*******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 OCTOBER 31 2022 1:13 AM EDT...
The Atlantic tropics are expected to remain active across the Caribbean region over the next week as follows:
(1) The tropical disurbance currently in the central Caribbean has become better organized and stronger... with the NHC upgrading it to potential tropcial cyclone fifteen in order to issue tropical storm advisories for Jamaica and the Cayman Islands. This system is at increased risk of approaching the Honduras-to-Belize to coastal region as a strong hurricane in the Wednesday/Thursday timeframe... see area of interest #43 section below for more information on this disturbance.
(2) The south part of the current western US upper trough is absorbing the upper trough that was over the south-central US and now over the central US. The south part of this upper trough is subsequently forecast to move toward and then into the western Atlantic over the next five days. Meanwhile during the same five day timeframe... the current northeastern Pacific upper trough will develop a frontal system across North America whose warm sector amplifies an upper ridge over eastern North America... with this upper ridge causing the western Atlantic upper trough to evolve into a cut-off upper vortex that drifts south toward the Caribbean. A pair of disturbances could emerge as a result of this upper vortex in the 5 to 7 day window... one tropical in the central Caribbean supported by split flow upper divergence between the south side of the vortex and east side of the current northwestern Caribbean upper ridge cell... a second tropical or subtropical disturbance over the northeastern Caribbean Islands (from the Dominican Republic to the Virgin Islands) or western Atlantic waters just north of the islands to be supported by the eastern divergence zone of the vortex. No areas of interest are being declared for either potential future disturbance at this time as it is not clear if the two disturbanes could simply merge into a sprawling area of low surface pressure with no consolidated center... which would result in widespread rainfall instead of tropical cyclone development.
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 #43 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 #43 (POTENTIAL TROPICAL CYCLONE FIFTEEN)... On Sunday afternoon aircraft reconnaissance was dispatched to the consolidating low pressure spin in the central Caribbean Sea. A small area of minimal (40 mph) tropical storm sustained winds was found on the north side of this system. At 5 PM EDT Sunday the NHC had upgraded this disturbance to potential tropical cyclone fifteen as it was already generating storm force winds... in order to issue tropical storm watches for Jamaica and the Cayman Islands. This system was still considered a disturbance rather than a tropical storm as the circulation is still elongated instead of circular... for example refer to the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) which shows a southwest-northeast elongated circulation... and as the thunderstorm activity was disorganized and lopsided to the east side of the circulation due to light westerly shear being imparted by lingering upper vorticity located just to the west. More recent satellite frames (around 11 PM EDT Sunday) show the thunderstorm activity becoming notably better organized with a pair of central thunderstorm bursts and outer curved band to the south... this system likely is on the precipice of becoming a tropical storm.
This system has been slow to move westward over the last few days due to weak steering currents caused by the subtropical low pressure area that has been in the vicnity of Bermuda. However recovering deep-layer easterly steering is expected to help this system pick up westward forward speed. In the upper-layers the steering will be provided by the south side of the current northwest Caribbean upper ridge cell. At the surface... easterly flow will increase as a surface ridge builds over the eastern US and Gulf of Mexico. Once the south portion of the current western US upper trough slides across the southeastern US and then the western Atlantic... its western convergence zone will be the mechanism to form and build the surface ridge. The debate remains as to how far north or south the westward track will occur. My forecast track remains on the south side of the model spread and NHC official forecast as their are no expected mechanisms to pull this system north from its current latitude during the forecast period... if anything the recent organization of the thunderstorm activity suggests the elongated circulation could be consolidating toward the south... and the NHC as of 11 PM EDT has nudged their forecast track southward due to the most recent model trends. Also noting that the models still project a southward bend in the track forecast toward the latter part of the 5-day forecast period as the Gulf/eastern US surface ridge gains strength... however the southward angle shown in the models has reduced as the models have also trended with a slightly more north position of the surface ridge. Correspondingly my updated track forecast points are nudged north and west relative to the previous in the longer range.
