Here's to Ted…

Fearless Fathauer has left the building.

It's official, Ted has retired:

Ted helped me get my first job in Alaska and I've learned a lot from him in the past 25 years. He was the last of the old school meteorologists here, who cut their teeth in the weather forecasting biz before computer models largely replaced the need for actual physical understanding. Ted's surface and upper air analyzes are a pleasure work with, painting the weather story of the day.

 Good Luck Ted!!

Unstable Temperatures

Here is a plot of hourly temperatures Sunday at a handful of sites in greater Fairbanks-land.

The low lying areas such has Goldstream Creek (GCSA2) and Woodsmoke PWS (WODA2) have been unable to pop the inversion due to the clearing that followed the occlusion, while high elevations, Clearly Summit (CLRA2) and Keystone Ridge (KERA2) have been breezy and in the warm air for a couple days now. At both valley and higher elevations temperatures have been fairly stable.

But look what's happening right near the Tanana River: Eielson AFB (PAEI) was cold, then gusty southeast winds broke through and temperatures have been very mild since mid morning. This is quite common at Eielson. Both Fairbanks Airport (PAFA) and Nenana Airport (PANN) have had big temperature swings during the day as the differing airmasses waffle back and both across these specific points. The Alaska Fish and Game Alaska Division of Geological & Geophysical Surveys* PWS on College Road (C6400)) has not had the swings in temperature as the airport but is a milder version of Goldstream Creek.

Note: There is a chance the Fairbanks Airport temperature swings are not real but represents intermittent sensor failure. However, given the overall situation, the reported temperature variations are probably real.

*Thanks to Chris S. for pointing out my incorrect attribution of the operator of this PWS. 

Denali Heat Wave

Temperatures Sunday morning have boomed into the 40s in Denali Park area with pretty decent chinook underway. Peak winds so far include 58 mph at Antler Creek RWIS (between Healy and Glitter Gulch), 49 mph at Healy (at the DOT camp) and 43 mph at the Otto Lake PWS. The NOAA-18 infrared image from just before 6am AST Sunday shows the occlusion in an arc across the central Interior. Note the mountain wave clouds just to the south of the high cloud edge.

Courtesy of NWS Alaska Region

Temperatures at 8am (ish) Sunday on the east side of the Park include:
Healy: 46F
Denali Park Airstrip: 45F
Antler Creek RWIS: 45F
Otto Lake PWS: 44F
Denali Park HQ: 41F

The high temperature of 42F at Denali Park HQ Coop is not a record for Dec 30th. That is still 48F set in 2000.

West of the Toklat River it's warm too:

Stampede Airstrip:42F
Wonder Lake: 44F
Kantishna: 44F

Delta Differences

Courtesy of the Weather Underground

For those familiar with the Delta Junction area, the plot at the left from the Weather Underground nicely illustrates the competing airmass regimes. From Fort Greely northward the Tanana Valley jet is blowing, draining the cold pool still sitting over the upper Tanana Valley. Just to the south, along the Delta River. chinook warmed airmass is in place. If/when the southerly flow breaks through look for temperatures to jump 20F or more in a few minutes at Fort Greely and the immediate Delta Junction area.

Clarification: This is data from about 10am AST Saturday

It has Began…

The big warm-up the numerical models have been advertizing for a week is here. The upper air sounding from early Saturday morning already had the temperature at freezing 900 meters up, 42F warmer than the surface. 

Temperatures have continued to rise since then; some 9am AST Saturday temperatures include:

• Eielson AFB: 8F
• Woodsmoke PWS: 8F (near North Pole)
• Goldstream Creek: 8F
• Fort Wainwright: 10F
• Fairbanks Airport: 11F
• UAF West Ridge: 16F
• College Hills: 26F
• Keystone Ridge: 31F
• Skyline Ridge: 34F

Temperatures near the Alaska Range Saturday morning are way up above freezing, including 9am temperatures of 38F at Healy and 41F at Bolio Lake south of Fort Greely.

The 9am GOES infrared image shows the fractured occlusion over the central Interior, and the next wound-up storm plowing northward through the Gulf of Alaska:

Courtesy of NWS Alaska Region

This will ensure warm winter weather in Fairbanks-land into the New Year.

