September 6, 2006

Where Are the Hurricanes?

Filed under: Oscillations,Tropical — Erin @ 9:48 pm

2006 has had a surprisingly slow hurricane season considering that it’s part of the active phase of the Atlantic Multidecadal Oscillation. Tropical Storm Florence is currently spinning in the Atlantic, flirting with the East Coast (but probably won’t make the commitment). Compare this with last year, when we were past the now infamous “K” name, and with 2004, which had already had two Category Four storms and a Category Five (Ivan) brewing.

Every single storm this year has struggled, from the smallest disturbance to the (so far) most powerful system of the year, Category One Hurricane Ernesto. They all experienced dry air and strong shear, which hindered development despite the overall warm sea surface temperatures that I have been documenting since May. Meanwhile, activity in the Pacific Basin has flourished; the eastern part of it is on the “K” name (Kristy). What’s causing this?

Well, the answer appears to be that meteorological boogeyman associated in the public mind with weird weather and general weather-related misfortune: El Niño. Meteorologists are starting to come to agreement that we are entering an El Niño and that it will impact the winter weather this year, as well as the remainder of the hurricane season. What doesn’t it impact?

Hmm…

Well, the weird thing is that Atlantic sea temperatures remain very warm. The Gulf of Mexico is warm enough to support a storm like Hurricane Camille (which had 200 mph winds), and much of the Atlantic can support a major hurricane. Ordinarily, El Niño is accompanied by cooler-than-normal Atlantic temperatures as well as unusual prevailing wind patterns that destroy tropical systems. The winds are there, but not the water temperatures. I wonder if global warming has caused our oceans to remain warmer than normal (whether for El Niño, La Niña, or neutral) for longer than normal. Thus far, this active hurricane cycle, which began in 1995, has had two strong El Niño years: 1997 and 2002. 2004’s hurricane season was cut short by a weak El Niño that developed late in that year, but only 1997 and 2002 experienced a powerful event. In both years, sea temperatures dropped with the onset of the El Niño conditions.

It’s something to think about.

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