*******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.*********
...TUESDAY OCTOBER 31 2023 12:45 PM EDT...
As the month of October is coming to an end... this busy Atlantic Hurricane Season continues to churn with the following disturbances being monitored:
(1) The surface low pressure just northeast of the northwestern Bahamas has ran out of time to become a tropical cyclone... see area of interest #49 section below for details.
(2) Surface pressures across a large area of the Caribbean Sea remain low... continuing to monitor the Caribbean for tropical cyclone formation in the days ahead... see area of interest #51 section below for more information.
(3) The remnant low pressure swirl of Tammy... located in the open central Atlantic... has potential to re-develop thunderstorms in a better upper wind environment in the 24 to 48 hour period. See area of interest #52 (remnants of Tammy) section below for more information.
AREA OF INTEREST #49... Due to the approach of a local upper trough from the eastern Gulf of Mexico... wind shear has increased over the surface low pressure swirl located just northeast of the northwestern Bahamas (located at 27.5N-76W as of 1200Z). Shear will increase further in the next 24 hours as the larger-scale upper trough over the United States nears. This system will continue northeastward into water temps below 26 deg C in the flow ahead of the surface cold front driven by the larger-scale upper trough... and become absorbed by the front by 24 hours. Given all of the above... tropical cyclone formation of this feature is not expected and this is my final statement on this area of interest on this blog.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Nov 1)... 0% chance of tropical cyclone formation (western Atalntic near 31N-71W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT***************************
Not in the official outlook
AREA OF INTEREST #51... Based on the curvature of thunderstorm squalls now heading into the central Caribbean from the eastern Caribbean... it appears the central Caribbean surface low near Jamaica and eastern Caribbean surface low are merging into a broad system south of Hispaniola (Haiti and the Dominican Republic). My updated forecast track below assumes the merger is completed in the next 24 hours... followed by a west-southwest track of the merged system toward Central America through 96 hours under the influence of the rather strong surface ridge now approaching from the western US. Even if this system were to become stronger/taller to couple with upper winds... the initial south slant in the forecast track from the push of the strong surface ridge will move this system into the south side of the current Caribbean upper ridge where the upper flow is forecast to also be east-northeasterly (ENE)... particularly as some of the current central tropical Atlantic upper vorticity tries to retrograde around the south side of the Caribbean upper ridge and toward this system... with the incoming upper vorticity from the east modulating the upper wind vectors from easterly (E) to east-northeasterly (ENE). Regarding peak odds of tropical cyclone formation... due to the increased organization of the aforementioned thunderstorm squalls I have raised them to 40%. Preferring in this update cycle to keep peak odds below 50% as this system may struggle to develop a well-defined center while in an initially broad state caused by the merger between the two surface lows as noted above... and as this system may have to contend with ENE shear while being on the south side of the Caribbean upper ridge cell rather than underneath it. The global models may be picking up on these negative factors as fewer members are developing this system compared to yesterday. Noting between 96 and 120 hours the forecast track is more westward into Central America instead of continuing west-southwest as the steering surface ridge shifts east which causes this system to begin rounding the southwest side of the ridge. The Caribbean upper ridge also shifts south and becomes more stacked with this system due to the push provided by a series of upper troughs passing over North America. I have odds of tropical cyclone formation above 0% by 120 hours despite landfall with Central America as this system may still be large/broad enough to take advantage of the low shear/outflow below the Caribbean upper ridge's core to develop into a tropical cyclone centered over land with offshore western Caribbean squalls containing the gusty winds. If development does not occurr toward the Caribbean side of Central America... it is possible this system in the long range goes on to trigger development toward far eastern Pacific side of Central America.