Seasonal Inversion

As we await the Great 2012-13 Mid-Winter Warm-up, here's a quick and easy way of assessing  daily inversion strength in Fairbanks-land over a seasonal basis. This is simply the difference in mean daily between the Fairbanks Airport and Keystone Ridge. Just a reminder: Fairbanks Airport elevation is 440' MSL and  Keystone Ridge, 14 miles northwest of the Airport is at 1600' MSL. Importantly, the climate day is the same, so this is a straight apples-to-apples comparison.

Until the snow cover was established in mid-October, the Airport was generally warmer than the Ridge. Since November 1st, the median "inversion strength" has been 15F. Only the snow of earlier this month was enough to completely disrupt the inversion. The strongest daily inversion was on December 22nd, when the Airport had a daily mean temperature of -39F and Keystone Ridge had a daily mean of -4F.

Christmas Weather in Fairbanks

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
145 PM AKST TUE DEC 25 2012

...CHRISTMAS DAY IN FAIRBANKS...

CHRISTMAS DAY 2012 IN FAIRBANKS WAS NOTABLE FOR THE BREAK IN THE
COLD SNAP THE GRIPPED THE AREA SINCE THE BIG SNOWS OF DEC 11TH TO
13TH. 

OVER THE PAST 108 YEARS...CHRISTMAS DAY HAS BROUGHT TEMPERATURES
AS LOW AS 56 BELOW IN 1961 AND AS WARM AS 34 ABOVE IN 1985.

THE SNOWIEST CHRISTMAS WAS IN 1999...WHEN 3.8 INCHES OF SNOW FELL. 
AN INCH OR MORE OF SNOW HAS OCCURRED ON CHRISTMAS DAY JUST 13
TIMES SINCE 1904.

FAIRBANKS ALMOST ALWAYS HAS A WHITE CHRISTMAS...AND THIS YEAR WAS
NO EXCEPTION....WITH A 17 INCH BLANKET OF SNOW. THE DEEPEST SNOW PACK
ON CHRISTMAS DAY WAS 39 INCHES IN 1970. ONLY ONCE HAS FAIRBANKS
NOT HAD A WHITE CHRISTMAS. IN 1934...THE GREATEST WINTER CHINOOK
IN FAIRBANKS WEATHER HISTORY EARLY THAT DECEMBER BROUGHT FIVE
DAYS IN A ROW WITH HIGHS IN THE 50S AND COMPLETELY MELTED THE THIN
SNOW PACK THAT HAD BEEN PRESENT. AFTER THE CHINOOK ENDED THERE WAS
ONLY MEAGER AMOUNTS OF SNOW UNTIL THE 26TH. AS A RESULT...CHRISTMAS
DAY 1934 HAD JUST A TRACE OF SNOW ON THE GROUND. EVERY OTHER
CHRISTMAS FOR WHICH THERE IS A RECORD HAD AT LEAST FOUR INCHES OF
SNOW COVER.

$$
RT DEC 12

Cold Snap Gone But Not Forgotten

Temperatures popped above zero early Christmas morning in the Fairbanks bowl, with no return to the deep cold anytime soon. Here's an update of daily mean temperature anomaly plot.  Since October 15th just under half of the days (33 of 69) have had a daily mean temperature 1.0 or more standard deviation below normal, which is a pretty healthy run of persistent below normal temperatures. The average temperature during that time is -8.3F. So far, ten days this winter have had a low temperature of 40 below or lower, which is about the average number for the whole winter. However, the numerical guidance is now in pretty good agreement that sustained above normal temperatures will be with us for the next couple weeks at least. This close to winter solstice, in valleys at least, a warm overall pattern will be tempered by strong inversions developing any time skies clear for any length of time. But no more 40 below in the foreseeable future.

Warming Up, But Still Cold

Courtesy of NWS Alaska Region

Winds aloft are now southerly over most of Interior Alaska. This is both warming the airmass and brought some areas of clouds that had been over the YT into region. The NOAA-18 Polar Orbiter infrared image from 619am AST Monday tells the tale. Clouds were mostly confined to areas north of 67N, after bringing somewhat "less cold" temperatures places that had been very cold, with highs Sunday of -22F at Eagle and -30F at Tok.

