Friday, November 30, 2012

Where is the Coldest Place in Alaska?

Regular reader Richard commented that Chicken frequently is cited as a place reporting very low minimum temperatures and asks what is the coldest place in Alaska. This is a question I regularly get, so here you go.

The first thing to keep in mind is the lack of good climate data over vast swaths of Interior and northern Alaska. Since the mid 1950s there have been only two Weather Service Offices in Interior Alaska (Fairbanks and McGrath), an area of something like 300,000 square miles. This is reasonably supplemented by several long term FAA stations: Northway, Big Delta/Fort Greely, Tanana, Bettles. Barrow is the ONLY long term climate site still operating on the North Slope, an area of about 85,000 square miles. There are a handful of long term sites (from a variety of observers) that are useful: Galena and Eagle, and some in the immediate Fairbanks. Everything else is hit or miss. Places you might think should have good long term climate data simply do not (e.g. Fort Yukon, Manley Hot Springs).

The lowest official temperature of record in Alaska is -80F, set in January 1971 at Prospect Creek, which was a pipeline construction camp at Mile 135 Dalton Highway (yes, there are many claims of lower temperatures). The lowest monthly average temperature (NCDC 1981-2010 normals) is Umiat, on the banks of the Colville River, about 140 miles southwest of Prudhoe Bay, with a January normal temperature of -21.3F, and a winter (Dec-Feb) normal of -19.3F.

Umiat, which started out as a Navy station during World War 2, is these days a logistics supply base for oil exploration and general access to the central inland North Slope. One family called Umiat home from the mid 1970s til about 2000, but before and after it is similar to Prudhoe Bay, in the it's no one's home but there are people there working in one capacity or another.

Umiat has the lowest winter mean temperature of any "settlement" in Alaska. That I am confident of (I wrote a paper about this back in the mid 1980s). However, based on 25 years of looking at weather satellite imagery of Alaska, I'm confident there are places upriver from Umiat that are colder. In fact, Umiat is often on the northern edge of the cold pool of air that develops on the north side of the Brooks Range. My guess is that some places southwest of Umiat (maybe near the confluence of the Colville and Killil Rivers) probably average 3-5 degrees cooler than Umiat. All these areas though are cold because it is hard to "warm up" rather than the super low temperatures that have historically been measured in the Interior. The lowest reliable temperature at Umiat, and the lowest I know of on the North Slope, is 66 below in February 1987. Lots of places in the Interior have been colder.

Turns out that today is a good day to discuss this topic. To the left is a NOAA-16 Polar Orbiter infrared image from 630am Friday. There is not much wind and hardly any clouds over the Interior, so the cold air pooled in valleys shows up nicely. To start with, there is nothing especially cold about Prospect Creek, or any of the Brooks Range valleys (including current or former climate stations at Chandalar Lake, Wiseman, Wild Lake, Coldfoot, Arctic Village). They all can get very cold in the right circumstances. Prospect Creek holds the record low simply because there happened to be a climate station, which was open for less than ten years, during a deep cold snap.

The Yukon Flats can be very cold. However, it's at low elevation (generally below 500; MSL), and areas north of the Yukon River can be breezy at times, breaking up the surface temperature inversion. The Yukon River Valley above the Flats can also be very cold, though there is practically no human habitation. The only community is near the Alaska-Yukon border at Eagle, which is at 900' MSL but is prone to downriver winds, breaking the inversion. The areas downriver from Eagle are less prone to wind. but are at slightly lower elevations. 

The Upper Tanana Valley also gets very cold: it is about 1000 feet higher elevation than the Yukon Flats, and there are areas that do not get much drainage wind (e.g. Tok area, Northway and the Tetlin flats in general). However, the Upper Tanana Valley is comparatively close to the Gulf of Alaska (so gets clouds from that direction), and is also far enough south (Northway is at, gasp, 63N) that the sun has some impact on daytime temperatures except for very close to the winter solstice.

