*******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.**********
...SATURDAY OCTOBER 22 2022 6:04 AM EDT...
As anticipated over the last few days... a deep-layered low pressure has developed in the open central Atlantic. Despite previous model runs showing otherwise... the surface layer of the deep-layered low pressure has developed a consolidated center and therefore now has potential to transition into a subtropical or tropical cyclone that will move toward the general direction of Bermuda in the days ahead. See area of interest #41 section below for more details.
Elsewhere... the current upper trough heading into the western Atlantic from the eastern United States is expected to become cut-off from the mid-latitude westerlies and remain amplified due to adjacent amplification of warm core upper ridging to the northwest and north... to be caused by the warm sectors of the current Canadian frontal cyclone and warm sector of a western US frontal cyclone that is forecast to develop over the next few days. In turn... the east side of the amplified and cut-off western Atlantic upper trough could host an environment of low shear and increased upper divergence conducive for the development of yet another subtropical or tropical disturbance between Bermuda... the Carolinas... and the Bahamas... or to the west-southwest of area of interest #41. However not currently adding a second area of interest in this region as models are not fully in agreement as of this writing on developing a subtropical disturbance in this region. However if later model runs converge on this scenario... or if future observations warrant... will add an additional area of interest in this region in future updates.
New to this site this year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development. In this scheme... will reset back to #1 at the start of next year (January 2023). The current area of interest in this blog post is designated #41 as the other numbers were used in previous birdseye view posts. This scheme is to reduce confusion as Atlantic tropical activity increases during the peak of the hurricane season... when multiple simultaneous areas of interest begin and end which previously required shuffling around the area of interest numbers from update to update.
AREA OF INTEREST #41... The upper trough and surface low pressure that has been in the open central Atlantic has become cut-off from the mid-latitude westerlies by a deep-layered ridge that has built to the north. The upper trough is now a small upper vortex located over the surface low... effectively creating a small deep-layered low pressure located at 28.8N-44.5W as of 0600Z this early morning. The deep-layered low pressure is now a feature accelerating westward around the south side of the deep-layered ridge and over the last several hours has developed a consolidated surface center featuring a cloud swirl with small pockets of showers and thunderstorms. As a result the NHC has added this system into their tropical weather outlook within the last 24 hours while now monitoring this system for signs of acquiring tropical characteristics... this also marks the forty-first Atlantic tropical area of interest I have monitored on this blog this year.
For the next 48 hours... the small upper vortex of the deep-layered low pressure system will be merging with a larger upper vortex to the southwest. This will embed the surface layer of the low pressure beneath a vigorous easterly jet between the north side of the merged upper vortex and south side of the deep-layered ridge. Therefore a brisk westward track of the surface low is anticipated in the short-term as shown in the outlook below. Although the surface low currently has limited showers and thunderstorms... I do agree with the NHC's 20% odds of subtropical cyclone formation as this system will reach warmer 28 deg C waters that may aid in an increase in this system's thunderstorm activity. These odds are on the low side as most models agree on weakening the surface low to a surface trough instead of forecasting a subtropical cyclone.
For 72+ hours... the norhtwest portion of the upper vortex to the south is expected to merge with a north fragment of the upper trough currently approaching from the eastern US... potentially resulting in a northwest-southeast tilted upper trough in the northwest Atlantic and offshore of the northeastern US. The forecast track of the surface low takes a northwest turn during this timeframe while becoming steered between the east side of the tilted upper trough and west side of the deep-layered ridge. Note for this timeframe that I switch from a subtropical to tropical designation in the outlook below as the surface low will be more in touch with the anticyclonic outflow of the upper-layers of the warm core deep-layer ridge. However I also taper down the development odds during this timeframe as the forecast track carries this system into water temps below 26 deg C and the upper air temps will be too warm to support instability over cooler waters. The outlook below is ended at 96+ hours... with 0% development odds shown... as this system likely transitions into a non-tropical frontal low to be supported by the divergence zone of the tilted upper trough. Models disagree in the long-range on whether or not this system passes over or just northeast of Bermuda. I have selected a more eastern forecast track based on the location of the upper divergence maximum of the tilted upper trough in the long range per the recent 0000Z GFS model run... given that this system will likely be transitioning into a less tropical feature to be supported by the upper trough. It is interesting to note that the 0000Z GFS itself... along with some other models... showed the surface low moving further west and into Bermuda perhaps while giving credence to the strength of the deep-layer ridge's surface layer... however I prefer to have the surface low follow the location of the tilted upper trough's divergence maximum which makes more sense for where the surface low will be located. However interests in Bermuda should be aware of this system for possible gusty winds and heavy rains by Tuesday morning should the western-outlier model runs verify... or if the forecast location of the titled upper trough shifts west in future model runs.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0600Z Oct 23)... 20% chance of subtropical cyclone formation (central Atlantic near 28.8N-52W)
IOH 48 Hr Outlook (0600Z Oct 24)... 20% chance of subtropical cyclone formation (central Atlantic near 29.5N-58W)
IOH 72 Hr Outlook (0600Z Oct 25)... 10% chance of tropical cyclone formation (just east-northeast of Bermuda near 33N-62.5W)
IOH 96 Hr Outlook (0600Z Oct 26)... 0% chance of tropical cyclone formation (northwestern Atlantic near 36N-66W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/). For ECMWF model used Tropical Tidbits (https://www.tropicaltidbits.com/analysis/models/)
0000Z (Oct 22) CMC Model Run...
**For area of interest #41... passes just northeast of Bermuda at 78 hours... subsequently turns north and strengthens into a non-tropical frontal cyclone approaching Nova Scotia and Newfoundland by 120 hours.
0000Z (Oct 22) ECMWF Model Run...
**For area of interest #41... weakens to a trough near 29N-49W at 24 hours... redevelops into a surface low over Bermuda at 72 hours... moves north-northwest toward the northeastern US coast by 120 hours while transitioning into a broad non-tropical frontal low.
0000Z (Oct 22) GFS Model Run...
**For area of interest #41... weakens to a trough near 27.5N-46.2W at 15 hours... trough passes over Bermuda at 72 hours... trough turns north-northwest toward the waters offshore of the northeastern US through 120 hours while gradually transitioning into a broad non-tropical frontal low.
**Upper trough currently moving into the western Atlantic from the eastern US becomes cut-off from the mid-latitude westerlies over next 120 hours due to upper ridging that builds to the north and northwest in the warm sectors of Canadian and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low near 27.5N-65.5W at 120 hours.
0000Z (Oct 22) NAVGEM Model Run...
**For area of interest #41... weakens to a trough near 29.5N-52W at 30 hours... redevelops into a surface low just east-northeast of Bermuda at 72 hours... subsequently strengthens into a non-tropical frontal low that moves north-northwest into the waters offshore of Nova Scotia and northeastern US by 120 hours.
**Upper trough currently moving into the western Atlantic from the eastern US becomes cut-off from the mid-latitude westerlies over next 120 hours due to upper ridging that builds to the north and northwest in the warm sectors of Canadian and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low near 29N-65W at 120 hours.