MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #24
*******Note that forecast 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 JUNE 5 2023 11:59 PM EDT...
For the northeastern Atlantic Ocean... the southeastern divergence zone of the upper vortex moving into the region has produced a rapid-forming surface frontal cyclone just southeast of the Azores. The National Hurricane Center is monitoring this frontal cyclone for possible acquisition of tropical characteristics... see area of interest #6 section below for additional details.
As done on this site starting last year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development throughout the year... resetting back to #1 at the start of each year. This scheme is so that each area of interest retains a numeric identity from update to update... which reduces confusion when simultaneous areas of interest begin and end when tropical activity increases during the Atlantic Hurricane Season. The current area of interest is tagged #6 as the first five were assigned in earlier birdseye view posts on this site.
AREA OF INTEREST #6...A cold core upper vortex from the north-central Atlantic has been sliding into the northeastern Atlantic while pushed by an expanding warm core upper ridge produced by the warm sector of the northwestern Atlantic frontal cyclone that has been gradually materializing offshore of Nova Scotia. The surface frontal low previously produced by this upper vortex has dissipated after it whirled into a position directly beneath the upper vortex core where there is a lack of divergence. The cycle is being repeated today as the southeastern divergence zone of the upper vortex has produced the rapid formation of a new frontal cyclone just southeast of the Azores... and by tomorrow the southward cold air transport on the west side of the frontal cyclone will have already pulled the cold core of the upper vortex toward itself (while the frontal cyclone also cyclonically orbits in the flow around the upper vortex) such that the two become stacked and the frontal cyclone begins its post-mature decay phase. The National Hurricane Center since 8 AM EDT Monday has introduced this frontal cyclone as an area of interest for possible subtropical development as the frontal cyclone potentially develops core thunderstorm activity and tropical characteristics in its post-mature decay phase.
During the post-mature decay phase... the frontal cyclone just southeast of the Azores will be parked over 20 deg C waters while the 200 mb height of the upper vortex's cold core is forecast to be just above 1190 dekameters. As noted in previous birdseye view posts on this site... I previously had not considered this system a tropical area of interest as I preferred to see water temps of at least 22 deg C given the forecast 200 mb height... or alternatively colder upper air temps (200 mb heights lower than 1190 dekameters) given the current water temps in the region... before considering that this system would have enough instability (enough contrast between warm waters and cold upper air temps) for thunderstorms and possible tropical characteristics. However this system is now a tropical area of interest by default as it is now in the NHC tropical weather outlook... and because there is also increasing thunderstorm activity appearing just north of the swirl center I have opted for odds of subtropical cyclone formation higher than the NHC's outlook as of this writing while setting them at 20%. Over the next 24 hours I forecast the frontal cyclone to cyclonically whirl toward the core of the upper vortex as the two become stacked... as discussed in the previous paragraph... which will place the frontal cyclone's center very close to the eastern Azores.
For the period between 24 and 48 hours... the models (except the less-reliable NAVGEM) have come into agreement on the future evolution of this system... and the forecast track in my outlook below is a reflection of the model consensus. Essentially the models show the eastern divergence zone of the upper vortex making yet another frontal cyclone to the east-northeast... with the south side of the new neighboring frontal cyclone pulling our tropical area of interest (near the eastern Azores) eastward and absorbing it with its south side. The forecast absorption is why I drop odds of subtropical cyclone formation to 0% by 48 hours. For the 48+ hour period... the upper trough fragment currently south of Greenland is expected to evolve into another cut-off upper vortex due to the ongoing amplification of the current north Atlantic upper ridge... with the absorbing frontal cyclone and upper vortex near the Azores lifting northward while orbiting around the second cut-off upper vortex south of Greenland. Because the absorbing frontal cyclone will be lifting northward into even cooler waters... and because it will broaden with multiple centers (instead of a single center customarily associated with tropical activity) due to the mutliplicity of upper divergence regions as the two upper vortices mingle and then merge... a second round of possible subtropical development is NOT expected for the absorbing frontal cyclone in the 48+ hour window.
The sprawling circulation of the current frontal cyclone just southeast of the Azores... and the adjacent frontal cyclone to form to the east-northeast and absorb the one currently near the Azores... will bring periods of heavy rainfall... coastal surf... and gusty winds to the Azores and Canary Islands thorugh Wednesday. Coastal surf will also be reaching the western shores of Portugal and Spain. These impacts will largely remain the same regardless of whether or not the frontal cyclone currently near the Azores acquires tropical characteristics.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jun 7)... 20% chance of subtropical cyclone formation (vicnity of eastern Azores near 37N-24.5W)
IOH 48 Hr Outlook (0000Z Jun 8)... 0% chance of tropical cyclone formation (northeastern Atlantic Ocean near 37.5N-17.5W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT***************************
Formation chance through 48 hours...10%
Formation chance through 7 days (168 hours)...10%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Jun 5) CMC Model Run...
**For area of interest #6... for the next 24 hours the surface low pressure currently just southeast of the Azores remains the dominant in the region... through 48 hours the center just southeast of the Azores becomes entangled with and absorbed by another low pressure center that develops east-northeast of the Azores... through 120 hours the surface low pressure east-northeast of the Azores goes on to have multiple centers while drifting northeastward to 43N-19W
1200Z (Jun 5) ECMWF Model Run...
**For area of interest #6... for the next 24 hours the surface low pressure currently just southeast of the Azores remains the dominant in the region... through 48 hours the center just southeast of the Azores becomes entangled with and absorbed by another low pressure center that develops east-northeast of the Azores... through 120 hours the surface low pressure east-northeast of the Azores goes on to have multiple centers while drifting northeastward to 44N-21.8W
1800Z (Jun 5) GFS Model Run...
**For area of interest #6... for the next 24 hours the surface low pressure currently just southeast of the Azores remains the dominant in the region... through 54 hours the center just southeast of the Azores becomes entangled with and absorbed by another low pressure center that develops to the northeast... through 120 hours the absorbing northeastern low pressure center goes on to have multiple centers while drifting north to 46N-20W
1800Z (Jun 5) NAVGEM Model Run...
**For area of interest #6... for the next 24 hours the surface low pressure center currently just southeast of the Azores remains the dominant in the region... through 36 hours the center just southeast of the Azores becomes entangled with and absorbed by another low pressure center that develops east-northeast of the Azores... the center east-northeast of the Azores goes on to drift east-northeastward toward 39.5N-18.5W through 54 hours with possible subtropical development... the possible subtropical cyclone subsequently curves northward in a cyclonic loop and reaches cooler water near 44N-21.5W by 120 hours where it would lose tropical characteristics