Which brings me to my candidate for the coldest area in Interior Alaska: the valleys of the Fortymile County. The Fortymile County is basically a high elevated plateau with winding rivers deeply cut into the plateau. The general elevation of the plateau is up around 2000-2500' MSL, with valleys, often very narrow, several hundred feet lower. The area was a focus for gold mining a century ago, but today is very sparsely populated. The Taylor Highway (BLM brochure map on the right), which is not maintained in winter, cuts through the Fortymile County, connecting the town of Eagle, on the Yukon River to the Alaska Highway. Chicken is the only community in the Fortymile County to have a post office.


The community of Chicken, and the current cooperative observer are in the valley of Chicken Creek, a small tributary of the Mosquito Fork Forty Mile River. Chicken does have the lowest mean January (and winter) average temperature in Interior Alaska, with a 1981-2010 normal January temperature of -20.9F (normal Dec-Feb temperature -16.3F).  There is nothing unique about the location of the coop station, Having been there, it looks to me to be completely representative of the area. It gets so cold because it is a high elevation valley well protected from any wind most of the time, maximizing radiational cooling. However, in spite of current NCDC normals, there is in fact less than 20 years of usable data from Chicken. If any currently active climate station can break the Prospect Creek record low, it's Chicken (which has been to 70 below twice in the past decade).

Chicken though is almost certainly not the coldest place in the Fortymile County. The short-lived O'Brien Creek co-op station, about 40 miles north of Chicken just north of the Fortymile River bridge was generally a bit colder (higher elevation, deeper valley) than Chicken. Because it was in a deep valley, it goes several months without actually seeing the sun.  It is in these kind valleys the absolute lowest temperatures are most likely to occur.

The lack of human habitation and the difficulty of getting automated equipment to work and record accurate extremely low temperatures makes documenting the extreme temperatures of this region difficult.




Thursday, November 29, 2012

Record Cold at Tok

One of my favorite places in Alaska was a bit nippy on Thursday...

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
944 PM AKST THU NOV 29 2012

...RECORD COLD AT TOK...

THE LOW TEMPERATURE THURSDAY AT TOK WAS 50 BELOW. THIS BREAKS THE
PREVIOUS RECORD LOW FOR NOVEMBER 29TH OF 46 BELOW SET IN 1955.

THE RECORD LOW FOR NOVEMBER IN TOK IS 59 BELOW SET IN 1963.

THE HIGH TEMPERATURE THURSDAY AT TOK WAS 43 BELOW. THIS IS THE
LOWEST DAILY MAXIMUM TEMPERATURE OF RECORD IN TOK IN THE MONTH OF
NOVEMBER...JUST NIPPING THE PREVIOUS RECORD OF 42 BELOW SET IN
1963 ON NOVEMBER 22ND. THE PREVIOUS RECORD LOW MAXIMUM DAILY
TEMPERATURE FOR NOVEMBER 29TH WAS 27 BELOW SET IN 1995.
 
$$ 
RT NOV 12 

A Cold November does not Portend a Cold Winter

To state the conclusion up front: the average November temperature in Fairbanks is of NO predictive value for the mean temperature of the upcoming winter.

November 2012 is going to be one of the coldest November of record (though not in the coldest three). What does this mean for the upcoming winter? Nothing at all.

Overall, the linear correlation between November mean temperature and the subsequent winter (December through February) mean temperature is only 0.12 (1919-2011). Looking just at the coldest Novembers, it is not any better.

Above is a scatter plot of the 20 coldest Novembers (1919-2011) and the mean temperature during the subsequent winter. Ten of those winters had mean temperatures above the 1919-2011 mean and ten were below the long term mean. Eight of the 20 Novembers wound up being colder than the following the winter. The coldest November (1926, with a mean of -11.2F) was followed by an exceptionally warm winter (mean temperature of +3.2).  

So feel free to forecast colder than normal for the upcoming winter. Looks like you have a 50-50 chance of being right. 

Getting Colder

It's getting to be positively winter-like in eastern Interior Alaska, with temperatures falling past 40 below this morning in some of the colder spots. Here's a NOAA-16 Polar Orbiter infrared image from 940am Thursday (White is colder, dark warmer). There are practically no clouds over the Interior except for a patch northeast of Fort Yukon.
Courtesy NWS Alaska Region
Some low temperatures this morning include:

Chicken Co-op: -52F
Tok CWOP: -50F
Dawson, YT: -46F
Eagle Co-op: -44F
Northway: -42F
Coal Creek RAWS: -42F

The low of -30F through 9am at the Fairbanks Airport is the lowest of the season thus far.

