Dr. Jeff Masters' WunderBlog

The U.S. and European cold blast: blame the NAO
Posted by: Dr. Jeff Masters, 4:00 PM GMT on January 07, 2010 +3
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
Categories: Winter Weather
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551. NRAamy 11:41 PM GMT on January 07, 2010    
I am already so tired of the cold here... I was trying to visualize myself in a cabana on the beach somewhere WARM in the Carabean with a great view of the beach and cold cervaza to cool me down as I perspired just sitting still...Dang, still not workin


eyes...you can drink a cold beer down on our beaches...heck, I may do that on Saturday!

;)

should be a toasty 78 degrees again.....
Member Since: January 24, 2007 Posts: 315 Comments: 31937
552. Drakoen 11:41 PM GMT on January 07, 2010    
The NWS is forecasting for a high of 45 on Saturday for my area in South Florida. I wonder if that's a mistake.
Member Since: October 28, 2006 Posts: 57 Comments: 29010
553. TampaSpin 11:43 PM GMT on January 07, 2010    
Quoting FLPandhandleJG:


I see very little green on that graphic...LOL
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554. FLPandhandleJG 11:44 PM GMT on January 07, 2010    
Quoting TampaSpin:


I see very little green on that graphic...LOL


ya i dont know how much that is true.. i sure hope to c sumthing later.. :P
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555. Drakoen 11:45 PM GMT on January 07, 2010    
Quoting TampaSpin:


I see very little green on that graphic...LOL


That graphic I find to not accurately present what is happening. I prefer this radar from intellicast:



Member Since: October 28, 2006 Posts: 57 Comments: 29010
556. eyesontheweather 11:46 PM GMT on January 07, 2010    
Quoting NRAamy:
I am already so tired of the cold here... I was trying to visualize myself in a cabana on the beach somewhere WARM in the Carabean with a great view of the beach and cold cervaza to cool me down as I perspired just sitting still...Dang, still not workin


eyes...you can drink a cold beer down on our beaches...heck, I may do that on Saturday!

;)

should be a toasty 78 degrees again.....
Better be careful.. I'm about to head in a direction of warmth
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557. ElConando 11:46 PM GMT on January 07, 2010    
i'm for casted to get ice pellets on Friday morning. What are ice pellets?
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558. FLPandhandleJG 11:46 PM GMT on January 07, 2010    
Quoting Drakoen:


That graphic I find to not accurately present what is happening. I prefer this radar from intellicast:




I know.. i had to tease.. lol its not looking good.. we need lil more moisture..
Member Since: August 15, 2008 Posts: 0 Comments: 1997
560. jipmg 11:47 PM GMT on January 07, 2010    
the graphics he posted before was innaccurate, its 44 in new orleans, not cold enough for snow.
563. Drakoen 11:48 PM GMT on January 07, 2010    
Quoting ElConando:
i'm for casted to get ice pellets on Friday morning. What are ice pellets?


Tiny ice balls
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564. Drakoen 11:49 PM GMT on January 07, 2010    
The NWS forecasting for highs in south Florida only in the 40s based on the GFS raw data. The MOS is warmer.
Member Since: October 28, 2006 Posts: 57 Comments: 29010
566. NRAamy 11:50 PM GMT on January 07, 2010    
Better be careful.. I'm about to head in a direction of warmth

come on down! we have a spare bedroom! and maybe you'll get to experience an earthquake while you're here! Woo hoo!!!!!!

:)
Member Since: January 24, 2007 Posts: 315 Comments: 31937
567. jipmg 11:52 PM GMT on January 07, 2010    
Quoting Drakoen:
The NWS forecasting for highs in south Florida only in the 40s based on the GFS raw data. The MOS is warmer.


Along with an 80% chance of rain, and temperatures falling into the low and mid 30s along metro areas

569. Patrap 11:53 PM GMT on January 07, 2010    
Some sleet is mixing in here as the cold air advection has begun in earnest.
Unless this stuff bouncing off my Truck hood is Salt..LOL
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570. Drakoen 11:54 PM GMT on January 07, 2010    
NWS MIAMI

