*******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.**********
...SUNDAY OCTOBER 23 2022 8:12 PM EDT...
A subtropical low pressure area continues to approach Bermuda from the east and has potential to bring heavy rainfall and gusty winds to the island by late Monday or early Tuesday... see area of interest #41 section below for an update on this system. In addition... models have come into better agreement that the cut-off upper trough currently offshore of the southeastern US will produce an additional subtropical surface low pressure area. This second subtropical low pressure area is expected to approach Bermuda from the southwest with potentially stronger impacts arriving by Thursday due to better upper air support for this second feature. See area of interest #42 section below for more information on the second feature.
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 are designated #41 and #42 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... A subtropical deep-layered low pressure system in the open central Atlantic continues to track westward toward the general direction of Bermuda while pushed around the south side of a deep-layered ridge to the north. This system has recently merged with a larger upper vortex to the southwest and an associated area of low surface pressure that was being generated by the eastern divergence zone of the larger vortex. In this merger... the surface circulation of the deep-layered low has become a less organized and broader surface trough. Although I do agree with the NHC lowering development odds as this system has become less organized... I have not quiet lowered the odds as far as the NHC while settling for 15% as the models also are in unanimous agreement on the surface trough re-strengthening into a surface low in the next 24 hours. The mechanism for the surface trough to re-develop into a surface low appears to be split flow upper divergence between the northwest quadrant of the large upper vortex in the region and southwest quadrant of the upper layers of the deep-layer ridge.
For the longer range... the north portion of the current upper trough that has recently emerged from the US east coast is expected to evolve into a northwest-southeast tilted upper trough. Therefore after passing over/near Bermuda... this system is expected to curve northwest in track between the tilted upper trough and southwest side of the deep-layered ridge. I drop tropical cyclone development odds to 0% for 48+ hours as this system moves into cooler waters and transitions into a less tropical system supported by the eastern divergence zone of the tilted upper trough. The long-range forecast track has shifted west due to a shift in the forecast position of the tilted upper trough... and this system is now likely to pass directly over Bermuda by late Monday or early Tuesday. Expect the potential for heavy rainfall and gusty winds for the island regardless of tropical cyclone formation or not.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 24)... 15% chance of tropical cyclone formation (east-southeast of Bermuda near 31N-60.5W)
IOH 48 Hr Outlook (1800Z Oct 25)... 0% chance of tropical cyclone formation (just northwest of Bermuda near 33.5N-65.5W)
AREA OF INTEREST #42... The south portion of the current upper trough that has recently emerged into the western Atlantic from the US east coast is expected to become cut-off from the mid-latitude westerlies by warm core upper ridging to amplify to the north and northwest... courtesy of the warm sectors of the current eastern Canada and western US frontal cyclones. Due to the amplified nature of the cut-off upper trough... upper divergence on the east side of the trough is expected to be sufficiently high and wind shear is expected to be sufficiently low to generate a potentially organizing subtropical surface low pressure area. Models have come into better agreement on this idea... therefore I have initiated a new area of interest associated with the upper trough. This marks the forty-second Atlantic tropical area of interest I have tracked on this blog this year.
Forecast track in the outlook below is northeastward toward the direction of Bermuda by day 5 and is based on the forecast location of the upper divergence maximum from this past 1200Z GFS model run. Initial odds of subtropical cyclone formation are set to 0% as the region of upper divergence on the east side of the upper trough is expected to be too elongated to support a consolidated surface low pressure spin. I raise development odds in the longer range once the upper trough acquires a northwest-to-southeast tilt which will induce a better-defined maximum of upper divergence needed for the formation of a consolidated surface circulation. I have selected low peak development odds of 25% as the model consensus showing the formation of a healthy surface circulation has only been recent... should these model trends persist odds will be raised in future updates. The subtropical designation is used in the outlook below to indicate the potential for this system becoming a hybrid... supported by the upper divergence on the east side of the cold core upper trough while at the same time aided by warm core outflow associated with thunderstorm latent heat release and the outflow warm core upper ridging forecast to be located just east of the upper trough.
