3N 40.7W 40 KT 45 MPH 12H 31/0600Z 39.0N 38.4W 40 KT 45 MPH 24H 31/1800Z 39.9N 35.0W 40 KT 45 MPH 36H 01/0600Z 39.8N 31.3W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 01/1800Z 38.9N 26.3W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 02/1800Z...DISSIPATED $$ Forecaster Zelinsky

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