CLOUDY...
RAINY...COLD...AND BLUSTERY WILL BEST DESCRIBE THE EXPECTED
WEATHER DURING THIS PERIOD...WITH RAIN CHANCES DIMINISHING FROM
NORTHWEST TO SOUTHEAST LATE SATURDAY NIGHT. REMARKABLY...HIGH
TEMPERATURES ON SATURDAY WILL LIKELY NOT MAKE IT OUT OF THE 40S
FOR MOST OF SOUTH FLORIDA...AND THERE IS STILL A VERY REMOTE
POTENTIAL...BASED ON PARTIAL THICKNESS PROGS FROM THE GFS/NAM...
FOR SOME SLEET/ICE PELLETS TO MIX WITH RAIN ACROSS THE NORTHWEST
HALF OF THE FORECAST AREA ON SATURDAY.
MAGNITUDE OF LOW-LEVEL COLD
ADVECTION WILL LIKELY INCREASE ON SATURDAY NIGHT...AS A
SECONDARY/POWERFUL MID-LEVEL VORT MAX MOVES EASTWARD ACROSS THE
NORTHEAST GULF COAST...INDUCING SURFACE CYCLOGENESIS OVER THE
ATLANTIC WATERS TO THE NORTHEAST OF THE BAHAMAS. AN ADVECTIVE
FREEZE APPEARS VERY LIKELY ACROSS NORTHWEST HALF OF THE FORECAST
AREA...WITH WIND CHILL WARNINGS ALSO LIKELY FOR A PORTION OF SOUTH
FLORIDA.

Member Since: October 28, 2006 Posts: 57 Comments: 29010
571. AwakeInMaryland 11:58 PM GMT on January 07, 2010    
Quoting ElConando:
i'm for casted to get ice pellets on Friday morning. What are ice pellets?


LOL! Well, if you have to ask, then...
They hurt like hell. Wear a helmet, goggles, and carry a blow-torch!

Ya'll are making me laugh hard -- it's a good thing!
Member Since: August 19, 2008 Posts: 32 Comments: 1918
572. HurricaneSwirl 11:58 PM GMT on January 07, 2010    
Dunno if its gonna snow... it got way too warm today. Predicted for today yesterday was 43. It actually got to 52. Right now it's still steady at 44.. And TWC's future cast has completely backed off on central GA. :(
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573. AllyBama 11:59 PM GMT on January 07, 2010    
Quoting Patrap:
Some sleet is mixing in here as the cold air advection has begun in earnest.
Unless this stuff bouncing off my Truck hood is Salt..LOL


lol..nothing like a little "rock salt" to go with that margarita!
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574. Drakoen 12:01 AM GMT on January 08, 2010    
Quoting HurricaneSwirl:
Dunno if its gonna snow... it got way too warm today. Predicted for today yesterday was 43. It actually got to 52. Right now it's still steady at 44.. And TWC's future cast has completely backed off on central GA. :(


I would wait until after midnight where the transition may occur over to a rain/snow mix
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575. Patrap 12:01 AM GMT on January 08, 2010    
Ooooo eeee allybama,that NW wind has picked up and itsa frosty one,slightly Polar tinged with a touch of U.S.Plains bouquet.


Lub it
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576. TheMom 12:03 AM GMT on January 08, 2010    
Quoting Floodman:


I've seen the temps drop 40 degrees in two-three hours; not in Florida, mind you, but the front you have coming in isn't like your usual January front...trust me, I'm in the middle of it
It was 55 on the way home but just sitting on the couch keep feeelin it getting cooler and cooler we have heat set at 70 might have to bump it up a few degrees. NWS has us sleet/snow from 4am-7am Saturday I'm soooo setting the alarm!
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577. jipmg 12:03 AM GMT on January 08, 2010    
sleet in the low 40s? o-0
578. Drakoen 12:03 AM GMT on January 08, 2010    
rain/snow line slowly pushing south

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579. Patrap 12:05 AM GMT on January 08, 2010    
One dosent need 32 at the surface for sleet ..Winter 101




Seen sleet here at 50 F
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580. HurricaneSwirl 12:07 AM GMT on January 08, 2010    
Quoting Drakoen:
rain/snow line slowly pushing south



That map shows a lot more moisture than the TWC map. Is that accurate? :o
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581. NRAamy 12:07 AM GMT on January 08, 2010    
Pat....aren't you supposed to be making some gumbo? Miss Sweet T is gonna clock you!

;)
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582. Patrap 12:07 AM GMT on January 08, 2010    


Now we can root for the GOM Low and shortwave thru Saturday!!!

Geaux Sneaux...!


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583. Drakoen 12:08 AM GMT on January 08, 2010    
Quoting HurricaneSwirl:


That map shows a lot more moisture than the TWC map. Is that accurate? :o


Yes it is...
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584. Patrap 12:09 AM GMT on January 08, 2010    
Quoting NRAamy:
Pat....aren't you supposed to be making some gumbo? Miss Sweet T is gonna clock you!

