January 8, 2007

The New, Improved, Super-charged El Niño

Filed under: Climate change,Oscillations — Erin @ 9:42 am

Also, African Rain Moves Westward?

UPDATED, 1/10/2007:
2006 was the warmest year on record, it was reported today, ahead of the previous title holder, 1998. 1998 was influenced heavily by the El Niño that began in 1997. And, sure enough, scientists have concluded that this year’s Niño was, effectively, super-charged by global warming. From the right-leaning Chicago Tribune:

In 1998, record high temperatures were driven by an unusually powerful El Nino current that disrupted weather patterns worldwide. The current El Nino, a periodic warming current that took shape last summer, is far weaker and has had only a moderate effect on global climate, several experts said.

“What we are seeing is much more than El Nino,” said climate analyst Kevin Trenberth at the National Center for Atmospheric Research in Boulder, Colo. “The overall pattern is consistent with our concepts of global warming.”

The original blog entry:
Part 1: El Niño 2006-07: Overachiever or Cheat?

As most people are aware, an El Niño formed in autumn of 2006 and has continued to this date. This event was basically single-handedly responsible for cutting off the 2006 hurricane season at the knees. El Niños do that — the last time we had one, it developed in late autumn of 2004 and ended a two-month streak of damaging hurricanes. And that one wasn’t even very strong. It was weak enough, in fact, that most articles in the popular press that talk about this year’s event don’t even refer to 2004; they say that the last El Niño was in 2002. The one this year is a moderate Niño.

This NOAA site shows the Oceanic Nino Index, an indicator of the temperature departure from the average for various three-month periods, going back to 1950. Positive values indicate El Niño-like conditions and negative values indicate La Niña. The site isn’t updated to reflect the new values, but they have increased past the levels of the 2004 Niño event.

The bottom line, though, is that this year’s event is not even close to the strength of the notorious 1997-1998 event. It is moderate. Mild.

Yet, during the most recent period of warmth for the Eastern United States, heat records were set in numerous eastern cities. The most common date for the old records?

Yep, 1997. There was a winter “heat wave” during the same time period during that year’s Niño as well. (Read more…)

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?


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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