Warm and Cold Spots in 2013

* Updated to add map showing those locations in Alaska that are colder than International Falls, MN.

Several months ago we looked at the locations that most frequently recorded the statewide cold and warm temperatures during 2012. Since practically all of the numbers for 2013 have been received by NCDC, we can now make some maps for 2013. The two maps below show the count for which stations in Alaska were identified as the cold and warm spot respectively for each day of the year in 2013. There is an important difference between these maps and the ones from last year. Knowing that a few cold spot locations are not included in the GHCN database, I manually downloaded the hourly observations for Anaktuvuk Pass, Arctic Village, and Fort Yukon. Unfortunately there was only about 1 month's worth of data for Umiat so it was left out of the analysis. There are surely other stations that could have been included as well.

If two (or more) stations tied for the lowest or warmest temperature for a calendar day, they each received a tally for the day. Of the 284 stations used in the analysis, only 66 had the distinction of being the cold spot in Alaska at least once in 2013. A total of 115 stations were the warm spot in Alaska at least once in 2013.

There are some interesting patterns. For the cold spot, it is almost on the North Slope or at a high elevation site during the summer and in an Interior valley during the winter. For the warm spot, nearly every day in winter it is located in Southeast but in the summer it can be in the Interior or the southern Mainland. As Rick has mentioned, the time of observation at Cooperative stations makes a difference. If the time of observation were standardized, the patterns might not change that much but the tallies certainly would.

Fairbanks Snow Stats Through February 6th, 2014

With the 4.3" of new snow today (2/6/2014) the prolonged snow drought is temporarily over. The season-to-date snow total is up to 40.2"; which is still 9.8" below the 1981-2010 normal for the date. Not a single day this winter has been seen a season-to-date snow total at or above the normal value. Anchorage has only spent two days above their normal value. The first chart below shows the season-to-date snowfall for every winter in Fairbanks since 1920-1921. All years are thin gray lines except for the current season (red), the normal value (black), and two composite values representing the max and min values for the date.

As we mentioned here and here, Fairbanks has a habit of being below normal in season-to-date snowfall but at or above normal for snow depth. The second chart below shows the current season-to-date snow depth and the normal season-to-date snow depth. Only a few days since November 10th have been below the normal value and it looks to stay that way for a while.

Open Bering Sea

Sea ice is considerably less extensive in the Bering Sea this winter than in recent years, and the extreme warmth of recent weeks has caused much of the ice that had formed earlier to break up and retreat.  The MODIS image below was taken on Sunday afternoon and shows very large areas of open water even in the northern Bering Sea and Norton Sound.  As for the central Bering Sea and Bristol Bay, there is very little sea ice, and the waters surrounding St Matthew Island and Nunivak Island are nearly ice-free.  The second image below shows the contrasting situation in mid-January 2012, when sea ice was very extensive.

 

The recent retreat of the Bering Sea ice is evident in the following time series chart, where the 2014 line shows a decrease of more than 100,000 km² since late January.  Remarkably, the sea ice extent is only marginally higher than it was 30 days ago.

According to the National Snow and Ice Data Center, the January mean ice extent in the Bering Sea this year was the least extensive since at least 2005.  The January mean ice extent maps for 2014, 2012, and 2005 are shown below.

Fairbanks Temperature Update

The chart below shows recent daily mean temperatures in Fairbanks, compared to the 1981-2010 normal; the gray lines show the +/- 1 standard deviation range around the daily normal values.  The see-saw pattern that began in mid-November ended abruptly in mid-January, giving way to very unusual warmth that persisted for most of the rest of the month.

Below is the January climate summary, courtesy of NWS Fairbanks.  Note that the summary says that the 45 °F on the 24th was the "warmest temperature recorded at the airport during the month of January" - this refers to January 2014, not the all-time record for January, which is 52 °F (Jan 16, 2009).

