*******Note that forecasts and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********
...WEDNESDAY NOVEMBER 17 2021 9:59 AM EDT...
Satellite image as of 0630Z. Areas of interest circled in yellow are not mentioned in the NHC tropical weather outlook. Areas circled in a green dashed line are in the NHC 5-day tropical weather outlook. Areas circled in a solid green are in the NHC 2-day tropical weather outlook:
NHC TAFB Surface Analysis 0000Z:
GFS Model Upper-Level Winds 0000Z:
A warm deep-layered ridge is expected to develop in the western Atlantic in the days ahead with the aid of the warm sector of the current central Canada frontal cyclone. The ridge is forecast to cut-off a large portion of the upper trough currently exiting eastern Canada into an upper vortex located just west of the Azores…with the divergence zone of the vortex in turn generating a surface cyclone in the days ahead. Models still vary on the shape and amplitude of the forecast upper ridge… which results in some solutions that have an elongated upper vortex with a broad upper divergence zone which in turn causes the forecast surface cyclone to be elongated with possible multiple centers instead of a singular circular center needed for subtropical development. In some solutions the elongation of the surface cyclone is exacerbated by forecast absorption of the current eastern Atlantic surface low. As a result I have not declared an area of interest for the forecast surface cyclone. However it should be noted that regardless of subtropical development… the surface cyclone is expected to generate a period of gusty winds and coastal sea swells for the Azores by 4+ days. This period of unsettled weather will likely last for a long stretch as the surface cyclone potentially becomes re-invigorated by the divergence zone of amplified upper vorticity to be deposited by the current western Canada upper trough… once that trough moves later moves into the Atlantic in the longer range.
Elsewhere… showers and thunderstorms have increased in the northwestern Caribbean Sea over the last 24 hours… along the decaying tail end of a cold front driven by the current eastern Canada frontal cyclone and supported by upper divergence ahead of upper vorticity currently over the southeastern United States. However westerly shear is expected to be too high for tropical development here due to the westerly flow ahead of the upper vorticity… especially as another batch of upper vorticity becomes deposited by the current western Canada upper trough and shifts east toward the northwestern Caribbean in the days ahead.
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
0000Z CMC Model Run...
**Current North Atlantic cold front develops a surface low west of the Azores at 66 hours with the support of an upper vortex to be left behind by the current upper trough exiting eastern Canada… frontal low intensifies into an elongated frontal cyclone southwest of the Azores through 108 hours while cyclonically whirling beneath the upper vortex… from 120 to 138 hours the surface cyclone obtains a circular structure and possible tropical character… by 144+ hours the surface cyclone whirls north-northwest toward the far North Atlantic while whirling toward upper vorticity to be left behind by the current upper trough over western Canada (once that trough later moves into the Atlantic)
1200Z (Nov 16) ECMWF Model Run...
**Current North Atlantic cold front develops a surface low northwest of the Azores at 72 hours with the support of an upper vortex to be left behind by the current upper trough exiting eastern Canada…frontal low becomes elongated with multiple centers through 120 hours while whirling in the current eastern Atlantic surface low… afterwards the frontal low shifts northwest while whirling toward upper vorticity to be left behind by the current upper trough over western Canada (once that trough later moves into the Atlantic)
0000Z GFS Model Run...
**Current North Atlantic cold front develops a surface low just northwest of the Azores at 63 hours with the support of an upper vortex to be left behind by the current upper trough exiting eastern Canada…frontal low intensifies into an elongated frontal cyclone just southwest of the Azores through 102 hours while cyclonically whirling beneath the upper vortex… through 126 hours and while whirling in and absorbing the current eastern Atlantic surface low the elongated surface cyclone shifts east into the Azores… afterwards the cyclone becomes more elongated (east-to-west) while whirling northwest out of the Azores and toward upper vorticity to be left behind by the current upper trough over western Canada (once that trough later moves into the Atlantic)
0000Z NAVGEM Model Run...
**Current North Atlantic cold front develops a surface low just west of the Azores at 72 hours with the support of an upper vortex to be left behind by the current upper trough exiting eastern Canada…frontal low intensifies into an elongated frontal cyclone just southwest of the Azores through 120 hours while cyclonically whirling beneath the upper vortex…through 156 hours the cyclone swings north into the Azores while whirling toward upper vorticity to be left behind by the current upper trough over western Canada (once that trough later moves into the Atlantic)