The U.S. and European cold blast: blame the NAO

By: Dr. Jeff Masters , 4:00 PM GMT on January 07, 2010

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The Deep South shivered through another frigid morning today, with low temperature records crumbling again over much of Florida. Lakeland hit 27°F, smashing the old record of 34°F; Melbourne hit 28°F, eclipsing the old record of 32°F; and West Palm Beach bottomed out at 37°F, besting the old record of 38°F. The cold wave is being driven by an unusual sharp and persistent kink in the jet stream that is being blocked from moving by a strong ridge of high pressure over Greenland. As a result, an exceptionally strong surface high pressure of 1055 mb over the North Central U.S. is pushing large amounts of cold, Arctic air southwards from Canada. No coldest January temperature records have been set yet from the cold blast, but the 500 largest U.S. cities have been averaging about 11 new daily low temperature records per day the first five days of January, according to the National Climatic Data Center. The cold will ease Friday in the Deep South, but return with a vengeance Saturday night though Monday morning, as another push of cold air descending from Canada promises to bring a cold wave that will approach the December 1989 and January 1977 cold waves in intensity, and may being some new all-time January low temperature records to the South.

Colder in Florida than Alaska and Greenland
The sharp kink in the jet stream has brought record warm temperatures to a few stations in Alaska and the Pacific Northwest this week, making much of coastal Alaska warmer than Florida. Cold Bay, Alaska, set a record high yesterday of 47°F, after recording a low temperature of 30°F. This made Cold Bay warmer than Pensacola, Florida, which had a high of 47°F and a low of 24°F. In fact, most of Florida--including Jacksonville, Tampa, Melbourne, and Tallahassee--recorded lows at or below the 27°F low recorded in Anchorage, Alaska yesterday. The jet stream kink has also brought temperatures more than 30°F above average to Greenland. The temperature in Narsarsuaq, Greenland at 10am EST today was 46°F, far warmer than most of Florida.


Figure 1. Departure of the surface temperature from average for the first three day of 2010 shows much colder than average conditions were present over the Southeast U.S., much of Europe, and Central Asia. Much warmer than average temperatures were present over the Northwest U.S., Greenland, the Arctic, and Southern Asia. A sharp kink in the jet stream was responsible for the temperature anomaly pattern. Image credit: NOAA/ESRL.

Snow in Florida?
It doesn't snow very often in Florida, and the Wikipedia list of snow events in Florida lists only seven such events over the decade of the 2000s. This weekend's cold wave may be able to generate some snow over isolated regions of Central Florida, though it appears that the odds of this happening are less than 30%. The most widespread snowfall in Florida history occurred on January 19, 1977, when snow fell over much of the state, with flurries as far south as Homestead. Snow flurries also fell on Miami Beach for the only time in recorded history.


Figure 2. North Atlantic Oscillation (NAO) index for September 9, 2009 - January 6, 2010 (black line) and forecast from the GFS model (red lines). The NAO index was strongly negative, near -2.0, for much of December and January. Image credit: NOAA/CPC.

The winter cold blast: blame the North Atlantic Oscillation (NAO)
Why has the winter been so cold over Eastern North America and northern Europe? Well, don't blame El Niño. El Niño winters are rarely this cold. Instead, blame the the North Atlantic Oscillation (NAO). The NAO is a climate pattern in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. It is one of oldest known climate oscillations--seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores High,the NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. Negative NAO winters tend to bring cold winters to Europe, and the prevailing storm track moves south towards the Mediterranean Sea. This brings increased storm activity and rainfall to southern Europe and North Africa.

