Inversion

The Sunday afternoon sounding from Fairbanks shows a decent 15C inversion in the lowest 500 meters. This is reflected in the late afternoon temperatures, which remain in the 20s below in the valleys and a little above zero in the hills. As usual, most of the increase is in the lowest 100 meters.

Big Inversion

A pretty decent inversion has developed overnight, with valley temperatures pushing 30 below and higher elevations near zero.

10AM Sunday temperatures include:

Woodsmoke PWS: -33F (near North Pole)
Eielson AFB: -29F
Fairbanks Airport: -27F
Goldstream Creek: -27F


Cleary Summit: +2F
Little Chena Ridge +1F (south of the Steese Highway)
Gilmore Trail PWS: -1F (1440' MSL)
Keystone Ridge: -2F

Cold in Context

Here's another view of the recent cold weather: the daily mean temperature plotted against the 1981-2010 normals; grey shading of plus/minus one standard deviation.



Here are standardized daily departures for 2011. Looked at this way, the recent cold snap was about as far from normal as the hot weather in late May. The coldest day, the 17th, with an average temperature of -35F, was 2.7 standard deviations below normal, almost the same as warmest day in, when the 28th was 2.9 standard deviations above normal. The height of cold snap was a couple days longer than the hot spell in May, but the total "excessive" (the area under the curve) will likely be somewhat greater in May than in the cold snap.

Thanksgiving Day

305pm November 24th from UAF West Ridge

Cold Persists near the Alaska Range

Unlike the Fairbanks area, clear skies have prevailed near the Alaska Range for past 36 hour. Here's the 1pm photo from Denali National Park right near the train station. The lack of clouds have allowed the cold temperatures to persist. At the Denali Park AWOS (partially visible in the photo just beyond the brown building), the high today was 20 below and low 36 below. At the DVCA2 RAWS, which is near the Wilderness Access Center and at a slightly lower in elevation than the AWOS, the high was -27F and the low -38F.

Recap of the November Cold Snap

The record setting cold snap of November 2011 is history. So, without the media hoopla, here’s what happened. It's important to emphasize that the "news" here is the early occurrence of the cold snap, rather than the absolute values of the temperatures. The exact same temperatures anytime between Thanksgiving and Valentines Day would be unexceptional.

The mean 500mb heights (30dm contours) for November 15-21 (courtesy of ESRL and NCEP/NCAR Reanalysis) show a classic pattern for cold weather in Interior Alaska, with a high over Chukotka and fairly low height northerly flow across most of mainland Alaska (I’ve added centers and arrows to indicate wind direction.



In the Fairbanks area, this was easily the coldest pre-Thanksgiving week of record. At the Airport, the lowest 7-day average temperature was -30.1F for November 15-21. The previous record was -26.5F was set November 7-13, 1989. For November as a whole, this was the third coldest event; November 24-30, 1909 and the same week in 1927 were colder.

Record lows were set at the Airport on six days (November 16th did not have a new record) and record low maximum temperatures were set November 16-19. The high temperature of -30F on the 17th is the second earliest high of -30F or lower in the winter (November 9, 1989 is the earliest). The low temperature of -41F on the 17th is the fifth earliest occurrence of -40F in the winter. Here's the plot of November record lows:




Elsewhere around the area, temperatures varied pretty much as is typical for this time of year. The average temperature for November 15-21 at the North Pole cooperative station was -37.7F, with six days with lows in the -40s and an absolute low of -49F on the 17th. At the other extreme, Keystone Ridge cooperative station, at 1600’ MSL, had an average temperature of -13.4F the same week and an absolute low of -28F on the 21st.

Most places with a long period of observations set six or seven daily records. Lowest temperatures for the cold snap include:

University Experiment Station: -41F
Eielson AFB: -41F
UAF West Ridge: -40F

As more cooperative info becomes available I'll update the extremes.

Impact of Clouds on Temperatures

The last 24 hours have featured a textbook example of the impact of clouds on valley temperatures in Interior Alaska in winter. Here is a plot of the hourly temperature at the Fairbanks Airport. Variations in temperature are completely related to changes in clouds cover: clears out for a few hours, the temperature drops 20 degrees. Clouds return, and the temperature pops right back up. In contrast, here on Keystone Ridge, the temperature has varied by 5 degrees in the same time, -1F to -5F

Inversion Collapses: Cold Snap Ends

Temperatures aloft warmed dramatically over the past 36 hours, and persistent cloud cover and a moderate pressure gradient have taken their toll on the inversion. Here is a plot of the lowest 1000 meters from the morning sounding from today and Monday.


At 2am today (Nov 23) the temperature at the Fairbanks Airport rose to 2 above. This effectively ends the cold snap. The numerical models have not distinguished themselves in glory with the end of this event, and that is directly related to the inability of the models to effectively resolve the processes in the very near surface (boundary layer). That said, the airmass remains chilly and if and when clouds break temperatures will again fall in the valley. However, the unprecedented nature of this cold snap is over. I'll have a wrap-up in the next couple days.

Fairbanks Cold Snap Update

For the week ending Nov 21, the average temperature at Fairbanks was -30.1F. This is, by far, the coldest 7-day average temperature so early in the season and the coldest week in November in the WB/NWS era (since 1930). In the early years, when observations were done by cooperative observers, the week ending on Nov 30th in 1909 and 1927 were colder.

