*******Note that forecasts 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 31 2020 5:12 PM EDT...
See area of interest section below for the central Caribbean surface low pressure spin that has been recently upgraded to a tropical depression.
AREA OF INTEREST #1 (RECENTLY UPGRADED TO TROPICAL DEPRESSION TWENTY-NINE)...The surface low pressure spin that formed in the southeastern Caribbean Sea yesterday has made its way into the central Caribbean while continuing to become better organized. This development has been allowed to occur as the western Atlantic string of upper vorticity that was previously shearing this disturbance has weakened and broken up into one string off to the east in the eastern Atlantic...and another string in the central Caribbean in the vicinity of Cuba...with an expanding anticyclone with low shear and upper outflow over this disturbance and between the strings of upper vorticity. Forecast track points below have been adjusted to the north and west due to the current position of the surface low pressure spin...with the track seeming to bend on a straight west trajectory in the latest satellite animation probably due to the strength of the surface ridge currently entering the west Atlantic form the eastern United States. Later in the forecast period...the strong upper trough currently over central Canada will pivot across North America...producing a strong surface ridge to the northwest beneath this upper trough's western convergence zone that will slow the track and also bend the track on a west-southwest angle...likely taking this system into Nicaragua and/or Honduras by day 3. Regarding intensity...given that this system is already showing signs of becoming a compact circulation...rapid intensity fluctuations will be possible as not as much surface pressure falls need to occur to bring winds up given the tight pressure gradient between the center and outside of small systems...and also as the thunderstorm latent heat release and resulting warm core upper outflow needed for surface pressure falls will be concentrated instead of spread out as we see in larger sprawling systems that take time to strengthen in their early stages. As a result...I forecast brisk strengthening till this system makes landfall in Nicaragua or Honduras in 60 hours. Note that I do not have a 60 hour forecast point due to my tradition of having forecast points spaced 24 hours apart...but I currently anticipate a high chance of this system being a category 2 hurricane for its 60 hour landfall intensity...followed by a weakening back to 80 mph category 1 strength as this system moves inland by 72 hours.
I recommend interests in eastern Nicaragua and eastern Honduras to begin preparations for potentially severe damaging winds and coastal storm surge that could arrive by late Monday into early Tuesday given that this system has tracked faster to the west in the last 24 hours and moved up timeline of likely impacts to a sooner time. Given the more north position of this system...Jamaica will see the northern rain bands of this system potentially containing gusty winds in the next 24 hours.
Update as of 5 PM EDT...the surface low pressure spin is now tropical depression twenty-nine...containing 35 mph maximum sustained winds with a 1006 mb central pressure...located at 15N-73.2W. This is slightly southwest of the spin noted at 16N-72.5W...perhaps an indication the surface and mid-level spins are not quiet aligned at this time.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1800Z Oct 31)...Surface low pressure centered in the central Caribbean Sea at 16N-72.5W
IOH 24 Hr Forecast (1800Z Nov 1)...45 mph maximum sustained wind tropical storm centered just south of Jamaica at 16.5N-77.5W
IOH 48 Hr Forecast (1800Z Nov 2)...80 mph maximum sustained wind hurricane centered east-northeast of Honduras at 15.5N-82W
IOH 72 Hr Forecast (1800Z Nov 3)...80 mph maximum sustained wind hurricane centered over northeastern Nicaragua just south of the Honduras border at 14.5N-84W
IOH 96 Hr Forecast (1800Z Nov 4)...Remnant low pressure centered over north-central Nicaragua at 13N-85.5W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...For area of interest #1...tropical cyclone formation suggested in central Caribean Sea near 15N-78W at 24 hours...while intensifying tropical cyclone makes landfall on north coast of Nicaragua at 72 hours...weakens to a remnant low over eastern Honduras at 108 hours...remnant low drifts back north-northeast into the western Caribbean Sea and regenerates into a tropical cyclone in the long range.
0000Z ECMWF Model Run...For area of interest #1...tropical cyclone formation suggested at 16N-80W at 48 hours...intensifying tropical cyclone makes landfall over eastern Honduas at 72 hours...after landfall drifts souhthwestward into western Nicaragua/Honduras border while weakening to a remnant low pressure by 96 hours.
1200Z GFS Model Run...For area of interest #1...tropical cyclone formation suggested at 15N-81.5W at 60 hours...while strengthening the tropical cyclone moves slowly but eventually makes landfall over the Nicaragua/Honduras border at 120 hours...tropical cyclone drifts northeastward back into the western Caribbean Sea in the long range.
0600Z NAVGEM Model Run...For area of interest #1...tropical cyclone formation suggested at 15N-77.5W at 30 hours...strengthens into an intense tropical cyclone that makes landfall over eastern Honduras at 90 hours...in long range tropical cyclone drifts northwestward to the east coasts of Belize and the Yucatan peninsula.