Area lows dip into 20s tonight


Published: Friday, January 17, 2003 at 6:01 a.m.
Last Modified: Friday, January 17, 2003 at 12:39 a.m.
With the coldest weather of the season coming up tonight, and more on its way this weekend, it's time to point the finger of blame not at the usual bad-weather culprit, El Nio, but at the North Atlantic Oscillation.
Low temperatures of 22 degrees are expected tonight and lows of 25 on Saturday night, according to the National Weather Service in Jacksonville.
But while there is an El Nio this year, it's not responsible for the cold weather that's come to North Central Florida this winter.
El Nio is a weather phenomenon involving surface warming of the eastern and central Pacific Ocean near the equator, which often causes extra rain in the southeastern United States.
"Typically, Florida is colder than normal in El Nio because it's rainier and cloudier," said Mike Halpert, head of forecast operations for the National Oceanic and Atmospheric Administration's Climate Prediction Center. "But this is an Arctic outbreak. That's not really associated with El Nio at all."
The cold air is due to a weather system called the North Atlantic Oscillation, Halpert said. The system is the biggest reason for climate changes in the eastern United States, he said.
The oscillation is associated with the position of the polar Arctic jet stream. When it's in a negative phase, as it is now, it allows cold Canadian air into the country and results in colder temperatures in the eastern United States, Halpert said.
"Over the past 20 years, we haven't seen it much," Halpert said. "We've been dominated by the opposite phase."
Forecasters don't know when this weather pattern will go away.
"Right now, we don't know what causes it to be in one phase or the other," Halpert said. "We're doing a lot of research to find out."
It's common for both positive and negative phases of the oscillation to stick around for months at a time, according to the Climate Prediction Center.
The El Nio is still expected to bring wet weather to Florida through at least March.
After a high temperature today of 48 degrees, lows will drop to 22 and recover only to 48 again Saturday, according to the National Weather Service.
Freezing temperatures are expected through the weekend with lows of 25 Saturday and Sunday nights.
A slow warm-up begins next week, with high temperatures of 62 degrees Monday and 65 on Tuesday with overnight lows of about 35.
Kathy Ciotola can be reached at 338-3109 or ciotolk@ gvillesun.com.

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