The warming in valleys that don't get any wind will be slow and limited because at this point there is no deep cloud layer likely to survival crossing the Chugach and Alaska Ranges over the next few days. Any place that does get wind though will see much warmer temperatures: compare the 9am AST Monday temperature of +1F at Nenana and -29F at Fairbanks International.

So what does this mean for the cold December in Fairbanks? The average temperature (at the Airport) for the first 23 days of the month is -23.0F, and this is about the bottom. I expect the final eight days of the month will finish up averaging a bit below normal (today and Christmas Day significantly so). At this point there does not seem to be a path for December 2012 to be in the top five coldest Decembers, even just considering the Weather Bureau/NWS era (since 1929), though this will very likely be the coldest December since 1980, when the monthly mean was -24.0F. This is yet another case (like, e.g. January 2006) where the lack of extremely low temperatures is keeping the mean temperature from being super low. No calendar day this month has had a high temperature in the -40s, and the monthly minimum of -48F is pretty underwhelming by historic standards. While urban effects/ice fog are playing some role, it can't be the whole story: December 2012 minimum temperatures of -58F at Tok and Chicken, -54F at Eagle Co-op, -55F at the Fort Yukon AWOS are all historically way off the mark.

Record Low Temperatures in Tok

SXAK79 PAFG 230543
RERAFG

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
843 PM AKST SAT DEC 22 2012

...RECORD LOW TEMPERATURES IN TOK

THE LOW TEMPERATURE AT TOK AS REPORTED BY THE NATIONAL WEATHER
SERVICE COOPERATIVE OBSERVER ON SATURDAY WAS 57 BELOW. THIS TIES
THE RECORD LOW FOR DECEMBER 22 PREVIOUSLY SET IN 1961.

THE HIGH TEMPERATURE SATURDAY IN TOK WAS 48 BELOW. THIS IS THE
LOWEST MAXIMUM TEMPERATURE OF RECORD FOR DECEMBER 22 IN
TOK...BREAKING THE PREVIOUS RECORD OF 45 BELOW SET IN 1957.

WEATHER OBSERVATIONS HAVE BEEN MADE IN TOK...THOUGH WITH GAPS IN
THE RECORD...SINCE 1954.

RT DEC 12

The Cold Goes On

Courtesy NWS Alaska Region

Here's a very nice NOAA-18 infrared image from 542am AST Saturday. Except for some clouds over the southern Yukon Territory and cirrus wisps over the Beaufort Sea, this is a clear sky image. The cold pooled in many valleys, the dramatically warmer hills. Tanana Valley jet other drainage wind regimes blowing over the flats on the north side of the Alaska.  The comparatively mild North Slope. You could do a seminar on Interior Alaska winter weather just from this image.

Some lows reported through 9am in Fairbanks-land Saturday include:

Woodsmoke PWS: -47F (near North Pole)
Goldstream Creek: -44F
Eielson AFB: -44F 
Fairbanks Airport: -43F
Fort Wainwright: -43F
UAF West Ridge: -37F
College Hills PWS: -21F
Skyline Drive PWS: -10F
Keystone Ridge: -6F
Cleary Summit RWIS: -3F

In the eastern Interior…

Eagle co-op: -54F
Fort Yukon Airport: -54F
Fort Yukon co-op: -53F
Coal Creek RAWS: -53F
Northway -50F

And we await the Chicken report…The Chicken RAWS up on the hills is -53F, a couple degrees colder than Friday. Do I hear a -60F?

Updated: Nope, we don't have a -60F at Chicken co-op: low of -57F.

Solstice Low Temperature Summary

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
339 PM AKST FRI DEC 21 2012

...A COLD WINTER SOLSTICE IN INTERIOR ALASKA...

TEMPERATURES IN CENTRAL AND EASTERN INTERIOR ALASKAN VALLEYS
AGAIN DIPPED INTO THE 40S AND 50S BELOW...MAKING FOR A MIGHTY
CHILLY WINTER SOLSTICE. HOWEVER...AS BRISK AS IT IS...NO LONG
TERM OBSERVING LOCATION SET A NEW RECORD LOW FOR DECEMBER 20TH. 

