*******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.**********
...WEDNESDAY NOVEMBER 18 2020 11:30 PM EDT...
Satellite image as of 0400Z (red indicates tropical cyclone or remnants of tropical cyclone...with “I” marking Iota. Green indicates an area of interest in the NHC tropical weather outlook. Yellow indicates an area of interest not in the NHC tropical weather outlook):
The following is a special update on the remnants of former tropical cyclone Iota and areas of interest in the Atlantic tropics being monitored for tropical cyclone formation. This is because I have not had time for a full update today due to other commitments. I plan on issuing the next full update tomorrow.
REMNANTS OF IOTA...Over the last day Iota weakened to a tropical depression while the center of circulation moved into El Salvador...and then a remnant low pressure center that has reached the eastern Pacific coast of Guatemala. The thunderstorm intensity in the remnant circulation has reduced such that the heavy rainfall potential has come to an end. The upper anticyclone with low shear and upper outflow in the Caribbean Sea extends to the eastern Pacific...so should the remannt low pressure of Iota emerge into the eastern Pacific and redevelop as an eastern Pacific tropical cyclone...I will not be forcasting it on this blog but instead only mention potential impacts to land areas...if any...on the home page bulletins of this site. This is my final statement on Iota on this blog as it is no longer a tropical cyclone.
AREA OF INTEREST #1...The surface trough of low pressure in the western Atlantic north of the eastern Caribbean Islands has been added to the NHC 5-day tropical weather outlook. This is due to a potential reduction in wind shear and increase in upper-level divergence once a string of upper vorticity to be left behind by the upper trough that has recently emerged from eastern North America potentially coalesces into an upper vortex over the western Bahamas (in response to an adjacent amplified warm eastern US upper ridge ahead of a mid-latitude front). The cold front tied to the upper trough will likely merge with the surface trough...with the merger potentially developing into a tropical disturbance in the more favorable upper winds to setup on the east side of the possible west Bahamas upper vortex. I currently forecast low 10% odds of tropical cyclone formation in 3 to 5 days in the waters northeast of the Bahamas as the GFS has backed off in showing a persistent western Bahamas upper vortex and as model support remains low.
AREA OF INTEREST #2...The tropical wave of low pressure currently moving westward through the Caribbean Sea has crossed 74W longitude as of 1800Z tonight. Meanwhile ahead of the tropical wave and in the vicinity of 12.5N-79W...surface pressure have been kept low in the wake of Hurricane Iota and a cluster of thunderstorms has persisted thanks to the outflow of a Caribbean upper ridge cell that remains stationary over the last several days. Therefore in this update I am increasing odds of tropical cyclone formation to 25% despite the ongoing lack of computer model support...and effective for the next 48 hours until the tropical wave moves west-southwest into southern Nicaragua and Costa Rica under the influence of the strong southeastern US surface ridge. Heavy rainfall with possible gusty winds from this tropical wave are expected by Friday or Saturday in southern Nicaragua and Costa Rica...and it should be noted that this is thankfully south of where Hurricanes Iota and Eta caused devastation.