Wednesday, November 28, 2012

Super Duper Inversion

Fairbanks-land is approaching an inversion strength of 40 degrees Wednesday morning. Some 9am AST temperatures include:

Woodsmoke CWOP: -34F  (near North Pole)
Goldstream Creek: -29F
Fort Wainwright: -29F
Fairbanks Airport: -25F
UAF West Ridge: -15F
College Hills CWOP: -10F (near top of Baline Hill)
Skyflight CWOP: -3F (ridge above Goldstream Creek)
Nenana Hills RWIS: 0F (at FNSB boundary on Parks Highway)
Wickersham Dome +7F
Keystone Ridge: +9F

Monday, November 26, 2012

Low Snow All Winter?

Fairbanks is going to wind up with 4.2" of snow for November and just 11.3" thus far this season. This is only the 14th lowest autumn snowfall in the WB/NWS era (1930-2012) and the lowest since just 2006. 

What does this mean for the rest of the winter? To the left is a histogram of total seasonal snowfall for the 20 least snowiest autumns (Sep-Nov) since 1930. As you can see, winding up with more than the long term normal average has occurred just three of twenty times, which turns out to be the same frequency of winters with less than 30" for the whole season. However, 45% of winters have wound up with 55" or more inches of snow, so even with a slow start like we've had this autumn, there is a decent chance, based on the historical record, that Fairbanks will wind up with "near to above normal" snowfall.

Sunday, November 25, 2012

A Strong Inversion Morning

Quite a strong inversion has developed over Fairbanks as the airmass has warmed under the high aloft that is centered over the southern Chukchi Sea.

Analysis by Environment Canada

The temperature plot from the morning sounding shows a temperature increase of 16C (27F) in the lowest two hundred meters (note: I have reason to believe that the surface temperature that was encoded of -26.1C is too warm: I've adjusted the surface temperature to the value of 11Z Fairbanks ASOS observation).
Late Sunday morning temperatures in Fairbanks-land range from 11 above at Wickersham Dome to 26 below at Fort Wainwright. Here on Keystone Ridge, the temperature hit 10 above Saturday evening but has been mostly in the 5 to 8 above range Sunday morning.

Saturday, November 24, 2012

Denali Super Inversion

Courtesy of the FAA
On Friday high temperatures in Denali National Park included 7 below at Wonder Lake Rangers Station, 8 below at the Toklat rest stop and 18 below at an automated observation near the Wilderness Access Center at the east end of the Park, but a whopping +28F  at Eielson Visitors Center. Why was Eielson so warm? At 3650' elevation and on the side of a mountain, it was well above any valley based inversion and into the warm air under the big high aloft that is controlling Interior Alaska weather this weekend. To the left is the view of Saturday morning sunrise on Denali, as seen from Eielson VC, where it was +22F at picture time.

Still Cool

Interior Alaska remains in a cool and dry weather pattern with persistent, though not extreme below normal temperatures. Here's an update through Friday of the standardized daily temperature departures. Although not as monolithic as last winter, below normal as been the rule for more than a month now.

Wednesday, November 21, 2012

Noon Sunshine

The solar noon view from Beaver Village, looking south across the Yukon River. Nice sundog too.

Happy Thanksgiving Day

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1200 PM AKST WED NOV 21 2012

...THANKSGIVING IN FAIRBANKS...

THANKSGIVING DAY IS A SOLIDLY WINTER HOLIDAY IN FAIRBANKS. SINCE
1904...THE AVERAGE HIGH TEMPERATURE ON THANKSGIVING DAY HAS BEEN 7
ABOVE AND THE AVERAGE LOW HAS BEEN 10 BELOW. THE SNOWIEST
THANKSGIVING WAS IN 1996...WHEN 6.1 INCHES OF SNOW FELL...WHILE ON
THANKSGIVING 1970 THERE WAS 36 INCHES OF SNOW ON THE GROUND. OVER
THE PAST 107 YEARS...THE WARMEST THANKSGIVING WAS IN 1943...WHEN
THE HIGH TEMPERATURE WAS 46 DEGREES. THE COLDEST THANKSGIVING WAS
IN 1927...WHEN THE HIGH WAS 45 BELOW AND THE LOW WAS 50 BELOW.