PUBLIC INFORMATION STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE FAIRBANKS AK
624 AM AKST SAT FEB 1 2014

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

JANUARY 2014 WAS EXCEPTIONALLY WARM AND DRY IN FAIRBANKS WITH THE
AVERAGE TEMPERATURE FALLING BELOW NORMAL ON ONLY 4 DAYS...HOWEVER
WITH THE WARM TEMPERATURES CAME TWO FREEZING RAIN EVENTS OVER A 3
DAY PERIOD THAT CREATED HAZARDOUS DRIVING CONDITIONS AND CLOSED
MANY LOCAL SCHOOLS FOR TWO DAYS.

JANUARY STARTED WARM WITH AVERAGE TEMPERATURES 10 TO 20 DEGREES
ABOVE NORMAL FOR THE FIRST 9 DAYS...HOWEVER TEMPERATURES PLUMMETED
FROM 15 ABOVE ON THE 8TH TO 41 BELOW ON THE 12TH AND 13TH. 41
BELOW WAS THE COLDEST TEMPERATURE RECORDED AT THE AIRPORT DURING
THE MONTH OF JANUARY.

WARM TEMPERATURES RETURNED AGAIN TO THE INTERIOR BY MID MONTH.
A HIGH PRESSURE RIDGE ALOFT THAT STRETCHED FROM NEAR HAWAII TO
NORTHERN ALASKA ALLOWED A PROLONGED CHINOOK EVENT THAT LASTED
FROM AROUND THE 20TH TO THE 28TH OF JANUARY TO DEVELOP OVER THE
INTERIOR. AVERAGE TEMPERATURES WERE 20 TO 40 DEGREES ABOVE NORMAL
THROUGH THIS PERIOD. THE TEMPERATURE SOARED TO 45 DEGREES AT THE
FAIRBANKS AIRPORT ON THE 24TH. THIS WAS THE WARMEST TEMPERATURE
RECORDED AT THE AIRPORT DURING THE MONTH OF JANUARY. THE WARM
TEMPERATURES WERE NOT UNIQUE TO FAIRBANKS AS SEVERAL SITES ACROSS
THE INTERIOR SET RECORDS INCLUDING AN ALL TIME RECORD HIGH
TEMPERATURE FOR THE MONTH OF JANUARY OF 52 DEGREES AT DENALI
NATIONAL PARK HEADQUARTERS ON THE 26TH.

THE AVERAGE HIGH TEMPERATURE FOR THE MONTH OF JANUARY AT THE
FAIRBANKS AIRPORT WAS 16.4 DEGREES ABOVE ZERO WHICH IS 15.3
DEGREES ABOVE THE NORMAL HIGH TEMPERATURE OF 1.1 DEGREES ABOVE
ZERO. THIS RANKS AS THE 7TH WARMEST OF 106 YEARS OF RECORD. THE
AVERAGE LOW TEMPERATURE FOR THE MONTH OF JANUARY AT THE FAIRBANKS
AIRPORT WAS 1.1 DEGREES BELOW ZERO WHICH IS 15.8 DEGREES ABOVE
THE NORMAL LOW TEMPERATURE OF 16.9 DEGREES BELOW ZERO. THIS RANKS
AS THE 7TH WARMEST OF THE 107 YEARS OF RECORD. THE AVERAGE
TEMPERATURE WAS 7.6 DEGREES ABOVE WHICH WAS 15.5 DEGREES ABOVE THE
NORMAL AVERAGE TEMPERATURE OF 7.9 DEGREES BELOW.

0.22 INCH OF PRECIPITATION FELL AT THE AIRPORT DURING THE MONTH
OF JANUARY WHICH IS 0.36 INCH BELOW THE NORMAL PRECIPITATION OF
0.58 INCH. THIS RANKS AS THE 20TH DRIEST OUT OF 103 YEARS OF
RECORD. ONLY 2.5 INCHES OF SNOW FELL AT THE FAIRBANKS AIRPORT
WHICH IS 7.8 INCHES BELOW THE NORMAL JANUARY SNOW FALL OF 10.3
INCHES. WELL ABOVE NORMAL TEMPERATURES ALLOWED A HIGH PROPORTION
OF THE PRECIPITATION THAT FELL TO FALL IN LIQUID FORM FURTHER
REDUCING THE AMOUNT OF SNOW FALL. THE 2.5 INCHES OF SNOW THAT FELL
RANKS AS THE 12TH LOWEST AMOUNT FOR A JANUARY TOTAL SNOW FALL.