Clouds and some light snow have arrived and overnight temperatures have been mostly in the 20s below in the valleys. On exposed hillsides and channeled valleys a breeze picked up too. Here at Keystone ridge at 6am, -10F with northeast winds about 15mph with gusts to about 25 mph. Air quality is good!

Solar Noon in Barrow

Here's the FAA webcam shot looking south from the Barrow airport. The photo was taken at 116pm AST, which is very close to solar transit.

Updated Records

Here's am update showing the record lows that have been set this month at Fairbanks. The low of -38F this morning breaks the previous record of -35 set in 1904.

Dramatic Cooling

Here are plots of the temperatures in the lowest 1000 meters from the upper air sounding at Fairbanks from 3am AST Sunday and 3am AST Monday. While the surface temperature was only about 3C cooler Monday morning that Sunday morning, temperatures aloft fell much more: over 10C at 100 meters above the ground; the temperatures aloft are now as cold or colder than last week.

The NOAA-19 Polar orbiter infrared image from 5am AST Monday shows lots of cloud scraps across the interior but not much organized yet.

Coldest Early Season Week of Record at Fairbanks

The airmass cooled dramatically during the day Sunday but few clouds showed up, allowing for another very cold day. At the Fairbanks Airport, the morning low of 34 below, but the temperature fell to 37 below during evening, breaking the previous record of 36 below set in 1993.

For the week of Nov 14-20, the average temperature at the Fairbanks Airport was -27.6F. This is the lowest weekly average temperature of record so early in the season. The previous record was -26.5F set Nov 7-13, 1989. It is also very close to the coldest week anytime in November since 1930, when the Weather Bureau began observations: currently that record is -27.9F set November 21-27, 1948. That record will likely be broken after today. Prior to 1930, there are a couple of end-of-November cold snaps that far exceed what we've had thus far: In 1927, the average temperature Nov 24-30 was -36.6F and the same week in 1909 had an average temperature of -34.3F

Cold Moving East

The eastern Interior hung on to clouds a couple days longer that central and western sections, but skies have cleared now and temperatures fallen. The low of 46 below at Northway ties the record low for November 20th. Other low temperatures include 46 below at the Tok PWS, 45 below at Chicken and 43 below at Eagle before the wind picked up.

This morning's photo is the 11am view from Lake Minchumina, looking southeast toward Denali and the sunshine.

How Unusual is this Cold Snap?

An interesting, and increasingly asked question is: "how unusual is this cold snap?"

First some more numbers, just looking at Fairbanks (1904-2010):

Saturday (Nov 19) was the fifth day (in a row) with the daily minimum temperature 35 below or lower. Only four other Novembers have had five or more days with low temperatures of 35 below or lower.

Thus far, three days have had maximum temperatures of -20F or lower (Saturday will likely be the fourth). Eleven other Novembers have had three or more such days and six have had four or more.

The lowest temperature (thus far) has been -41F; this been exceeded in nine other Novembers.

However, this event is occurring not toward end of November, but around the middle of the month.

At the close of Saturday, the 7-day average temperature will be about -22F; there have been five other years that had a 7-day average temperature of -20F or lower ending November 20th or earlier. The coldest 7-day average temperature ending on or before November 20th is -26.5F, which occurred on the week ending November 13, 1989. In second place is Nov 11-17, 1956 at -23.9F.

Another way to look at this, though probably of dubious value, is to ask when the last time a cold snap set four daily record lows? Answer: September 1992, a "black swan" event if ever there was one in Interior Alaska. I say dubious because three of the four records broken were what are sometimes called "low hanging fruit", as can be seen in this plot of November daily record lows for Fairbanks:



Disclaimer: While I have doubts about the veracity of some of the pre-1930 data, it's what the NWS uses for daily records, so I include it here.

The three record lows of 33 below were the only records that high after November 4th. From this point onward only one day has a record lower warmer than -36F.

So, is this event unprecedented; no. Unusual? You bet; similar cold snaps at this time of year have occurred only a handful times in the past 106 years, and this may approach the coldest early season prolonged cold snap (before late November), though I'd guess at this point the 7-day record low mean of -26.5F set in 1989 will stand.

Strong Inversion

Back home now, so more useful posts, and I can comment too!!

Here's a plot of the lowest 500 meters of the upper air sounding from Fairbanks this (Saturday) morning. A fairly typical "strong inversion" situation, worth 30+ degrees F. Readily reflected in the surface observations.

At 8am…

Fairbanks Airport -35F
Eielson AFB -37F
Woodsmoke PWS -41F (near North Pole)

Cleary Summit -3F
Keystone Ridge -5F
Parks Highway RWIS -8F (at FNSB border)

Looks like this will change early next week as a tight cold low drops south from the high Arctic into the western Interior. I expect the inversion will largely break with clouds and light snow. There is a good chance that the hills will have somewhat lower temperatures than earlier this week while the lowlands will be substantially warmer than it has been.

Cold Continues

Summary from my colleague Corey B. with a nice summary of where this cold snap stands for so early in the season:

Public information Statement
National Weather Service Fairbanks AK
304 Am AKST Sat Nov 19 2011


…The Records Continue to Fall at Fairbanks...