;)


Gumbo simmering..I got it down to a science.

PHd's in Gumbo are as rare a Degreed Met here,.dawling
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585. BioChemist 12:11 AM GMT on January 08, 2010    
It looks like the rain will end in Pensacola before any transition to sleet or snow.

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586. TampaSpin 12:12 AM GMT on January 08, 2010    
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587. jipmg 12:12 AM GMT on January 08, 2010    
Quoting HurricaneSwirl:


That map shows a lot more moisture than the TWC map. Is that accurate? :o


TWC? Since when were they ever accurate?

588. Grothar 12:13 AM GMT on January 08, 2010    


It looks like advect training of copious precipitation in the mid to lower atmosphere about to prevade over the southern peninsula of Florida. How is that for a forecast????
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589. Patrap 12:13 AM GMT on January 08, 2010    
oooooo Eeee Cher,..

CONUS 18 hr forecast Map


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590. Patrap 12:15 AM GMT on January 08, 2010    
I like it grothar,but how about the "Icy finger-O-Doom"..?
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591. Grothar 12:15 AM GMT on January 08, 2010    
Quoting Patrap:


Gumbo simmering..I got it down to a science.

PHd's in Gumbo are as rare a Degreed Met here,.dawling


Hey Pat! Remember the days when we hoped it would get into the 20's during Cold Weather training??? Good preparation for us.
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592. HurricaneSwirl 12:16 AM GMT on January 08, 2010    
Quoting jipmg:


TWC? Since when were they ever accurate?



I've just been following them because they update the fastest on temps.. which im following very closely.

42!
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593. Patrap 12:16 AM GMT on January 08, 2010    
Quoting Grothar:


Hey Pat! Remember the days when we hoped it would get into the 20's during Cold Weather training??? Good preparation for us.


I liked the cool issue Sunglasses too..

Man we were Hip..
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594. TampaSpin 12:17 AM GMT on January 08, 2010    
Look at post 586.....see the other disturbance in Texas that the other piece of energy is creating...watch that grow.
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595. Grothar 12:18 AM GMT on January 08, 2010    
Quoting Patrap:
I like it grothar,but how about the "Icy finger-O-Doom"..?


You know me, I don't like to get too technical on the blog.
Member Since: July 17, 2009 Posts: 56 Comments: 19515
596. jipmg 12:19 AM GMT on January 08, 2010    
55 in miami, dropping kinda fast for cloudy conditions and an east wind..
597. TampaSpin 12:19 AM GMT on January 08, 2010    
Atlanta might have some major traffic issues coming tonite.
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598. eyesontheweather 12:22 AM GMT on January 08, 2010    
Quoting NRAamy:
Better be careful.. I'm about to head in a direction of warmth

come on down! we have a spare bedroom! and maybe you'll get to experience an earthquake while you're here! Woo hoo!!!!!!

:)
Told ya to be careful. See if I can manage a couple more days... BTW, already done the earthquake fun
Member Since: August 25, 2008 Posts: 0 Comments: 613
599. TheMom 12:22 AM GMT on January 08, 2010    
Quoting FLPandhandleJG:


Ya but it is still different tho.. up north expects to get cold sometimes ya'll get rediculous colds.. But when u see an artic air mass come down like this, you dont see it that often for the south and for Florida.. yes we know jackets and other weather gear should help.. But we got citrus to worry about, most of our water mains are outside instead in the ground.. and most importantly half to most floridans dont have heaters or dont check them, that can be a problem.. we know its cold but its other things just that.. theres my 2cents worth..
Don't want to get in a "measuring contest" but a lot of Floridians don't have winter coats that are for this kind of cold. I'm seeing kids waiting for their buses in a couple hoodies since that is there coats.
I am the overprotective parent sooo this is my kid lol
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600. atmoaggie 12:24 AM GMT on January 08, 2010    
Quoting TampaSpin:


I see very little green on that graphic...LOL

I promise that there was no snow and very little sleet in Slidell 30 minutes ago, mostly just rain. (and 46F on the auto thermometer)

(that is just inside LA, directly west of MS gulf coast -or- NE of NOLA)

And in Covington (20 miles west of Slidell) no snow. None. And rain over.
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601. Patrap 12:27 AM GMT on January 08, 2010    
Why I declare,..say it aint so?
LOL
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About JeffMasters
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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