Hurricane Eta, peaking overnight as a potentially catastrophic category 4 storm with 150 mph winds, was slowly weakening early Tuesday afternoon as it inched west-southwestwards at 5 mph, just off the coast of northeastern Nicaragua. Eta is expected to bring catastrophic winds and storm surge on Tuesday afternoon as it makes landfall in Nicaragua. The hurricane’s very slow westward track inland over Central America during the week is expected to result in catastrophic rains of up to 35 inches in Nicaragua and Honduras, with devastating rains also affecting adjoining nations.

At 10 a.m. EST Tuesday, Eta was a category 4 hurricane with 145 mph winds and a central pressure of 938 mb. Satellite images showed heavy rains from Eta affecting most of Central America, Jamaica, the Cayman Islands, and portions of Mexico. A personal weather station on the north central coast of Honduras at Belfate found a three-day rainfall amount of 14.47 inches by 11 a.m. EST Tuesday.

On Monday, Eta put on a remarkable burst of rapid intensification, its 150 mph winds tying with Hurricane Laura as the strongest Atlantic hurricane of 2020. Eta’s pressure bottomed out at 923 mb – the lowest pressure observed in the Atlantic this year. According to an analysis by Sam Lillo, Hurricane Eta deepened from 1005 mb to 923 mb in 48 hours – a drop of 82 mb. Only three other storms on record in the Atlantic have deepened at that rate or more: Andrew (1992) Rita (2005), and Wilma (2005).

As Eta intensified, its eye shrank to a tiny seven miles in diameter. The eyewall surrounding this tiny eye grew unstable and began to collapse Monday night, and Eta developed an outer eyewall, concentric with the tiny inner eyewall, in a process known as an eyewall replacement cycle (ERC). This ERC weakened Eta noticeably on Tuesday morning, but not enough to significantly change its expected catastrophic impact on Nicaragua and surrounding nations.

According to NOAA’s Historical Hurricane Tracks database, only four category 4 or 5 Atlantic hurricanes, prior to Eta, had ever been observed in November: the Cuba Hurricane (1932), “Wrong-Way” Lenny (1999, so named because of its unusual eastward motion), Michelle (2001), and Paloma (2008). Lenny made landfall on Sint Maartin, an island in the northeast Caribbean Sea, as a category 2 storm, and the other three all made landfall in Cuba at category 4 strength. The 1932 Cuba hurricane, the only Cat 5 ever observed in November, peaked with 175 mph winds on November 6, 1932.

Eta’s storm surge

According to storm surge expert Dr. Hal Needham (see his Tuesday morning post on Eta here), a good analogue storm for Eta might be Hurricane Felix of 2007, which struck northeastern Nicaragua as a category 5 hurricane with 160 mph winds. Felix generated a storm surge of at least 18 feet, the highest storm surge on record in Central America, according to the global storm surge database, U-Surge. The other good analogue storm might be a 1906 hurricane that made landfall at category 3 strength in Nicaragua with a storm surge of 15 feet. Needham expects that Eta’s surge will be about 14-17 feet, the result of the storm’s relatively small size and its having lower wind speeds than Felix. The National Hurricane Center is predicting a storm surge of 14-21 feet.

Eta’s rains

It’s significant and encouraging that Eta’s landfall location is relatively sparsely populated, and a concerted evacuation effort has taken place there. However, Eta is expected to tap the moisture supply from two oceans, the Atlantic’s Caribbean Sea and the Eastern Pacific, so it will be able to dump truly catastrophic rainfall amounts of 10 – 25 inches over a large portion of Central America. These rains are the primary threat posed by the hurricane. The northwestern coast of Honduras this week is to receive the longest-lasting onshore winds from Eta, and that region is at highest risk of getting rainfall amounts of more than 30 inches.

Forecast for Eta for the week

A ridge of high pressure to the north of Eta will force the storm on a generally west to west-southwestward motion through landfall in northeastern Nicaragua on Tuesday. Eta will then angle toward the west-northwest as it moves slowly inland at less than five miles per hour from Wednesday into Thursday. The high terrain of Nicaragua and Honduras should reduce Eta to a remnant low by Thursday, but Eta’s remains will still have plenty of spin and moisture. Come Friday, November 6, a trough of low pressure to the north of Eta’s remains will create upper-level southwesterly winds, which are expected to pull the system northeastwards into the western Caribbean.

An uncertain and concerning long-term forecast

GFS and European models have been consistently predicting that Eta, or its remnants, will emerge over the southwestern Caribbean late this week and reorganize, potentially becoming a powerful hurricane again by early next week. The re-energized Eta would be trapped to the south of a strong ridge of high pressure, resulting in slow and erratic motion that will potentially allow the storm to dump dangerously heavy rains over portions of Central America, eastern Mexico, Cuba, the Cayman Islands, and South Florida.

Also see: Unusually warm sea temperatures fueled Harvey’s devastating rains

The steering pattern over the region will be very complex next week, with a low pressure system over the northern Gulf of Mexico surrounded by three high pressure systems, all competing to steer Eta. As a result, the long-term fate of Eta is highly uncertain, and it may not be until Friday, November 6, when Eta’s remains emerge over the western Caribbean, that it’s clearer where the storm will go.

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Posted on November 3, 2020(1:25pm EST).