Given the current forecast... the area most likely to see rainfall from this systme within the next few days includes the Dominican Republic... Haiti... eastern Cuba... and Jamaica. By days 4 and 5 the rainfall potential shifts southwest toward Nicaragua and Honduras... this is also the area most likely to see tropical cyclone impacts (gusty winds and coastal surf) should tropical cyclone formation in fact occur.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Nov 1)... 0% chance of tropical cyclone formation (south of the Haiti/Dominican Republic border near 15.5N-72W)
IOH 48 Hr Outlook (1200Z Nov 2)... 10% chance of tropical cyclone formation (south of Haiti near 15.5N-74W)
IOH 72 Hr Outlook (1200Z Nov 3)... 25% chance of tropical cyclone formation (south of Jamaica near 15N-77W)
IOH 96 Hr Outlook (1200Z Nov 4)... 40% chance of tropical cyclone formation (offshore of northeastern Nicaragua near 14.5N-81.5W)
IOH 120 Hr Outlook (1200Z Nov 5)... 30% chance of tropical cyclone formation (inland and in vicinity of Nicaragua/Honduras border near 14.5N-85W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT***************************
Formation chance through 48 hours... 30%
Formation chance through 7 days... 70%
AREA OF INTEREST #52 (REMNANTS OF TAMMY)... The remnant cloud swirl low pressure of Tammy... located at 25N-50W as of 1200Z today... continues to meander in the open central Atlantic while now bending back westward in track in response to the current northwest Atalntic deep-layer ridge. Through 48 hours... as the steering deep-layer ridge passes to the north... ex-Tammy is forecast to continue west and then northwest. This system has been void of thunderstorms while suppressed by upper convergence on the southeast side of the ridge's upper layers. However in 24 to 48 hours ex-Tammy is on track to move below the southwest quadrant of the deep-layer ridge's upper layer where wind shear is low and upper outflow is increased... therefore I assign odds of tropical cyclone formation above 0% by 48 hours (I have dropped them to 0% for the timeframe now 24 hours away as satellite pictures indicate the surface low of ex-Tammy has weakened enough that immediate tropical cyclone formation is no longer possible). I keep peak development odds low as the global models as of this writing do not call for ex-Tammy to make a comeback. Between 48 and 72 hours the surface frontal zone currently over the eastern US and its associated upper trough will have moved into the Atlantic... with the flow ahead of these features turning Tammy northeastward. If Tammy does indeed live beyond 48 hours... it has some potential to be absorbed by the incoming cold front by 72 hours. It is also possible Tammy misses the front and meanders back on a westward drift due to the surface ridge behind the front... however in that scenario Tammy's potential for re-development would also be ended due to arrival into shearing mid-latitude upper westerly winds. As such the outlook below is ended at 72 hours with 0% development odds.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
IOH 24 Hr Outlook (1200Z Nov 1)... 0% chance of tropical cyclone formation (central Atlantic near 25N-54W)
IOH 48 Hr Outlook (1200Z Nov 2)... 10% chance of tropical cyclone formation (central Atlantic near 28N-57W)
IOH 72 Hr Outlook (1200Z Nov 3)... 0% chance of tropical cyclone formation (central Atlantic near 31N-54.5W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT***************************
Not in the official outlook
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields(http://moe.met.fsu.edu/tcgengifs/).
0000Z (Oct 31) CMC Model Run...
**For area of interest #49... surface low currently just northeast of the northwestern Bahamas moves northeastward and becomes absorbed by developing frontal low to the north by 30 hours.
**For area of interest #51... no development shown
**For area of interest #52... remnant low of Tammy drifts west-southwest and weakens to a trough near 24N-51.5W at 24 hours... trough dissipates shortly thereafter
0000Z (Oct 31) ECMWF Model Run...
**For area of interest #49... surface low currently just northeast of the northwestern Bahamas moves northeastward and becomes absorbed by developing frontal low to the north by 30 hours.
**For area of interest #51... no development shown
**For area of interest #52... remnant low of Tammy curves west-southwest and then westward and weakens to a trough near 25N-54W at 36 hours... trough dissipates shortly thereafter
0600Z (Oct 31) GFS Model Run...
**For area of interest #49... surface low currently just northeast of the northwestern Bahamas moves northeastward and becomes absorbed by developing frontal low to the north by 24 hours.
**For area of interest #51... coalesces into a better-defined tropical low just northwest of the Guajira peninsula of Colombia at 75 hours... tropical low makes landfall on east coast of Nicaragua at 120 hours
**For area of interest #52... remnant low of Tammy curves west-southwest and then westward and weakens to a trough near 25N-55W at 36 hours... trough dissipates shortly thereafter
0600Z (Oct 31) NAVGEM Model Run...
**For area of interest #49... surface low currently just northeast of the northwestern Bahamas moves northeastward and becomes absorbed by developing frontal low to the north by 24 hours.
**For area of interest #51... coalesces into a better-defined tropical low south-southeast of Jamaica at 60 hours... tropical low moves west-southwest and makes landfall on the Nicaragua/Costa Rica border at 108 hours shortly after which time it dissipates
**For area of interest #52... remnant low of Tammy curves west-southwest and then westward and weakens to a trough near 25N-52.5W at 24 hours... trough subsequently curves northwestward and reaches 28.5N-56W at 48 hours shortly after which time it dissipates