AT FAIRBANKS INTERNATIONAL AIRPORT...THE LOW SINCE MIDNIGHT HAS
BEEN 46 BELOW...MAKING THIS THE EIGHTH DAY THIS MONTH WITH A LOW
OF 40 BELOW OR LOWER. THE LAST TIME DECEMBER HAD THIS MANY
40 BELOW DAYS WAS BACK IN 1980.

OTHER VALLEY LOW TEMPERATURES FRIDAY IN THE FAIRBANKS AREA
INCLUDED...

WOODSMOKE...................51 BELOW (NEAR NORTH POLE)
BADGER AND RAPP ROAD........49 BELOW (NEAR NORTH POLE)
FORT WAINWRIGHT.............48 BELOW 
GOLDSTREAM CREEK............47 BELOW 
EIELSON AFB.................46 BELOW

ELSEWHERE IN INTERIOR ALASKA LOWS INCLUDE...

CHICKEN.....................58 BELOW
TOK.........................56 BELOW
FORTYMILE RIVER.............54 BELOW
EAGLE.......................52 BELOW 
FORT YUKON..................52 BELOW
NORTHWAY....................51 BELOW 
SALCHA RIVER MILE 25........51 BELOW
NENANA......................47 BELOW
CENTRAL.....................46 BELOW 
DENALI PARK TRAIN STATION...42 BELOW 
FORT GREELY.................41 BELOW 
DENALI PARK HQ..............31 BELOW

$$
RT DEC 12

Inversion Nirvana

Here's a plot of hourly temperatures in the past 24 hours for Goldstream Creek, College Hills and Keystone Ridge, representing low, middle and high elevations. At 10am Friday the inversion now exceeds 40 degrees between the cold spots in the Fairbanks Bowl to locations above  2000' MSL. Typically inversions this strong happen just a few times a winter.


9 to 10am temperatures:

Fort Wainwright: -44F
Fairbanks Airport : -41F
College Hills: -23F
Skyline Drive: -13F
Keystone Ridge: -6F
Cleary Summit: -2F
Wickersham Dome -1F

Still Cold…but No Silliness

Thursday evening I was amused by various Facebook posts with someone somewhere forecasting a low of 60 below for this morning at Fort Wainwright. Not only would such a temperature be extremely unusual, even a cursory look at the meteorology would have suggested that was highly unlikely: the air mass was already warming, as evidence by the gradually rising temperatures at higher elevations. This morning's sounding shows  moderate surface based inversion (by Fairbanks standards) with the air 500 meters up about 20C (36F) warmer than at the surface.

As I wrote about last winter, at 65 degrees north latitude there is no appreciable solar heating in the weeks around winter solstice, which means there is no change in solar heating that would cause one to think the temperature would drop overnight. The lack of auto traffic overnight can result in thinning of ice fog (though that's not a hard and fast rule), which can allow for surface cooling if the ice fog thins enough. In general though, with a gradually warming airmass, no clouds and no wind, Interior Alaska valley temperatures in late December should be nearly steady, eventually rising a bit. 

Courtesy of IARC

The 2-day plot of the 2-meter temperatures from the sensor near Smith Lake on the UAF Campus shows all this nicely: there is no sign of any afternoon solar related temperature increase and since about 4pm Thursday there is has been minimal temperature variaiton.





Low temperatures since Thursday afternoon include:

North Pole: -51 (thru 11pm Thursday)
Woodsmoke PWS: -49F (near North Pole)
Fort Wainwright: -48F
Fairbanks Airport: -47F
Golstream Creek: -47F
Eielson AFB: -46F 
UAF West Ridge: -38F
College Hills: -30F

Cold…But Not as Cold as It Used to Be

It's another brittle morning in Fairbanks-land, with temperatures in the 30s and 40s below in the valleys, and even most hill sites near or below 20 below. At the Fairbanks Airport the temperature did nick down to 40 below just before midnight Wednesday evening, so today, Thursday, with a low so far of 44 below makes this the sixth day in a row with a low of 40 below or lower.  The last time there was a six day streak of 40 below lows wholly in December was 1975 (but several asterisks for recent  as long or longer streaks partly in December: Nov 29 through Dec 04 1990, Dec 28, 1999 through Jan 05, 2000 and Dec 28, 2008 through Jan 11, 2009).

Here's a plot of temperatures in the lowest 1000 meters from the Thursday morning sounding. This morning's comparison though is to one of the great cold snaps in modern times. The blue line is the sounding from the afternoon of December 27, 1961.

