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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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