MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #163
*******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.**********
...MONDAY NOVEMBER 15 2021 9:00 AM EDT...
Satellite image as of 1300Z. 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 1800Z (Nov 14):
GFS Model Upper-Level Winds 0000Z:
See area of interest #1 section below for an update on the potential for subtropical development to the south of the Azores over the next couple of days. Elsewhere… another deep-layered ridge is forecast to develop in the western Atlantic in the days ahead with the aid of the warm sector of another strong fronts system to cross North America. This will result in the currently cold central Canada upper trough (the one driving the frontal low that recently passed through the Great Lakes) evolving into a rather cold cut-off upper vortex just west or southwest of the Azores in the days ahead. This upper vortex with its eastern divergence zone may re-energize the forecast surface remnants of Area of Interest #1 by next week… with the de-stabilizing cold temperatures of the upper vortex potentially allowing the remnants to have a second chance at becoming tropical. Alternatively the upper vortex may produce its own separate surface cyclone that may acquire tropical characteristics by next week. If these computer model trends continue… will declare new area of interest or extend the outlook for area of interest #1 as needed in future updates.
AREA OF INTEREST #1...The warm sector of a series of surface lows from the Great Lakes to Canada has produced a warm deep-layer ridge that spans the western and northern Atlantic. This ridge has cut-off the south part of the current northeast Atlantic upper trough into an upper vortex… and the surface frontal low that was forming near the Azores over the weekend has whirled south into the vortex. As of 0600Z this morning the surface low’s center passed 34N-30W. The upper vortex and surface low are expected to drift southwest around the deep-layered ridge over the next couple of days… and will continue to watch for signs of thunderstorm activity and possible tropical characteristics as the upper vortex is cold (below 1200 dekameters in height)… which will aid in instability despite water temps in the mid-20s of deg C. There was a band of showers on the south side of the surface low overnight… which has since fizzled out as of this morning and therefore I have lowered subtropical development odds to 30%. I did not lower odds further as the upper vortex is still cold and activity could return.
The deep-layered ridge currently has its upper layer to the northwest... and surface layer (supported by the eastern convergence zone of the upper layer) passing to the north. This will result in the surface layer pushing the surface low on a more westward angle in track while the upper layer keeps the upper vortex more toward the east... and the surface low is expected to migrate beneath the west side of the upper vortex by 48 hours as a result. Conditions beneath the west side of the upper vortex will tend to be hostile for subtropical development with northerly wind shear and upper convergence… and therefore my odds of subtropical development are dropped to 0% for the 48 hour timeframe.
In future updates… the outlook for this system may have to be extended beyond 48 hours as another cold upper vortex becomes deposited near this system and potentially re-energizes it over the next several days. See the intro section of this post for more details.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0600Z Nov 16)… 30% chance of subtropical cyclone formation (eastern Atlantic near 31.5N-31.5W)
IOH 48 Hr Outlook (0600Z Nov 17)… 0% chance of subtropical cyclone formation (eastern Atlantic near 28N-36W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Nov 14) CMC Model Run...
**For Area of Interest #1... frontal low shifts southwest to 33N-32.5W through 30 hours while potentially acquiring tropical characteristics… continues southwest to 25N-35W through 84 hours while weakening to a remnant trough.
**Current cold front over Great Lakes reaches North Atlantic near 40.5N-34.5W at 102 hours where a frontal low forms… through 168 hours the frontal low undergoes a cyclonic loop just west of the Azores as an upper vortex cuts-off overhead… with the frontal low potentially acquiring tropical characteristics
1200Z (Nov 14) ECMWF Model Run...
**For Area of Interest #1... frontal low shifts southwest to 33N-30.5W through 24 hours while potentially acquiring tropical characteristics…continues southwest to 28N-34W through 120 hours while weakening… becomes re-energized and whirls north by 144+ hours to a location just southwest of the Azores due to eastern divergence zone of a cut-off upper vortex to be deposited by current frontal system over Great Lakes… makes a second attempt at acquiring tropical characteristics beneath this vortex by 168 hours
0000Z GFS Model Run...
**For Area of Interest #1... frontal low shifts southwest to 32.5N-32.5W through 24 hours while featuring multiple centers which may limit potential for tropical development… continues southwest to 22.5N-36W through 90 hours while weakening to a remnant trough.
**Current cold front over Great Lakes reaches North Atlantic near 40N-34W at 93 hours where a frontal low forms… through 138 hours the frontal low undergoes a cyclonic loop just west of the Azores as an upper vortex cuts-off overhead… with the frontal low potentially acquiring tropical characteristics
1200Z (Nov 14) NAVGEM Model Run...
**For Area of Interest #1... frontal low shifts southwest to 32N-32.5W through 24 hours while potentially acquiring tropical characteristics…continues southwest to 26N-35W through 120 hours while weakening…becomes re-energized and whirls north by 144+ hours due to eastern divergence zone of a cut-off upper vortex to be deposited by current frontal system over Great Lakes… makes a second attempt at acquiring tropical characteristics beneath this vortex near 33N-32.5W by 168 hours