October Ushers in Highest Likelihood of Hurricanes in South Florida

In the 2012 Atlantic hurricane season, we have had 14 tropical storms so far, 8 of which became hurricanes, and just 1 of those became a major (Category 3+) hurricane. An extremely unusual aspect of the season is that essentially all of the hurricane activity occurred north of 25N! Only Ernesto briefly reached minimal hurricane intensity in the tropics just prior to hitting the Yucatan peninsula in early August. All other hurricanes were in the subtropics or mid-latitudes. The season’s only major hurricane so far (Michael) formed from an upper-level cold low pressure system, not from an easterly wave or anything connected to the tropics.

As we head into October, the fifth month of the official Atlantic hurricane season, it’s very important for us in south Florida to realize that this is the greatest hurricane risk month. More hurricanes directly hit or affect southern Florida in October than in any other month. In the graphic shown below, the gray circle is 300 miles across and centered on far western Broward County – designed to include all of southern Florida and immediate surrounding ocean. Any storm of hurricane intensity (sustained winds of 75mph+) whose center passed within that circle is shown in the colored lines, and the legend in the lower right corner associates the color with a category on the Saffir-Simpson scale (yellow is Category 1, orange is Category 2, etc). Finally, the coastal counties are shaded by historic landfall frequency, with darker reds corresponding to more frequent, and pale reds corresponding to less frequent. The monthly tally of tracks passing through the circle is indicated in parentheses below the month. Keep in mind that all of these storms were hurricanes – tropical storms and depressions are not included; and most importantly, never focus on exactly where the center of the track is. Destructive winds, tornadoes, flooding rains, and inundating storm surges can and do occur for hundreds of miles away from the center; so even tracks on the fringe of the circle likely brought severe weather conditions to the mainland.

Another interesting aspect of these maps is that in August and September, southern Florida is most likely to get struck by a storm coming from the southeast. But in October, the dominant direction is from the southwest… due to storms coming from the Gulf of Mexico and western Caribbean, the more favored areas for hurricane formation later in the season.

On the topic of landfalls, do you remember the last time a major hurricane made landfall on the U.S.? It was Hurricane Wilma, on the morning of October 24, 2005, and it hit southern Florida at Category 3 intensity. That was 2,535 days ago, an utterly unprecedented span between major U.S. hurricane landfalls. Streaks that even approach this long are very rare, and only two other spans of over 2,000 days have occurred since 1900. Why has it been so long? Pure luck. There have been several major hurricane landfalls since 2005 in other countries (Nicaragua, Mexico, Cuba, Virgin Islands, Bahamas, and close encounters in Jamaica and Belize), so it definitely isn’t correct to say that seasons since 2005 have been quiet … far from it. No one knows exactly when our lucky streak will end, but I can say with 100% certainty that it will end eventually!

Finally, we are still tracking Hurricane Nadine, which has been around since September 11 (the wave that would become Nadine actually left the African coast on September 7). It’s currently about 550 miles west of the Azores, and is a Category 1 hurricane with 75mph sustained winds. To accurately compare its longevity to historical storms, we need to discount the extra-tropical portions of its lifetime; doing so yields a total of 19.00 days as of this morning at 8am, which is certainly quite long, but not long enough to set any records just yet. This table puts Nadine’s lifetime in perspective among the record holders:

1st 28.00 days Hurricane #3* (1899)
2nd 27.25 days Hurricane Ginger (1971)
3rd 24.75 days Hurricane Inga (1969)
4th 22.00 days Hurricane Kyle (2002)
5th 21.00 days Hurricane #4* (1926)
… (four other storms) …
10th 19.00 days Hurricane Nadine (2012)

* These storms were prior to the satellite era when it was very easy to miss some of a storm’s existence, so these totals are likely underestimates.

Brian McNoldy
Senior Research Associate
& Author of Tropical Atlantic Update
Follow Brian on Twitter: @BMcNoldy

Leave a Reply

Your email address will not be published. Required fields are marked *