The early winter November cold snap continues to re-write the
record books at Fairbanks. The current cold snap will go down in
the record Books as one Of the most severe early season cold snaps
at Fairbanks.

The high temperature yesterday at the Fairbanks International
Airport was 21 below. This breaks the previous record low maximum
temperature Of 19 below Which was established in 1969. The low
temperature yesterday Of 36 below breaks the previous record low
For the date Of 33 below also set in 1969.

At 213 Am this Morning...the temperature at the Airport dropped to
36 below. This breaks the old record low For November 19th of 33
below in 1969.

Today (Saturday) marks the 5th consecutive day with a low
temperature Of 30 below or colder at the Airport. This Ties with
1956...1969 and 1989 For the most consecutive days with a
temperature of 30 below or colder so early in the winter season.

The low temperature has now been 35 below or colder each Of the
last 5 days. This has never happened before so early in the
winter season at Fairbanks. The old record was only 2 days...and
was Last recorded in 1989.

The high temperature has now been 20 below or colder each Of the
last 3 days. This ties with 1989 For the most consecutive days
with a high temperature Of 20 below or colder so early in the
winter season.

Temperatures Over the Next Week Are Expected to Remain Well below
normal. A Cold low will drop out Of the Arctic and into the
western Interior early next week. The Airmass aloft will be colder
than the airmass currently across the Interior. However...there is
fairly high confidence that this next push Of cold air will be
accompanied by clouds and flurries. The clouds will act as an
insulator and keep temperatures somewhat warmer than this past
week. Temperatures much of next week Are expected to be in a range
of 10 to 25 below. There will likely be little difference in the
temperatures next week between the hills and valleys as the clouds
and depth of the cold air will prevent a low level inversion.

$$

CB

Record Low Friday

Update:

Another record so far early Friday, thanks to the record lows being significantly warmer. Fairbanks Airport 39 below breaks the previous record of 33 below set in 1969.

Low temperatures for Friday will be completely dependent on end time of the climate day, as temperatures are rising. For example, the low of 39 below at UAF West Ridge is a record; that was the temperature at 9am Thursday, and at 9am Friday it was up to 23 below. Temperatures in the hills are approaching zero, so about a 30 degree inversion this morning.

Few more record lows

A few more record lows were set Thursday in the Interior.

Fairbanks Airport: -41F old record -39F in 1969
North Pole: -49F old record -46F n 1969
Eielson: -43F old record -40F in 1969
UAF West Ridge: -40F old record -35 in 1969

The reported low in the Interior of -54F at Manley Hot Springs looks suspect, as this is seven degrees colder than the 9am temperature, when there was ice fog and no wind. Manley does not usually run so much colder than Tanana (low -42F) in these situations. Not impossible, but suspect.

Why are North Pole and Eielson Colder than Fairbanks?

While the North Pole and Eielson areas aren't always colder than Fairbanks, that is often then case in the winter (when there is not a Chinook) and for summertime low temperatures.

First, even more so than Fairbanks, North Pole is a flat land with lots of old sloughs and channels of the Chena and Tanana Rivers that provide good places for cold air to pool.

Second, there hardly any human development to the east and northeast of North Pole, while to the northeast of the Fairbanks Airport is, well, Fairbanks City. This is important in winter because the prevailing drainage flow of air is from higher to lower elevations, which in both cases is (north)east to (south)west.

Third, the North Pole is in "collection" area for cold air draining down the Chena River valley and far from any significant ridges. This helps keep wind speeds in North Pole very low in winter. The Fairbanks airport, in part influenced by nearby Chena Ridge, sometimes gets more wind in the winter than North Pole, which allows for more mixing of air, which keeps it from being quite as cold as North Pole.

More Record Lows

Here's the NOAA-19 Polar orbiter infrared image from 2pm AST Wednesday, showing cold air pooled in the valleys and clouds south and east of Fairbanks.

A few more record lows have been registered in the Fairbanks area, including 37 below at UAF West Ridge and 46 below at North Pole. This is not the coldest weather so early in the season. In 1989 a similar cold snap produced a low temperature of 46 below to North Pole and 44 below at Eielson AFB on November 13th.

Record Low at Fairbanks and Eielson AFB

The low temperature Tuesday at Fairbanks International reached 35 below at 1114pm. This is a new record for November 15th, breaking the previous record of 33 below set in 1969. Eielson AFB has already set a record low for Wednesday, November 16th. At 4am AST the temperature at Eielson was 38 below, breaking the previous record for 37 below set in 1956. North Pole had a low of 39 below on Tuesday, one degree shy of the record low of 40 below also set in 1969.

The inversion is slowly growing, with temperatures in the hills steady in the teens below.

Cold is Here

Not much of an inversion on this afternoon's RAOB from Fairbanks. Here's the plot from the University of Wyoming. At least a few record lows are likely to fall over the next 24 hours. Fairbanks is 28 below at 6pm, and the record is 33 below. The record for Wednesday at Bettles is only 42 below, which cold also be broken.