Regarding intensity... the opportunity for instensification will increase by 24+ hours once the lingering disruptive upper vorticity to the west dissipates while isolated from high-latitude cold air... and the opportunity for instensification will remain up until this system makes landfall either on the north Honduras coast... Guatemala Caribbean coast... or Belize coast. Warm waters and low shear/outflow beneath the northwestern Caribbean upper ridge cell are the factors that will benefit this system. This system also appears to be relatively small in size and the models agree on this system maintaining a compact structure... note small systems tends to have quick intensity changes both up and down as the pressure gradient between the center and outside of a small storm is greater relative to a larger storm undergoing a similar change in central pressure. In other words rapid intensification is on the table... and combined with the already-improving organization of the thunderstorm activity I forecast this system to peak as a category 2 hurricane which is a notch higher than the NHC's forecast as of this writing which projects a category 1 peak. I have not shown a higher intensity forecast as the southern forecast track I have elected for at this time increases land interaction with Honduras earlier... at 60+ hours.
Regarding the impact to land areas:
(1) A tropical storm watch is in effect for Jamaica as of this writing for potential impacts from this system by tonight. Heavy rainfall is possible... along with a medium instead of high chance of gusty winds along the south coast as the circulation center is forecast to pass to the south.
(2) A tropical storm watch is in effect for the Cayman Islands as of this writing in the event this system consolidates or tracks toward the north. The potential for gusty winds and rainfall here is low as their are no signs of this ocurring so far.
(3) Interests along the north coast of Honduras... the Caribbean coast of Guatemala... and coast of Belize should be aware of this system as it has increased potential to move into the region as a strong hurricane by Wednesday afternoon through Thursday night... with impacts arriving sooner further east and later further west. Gusty winds and coastal surf will be hazards to consider... with more damaging winds and coastal storm surge occurring near where the center of circulation tracks. A more northern track will result in the inland spreading of heavy rainfall and gusty winds across central and northern Belize and northern Guatemala... a more southern track as shown by my current forecast below will result in the inland spreading of heavy rainfall and gusty winds across northwestern Honduras... central Guatemala... and southern Belize.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Oct 31)... 40 mph maximum sustained wind tropical low centered south of Haiti at 15.8N-74.1W
IOH 24 Hr Forecast (0000Z Nov 1)... 50 mph maximum sustained wind tropical storm centered south of Jamaica at 16N-77.5W
IOH 48 Hr Forecast (0000Z Nov 2)... 80 mph maximum sustained wind hurricane centered in the western Caribbean Sea at 16N-81.5W
IOH 72 Hr Forecast (0000Z Nov 3)... 105 mph maximum sustained wind hurricane centered just offshore of the north-central Honduras coast at 15.8N-85.5W
IOH 96 Hr Forecast (0000Z Nov 4)... 70 mph maximum sustained wind tropical storm centered just inland and just east of the Honduras/Guatemala border at 15.5N-88.5W
IOH 120 Hr Forecast (0000Z Nov 5)... Dissipating over western Guatemala near 15.2N-91W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Oct 30) CMC Model Run...
**For area of interest #43... tropical low passes just south of Jamaica at 24 hours... tropical cyclone formation suggested west-southwest of the Cayman Islands and near 17.9N-83.8W at 60 hours... after additional strengthening makes landfall as a compact tropical cyclone on the north coast of Belize at 90 hours... weakens to an inland remnant low that dissipates over the Guatemala/Belize border at 120 hours
1200Z (Oct 30) ECMWF Model Run...
**For area of interest #43... tropical low passes just south of Jamaica at 30 hours... becomes a western Caribbean tropical depression near 17.5N-85W at 66 hours... strengthens to a tropical storm that makes landfall over the central coast of Belize at 84 hours... weakens to a southwestward-moving inland remnant low that dissipates over the Belize/Guatemala border at 96 hours.
1800Z (Oct 30) GFS Model Run...
**For area of interest #43... tropical low passes just south of Jamaica at 24 hours... becomes a tropical depression just offshore of northeastern Honduras at 54 hours... develops into a briksly-strengthening compact tropical storm at this location at 60 hours... makes landfall over the north coast of Belize at 81 hours as a compact hurricane... crosses northern Belize/Guatemala border as a compact inland tropical storm at 90 hours... as an inland remnant low dissipates over northern Guatemala/Mexico border at 96 hours.
1200Z (Oct 30) NAVGEM Model Run...
**For area of interest #43... tropical low passes just south of Jamaica at 36 hours... becomes a tropical depression just south of the Cayman Islands at 54 hours... becomes a tropical storm near 17.5N-83.8W at 66 hours... makes landfall over the southern coast of Belize at 90 hours... as an inland remnant low dissipates over the southern Belize/Guatemala border at 102 hours.