The winter of 2009 - 2010 has seen a very strong negative NAO, causing much of our cold weather over Eastern North America and Europe. The NAO index for the month of December 2009 was -1.93, which is the third lowest NAO index since 1950 for a winter month (December, January, or February). The only winter months with a lower NAO index were February 1978 (-2.20) and January 1963 (-2.12). January 1963 was one of the coldest months on record in the UK and the Eastern U.S.. February 1978 was the coldest February on record for five U.S. states, and featured the historic blizzards in both the U.S. and UK. The NAO so far for January 2010 has continued to stay strongly negative, ranging between -1.5 and -2.1. However, the blocking ridge over Greenland is forecast to weaken next week, allowing the sharp kink in the jet stream to straighten out. This will increase the NAO index to more typical values, allowing a return of more ordinary winter weather to the U.S. and Europe.

Jeff Masters

From The Porch 1 (suzi46)
from our porch view of sunrise this morning..totally different from the 'splendiferous' shots 1-8 taken from the top of our field overlooking the mountains
From The Porch 1
First snow (Rowdyblue)
of winter in South Mississippi.
First snow
Wind blown snow (bikesnapper)
Like sand dunes or Antelope Canyon
Wind blown snow

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Good morning and good afternoon everyone..
Member Since: Posts: Comments:
Quoting RitaEvac:


looks similar to the back yard in Christmas Story movie

Oh, yes it does!
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Quoting AwakeInMaryland:
It's so cute that T-Dude's swingset is still in his backyard...


lol! I remember I had a similar swing set contraption at my house still I was around 6. My sister used it when she was young and then I did, however, it got rusted from a lack of paint so my parents had to throw it out, although the small concrete slabs with a hole in them where the poles would go can still be seen just under the grass.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting AwakeInMaryland:
It's so cute that T-Dude's swingset is still in his backyard...


hahahahaha lol
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting tornadodude:


haha I do have two little bro's :P

Oh my gosh, your poor mommy!

Weather here -- not so bad, sunny. Tonight, tomorrow a.m. - 1-inch snow

Currently: 36°F
Fair
38°F | 29°F
Member Since: Posts: Comments:
Quoting ElConando:
For the second day in a row the low of today missed the record low by 1 degree. Low of 18: record low: 17


That 1 degree difference is because of Climate Change...or as some don't want to say anymore Global Warming...LOL
Member Since: September 2, 2007 Posts: 179 Comments: 20450
Quoting RitaEvac:
Since this is the south, and doesnt stay cold long until now, might try the old sticking my tongue on the flag pole to see if it works down here too.

It does. And if you do it, I might bust a gut laughing at you.
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Quoting Floodman:
Thanks, Doc!

Tampa, quit baiting people, it's not nice...

For the record, I found it amusing...
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Tallahassee NWS Discussion

NOT MUCH CHANGE FROM THE PREVIOUS FORECAST PHILOSOPHY IN TERMS OF
PRECIPITATION TYPE. LOW LEVELS ARE ALREADY TOO WARM TO SUPPORT ANY
FROZEN PRECIP...AND WILL CONTINUE TO WARM THROUGH THE DAY. THEREFORE
WILL CONTINUE WITH THE ALL RAIN FORECAST FOR NOW. GOING TO BE VERY
CLOSE THOUGH ON THE VERY BACK END OF THE SHOWERS. SHALLOW LOW LEVEL
ARCTIC AIRMASS IS FOLLOWING RIGHT ON THE HEELS OF THE RAIN BAND.
LOCAL HIGH-RES WRF SOUNDING PROFILES SUPPORTING ICE PELLETS
BASICALLY LINE UP DIRECTLY WITH THE BACK END OF THE SHOWERS. SO
IF...IF THIS AIR CAN BRIEFLY OUTRUN THE BACK SIDE OF THE RAIN LATE
TONIGHT...THEN IT IS NOT OUT OF THE QUESTION THAT A FEW LOCATIONS
MIGHT SEE ICE PELLETS MIX IN FOR A BRIEF TIME. HOWEVER...WOULD BE SO
BRIEF AND LIGHT AS TO HAVE NO IMPACT. LOW TEMPERATURES BY SUNRISE
WILL RANGE FROM THE UPPER 30S/LOWER 40S AHEAD OF THE FRONT ACROSS
THE SE BIG BEND TO THE UPPER 20S/LOWER 30S FOR THE REMAINING ZONES
BEHIND THE BOUNDARY.