First 40 Below

The first 40 below temperatures of the season occurred overnight in the northern Interior. Some low temperatures through 5am Tuesday include 44 below at Arctic Village, 43 below at the Coldfoot SNOTEL and 40 below at Chalkyitsik RAWS (half way bewteen Chalkyitsik and Fort Yukon)

November Chill Starts

Updated:

Temperatures are falling smartly now over most of the Interior as the airmass cools and cloud cover begins to break. Here is the NOAA-19 infrared image from 5am AST Monday. Some lows through 10am AST temperatures include 38 below at Arctic Village, 36 below at Norutak Lake, west of Bettles, 33 below at the Beaver Creek RAWS southwest of Fort Yukon and 32 below at the Coldfoot SNOTEL and the Jim River DOT camp at Mile 136 Dalton Highway.

Record lows at Fairbanks are 33 below on Tuesday (in serious jeopardy) and 41 below on Wednesday, which also might go down.

We are now close enough to winter solstice that there will be very little solar based diurnal trend.

Cold Weather on the Way

Unusually cold weather is on the way for Interior Alaska for the upcoming weak. Here is the 12Z ECMWF valid at 3am AST Wednesday 500mb heights and 850mb temperatures (the color field). I've flipped the image so that the view is "Alaska-centric". The purple color over the eastern Interior and the western Yukon is -24C, and there is a core of colder than -28C over east of Northway. This is easily cold enough to support valley temperatures of 40 to 50 below in places the go clear and calm for a couple of days. This is pretty cold for mid November. With the airmass this cold inversions will not start off especially strong, but by late in the week inversions may become stronger.

Bering Sea Superstorm

Here's a plot of the sea height at Nome. The peak level was 9.95' above the Mean Lower Low Water level. This was a couple of feet lower than the November 1974 storm. Here's a link to a short video of the storm at Little Diomede.

I'm traveling so blogging will be intermittent.

Bering Sea Superstorm

NOAA-19 Polar Orbiter visible image from 155pm AST Tuesday. Winds are starting to crank up now along the coast. Peak winds at 3pm include 46mph at Nome and 59 mph at Wales.

Bering Sea Superstorm

130pm AST GOES visible image, from NWS Alaska Region:



And the 12Z Tuesday ECMWF Sea Level Pressure, 1000-500mb thickness and precip amount forecast valid 3am AST Wednesday. That's a 948mb closed contour just west of Saint Lawrence Island:

Bering Sea Superstorm

Here's the 9am Tuesday analysis from the Ocean Prediction Center:

Bering Sea Superstorm

Here is the forecast from the 12Z Tuesday Nov 08 NAM valid 3am AST Wednesday Nov 09. That's a 946mb center west of St Lawrence Island. While storms this strong occur in the southern Bering Sea on occasion, it seems that this is one of the very strongest of record in the northernmost Bering. The November 1974 storm, which produced the worst flooding of record at Nome, bottomed out around 950 mb very near Gambell. Major coastal flooding is likely some place along the southern Seward Peninsula coast on Wednesday.

Potentially Calamitous Storm for Western Alaska

The numerical models have been forecasting a major storm in the northern Bering Sea for mid-week since Thursday, and are now coming into focus. Here is the 3AM AST (1200 UTC) run of the GFS, with a 944mb low just northwest of St Lawrence Island at 3am Wednesday. This is very likely to produce major coastal flooding on the southern Seward Peninsula coast. The models are also forecasting the low to remain very strong as it moves into the Chukchi Sea, and this could well cause major flooding at Kivalina Wednesday night or Thursday, and even the western North Slope coast after that. The current sea ice coverage analysis from the US Navy shows no significant ice cover in the Bering or Chukchi Seas.




This will be a dangerous storm.

Snow

Highly variable snow in the Fairbanks area Friday afternoon into Saturday morning. Airport picked up 2 inches of snow, as did UAF West Ridge. Higher amounts north of town,
including 3.4 inches at Mile 42 Steese and a whooping 6.1 inches at Keystone Ridge. The snow was powdery, with mostly 20-30 to 1 snow to liquid ratios.

The highest storm total reported in the western Interior was an impressive 14 inches at Galena.

Chilly morn in the Eastern Interior

Temperatures fell well into the 20s below in the valleys from Eielson eastward Thursday morning. Lows included 28 below at Chicken, 27 below at Delta 6N and 24 below at Tok and Northway.

Barrow in October

It was another very mild October in Barrow, thanks to the lack of sea ice until the last days of the month. The average temperature of 22.8F was 5.6 degrees above the (new 1981-2010) normal. Here is a plot of October mean temperature in Barrow since 1920. It is plain that there is no precedent in the past 91 years for the sustained warm Octobers that Barrow has in the past ten years. Note also the bottom red line: this is simply the 5-year running standard deviation. The collapse of variability in the past decade is amazing, but completely expected: Barrow now has a maritime climate in October. This is the cleanest case of ongoing change climate in the instrumental record in Alaska

October Weather Summary

The October summary for Fairbanks…

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
900 AM AKDT TUE NOV 1 2011

...MONTHLY WEATHER SUMMARY FOR FAIRBANKS ALASKA...

...OCTOBER 2011 IN FAIRBANKS...MILD AND DRY...

FAIRBANKS WAS CONSISTENTLY MILD AND DRY IN OCTOBER. DAILY
TEMPERATURES WERE ABOVE NORMAL ON 24 DAYS DURING THE MONTH....AND
NO DAY WAS MORE THAN TWO DEGREES COOLER THAN AVERAGE. MEASURABLE
PRECIPITATION FELL ON JUST 7 DAYS.