This outlook very well means that Bermuda could see impacts from this forecast subtropical disturbance... just a few days after area of interest (AOI) #41 passes over/near Bermuda. I recommend interests in Bermuda should also be aware of potential impacts from this forecast system to arrive by Thursday. In addition to heavy rainfall... this system is more likely to bring coastal surf and gusty winds to the island than AOI #41 as the surface circulation has potential to be stronger from better upper air support (more upper divergence).
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 24)... 0% chance of subtropical cyclone formation (east of the central Bahamas and north of the eastern Bahamas near 25N-74W)
IOH 48 Hr Outlook (1800Z Oct 25)... 0% chance of subtropical cyclone formation (western Atlantic near 25N-70W)
IOH 72 Hr Outlook (1800Z Oct 26)... 10% chance of subtropical cyclone formation (western Atlantic near 25N-68.5W)
IOH 96 Hr Outlook (1800Z Oct 27)... 20% chance of subtropical cyclone formation (south-southwest of Bermuda near 28.5N-66W)
IOH 120 Hr Outlook (1800Z Oct 28)... 25% chance of subtropical cyclone formation (just north of Bermuda near 34N-65W)
...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 23) CMC Model Run...
**For area of interest #41... surface trough develops two circulation centers east of Bermuda by 42 hours (one at 32N-63.5W and a second one at 31.8N-57.5W)... the western of the two circulation centers passes just northeast of Bermuda at 54 hours... by 72 hours both circulations turn north and merge into a singular broad low pressure area losing tropical characteristics near 36.5N-65W... the broad non-tropical low turns northeast and reaches 42.5N-57.5W at 120 hours.
**For area of interest #42... Upper trough currently offshore of the southeastern US becomes cut-off from the mid-latitude westerlies over next 96 hours due to upper ridging that builds to the north and northwest in the warm sectors of the current eastern Canada and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low near 28.5N-64.5W at 132 hours.
0000Z (Oct 23) ECMWF Model Run...
**For area of interest #41... surface trough develops a surface low just southeast of Bermuda at 48 hours... surface low accelerates northwest while losing troipcal characteristics and is located just offshore of Massachusetts and Maine by 96 hours... between 96 and 120 hours becomes absorbed over Atlantic Canada by an incoming frontal cyclone from the west (this frontal cyclone forecast to emerge from southern split of current western US frontal cyclone)
**For area of interest #42... upper trough currently offshore of the southeastern US becomes cut-off from the mid-latitude westerlies over next 96 hours due to upper ridging that builds to the north and northwest in the warm sectors of the current eastern Canada and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low just southwest of Bermuda at 120 hours.
1200Z (Oct 23) GFS Model Run...
**For area of interest #41... surface trough develops a surface low just southeast of Bermuda at 30 hours... center of surface low moves over Bermuda at 39 hours after which time it turns northwest and loses tropical characteristics while accelerating northwestward... center of non-tropical remnant low moves into Cape Cod Massachusetts at 81 hours... at 99 hours becomes absorbed over Atlantic Canada by an incoming frontal low from the west (this frontal low forecast to emerge from southern split of current western US frontal cyclone)
**For area of interest #42... upper trough currently offshore of the southeastern US becomes cut-off from the mid-latitude westerlies over next 72 hours due to upper ridging that builds to the north and northwest in the warm sectors of the current eastern Canada and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low near 26N-65W at 84 hours... strengthens into a subtropical cyclone located just southwest of Bermuda and near 31N-66W at 120 hours.
1200Z (Oct 23) NAVGEM Model Run...
**For area of interest #41... surface trough develops a surface low located near 31.2N-61W at 24 hours... center of surface low passes just north of Bermuda at 42 hours... subsequently turns northwest and then north while losing tropical characteristics and passes just east of Massachusetts at 78 hours... through 102 hours the remnant non-tropical low loses identity across Atlantic Canada and along an incoming cold front from the west (this cold front forecast to be driven by the current western US frontal cyclone over the next few days)
**For area of interest #42... upper trough currently offshore of the southeastern US becomes cut-off from the mid-latitude westerlies over next 96 hours due to upper ridging that builds to the north and northwest in the warm sectors of the current eastern Canada and western US frontal cyclones... eastern divergence zone of cut-off upper trough produces a subtropical surface low near 27N-65W at 102 hours... strengthens into a subtropical cyclone located just southwest of Bermuda and near 31N-66W at 120 hours.