Notice that surface temperature on the ice foggy afternoon was about 4C colder than this morning. But look at the temperatures above the valley floor: there was no surface-based inversion at all (deep, prolonged ice fog). Temperatures 200 meters up were about 18C colder that afternoon than this morning, and the temperature was colder than -40F through almost the entire lowest kilometer.. At the peak of the 1961 cold snap, the UAF West Ridge coop site (the observation site at the time was near what is now the Jack Townshend Point near the Museum of the North) recorded a low of -66F, by far the lowest of record there. Fairbanks Airport recorded a low of 62 below on December 29, 1961, the all-time record low for December.

Updated Temperature Anomaly Plots

Here are daily mean temperatures and associated anomaly plots for Fairbanks for 2012. Recall that the shaded area on the top plot is one standard deviation from the mean, so temperatures inside the shaded area can be considerable "close to normal". Sunday, with a standardized departure of -2.63 was the most anomalous day since Dec 4, 2012, which had a standardized departure of  +2.73. 

A Tanana Valley Jet and other Exicting Developments

Valley temperatures have moderated a bit around Fairbanks, though hill temperatures have leveled out. To the left is a plot of the temperature in the lowest kilometer from the past three soundings (nominal times 3AM Monday, 3PM Monday and 3AM Tuesday). The warming as continued on the valleys since early this morning. Almost everywhere is now up to -30F or warmer.

The core of the cold air has moved into the eastern Interior, with lows this morning of 51 below at Northway and 48 below (thru 8am) at Chicken. Meanwhile, our friends in the Delta Junction are being buffeted by 15 to 40 mph and temperatures in the teens below in a classic "Tanana Valley Jet". This happens when cold air in the Upper Tanana Valley moves downriver (in response to lower pressure to the west) and is squeezed through the constriction in the valley near Cathedral Rapids. Since air is a fluid, the velocity has to increase to move through the constriction. The result: strong down-valley winds from about Dot Lake westward across the Delta Junction area and the Tanana Flats south of Fairbanks. On occasion the jet makes it all the way to Nenana, which it did in this case (temperatures was still -41F at 11pm but has been as around 6 below for some hours down with a gusty east wind).

The NOAA-18 1km resolution infrared image from 630am Tuesday shows this in detail.

The cold air pooled in the Upper Tanana is evident (along with the cold valleys of the Fortymile County and the Yukon Flats). The Tanana Valley Jet shows up as the streaky looking of darker color (warmer temperatures) west of the Tetlin Flats.  

Still Warm…Aloft at Least

Fairbanks-land inversions continue to grow early Monday evening: at 6pm, it was above zero in the warmest higher elevations and still in the 40s below on the valley bottoms

Warming Aloft

Temperatures have started to rise above the valley floor in Fairbanks-land. On the right are plots of the temperature in the lowest 1000 meters from Sunday morning and Monday morning soundings. Above about 25 meters above the ground the sounding is warm Monday morning than Sunday morning, with the most dramatic warming between 200 and 400 meters AGL. Since then temperatures have continued to rise: at 10am temperatures are up to 11 below on Cleary Summit, 14 below at Wickersham Dome and 16 below on Keystone Ridge.

Coldest December Temperature

View from UAF West Ridge Sunday, Dec 16, 2012

Updated:

Through 8am Monday the low temperature at Fairbanks Airport has been 48 below. This is not only not a record low for December 17th (52 below in 1917), but on only two days in December (the 1st and 2nd) would 48 below be cold enough for a new record.

That said, this is the coldest December temperature since 1999, when the temperature fell to 53 below on New Years Eve (and the dense ice fog caused cancellation of the big fireworks planned to celebrate the end of the millennium). Even more notably, this is the lowest pre-Christmas temperature in Fairbanks since 1977, when it dipped to 52 below on December 13th.

Updated:
Specific low temperatures Monday include:

Fairbanks Airport: -48F
Fort Wainwright: -48F
Woodsmoke PWS: -48F (near North Pole)
Salcha River 25 Mile: -47F
Goldstream Creek: -46F
Eielson AFB: -44F
UAF West Ridge: -41F
College Hills: -30F
Keystone Ridge: -25F