OVERALL...THE AVERAGE HIGH TEMPERATURE AT THE AIRPORT WAS 37
DEGREES AND THE AVERAGE LOW 21 DEGREES. THE AVERAGE TEMPERATURE OF
28.9 DEGREES WAS 4.7 DEGREES WARMER THAN NORMAL. IN THE PAST TEN
YEARS...EIGHT OCTOBERS HAVE BEEN WARMER THAN AVERAGE.

THE HIGH TEMPERATURE FOR THE MONTH AT THE AIRPORT WAS 57 DEGREES ON
THE 2ND. THE LOW TEMPERATURE OF 2 BELOW OCCURRED IN THE LAST HOUR
OF THE MONTH...AND WAS FIRST SUBZERO TEMPERATURE OF THE SEASON. BY
COMPARISON...IN THE PAST 50 YEARS THE AVERAGE DATE OF THE FIRST
TEMPERATURE OF ZERO OR LOWER AT THE AIRPORT IS OCTOBER 28TH.

TOTAL PRECIPITATION...NEARLY ALL OF WHICH FELL AS SNOW...TOTALED
JUST 0.32 INCHES...LESS THAN 40 PERCENT OF NORMAL. THIS WAS THE
DRIEST OCTOBER SINCE 1998.

SNOWFALL TOTALED 4.2 INCHES...LESS THAN HALF OF NORMAL. WHILE THE
FIRST MEASURABLE SNOWFALL DID NOT OCCUR UNTIL OCTOBER 13TH...TWO
WEEKS LATER THAN AVERAGE...THE PERMANENT WINTER SNOW COVER WAS
ESTABLISHED ON THE 18TH...WHICH IS EXACTLY NORMAL. ON HALLOWEEN
THE SNOW DEPTH STOOD AT 3 INCHES...COMPARED TO THE LONG TERM
AVERAGE OF 5 INCHES. SNOWFALL TOTALS IN OCTOBER WERE SOMEWHAT
HIGHER NORTH OF TOWN...WITH 11 INCHES NEAR CHATANIKA AND 9 INCHES
AT KEYSTONE RIDGE.

LOOKING AHEAD TO NOVEMBER...AVERAGE TEMPERATURES FALL SHARPLY EARLY
IN THE MONTH...THEN MORE SLOWLY IN THE SECOND HALF OF NOVEMBER.
THE AVERAGE HIGH TEMPERATURE FALLS FROM 18 ON THE FIRST TO 7 ABOVE
THE LAST WEEK OF THE MONTH. THE AVERAGE LOW TEMPERATURE FALLS FROM
3 ABOVE ON THE 1ST TO 11 BELOW ON THE 30TH. NOVEMBER IS TYPICALLY
THE SNOWIEST MONTH OF THE WINTER IN FAIRBANKS...AVERAGING OVER 13
INCHES ACCUMULATION. IN THE PAST 106 YEARS...TEMPERATURES HAVE RANGED
FROM A HIGH OF 54 DEGREES IN 1936 TO A LOW OF 54 BELOW IN 1906.
SNOWFALL IN NOVEMBER HAS VARIED FROM 0.2 INCHES IN 1953 TO 54
INCHES IN 1970. POSSIBLE SUNSHINE DECREASES FROM JUST UNDER EIGHT
HOURS ON THE FIRST TO LESS THAN 5 HOURS ON THE 30TH.

THE FORECAST FOR NOVEMBER IN FAIRBANKS FROM NOAA`S CLIMATE
PREDICTION CENTER CALLS FOR SLIGHTLY INCREASED CHANCES OF
SIGNIFICANTLY BELOW NORMAL TEMPERATURE.

Coldest of the Season so Far

A cool airmass is in place over much of the Interior Alaska this Halloween morning. Over a small portion of the western Interior, skies cleared overnight, allowing temperatures to fall to the lowest levels of the early inter season. Here is the NOAA-19 Polar Orbiter infrared satellite photo from about 630am Monday. The clear skies in portions of the Middle Yukon, Koyukuk and Kobuk valleys stand out in this scale as the bright white colors and hints of the dendritic pattern that shows the cold air pooled in valley. Farther east, warmer (darker) and more uniform areas show a nearly continuous stratocumulus cloud cover. Though 10am, low temperatures include 18 below at Huslia, 17 below at the Selawik River RAWS (well upriver of the village of Selawik) and 11 below at Kaltag.

Fairbanks Finally Gets an Inch

Snowfall at the Fairbanks airport on Sunday was 1.0 inches. This is the first day with an inch or more of snow this season, and three weeks later than average. The snow was classic "arctic front" snow, produce by the lift associated with the eastward push of cold low level air. Here at Keystone Ridge I measured 2.1 inches, and out at Mile 42 Steese Highway, the coop observer reported 2.6 inches.

First 40 below of the Winter--In Siberia

Oymyakon, one of the notorious cold spots in eastern Siberia, reported a low Sunday morning (Siberia time, OCT 30th UTC) of -42F. This is the first 40 below of the season at Oymyakon and as far I know in Siberia.

Sea Ice at Barrow

The Sea Ice cam at Barrow was out of service for quite a while, but it's back now.
Here's an image from 10 AM Saturday from the UAF Sea Ice Group, showing unconsolidated sea ice offshore. Well, it is almost Halloween. More to come on Barrow as they wrap up yet another mild October.