THE FORECAST FOR THANKSGIVING DAY 2012 CALLS FOR MOSTLY CLEAR
SKIES WITH DAYTIME TEMPERATURES GENERALLY ZERO TO 15 BELOW. 

$$
RT NOV 12

Paltry Snow Cover

Here are some snow depths around Alaska the day before Thanksgiving:

Northway: 14 inches
Tok: 14 inches
Chicken: 12 inches
Circle Hot Springs: 12 inches
Eagle: 10 inches
McGrath: 9 inches 
Denali NP Headquarters: 8 inches
UAF West Ridge: 7 inches
Fairbanks Airport: 6 inches
Anchorage: 2 inches
Kotzebue: Trace
Nome: Trace

These amounts are all below normal except for the upper Tanana Valley, which is near or even slightly above normal.

Sunday, November 18, 2012

Why is It Dry and Cold?

Why has it been unusually dry and cold in Interior Alaska thus far this month? The image at the right, from the NCAR/NCEP reanalysis, plots the mean sea level pressure for the first 16 days of November. High over the Brooks Range and low over the eastern Gulf of Alaska. Hard to get much snow north of the Alaska Range with that pattern.

Just Like Winter



What I did at work today...
 
 
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
211 PM AKST SUN NOV 18 2012

...COLD SUNDAY IN NORTHEAST INTERIOR ALASKA...

A COLD AIR MASS COVERS ALL OF INTERIOR ALASKA THIS WEEKEND. WITH
STRONG HIGH PRESSURE OVER THE NORTH SLOPE AND BROAD LOW PRESSURE
OVER THE GULF OF ALASKA...MANY AREAS HAVE ENOUGH WIND TO KEEP
STRONG INVERSIONS FROM FORMING. HOWEVER...IN THE UPPER YUKON
VALLEY AND ON THE SOUTHERN YUKON FLATS...WINDS HAVE REMAIN NEARLY
CALM. THIS HAS ALLOWED TEMPERATURES TO DROP TO UNUSUALLY LOW
LEVELS FOR THIS EARLY IN THE WINTER.

SOME LOW TEMPERATURE SO FAR SUNDAY INCLUDE...

BIRCH CREEK....................46 BELOW
BEAVER CREEK (YUKON FLATS).....45 BELOW
AMERICAN CREEK NEAR EAGLE......44 BELOW
COAL CREEK.....................43 BELOW
CENTRAL........................41 BELOW 
EAGLE COOPERATIVE OBSERVER.....41 BELOW 
EAGLE AIRPORT..................39 BELOW

IN CONTRAST...AT THE FORT YUKON AIRPORT...WHERE THERE HAVE BEEN 
PERSISTENT NORTHEAST WINDS OF 15 TO 25 MPH...THE LOW TEMPERATURE
SUNDAY HAS BEEN JUST 8 BELOW.

IN THE FAIRBANKS AREA ALMOST ALL AREAS HAVE HAD WIND FOR THE PAST DAY...SO 
TEMPERATURES ARE GENERALLY ZERO TO 10 BELOW.

$$
RT NOV 12

Saturday, November 17, 2012

Inversion Busting Winds

After diminishing for about 12 hours late Thursday night and Friday morning, winds picked back up Friday afternoon, and in spite of clear skies, winds overnight broke through the inversion, producing dramatic temperature swings in valley locations. Here's a high frequncyplot of temperatures from a suite of sensors near Smith Lake, off the west end of UAF West Ridge, showing a temperature rise of more than 10C in just a few minutes:

Courtesy UAF/IARC
Below is a plot of the hourly temperatures from Keystone Ridge, Goldstream Creek and Fairbanks Airport. Keystone Ridge, where winds have been northeast 15 to 30 mph since late Friday afternoon,  shows steady gradual cooling.The Goldstream Creek site shows, like Smith Lake, temperatures rising dramatically Friday evening, with gradual cooling since then. This well mixed boundary layer reflects the turbulent mixing produced by the winds. The situation at the Airport is more complex. The temperature did not pop-up until just before midnight, and a pool of cold air sloshed back over the airport between 5 and 7am. This cold pool is now being eroded away.


