It’s nearly that time of year when we give thanks — that the Atlantic Basin hurricane season is over.
The season runs through November 30, and though there have been hurricanes in the last half of November, they are rare and only three have ever reached major hurricane (category three or higher) strength after November tenth.
This year has been a slow one for Atlantic tropical systems, as is normal for a strong El Niño year. So it is no surprise that November probably won’t produce a named system (named systems require winds of 39 miles per hour or greater).
The Indian Ocean is on the other side of the world and the other side of the cyclone statistics this November. Back-to-back cyclones of hurricane strength have formed in the Arabian Sea, one the equivalent of category five, and moved towards Yemen, where they never even had a tropical storm make landfall previously.
Atlantic Basin November Hurricanes
From 1851 through 2014, 57 hurricanes have formed in the Atlantic Basin in November. This is approximately one every three years, or about five percent of the total of 987 hurricanes that formed during that period. Of the 57 November hurricanes, only seven (about twelve per cent) reached major hurricane status with winds over 115 miles per hour, and of those, only three occurred after the tenth of the month. Overall, about 40% of all hurricanes reach category three strength.
The four early-November major hurricanes all reached category four strength (winds over 135 miles per hour), while of the three that occurred later in the month, only one reached category four. The three major hurricanes that occurred after November tenth were:
- Hurricane Seven, November 17-18, 1912 (this was before hurricanes had names) formed in the southern Caribbean and wandered north. It never struck land of any size, though it came close to Jamaica. Top winds were estimated at a bare-minimum major hurricane strength of 115 miles per hour.
- Hurricane Kate, November 20-21, 1985, developed north of Puerto Rico and moved west. Kate avoided the hurricane graveyard of mountainous Hispaniola and Cuba, swirling just north of the coasts into the Gulf of Mexico. Kate became a major hurricane with top winds of 120 miles per hour in the central Gulf and curved north. The storm struck the Florida Panhandle as a category one hurricane.
- Hurricane Lenny, known as “Wrong Way Lenny” because it moved from west to east, formed in the western Caribbean in 1999. The storm moved east and strengthened into a powerful category four hurricane with winds of 155 miles per hour, just shy of category five, as it crossed the Virgin Islands on November 17. Lenny continued east into the Atlantic and dissipated in the middle of the ocean.
The Points Of Origin Of Late-Season Hurricanes
The points of origin for hurricanes in the Atlantic Basin during the middle of November are clustered in the southern Caribbean, and north and northeast of the Leeward Islands.
Frequently the storms originate on old frontal boundaries. As “Wrong Way Lenny” showed, movement can be erratic at this time of year, as mid-latitude westerlies begin to encroach on the subtropical easterly flow of summer.
November Hurricanes In The Eastern Pacific
The eastern Pacific hurricane season begins two weeks earlier than the Atlantic season, but they both end on November 30. The eastern Pacific tends to ramp up and wind down earlier. June and July are more active in the Pacific, but after that there are more Atlantic storms. October and November storms are rare in the eastern Pacific; this year’s late-October Hurricane Patricia, by some estimates the strongest hurricane ever, took meteorologists by surprise.
November, 2015: Spotlight On The Arabian Sea
The Indian Ocean tropical cyclone season is bifurcated two ways: East and west of India; before and after the monsoon.
More storms normally form in the Bay of Bengal, east of India, than in the Arabian Sea, west of India. But not this month.
Though Super-Cyclone Chapala reached maximum intensity on Oct. 30 with winds of 160 miles per hour, it made landfall in Yemen on November 3.
Decoded Science is calling it a November storm. Killing eight people, Chapala dumped many years’ worth of rain on the normally dry Arabian Peninsula.
Now Comes Severe Cyclone Megh. Not as strong as Chapala, with winds barely over 100 miles per hour, Megh would still have been the most powerful cyclone to make landfall in Yemen by a wide margin if not for Chapala.
The forecast has shifted slightly north in the last day, and Megh, once forecast to slice through the northern tip of Somalia, will stay over water and make landfall in southern Yemen on Tuesday as a category one hurricane with winds of 80 miles per hour.
Could The Arabian Sea Cyclones Be Caused By Global Warming?
Hundred-year weather events — even thousand-year events — are cropping up with alarming frequency. A recent study published in the Bulletin of the American Meteorological Society links fourteen of last year’s extreme weather events to global warming. Certainly it is reasonable to conclude that a warmer earth will mean warmer ocean water temperatures, and empirical evidence supports this conclusion. Other things being equal, warmer water, the energy driver of tropical systems, should lead to more — and more powerful — tropical cyclones. Of course there’s always a caveat: Feedback matters.
The Atlantic had fewer hurricanes than normal this year; the Pacific had a blockbuster year. And what to make of tandem cyclones where normally cyclones never go? It could be just coincidence. Or it could be the beginning of a brave new world.