Meteorological Winter Begins

The power of the waning sunshine was in evident Friday in Fairbanks-land. With no winds and no more than some cirrus, the morning inversion could not quite break, resulting in high temperatures Friday afternoon slightly lower than in the hills (high of 25F at Keystone Ridge, 22F at the Airport, 21F at Goldstream Creek). I hereby declare meteorological winter underway. This is quite important: I have to know what tags to include on these posts :)

Strong Inversion

Mild air aloft, clear skies and a thin but continuous snow cover allowed for a strong inversion to develop overnight. Here is a plot of temperatures in the lowest 1200 meters from the upper air sounding launched at Fairbanks about 3am ADT Friday.

Low temperatures in Fairbanks-land through 10am reflect this:

Eielson AFB: -4F
Woodsmoke PWS: -2F
Goldstream Creek: -2F
Fairbanks Airport: +4F
Fort Wainwright: +5F
UAF West Ridge: +6F

Goldstream Hills CWOP: 19F (1100'MSL)
Ester Dome CWOP: 19F
Keystone Ridge: 18F
Cleary Summit: 18F
Parks Hwy RWIS near FNSB Boundary: 18F

Heavy Snow

It looks like there was area between Healy and Nenana that received a decent snowfall Wednesday. The Clear Sky Lodge Coop site, near Mile 280 on the Parks Highway, reported 6.2 inches of snow, and the Kobe Hill Coop site, a bit west of the Nenana River bridge, reported 6.8 inches. The fairly wretched webcam imagery from the DOT at the bridge shows the road is not snow covered.

Snowfall in Fairbanks-land was light: no reports of more than two inches, with less than an inch in town.

Big Storm, Big Chinook

A vigorous storm plowed across the western Gulf of Alaska Monday night and early Tuesday. The 10AM ADT surface analysis from the Ocean Prediction Center:



Lots of warm air being pumped north, then chinooked off the Alaska Range and into the southern Interior. The surface inversion has broken almost everywhere in Fairbanks-land, with temperatures in the 40s.

Update: Through 4pm ADT Tuesday, some high temperatures include

Two Rivers PWS: 47F
Woodsmoke PWS: 46F (near North Pole)
Gilmore Creek Coop: 46F (near Fox)
Fairbanks Airport: 44F
Eielson AFB: 46F
Keystone Ridge: 42F
Nenana: 41F
Cleary Summit: 41F

Brooks Range Morning

Arctic Village Sunday morning, as seen from the FAA webcam. The low ground fog probably indicates a little open water remains...though with a low temperature of 4 below this morning that will not last long.

Near Zero in the Lowlands

Now that there is a thin but continuous snowpack, the inversion growing season is well underway in Fairbanks-land. Clear skies overnight allowed temperatures to dip to right around zero in the colder low spots. Some minimum temperatures Friday morning included

Woodsmoke CWOP: 0F (near North Pole)
Goldstream Creek: +2F
Eielson AFB: +6F
Fairbaks Airport: +11F

In the eastern Interior there were a couple of subzero reports:
Circle Hot Springs: -2F
Chicken: -2F

With a fairly mild airmass in place, the hills were no where near as cold:

Keystone Ridge: 20F
Parks Highway RWIS: 21F (at FNSB boundary)
Cleary Summit: 23F

1981-2010 Normals

Here's a couple of plots showing how the 1981-2010 normals that became effective August 1st have changed from the 1971-2000 normals at a number of first order stations around Alaska. Of particular note is that all the locations at least a little be wetter, and all locations are warmer. While the absolute temperature changes are largest in winter, the standardized change (the change divided by the standard deviation, not shown) is actually largest in June at nearly all the sites. This has important ramifications for both hydrology and fire weather. The big changes in precipitation at a few sites (but mostly Barrow) reflect a few really wet months in what are otherwise dry times of year, and highlight a problem with using the mean value of precipitation (and snowfall too) as "normal". In these cases the median is a much better statistic for expressing "normal".

Fairbanks First Measurable Snow

I had not posted on this before due to conflicting data, but now this has been cleared up. The first measurable snow for Fairbanks was on Thursday, October 13th, with 0.1" of snow. This is two weeks later than the mean first measurable snow.

More "significant" snow, i.e. several tenths of an inch, fell early Sunday morning. Here is the 1030am ADT view from UAF West Ridge,from the Alaska Climate Research Center Webcam.

2011 Temperatures

Here's a plot of temperatures thus far in 2011 at Fairbanks. I've plotted the mean daily temperature against the 1980-2010 normals and standard deviation. So, where the green line (2011 data) falls outside of the shaded area, this represents a statistically significant deviation from the expected. This way of looking at variations from normal is much more useful than the raw "departure from normal" in places with continental type climates, or high latitudes in general, where the potential variation in temperatures is much greater during the cold season than the warm season.

The very warm weather at the end of May is the most prominent feature, and to a lesser extent the cold weather in mid to late February. This autumn, the mild weather has been consistent, but not much outside of "expected" range.

World gone White, or Not

Warm advection snow associated with the storm centered near the Bering Straits overspread central Interior Alaska Thursday morning. Here on Keystone Ridge, here's the view as of about 3pm ADT:



A little more than half an inch. Normally not much for mid October, but we'll take it.

