MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #165
*******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.**********
...FRIDAY OCTOBER 30 2020 12:25 PM EDT...
See remnants of Zeta section below for a final statement on the former tropical cyclone. See area of interest section below for the new surface low pressure spin that has materialized in the southeastern Caribbean Sea being monitored for tropical cyclone formation.
REMNANTS OF ZETA...As of yesterday afternoon...Tropical Storm Zeta was exiting the mid-Atlantic states of the United States and was moving very rapidly into the open northwestern Atlantic while transitioning into a remnant frontal low pressure along the front extending eastward from the much larger frontal low pressure now over the east coast of the United States. The remnant low is now embedded in a strong upper westerly jet being generated by the sharp air mass contrast between the warm western Atlantic upper ridge to the south and cold upper trough currently exiting eastern Canada to the north. The latest model consensus is that the remnant low of Zeta has some life ahead of it...as the jet will throw Zeta into the eastern divergence zone of the aforementioned upper trough from eastern Canada...causing Zeta to re-intensify as a remnant frontal cyclone that moves into the northern British Isles by 48 hours (Sunday morning). Meanwhile the current north Atlantic frontal low to the east-northeast of Zeta will also intensify into a much larger frontal cyclone...which will likely absorb the smaller remnant frontal cyclone of Zeta after it departs the northern British Isles. This is my final statement on Zeta on this blog as it is no longer a tropical feature.
AREA OF INTEREST #1...A surface low pressure disturbance has formed in the southeastern Caribbean Sea as the tropical wave that crossed the Lesser Antilles islands yesterday and second tropical wave that has crossed the islands today are melting together...and surface pressures have been kept low by upper anticyclonic outflow that is expanding in the wake of the decaying western Atlantic upper vorticity string. The surface low pressure has already become much better organized than yesterday while producing a small central area of thunderstorms that crossed the southern Lesser Antilles island chain last night...and this central area of thunderstorms continues to show rotation through this morning. And combined with the strong model consensus showing tropical cyclone formation...I have begun a tropical cyclone formation forecast as outlined below. Forecast track is based on the strong model agreement that the surface low pressure will track west-northwest into 15N latitude over the next 48 hours while steered by the southwest side of the eastern Atlantic surface subtropical ridge...soon to be re-enforced by a surface ridge to build over the United States and head rapidly out to sea under the western convergence zone of the fast-moving upper trough currently over the eastern United States. After that time...a strong upper trough currently southeast of Alaska and making landfall over western 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 days 4 and 5. 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 the strength 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 into a strong tropical storm by 48 hours...and I refrain from showing hurricane strength during that time as the western part of the western Atlantic upper vorticity string may settle over the north-central Caribean Sea and Cuba...potentially limiting the northwestern outflow of this system. After 48 hours...the 0600Z GFS indicates that the aforementioned upper vorticity will have dissipated...so I forecast a steeper intensification rate and major hurricane strength by day 4. Rapid weakening to a remnant low is then shown by day 5 due to the small size of this system and current track forecast that takes this system inland into Nicaragua. Interests in eastern Nicaragua and eastern Honduras should continue to watch this situation very carefully as we could be dealing with a severe wind and coastal storm surge event by Tuesday...preparations may have to start this weekend.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Oct 30)...Surface low pressure centered in the southeastern Caribbean Sea at 13N-64W
IOH 24 Hr Forecast (1200Z Oct 31)...35 mph maximum sustained wind tropical depression centered in the central Caribbean Sea at 14N-69W
IOH 48 Hr Forecast (1200Z Nov 1)...60 mph maximum sustained wind tropical storm centered in the central Caribbean Sea at 15N-74W
IOH 72 Hr Forecast (1200Z Nov 2)...95 mph maximum sustained wind hurricane centered in the central Caribbean Sea at 15N-79W
IOH 96 Hr Forecast (1200Z Nov 3)...115 mph maximum sustained wind major hurricane centered offshore of Nicaragua at 14N-82W
IOH 120 Hr Forecast (1200Z Nov 4)...Remnant low pressure centered over northwestern Nicaragua at 13N-86W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
0000Z CMC Model Run...For area of interest #1...tropical cyclone formation suggested in central Caribean Sea near 15N-75W at 48 hours...while intensifying signficantly tropical cyclone approaches waters just east of the Nicaragua/Honduras border at 90 hours...after briefly stalling offshore the strong tropical cyclone makes landfall on the Nicaragua/Honduras border at 120 hours.
0000Z ECMWF Model Run...For area of interest #1...tropical cyclone formation suggested at 16N-80W at 72 hours...intensifying tropical cyclone makes landfall over eastern Honduas at 96 hours...after landfall drifts souhthwestward into western Nicaragua while weakening to a remnant low pressure by 120 hours.
0600Z GFS Model Run...For area of interest #1...tropical cyclone formation suggested at 15N-78W at 60 hours...strengthenes into a compact and strong tropical cyclone...while turning on a southwestward track makes landfall on the east coast of Nicaragua at 114 hours...remnant low pressure gradually drifts back north-northeastward into the central Caribbean Sea in long range and regenerates into a tropical cyclone.
0600Z NAVGEM Model Run...For area of interest #1...tropical cyclone formation suggested just south of the Cayman Islands at 18N-80.5W at 90 hours...while turning southwestward makes landafall over eastern Honduras at 120 hours...remnant low pressure drifts back northward into the western Caribbean Sea in the long range.