On November 8, a tropical wave entered the Caribbean sea. It was producing disorganized thunderstorms throughout the Leeward Islands and Puerto Rico. It moved southwestward over the following days into a more favorable upper-level environment and the disturbance began to organize. On November 13, it was organized enough to be designated Tropical Depression Thirty-One. The depression's circulation was large, with an evident spin on satellite imagery and a convective band extending south and west. Later in the afternoon, the storm was upgraded to Tropical Storm Iota, the record-breaking thirtieth named storm of the 2020 season, and the first ever use of the name "Iota".
When it was first named, Iota was rather disorganized; the mid-level center was well southeast of the low-level center, while the latte was intermittently exposed. This was possibly due to lingering westerly shear, but this was quickly declining. Nevertheless, the storm took about a day to get fully stacked and its winds only increased a bit in the meantime. Though a ridge was gently steering Iota, it didn't move a ton on November 14. In fact, it moved south-southwestward for a time and the vigorous bands south of the center were low enough in latitude to impact northwestern Colombia. That evening, an inner core developed and rapid intensification began.
Overnight, Iota became a hurricane. It underwent an interesting structural shift the morning of the 15th, when an eyewall replacement cycle seemed to take place, even before an eyewall had completely formed. This left the storm with weaker winds and convection temporarily but a higher radius of maximum winds. Meanwhile, the central pressure continued to drop steadily, indicating that the changes were internal and that Iota was still strengthening. The cyclone also assumed a steadier course just north of west that it would maintain through landfall.
An eye appeared intermittently on satellite imagery during that day and the hurricane attained category 2 that evening. Then, an enormous burst of intensification ensued overnight, only the latest of a string of such episodes in the extraordinary 2020 season. During this period, Iota's pressure dropped 26 mb in a single six-hour period, along with a 10 mb drop in a single hour as recorded by reconaissance aircraft. In just 12 hours, the storm went from a 105 mph, 960 mb category 2 hurricane to its peak intensity as a 155 mph, 917 mb category 5 hurricane by the morning of November 16*. This made Iota the strongest storm of the 2020 season, surpassing Eta from a few weeks earlier. On top of this, 2020 became the first hurricane season ever with two major hurricanes in November.
*Note: Iota was operationally classified to have peaked as a category 5 hurricane with maximum winds of 160 mph; however, post-season analysis indicated that the surface wind estimates from aircraft reconnaissance may have been a bit too high, prompting a lowering of estimated peak winds to 155 mph. Though a minor change, this means Iota is no longer considered to have attained category 5 intensity.
Iota maintained top-end category 4 status for some of the day, but underwent another eyewall replacement cycle during the afternoon, which weakened it a bit before landfall. Nevertheless, the cyclone was an extremely intense hurricane when it made landfall in Nicaragua that evening. Tragically, its landfall point was less than 100 miles from Eta's, which had hit only a few weeks earlier. After landfall, Iota quickly weakened as it traversed increasingly mountainous terrain. Some high elevation areas of Nicaragua and Honduras recorded over 20 inches of rain during the storm's passage. It lost hurricane status around midday local time on November 17. The degradation of the circulation was relatively slow for a cyclone over land, though, and the center was still quite evident on satellite imagery as Iota passed inland into southern Honduras that evening.
The storm weakened to a tropical depression early on November 18, crossing into El Salvador, and dissipated a few hours later somewhere near the Pacific coastline. Even though the remnants of Iota moved back over water in the eastern Pacific, conditions there did not favor development.
The above image shows Hurricane Iota at category 4 intensity on November 16.
The conditions in the western Caribbean were extremely favorable for hurricane developement in October and November 2020. Iota formed in this same area and was the second category 4 landfall in two weeks in Nicaragua.
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