An Unprecedented Event on October 18-19, 2005

Two years ago, I remember leaving the National Hurricane Center (NHC) for home sometime around midnight while Hurricane Wilma was strengthening in the northwestern Caribbean Sea.

Just as I was about to fall asleep, the phone rang. It was Dr. Lixion Avila, the Senior Hurricane Specialist on duty at the NHC. Lixion told me that a Hurricane Hunter plane had just reported a minimum central pressure of 901 millibars in the eye of Wilma. Over the period from 7:10 pm EDT on October 18th to 12:33 am EDT on October 19th, the central pressure fell from 954 to 901 millibars, which is a remarkable deepening rate of 9.9 millibars per hour.

I thanked Lixion for calling and tried to fall asleep. Around 4:00 am EDT, Lixion called back and, with great excitement that comes from knowing a historical record has just been set, simply said “884 millibars.”

The last observation had come in from that particular reconnaissance plane and the pressure had dropped further to 884 millibars as measured from a dropsonde released in the eye of Wilma. The surface winds from the dropsonde were measured at 27 mph, so the dropsonde probably did not capture the lowest pressure in Wilma’s eye.

The minimum central pressure was later estimated at the time of peak intensity (8:00 am on October 19th) to be 882 millibars which was a new record low value for a hurricane in the Atlantic basin (surpassing the previous record low pressure of 888 millibars in 1988’s Hurricane Gilbert).

The NHC Tropical Cyclone Report on Wilma written by Richard Pasch, Eric Blake, Hugh Cobb, and Dave Roberts can be found at http://www.nhc.noaa.gov/pdf/TCR-AL252005_Wilma.pdf.

Within a 24 hour period, Wilma had intensified from a 70 mph tropical storm to a 175 mph category 5 hurricane. This was an unprecedented event for an Atlantic tropical cyclone. It is indeed fortunate that this ultra-rapid strengthening occured over open waters of the Caribbean, and not just prior to landfall. I learned a couple of things that night: 1) Just when I thought I had seen everything the 2005 hurricane season could bring, nature still had a surprise in store for us; and 2) I should have moved the phone in my bedroom to my side of the bed. My wife is not into millibars.

Hurricane Wilma was the 22nd named storm in the record-breaking 2005 Atlantic hurricane season which included four major hurricanes (category 3, 4 or 5 on the Saffir-Simpson Hurricane Scale) striking the United States (Dennis, Katrina, Rita and Wilma). Wilma eventually devastated the northeastern Yucatan Peninsula and also caused extensive damage over southern Florida. The 2005 season continued with six additional storms developing after Wilma, finally ending with the dissipation of Tropical Storm Zeta on January 6, 2006.

What a difference a couple of years makes. There are currently no tropical cyclones being tracked and nothing on the immediate horizon in the Atlantic. Although there are still nearly six weeks left to the official 2007 Atlantic hurricane season, let us hope that by the end of November we will be primarily talking about the less-than-forecast activity experienced this year and trying to figure out why many of the seasonal hurricane forecasts busted.

Of course, there are some folks on the Yucatan peninsula who would argue that this was indeed an active season for them with the landfalls of two Category 5 Hurricanes, Dean and Felix. Remember, it only takes one hurricane over your community to make for a bad year.

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One thought on “An Unprecedented Event on October 18-19, 2005

  1. Max,

    When you get a moment, could you elaborate on the source of the upper-level winds which (fortunately) became predominate during the latter half of September. Whatever the cause, I hope we can bottle it.

    Many thanks.

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