MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #181
*******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.**********
...SUNDAY NOVEMBER 15 2020 9:32 PM EDT...
See remnants of Theta section for a final statement on the former tropical storm. See Hurricane Iota section below for the only currently active tropical cyclone in the Atlantic basin. See area of interest sections below for an areas being monitored for tropical cyclone formation.
REMNANTS OF THETA...Northerly wind shear and upper convergence on the east side of a deep-layered ridge...in addition to water temps in the low 20s of deg C...have brought an end to Theta as a tropical cyclone while centered just southwest of Madeira Island. Theta is now a remnant cloud swirl surface low pressure void of thunderstorms and has winds below tropical storm force. Theta has been drifting very slowly eastward in conflicting steering between the deep-layered ridge to the west and a surface ridge over Europe to the east being supported by the western convergence zones of upper troughs moving into Europe. Over the next day or so...the remnant of Theta will be pulled northward into the current northwest Atlantic frontal cyclone once that cyclone nears. No significant impacts are expected from Theta’s weak remnant...this is my final statement on Theta on this blog as it is no longer a tropical cyclone.
HURRICANE IOTA...The cool core north Caribbean upper trough that previously blocked the northern outflow of Iota has dissipate under the continued latent heat release of Iota’s thunderstorms...and the outflow of Iota is now vibrant in all quadrants of the circulation such that the tropical storm intensified to a hurricane in the early morning hours. The hurricane has been steadily intensifying throughout the day such that it remains a category 1 as of 4 PM EDT...but a high end one with 90 mph maximum sustained winds. More rapid intensification has not occurred as the hurricane had reduced thunderstorm activity on colorized infrared satellite after acquiring an eye. Although very recently the eye has shrunk to pinhole size and thunderstorm intensity is back up...the strongest thunderstorms have so far failed to make a solid ring around the pinhole eye. My intensity forecast remains the same as yesterday and brings the hurricane to a top end category 4 for the expected landfall on the Nicaragua coast. This could be an overly aggressive intensity forecast if Iota never achieves a full ring of strong thunderstorms around the eye....but since this is hard to predict I will leave the intensity forecast the same for now.
My forecast track points for Iota are shifted north due to the current position of the hurricane...and some north angle is kept in the forecast through 24 hours due to the surface ridge weakness created by the current eastern North America frontal cyclone. After that time...the western convergence zone of the amplified and strong upper trough tied to the frontal cyclone will produce a strong surface ridge over the south-central United States. This ridge will keep Iota’s westward track slow and bent on a southward angle due to its strength and position relative to Iota.
Needless to say...this forecast remains exceptionally terrible news as we are likely in for a second wave of catastrophe in Nicaragua and Honduras only recently after Hurricane Eta devastated this region with powerful winds and catastrophic rainfall flooding...and unfortunately interests here need to do rush preparations for Iota to completion by tomorrow morning as conditions will begin to deteriorate by tomorrow night. In addition to catastrophic wind and coastal storm surge near the landfall area...the mudslide and flooding potential is also high with Iota due to the slow forecast track...and now extends to Costa Rica and El Salvador given the large size of the storm.
Update as of 7 PM EDT...Iota is now a category 2 hurricane with 100 mph maximum sustained winds. No changes to the intensity forecast shown below.
0 Hr Position (1800Z Nov 15)...90 mph maximum sustained wind hurricane centered in the central Caribbean Sea at 13.3N-79.3W
IOH 24 Hr Forecast (1800Z Nov 16)...130 mph maximum sustained wind major hurricane centered offshore of northeastern Nicaragua at 14.3N-81.5W
IOH 48 Hr Forecast (1800Z Nov 17)...155 mph maximum sustained wind major hurricane centered on the coast of Nicaragua at 13.8N-83.5W
IOH 72 Hr Forecast (1800Z Nov 18)...45 mph maximum sustained wind tropical storm centered over northwestern Nicaragua at 13.3N-85.5W
IOH 96 Hr Forecast (1800Z Nov 19)...Remnant low pressure centered just inland from the eastern Pacific coast along Nicaragua/Honduras border at 12.8N-87.5W
AREA OF INTEREST #1...An upper vortex northeast of the Lesser Antilles has become cut-off from the current eastern Atlantic upper trough by the deep-layered ridge that recently moved into the central Atlantic. A surface trough of low pressure has formed in the eastern divergence zone of the upper vortex...which should begin to track northwest around the north side of the upper vortex and toward a surface ridge weakness from the frontal cyclone to exit eastern North America. A southwest track is likely by 96+ hours as the surface ridge weakness closes and a strong surface ridge over the southern US approaches. Some development of the surface trough is possible from low shear and upper outflow to occur northeast of the upper vortex and on the southwest side of the deep-layered ridge. However I have lowered peak odds of development to 10% for the next five days due to the current lack of widespread thunderstorm activity...and drop them to 5% as this disturbance will likely be exposed to some southwesterly shear to be generated by the upper trough tied to the frontal cyclone that will exit eastern North America. The shear is expected to persist through 120 hours due to upper vorticity to be left behind by the upper trough. A subtropical designation is used for the first 24 hours of the outlook due to entanglement with the cold core upper vortex...followed by a tropical designation as the surface trough disturbance decouples from the upper vortex due to the low-level steering.