Friday, November 16, 2012

A Bright and Sunny Morn

Courtesy of Alaska Climate Research Center

It's a lovely day in Fairbanks-land, with blazing sunshine and temperatures to warm the hearts of any Alaskan. Lows this morning include:

Woodsmoke PWS: -30F (near North Pole)
Goldstream Creek: -29F
Eielson AFB: -28F
Two Rivers PWS: -27F
Fairbanks Airport: -26F
UAF West Ridge: -20F
College Hills PWS: -13F (near top of Balaine Hill)
Gilmore Creek CRN: -5F
Wickersham Dome: -2F
Keystone Ridge: -1F
Clearly Summit: +1F

Wednesday, November 14, 2012

Barrow Still Hot

Here's an update of the analysis of the ongoing ultra-warm autumn at Barrow, now that there is some sea ice in the area. Through the first 13 days of November the average temperature at Barrow is 9 degrees above normal (compare to Fairbanks, which is more than 8 degrees below normal for the same period). The plot shows the daily temperature departure from normal since September 1. Since September 11th, only two days have had an average temperature even slightly below normal. It is entirely possible that this will be the warmest autumn (September-November) of record in Barrow (current record is 25.8F set in 1998). 

Tuesday, November 13, 2012

Strong Inversion Monday Morning

Here's a plot of the low level temperatures from the Monday morning sounding at Fairbanks. This isn't, overall, an especially strong inversion by Interior Alaska standards, but the steep temperature increase of 23 degrees in just 76 meters is quite impressive. Clouds moved in Monday morning and weakened the inversion in by the afternoon.

Monday, November 12, 2012

40 below on the Flats

Fort Yukon 940am Monday, courtesy of the FAA
The Chalkyitsik RAWS (which is half way between fort Yukon and Chalkyitsik) hit 40 below Monday morning. I believe that this is the first 40 below of the season. The Beaver Creek RAWS has been down to 36 below the Fort Yukon AWOS to 33 below. 

Blogging to Resume

I had to leave Alaska on a family emergency last and had limited internet access. I'll get to questions and have new posts soon. Rick

Saturday, November 3, 2012

October Summary for Fairbanks

Here's the summary for October

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1104 AM AKDT FRI NOV 2 2012

...OCTOBER 2012 WEATHER SUMMARY FOR FAIRBANKS ALASKA...

OCTOBER WEATHER IN FAIRBANKS STARTED OUT WARM AND WET BUT
PROGRESSED INTO A FAIRLY COOL AND DRY PATTERN TOWARD THE MIDDLE OF
THE MONTH. CHINOOK WINDS CREATED UNSEASONABLY WARM TEMPERATURES IN
PARTS OF THE INTERIOR ON THE 4TH UNTIL A WIND SHIFT TO WESTERLIES
BROKE DOWN THE CHINOOK AND PUSHED A NOTABLE AMOUNT OF LATE SEASON
RAIN INTO TOWN ON THE 7TH AND 8TH. ON THE 7TH...0.21 INCHES OF
PRECIPITATION CLAIMED A NEW DAILY RECORD PRECIPITATION FOR
FAIRBANKS AND ON THE 8TH...0.55 INCHES WAS JUST SHY OF THE DAILY
RECORD OF 0.59 INCHES SET IN 1916. THE HIGHEST DAILY PRECIPITATION
OF THE MONTH WAS THE 0.55 INCHES WHICH FELL ON THE 8TH IN THE FORM OF
RAIN. THIS WAS THE HEAVIEST RAIN IN OCTOBER IN FAIRBANKS SINCE
1986.