Meanwhile, here's a view of UAF West Ridge just before 4pm ADT:



The most important reason for the difference is that there has been very little precipitation in town, with only a trace liquid at the Airport through 4pm ADT.

Freezing at last

With a low of 19F this morning, Fairbanks will have the first day this autumn with a mean temperature below freezing today, October 12th. This is right at the 90 percentile of the distribution. That is, only 10 percent of years 1930-2011 have the first day with a mean temperature below freezing on October 12 or later. At this point it looks like except for a brief chinook Friday/Saturday, the freezing season is upon us. No if we could just get some snow…

Brooks Range Snow Drought

It isn't just Fairbanks-land that's suffering from a dearth of snow. Here's a lovely morning photo (courtesy of the FAA) from Arctic Village in the eastern Brooks Range. Frosty, but snowfree, at valley elevation (about 2000' MSL). There are no long term stats for this part of the world, but my sense is that it very unusual to go into mid-October without a snow cover at Arctic Village.

Active Sky at Northway

A tight low aloft produced a small area of snow showers in the far southeast Interior on Saturday. Here is a dramatic looking photo from the FAA webcam at Northway about 1230pm ADT Saturday.

Still No Snow for Fairbanks

Snow is getting closer to Fairbanks. There was a report of eight inches of snow at Summit Lake (on the Richardson Highway), elevation 3200' MSL, Friday night and early Saturday, and some places above 2000' MSL around Fairbanks had a skiff of snow in a brief shower Friday evening. Still, the greater Fairbanks metro area has yet to have measurable snow. We are now past the 75th percentile of dates with measurable snow, i.e. more three-quarters of the time Fairbanks has received measurable snow by this point in the calendar. Here is a histogram showing how the dates are distributed:



The lack of snow is not (just) because it's been too warm. There has been hardly any precipitation recently. Since September 17th the Airport has received just 0.04 inches of precipitation, and none measurable in the past two weeks.

The current forecast is for very little chance of any snow (or rain) in Fairbanks at least through Tuesday and probably beyond that.

Winter Encroaches

Alessio Gusmeroli, PhD, Postdoctoral Fellow at the UAF Geophyscial Institute took this photo on Sunday, October 2nd near Twelve Mile Summit on the Steese Highway. Elevation roughly 3000' MSL.

Coldest of the Season so Far

Clear skies overnight allowed valley temperatures to fall to the lowest levels of the autumn thus far. Lows included:

Goldstream Creek: 15F
Woodsmoke PWS: 16F (near North Pole)
Eileson AFB: 18F
Gilmore Creek: 20F near Fox
Fairbanks Airport: 23F
UAF West Ridge: 23F

In the hills this was not the coolest night so far: lows were at or just slightly below freezing. Here on Keystone Ridge, the low was 30F but the heavy frost sure was pretty.

More on First Freezing Day

I'm a big believer in the maxim "statistics don't lie, only people do". Okay, I've never actually heard anyone but me say that, but still…

So, here are the statistics on when in the autumn Fairbanks has its first day with the daily mean temperature below freezing. It turns out that the average date in the WB/NWS era (1930-2010) is October 3rd. The time series shows a weak but statistically insignificant trend toward later dates:



When we put the dates into a histogram, we see that presently (Oct 04) we're right in the peak of the distribution:




If Fairbanks were to go through the weekend without a day with a mean temperature below freezing, that would be beyond the 75th percentile and into the realm of "unusually late".

New Barrow Webcam

The long awaited FAA webcam at Barrow is now online. This does not have a coastline view like the UAF Sea Ice program does, but should be more reliable. Here's the view looking east across the runway noon Tuesday.

No Freezing Degree Days

Here on Keystone, through Monday, October 3rd, there has been no freezing degree days (FDD) yet, which makes this the latest in the autumn we've gone with zero FDD. What is a freezing degree day? It's the sum of 32F minus the daily mean temperature. Like most degree day statistics, there are no negative values: if the mean temperature is above freezing, the FDD is zero.

However, there are only 16 years of obs here on the hill, and two years, 2001 and 2006, had only 1 FDD through Oct 3rd.

If we look at the Fairbanks data for FDD, it turns out that it is by no means unusual to go this late in the autumn without any FDD yet. In 2009, 1979 and 1943, there were no FDD until October 18th, and the record warm October 1938 had no FDD until the 27th.

This is not quite an apples to apples comparison; I'd expect Keystone Ridge to have earlier occurrence of FDD, but it's probably safe to say that the lack of freeze not yet terribly unusual. The current numerical guidance suggests though that it will be at least the weekend and probably longer, so the lack of freeze may become extreme.

5th Warmest September of record at Barrow

Last month was the 5th warmest September of record at Barrow. Here are the rankings, temperatures in degrees F.

1. 37.7 (1998)
2. 37.6 (2007)
3. 37.4 (2010)
4. 36.8 (1986)
5. 36.7 (2011)

Weather observations start in Oct 1921 in Barrow, so this is based on 90 years of data.

September Summary

The Fairbanks-land weather summary for September…

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1142 AM AKDT SAT OCT 1 2011

...SEPTEMBER 2011 IN FAIRBANKS...

...DRY AND MILD...