IOH 24 Hr Outlook (1800Z Nov 16)...0% chance of subtropical cyclone formation (central Atlantic near 20.5-55W)
IOH 48 Hr Outlook (1800Z Nov 17)...10% chance of tropical cyclone formation (central Atlantic near 22.5N-60W)
IOH 72 Hr Outlook (1800Z Nov 18)...5% chance of tropical cyclone formation (western Atlantic near 23.5N-65W)
IOH 96 Hr Outlook (1800Z Nov 19)...5% chance of tropical cyclone formation (western Atlantic near 22N-67.5W)
IOH 120 Hr Outlook (1800Z Nov 20)...5% chance of tropical cyclone formation (just east of the eastern Bahamas near 21N-70W)
AREA OF INTEREST #2...The GFS model has been forecasting development from the tropical wave of low pressure currently crossing 65W longitude in the eastern Caribbean Sea...as the wave later enters the central Caribbean Sea in the wake of Iota and potentially taps into favorable upper winds in a Caribbean upper ridge cell to persist. The NHC has added this tropical wave to their 5-day tropical weather outlook...and therefore I have introduced the wave as an area of interest. I forecast 0% odds of development in the next 48 hours due to exposure to upper convergence on the southwest side of the upper vortex tied to area of interest #1 for the next 24 hours and dominance of Hurricane Iota’s surface inflow and upper outflow. I agree with the NHC longer term low odds of 20% as only the GFS model has been championing development. The westward track of the tropical wave should slow from its current 5W longitude per day pace due to the surface ridge weakness to be induced by the current eastern North America frontal cyclone as it pushes toward the western Atlantic...followed by some increase in forward speed with some
southward angle in track by 72+ hours as a strong surface ridge over the southern US approaches. This forecast track brings this tropical wave close to Nicaragua by day 5...but since the wave is currently inactive thunderstorm-wise and since there is low computer model support for development at the present time it is hard to gage how much significant impact could occur if any. Therefore have not included this tropical wave on the home page bulletins of this site.
IOH 24 Hr Outlook (1800Z Nov 16)...0% chance of tropical cyclone formation (eastern Caribbean Sea near 15N-67.5W)
IOH 48 Hr Outlook (1800Z Nov 17)...0% chance of tropical cyclone formation (central Caribbean Sea near 15N-70W)
IOH 72 Hr Outlook (1800Z Nov 18)...10% chance of tropical cyclone formation (central Caribbean Sea near 15N-74W)
IOH 96 Hr Outlook (1800Z Nov 19)...15% chance of tropical cyclone formation (central Caribbean Sea near 14N-78W)
IOH 120 Hr Outlook (1800Z Nov 20)...20% chance of tropical cyclone formation (just offshore of northeast Nicaragua near 13.5N-82W)
...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 Hurricane Iota...makes landfall on Nicaragua/Honduras border as a strong hurricane at 48 hours...weakens to a remnant low over western Honduras at 78 hours. For area of interest #1...no tropical cyclone formation shown. For area of interest #2...no tropical cyclone formation.
0000Z ECMWF Model Run...For Hurricane Iota...makes landfall just south of the Nicargua/Honduras border as a strong hurricane just after 72 hours...weakens to a remnant low over western Honduras by 96 hours. For area of interest #1...no tropical cyclone formation shown. For area of interest #2...no tropical cyclone formation.
0600Z GFS Model Run...For Hurricane Iota...makes landfall over the Nicaragua/Honduras border as a strong hurricane at 48 hours...weakens to a remnant low over the central Nicaragua/Honduras border at 78 hours. For area of interest #1...no tropical cyclone formation shown. For area of interest #2...tropical wave currently at 65W becomes a tropical low pressure in the central Carribean Sea at 14N-79.5W at 120 hours...no tropical cyclone formation suggested in the long range.
0600Z NAVGEM Model Run...For Hurricane Iota...makes landfall over northeastern Honduras at 54 hours as a strong hurricane...weakens to a remnant low while moving across southern Belize and northwestern Honduras by 102 hours. For area of interest #1...no tropical cyclone formation shown. For area of interest #2...no tropical cyclone formation.