AFTER THREE MONTHS OF BELOW NORMAL PRECIPITATION...OCTOBER MADE A
COMEBACK WITH A TOTAL OF 1.38 INCHES OF PRECIPITATION...WHICH IS
0.55 INCHES ABOVE NORMAL FOR THE MONTH. DESPITE THE ABOVE NORMAL
PRECIPITATION AMOUNTS...THE SNOWFALL AT FAIRBANKS INTERNATIONAL
AIRPORT THE TOTAL OCTOBER SNOWFALL OF 7.1 INCHES WAS 3.7 INCHES
BELOW NORMAL. UNLIKE MOST YEARS IN FAIRBANKS...THE FIRST MEASURABLE
SNOW ON THE 14TH REMAINED ON THE GROUND TO ADD TO THE DEVELOPMENT
OF THE WINTER SNOW PACK (1 INCH OR GREATER) ON OCTOBER
15TH...RATHER THAN MELTING. IT IS COMMON FOR THE FIRST MEASURABLE
SNOWFALL TO MELT...AND THE SNOW PACK TO DEVELOP WITH LATER SNOWS.

THE FIRST TRACE OF SNOWFALL OCCURRED ON SEPTEMBER 30TH THIS
YEAR...A WEEK LATER THAN THE AVERAGE OF SEPTEMBER 21ST. THIS YEARS
FIRST MEASURABLE SNOWFALL (GREATER THAN OR EQUAL TO 0.1 INCH) WAS
NEARLY TWO WEEKS LATER THAN NORMAL ON OCTOBER 14TH AS COMPARED TO
THE AVERAGE FIRST MEASURABLE SNOWFALL DATE WHICH IS OCTOBER 1ST.
THE GREATEST SNOWFALL OF THE MONTH WAS 2.9 INCHES WHICH FELL ON
THE 29TH.

DURING THE INDIAN SUMMER EARLY IN THE MONTH...ON OCTOBER 4TH...
FAIRBANKS AIRPORT REACHED 61 DEGREES...JUST SHORT OF THE RECORD
HIGH FOR THE DAY OF 62 DEGREES SET IN 1923. ON THE 4TH...COLLEGE
OBSERVATORY COOPERATIVE WEATHER STATION REPORTED A NEW RECORD HIGH
OF 59 DEGREES WHICH EXCEEDED THE PREVIOUS RECORD OF 58 DEGREES SET
IN 2001. THE LOW TEMPERATURE OF THE MONTH AT THE AIRPORT WAS 11
BELOW ON THE 24TH...FAR FROM THE RECORD DAILY LOW OF 22 BELOW SET
IN 1935.

OVERALL...THE AVERAGE HIGH TEMPERATURE AT THE FAIRBANKS AIRPORT
WAS 30.3 DEGREES AND THE AVERAGE LOW TEMPERATURE WAS 14.7 DEGREES.
THE AVERAGE TEMPERATURE OF 22.5 DEGREES FOR THE MONTH OF OCTOBER
WAS 1.7 DEGREES BELOW NORMAL...AND THE COOLEST OCTOBER SINCE 2008.

LOOKING AHEAD TO NOVEMBER...THE WANING DAYLIGHT IS ARGUABLY THE
MOST NOTICEABLE FEATURE OF NOVEMBER. FAIRBANKS LOSES NEARLY 3
HOURS OF DAYLIGHT IN THE MONTH OF NOVEMBER FROM 7 HOURS AND 46
MINUTES OF DAYLIGHT ON THE 1ST WITH A NOON SUN ANGLE OF 10
DEGREES...TO 4 HOURS AND 44 MINUTES OF DAYLIGHT ON THE 30TH WITH A
NOON SUN ANGLE OF 3 DEGREES. THE AVERAGE HIGH AND LOW ON THE 1ST
IS 18 ABOVE AND 3 ABOVE RESPECTIVELY...AND ON THE 30TH IS 7 ABOVE
AND 11 BELOW RESPECTIVELY. THE RECORD HIGH TEMPERATURE IN NOVEMBER
IS 54 DEGREES SET IN 1936 AND THE RECORD LOW IS 54 BELOW SET IN
1909.

Friday, November 2, 2012

Snow Drought

Courtesy of the FAA
Here in Fairbanks snowfall is only about 60% of normal for the season thus far, but it could be worse. Here is a Friday afternoon webcam photo from Kaltag, in the western Interior. Kaltag, on the east side of the Nulato Hills, is one of the snowiest low elevation places in Interior Alaska, with an mean annual snowfall of something around 120 inches. However, as you can see, thanks to the big aloft aloft that has been place for more than two weeks now, there is no snow on the ground at all.

