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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3201. StormChaser81 2:39 PM GMT on January 11, 2010    
Quoting presslord:
Question: does the freeze kill the entire citrus tree...or just the fruit?


Damages the inside of the fruit.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
3203. AussieStorm 2:41 PM GMT on January 11, 2010    
Good Morning all... 1:40am and still toasty warm, I am going to have fun trying to get to sleep tonight.
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3204. lickitysplit 2:42 PM GMT on January 11, 2010    
I miss Dr. Masters.
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3205. IKE 2:44 PM GMT on January 11, 2010    
Quoting lickitysplit:
I miss Dr. Masters.


?

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3206. StormChaser81 2:45 PM GMT on January 11, 2010    
32 degrees in St. Petersburg, FL. Had a thick layer of Ice in the back on my truck this morning from the sprinkler system.

Lots of reports coming in about little ponds or standing water being frozen with thin coat of ice.
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3207. lickitysplit 2:46 PM GMT on January 11, 2010    
I'm ready for a new Dr. Master's post. No offense to you guys but...
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3208. AussieStorm 2:46 PM GMT on January 11, 2010    
Quoting lickitysplit:
I miss Dr. Masters.

It's only been 4 days since this Blog was started. maybe his PC has frozen.
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3209. tornadodude 2:47 PM GMT on January 11, 2010    
Quoting lickitysplit:
I'm ready for a new Dr. Master's post. No offense to you guys but...


do you update your blog often?
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3210. ElConando 2:49 PM GMT on January 11, 2010    
we've had below freezing low temps since jan 2. And predicted to have below freezing low temps through wed night. Fri and Sat are gonna be nice lows in my mid 40s mmmmm.
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3211. AussieStorm 2:49 PM GMT on January 11, 2010    
Quoting tornadodude:


do you update your blog often?

I haven't been to my blog for ages... might go now
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3212. lickitysplit 2:49 PM GMT on January 11, 2010    
Re:3209

Nah. I'm just here to read Dr. Masters.

Maybe his PC did freeze. Unless he was in Greenland where its in the 40s!
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3213. tornadodude 2:50 PM GMT on January 11, 2010    
Quoting lickitysplit:
Re:3209

Nah. I'm just here to read Dr. Masters.

Maybe his PC did freeze. Unless he was in Greenland where its in the 40s!


oh ok, I was gonna say you could work on your blog if you were getting bored, just a suggestion :p
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3214. ElConando 2:51 PM GMT on January 11, 2010    
Just making sure is the N gulf storm still shown as nasty on the models?
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3215. AussieStorm 2:52 PM GMT on January 11, 2010    
Quoting AussieStorm:

I haven't been to my blog for ages... might go now

Yep, my blog is still there, and still automatically updating. Gotta love technology,
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3216. tornadodude 2:53 PM GMT on January 11, 2010    
I run out of ideas for my blog :p
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3217. HurricaneHunterGal 2:53 PM GMT on January 11, 2010    

Icicles that formed from the sleet in Orlando on Saturday!
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3218. HurricaneHunterGal 2:55 PM GMT on January 11, 2010    

Icicle on a leaf that formed from the sleet in Orlando on Saturday
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3219. HurricaneHunterGal 2:58 PM GMT on January 11, 2010    

More mini icicles from the sleet in Orlando on Saturday
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3220. atmoaggie 2:59 PM GMT on January 11, 2010    
Warming up fast here after bottoming out at 14 F:

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3221. WaterWitch11 3:00 PM GMT on January 11, 2010    
Quoting presslord:
hhhmmm...killing the fruit is bad...killing the tree would be catastrophic...


we had a couple days of freezing here about a month ago. for one day we did not cover our lemon trees. it made the fruit pull away from the peel on the inside and there was no juice left in the fruit. even though it takes them awhile to figure out if the crops are damage, i would have to say that they are probably damaged for this this season. grandpa has a citrus orchard in so. california and when it freezes if they don't run those smut pot things their crops are toast for that season. JMO
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3222. tornadodude 3:00 PM GMT on January 11, 2010    
Happy birthday Atmo!
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3224. tornadodude 3:04 PM GMT on January 11, 2010    
I'll be back later guys, time for math :P

loved my Communications class tho!
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3225. atmoaggie 3:11 PM GMT on January 11, 2010    
Quoting ElConando:
Just making sure is the N gulf storm still shown as nasty on the models?

The latest GFS run keeps it offshore until FWB, which the models having been trending to.

This could keep the severe threat to a minimum...that and a lack of surface warmth.

And it isn't as deep in the models as before. We used to have solutions of a sub-1000 mb low, now closer to 1005mb. Still will have rain, near-TS force winds, and the scattered T-storm, but will be a far cry from a 998 mb low tracking along, but just inland or, the GoM coastline.

We will know there is a solid low, but likely not a damaging system for a lot of folks.

SPC recognizes a threat will exist, but not all that impressed, either.

...
HOWEVER...CONSIDERABLE VARIABILITY LINGERS CONCERNING THE MANNER IN WHICH THIS FEATURE LIFTS OUT ACROSS THE GULF OF MEXICO AND SOUTHEASTERN U.S...AND THE STRENGTH/TRACK OF AN ASSOCIATED DEVELOPING SURFACE CYCLONE. ENOUGH INDICATIONS ARE PRESENT TO SUGGEST THAT AT LEAST LOW SEVERE PROBABILITIES WILL EXIST ACROSS PORTIONS OF THE CENTRAL/EASTERN GULF COAST... INCLUDING THE FLORIDA PENINSULA...PERHAPS NORTHEASTWARD THROUGH THE SOUTH ATLANTIC COAST...THIS COMING FRIDAY INTO SATURDAY. BUT...BOUNDARY LAYER DESTABILIZATION OVER THE GULF OF MEXICO SUPPORTIVE OF A MORE SUBSTANTIAL THREAT IS FAR FROM CERTAIN. WITH SUBSTANTIVE MOISTENING OVER THE NORTHERN AND EASTERN GULF OF MEXICO NOT LIKELY TO COMMENCE UNTIL LATE THIS WEEK.../POTENTIAL TOO LOW/ CATEGORIZATION FOR THE RISK OF A REGIONAL SEVERE WEATHER EVENT IS BEING MAINTAINED.
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3226. atmoaggie 3:13 PM GMT on January 11, 2010    
Quoting tornadodude:
Happy birthday Atmo!

Thanks, dude.

Hope yours was swell (at your age, you might have to look up that word...j/k)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
3227. TampaSpin 3:16 PM GMT on January 11, 2010    
We could really see one heck of a Snow Storm from this in the Tennessee Valley and NorthEast. And very severe Weather in the South!




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3228. nrtiwlnvragn 3:21 PM GMT on January 11, 2010    
New Blog
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3229. atmoaggie 3:26 PM GMT on January 11, 2010    
.
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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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