Tropical storm forms in the central Caribbean Sea late yesterday
Eta is the 28th tropical storm of the 2020 hurricane season and ties 2005 for the most tropical storms in an Atlantic hurricane season since records began in 1851.
Discussion:
While the satellite appearance of Eta has slowly improved over the last 24 hours, the system lacks any defined inner core at the moment with scattered convection near/over the center and a large band well to the northeast and east of the center. Eta is a fairly large system and such systems generally take time to consolidate and develop. Eta is moving westward and this motion is expected to continue for the next 72 hours.
Track:
Eta is under the influence of a weak mid level ridge that extends from the Atlantic Ocean to near Cuba which is forcing the system toward the west. Strong high pressure building over the Gulf of Mexico will impart an increasingly WSW motion to Eta in about 36 hours and this motion should continue through landfall over either Honduras or Nicaragua by 60 hours. After landfall the system is expected to significantly slow down as the high pressure ridge over the Gulf of Mexico begins to weaken and a weakness begins to develop over the SE US. The main question is how strong and how far south is Eta as this weakness develops and is there enough of a defined system remaining to get pulled northward over the western Caribbean Sea and potentially the SE Gulf of Mexico. Given the expected land interaction and general slow motion beyond 72 hours, the latter portion of the track forecast is of lower than average confidence.
The official NHC forecast is near the center of the guidance cluster through 72 hours and then slightly south and west of the multi-model consensus through 120 hours. Adjustments in the track are likely over the next several days.
Intensity:
While Eta is in a favorable upper level pattern over very warm sea surface temperatures for development, the system has a fairly large circulation which is taking time to consolidate. Once an inner core forms, intensification is likely and in fact there could be a period of rapid intensification prior to Eta making landfall over central America. There is a large degree of uncertainty on how much Eta may interact with central America. Along the current forecast track, Eta would weaken significantly as the cyclone would interact with the high mountain areas over central America, but should the system slow or stall further to the east it would remain east of the highest mountains and weakening would be more gradual. The longer range intensity forecast is strongly tied to the long range track and land interaction.
Jeff Lindner
Director Hydrologic Operations Division/Meteorologist
Harris County Flood Control District