Thursday, November 1, 2012

Record Warm October in Barrow

We knew this was coming, but it’s now in the books: Barrow recorded the warmest October in more than nine decades of unbroken climate observations. The first plot shows the daily high and low temperatures this past month (the 1981-2010 normals are shaded for comparison). The high temperature was above normal every single day: the low temperature dipped below normal on just two days.
The mean temperature for the month was 27.5ºF, which is 2.0 degrees higher than the previous warmest October (set in 2006) and 10.3 degrees warmer than the 1981-2010 normal.

How does this compare to the historical data? Although this past October set a new record, it is obviously in keeping with a now decade long pattern of very warm Octobers, as illustrated in the plot below. The black line is simply the average temperature for the five Octobers up to and including any given year. It's noisy, but obviously the later 1930s and 1940s were mild and the 1970s and 80s were cool. After the mid-1990s there was a steep rise that has flattened out now at a level far higher than any five year period in the 1930s or 40s. The orange line really tells the tale:  this is the five year running standard deviation of mean October temperatures. Even during the warm 1930s and 40s there was roughly the same year-to-year variability as in the cold 1980s and 90s. However, that variability has collapsed in the past decade: October temperatures are not varying by very much at all these days.


It’s not just that some Octobers have been warm recently, it’s every October for the past decade has far above normal, and six of the ten warmest Octobers have occurred since 2002. The next plot shows the deviation in the mean temperature each October from the 1920-2001 mean. There is nothing special about the 1920-2001 period except that it ends right before the current streak of warm Octobers starts. Choosing a different long term average simply moves the zero line up or down. The patterns remains the same: the past decade of warm Octobers at Barrow is unprecedented: there is nothing like this streak in the past nine decades.


There’s no mystery why Barrow has become so warm in October: lack of near-shore sea ice. Prior to the late 1990s, the Arctic sea ice was typically either at Barrow or not far to the north and northwest by mid-October; in some years the ice was largely in place early in the month (an in rare occasions ice was in place in September). This allowed cold air to move from the high Arctic onto Alaska’s North Slope with little warming. Air over sea ice, which quickly becomes snow covered, can become (or remain) much colder than over the open ocean. The freezing point of sea water is 29F (lower than fresh water due to dissolved salts in sea water), so the temperature of air that had cooled to much lower temperatures over ice but then moves over water will fairly quickly approach that of the water. This is an important point: it’s not just whether the sea ice is at Barrow or not. The distance to the ice edge matters a lot. A fetch of 400 miles over open water (which is about what it was at the beginning of the October) will have a much bigger impact on air temperature than an ice edge 40 miles away, which will have a bigger impact than the ice edge four miles away. This of course is the same everywhere over open oceans: air temperature is close to the ocean surface temperature.

Below is the sea ice analysis for Halloween from the NWS Anchorage Sea Ice Desk. There is still 50 to 250 miles of open water between Barrow and the sea ice, depending on direction.


Once the ice closes in, the strong forcing to much warmer than normal temperatures caused by open ocean will be gone, and overwinter and spring temperatures are Barrow will depend more on prevailing atmospheric patterns.

Variable Winds Modulating Temperatures

1200 UTC Surface Analysis courtesy of Environment Canada
An interesting wind situation has prevailed in the past day over the Fairbanks area, with widespread northeast winds right down to the valley floor. The average wind at the Fairbanks Airport on Wednesday was 14.1 mph. This is most unusual this time of year for a northeast wind event: persistent winds this strong in winter typically occur with southwest flow following a frontal passage. The surface analysis for 4am ADT Thursday from Environment Canada shows the 1039bm high over the Brooks Range, with a decent, though not extreme pressure gradient over Interior Alaska.  The winds Thursday morning have slacked in some valley areas, allowing temperatures to fall smartly: down to 11 below at Woodsmoke near North Pole and 4 below at Fort Wainwright and Fairbanks International. However, one of the usual cold spots, Goldstream Creek, had puffs of wind all night. The temperature dipped to 2 below about 3am, then was back up to 7 above by 730am.