COLD AIR ADVECTION CONTINUES FROM THE NORTHWEST THROUGH THE DAYLIGHT
HOURS FRIDAY. CLASSIC SHALLOW ARCTIC AIRMASS PROFILE SHOWN BY ALL
GUIDANCE WILL ONLY ALLOW FOR A LIMITED REBOUND IN TEMPS. HIGHS
LIKELY REMAINING IN THE UPPER 30S TO NEAR 40 NORTH AND WEST OF A
LINE FROM PANAMA CITY TO TALLAHASSEE AND VALDOSTA. FURTHER SOUTH
LOWER TO MIDDLE 40S WILL BE BEST WE CAN DO. WILL BE ALSO BE BREEZY
FROM THE NORTHWEST WITH WIND CHILLS MAKING IT FEEL EVEN COLDER.
CURRENT GRIDS SUPPORT WIND CHILL ADVISORY CRITERIA FRIDAY NIGHT AS
TEMPERATURES FALL THROUGH THE 20S WITH NORTHERLY WINDS AROUND 10 MPH.

Member Since: August 11, 2008 Posts: 0 Comments: 2315
Since this is the south, and doesnt stay cold long until now, might try the old sticking my tongue on the flag pole to see if it works down here too.
Member Since: Posts: Comments:
For the second day in a row the low of today missed the record low by 1 degree. Low of 18: record low: 17
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting tornadodude:
here is my backyard



looks similar to the back yard in Christmas Story movie
Member Since: Posts: Comments:
Quoting AwakeInMaryland:
It's so cute that T-Dude's swingset is still in his backyard...


haha I do have two little bro's :P
Member Since: June 28, 2006 Posts: 25 Comments: 8360
It's so cute that T-Dude's swingset is still in his backyard...
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Good morning! Gonna be a nice afternoon high of 56! first time its gone over 50 since I have gotten back to Tallahassee. I'll enjoy it while it lasts as by tomorrow evening its back to the ice box.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting Floodman:


I believe you have more coming ,dude...central and east central MO are still getting it and that's moving more or less your way


sounds good (:
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Everybody say Happy Birthday to LST today...she's had a LongStrangeTrip...(explained in part by the fact that she is married to Floodman!!



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U betcha,,preps all done here
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Quoting Patrap:
brrrr.........skee



Yeah, Pat, your overnights are about to be cold...
Member Since: Posts: Comments:
30% chance of SNOW in Central Florida, I'll take any chance, wish I knew the time frame of when we could expect it. My thinking is it will be very early in the morning which means I might not be getting any sleep friday night, because im not missing snow or sleet in Florida. Might be another 20 years if this happens. =)
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Another pulse of energy coming into New Mexico...hUM i wonder how that will play out.



Member Since: September 2, 2007 Posts: 179 Comments: 20450
Quoting tornadodude:
here is my backyard



I believe you have more coming ,dude...central and east central MO are still getting it and that's moving more or less your way
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brrrr.........skee

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here is my backyard

Member Since: June 28, 2006 Posts: 25 Comments: 8360
My hometown in Missouri is even better:

Fulton MO
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Quoting Floodman:
Thanks, Doc!

Tampa, quit baiting people, it's not nice...


HEEHEHE.....never hurts to try!
Member Since: September 2, 2007 Posts: 179 Comments: 20450
Current conditions in Fort Worth TX; I note that the dew point has dropped some 4 degrees in the last hour; the real cold stuff is almost here...

Fort Worth
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Thanks, Doc!

Tampa, quit baiting people, it's not nice...
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Thanks Dr. Masters! So is this the blame of Climate Change also?
Member Since: September 2, 2007 Posts: 179 Comments: 20450

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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