SEPTEMBER WAS A PLEASANT AUTUMN MONTH WITH PERSISTENTLY ABOVE
NORMAL TEMPERATURES AND MOSTLY DRY DAYS.

ONLY THREE DAYS DURING THE MONTH HAD AN AVERAGE DAILY TEMPERATURE
EVEN SLIGHTLY BELOW NORMAL...WHILE AN EQUAL NUMBER OF DAYS HAD AN
AVERAGE DAILY TEMPERATURE MORE THAN 10 DEGREES ABOVE NORMAL.

OVERALL...THE AVERAGE HIGH IN SEPTEMBER AT THE FAIRBANKS
INTERNATIONAL AIRPORT WAS 59 DEGREES AND THE AVERAGE LOW WAS
39 DEGREES. THE AVERAGE TEMPERATURE FOR THE MONTH OF 49.0 DEGREES
MADE THIS THE 10TH WARMEST SEPTEMBER IN MORE THAN A CENTURY OF
WEATHER OBSERVATIONS IN FAIRBANKS. THIS IS THE 7TH CONSECUTIVE
SEPTEMBER TO BE SIGNIFICANTLY WARMER THAN NORMAL...AND FOUR OF THE
TEN WARMEST SEPTEMBERS OF RECORD HAVE OCCURRED IN THE PAST 20
YEARS.

THE HIGH TEMPERATURE AT THE AIRPORT FOR SEPTEMBER WAS 72 DEGREES ON
THE 5TH AND 13TH...WHILE THE LOW OF 28 DEGREES OCCURRED LATE IN
THE EVENING ON THE 30TH. THE FIRST FREEZE OF THE AUTUMN AT THE
AIRPORT OCCURRED ON THE 25TH...WHICH TIED WITH 2006 FOR THE SECOND
LATEST FIRST FREEZE OF RECORD. AMAZINGLY...ALTHOUGH THE LONG-TERM
AVERAGE DATE FOR THE FIRST FREEZE AT THE AIRPORT IS SEPTEMBER
7TH...THIS IS THE SIXTH CONSECUTIVE YEAR IT HAS BEEN AFTER
SEPTEMBER 20TH.

EVEN IN TYPICALLY COLDER LOW LYING AREAS...TEMPERATURES IN
SEPTEMBER FAILED TO DROP BELOW THE 20S...WITH MONTHLY LOWS OF
20 DEGREES AT GOLDSTREAM VALLEY BOTTOM AND 23 DEGREES AT WOODSMOKE
NEAR NORTH POLE.

PRECIPITATION WAS SIGNIFICANTLY BELOW NORMAL. THE TOTAL FOR THE
MONTH OF 0.65 INCHES AT THE AIRPORT IS ABOUT 60 PERCENT OF NORMAL.
MEASURABLE RAIN FELL ON JUST NINE DAYS...AND ABOUT TWO- THIRD OF
THE MONTHLY TOTAL FELL ON THE 9TH AND 10TH. THE FIRST SNOW
FLURRIES OF THE SEASON FELL ON THE LAST DAY OF THE MONTH OVER MUCH
OF THE AREA. AT THE AIRPORT THIS IS ABOUT A WEEK LATER THAN NORMAL
FOR THE FIRST SNOW.

AUTUMN COLORS SEEMED UNUSUALLY LONG LIVED IN SEPTEMBER...AND ONLY
AFTER THE EQUINOX WERE TREES LARGELY BARE. THE MONTH ALSO FEATURED
SEVERAL NIGHTS WITH ACTIVE NORTHERN LIGHTS.

LOOKING AHEAD TO OCTOBER...THE WINTER SNOW PACK IS NEARLY ALWAYS
ESTABLISHED SOMETIME DURING THE MONTH...AND THIS HELPS
TEMPERATURES TO FALL DRAMATICALLY. THE AVERAGE HIGH TEMPERATURE
DROPS FROM 45 ON THE 1ST TO 19 ON HALLOWEEN...WHILE THE AVERAGE LOW
TEMPERATURE FALLS FROM 28 DEGREES ON THE FIRST TO 4 ABOVE ON THE
31ST. TOTAL PRECIPITATION AVERAGES 0.83 INCHES AND AVERAGE
SNOWFALL 10.8 INCHES. SIGNIFICANT AMOUNTS OF RAIN ARE UNCOMMON IN
FAIRBANKS AFTER THE FIRST WEEK OF THE MONTH. THE PERMANENT
WINTER SNOW COVER IS ESTABLISHED...ON AVERAGE...ON OCTOBER 18TH.
POSSIBLE SUNSHINE DECREASES FROM OVER 11 HOURS DURING THE FIRST
THREE DAYS OF THE MONTH TO LESS THAN EIGHT HOURS ON THE 31ST. THE
FORECAST FOR THIS OCTOBER FROM NOAA'S CLIMATE PREDICTION CENTER
CALLS FOR SLIGHTLY INCREASED CHANCES OF SIGNIFICANTLY BELOW NORMAL
TEMPERATURES.

$$
RT OCT 2011

Saturday Morning at Home

The snow came in a shower just before dark Friday evening. All melted by Saturday mid-afternoon.

Brooks Range Snow

October dawns white in the Brooks Range: Saturday morning photo from the FAA webcam at Chandalar DOT camp at Mile 239 on the Dalton Highway.