LOOKING AHEAD TO FEBRUARY WITH THE CLIMATOLOGICALLY COLDEST PART
OF WINTER BEHIND...AND AVAILABLE DAY LIGHT INCREASING AT NEARLY
SEVEN MINUTES PER DAY...A NOTICEABLE DIURNAL TEMPERATURE RANGE
WILL BE FELT...ESPECIALLY BY THE END OF THE MONTH. THE AVERAGE
HIGH TEMPERATURE AT THE FAIRBANKS AIRPORT INCREASES FROM 3 DEGREES
ABOVE ON THE 1ST TO 17 DEGREES ABOVE ON THE 28TH. THE AVERAGE LOW
TEMPERATURE INCREASES FROM 16 BELOW ON THE 1ST TO 10 BELOW ON THE
28TH. TEMPERATURES IN FEBRUARY HAVE RANGED FROM 50 ABOVE IN 1943
TO 58 BELOW IN 1947 AND MOST RECENTLY IN 1993. THE NORMAL
PRECIPITATION FOR FEBRUARY IS 0.42 INCHES. AVERAGE SNOWFALL IN
FEBRUARY IS 8.1 INCHES. AVAILABLE SUNSHINE INCREASES FROM 6 HOURS
AND 59 MINUTES ON THE FIRST TO 10 HOURS AND 2 MINUTES ON THE 28TH.

THE OUTLOOK FOR FAIRBANKS FOR FEBRUARY FROM THE CLIMATE PREDICTION
CENTER CALLS FOR EQUAL CHANCES OF ABOVE...NEAR NORMAL OR BELOW
NORMAL TEMPERATURES. THE CLIMATE PREDICTION CENTER IS ALSO
CALLING FOR EQUAL CHANCES FOR ABOVE NORMAL...NEAR NORMAL OR BELOW
NORMAL PRECIPITATION.

OBSERVED LAST MONTH...01/2014

                         OBSERVED   RANK
AVG MAX TEMP (F)             16.4   7TH WARMEST OF 106 YEARS
AVG MIN TEMP (F)             -1.1   7TH WARMEST OF 107 YEARS
AVG TEMP (F)                  7.6   7TH WARMEST OF 106 YEARS
TOTAL PRECIPITATION (IN)      0.22 20TH DRIEST OF 103 YEARS TOTAL
SNOW (IN)                     2.50 93RD SNOWIEST OF 104 YEARS

$$

CCC

Barrow Cools Aloft

The atmosphere above Barrow finally cooled to below freezing at all levels this morning, after a record-setting period of mid-winter warmth.  The chart below shows the 850 mb temperature (red line) and the maximum temperature at any height measured in the balloon soundings (blue line) since January 24.  Above-freezing temperatures were measured at some height above ground at every observation between 3 am AKST January 26 and 3 pm January 31, a total of 132 hours or five and a half days.

The previous record for longest observed stretch of above-freezing conditions aloft in January through March was 72 hours or 3 days, during January 24-27, 1983.  However, it should be noted that the vertical resolution of the sounding measurements has improved over time, so it has become less likely over time that above-freezing temperatures aloft could be missed by the balloon measurements; this might make it "easier" to maintain a continuous stretch of above-freezing observations.  Looking only at the 850 mb measurements, which have been reported consistently since 1948, the longest stretch of above-freezing temperatures in December through March was 48 hours (in 1953, 1958, and 2007), compared to 72 hours in the event of recent days.

It is also worth noting that the previous January-February record highest temperature at any height, +7.8 °C, was exceeded for three consecutive measurements in this event.  The new record is +9.2 °C.

Alaska Winter Advisory / Warning Critera

As a follow-up to yesterday's post, here are maps depicting the winter warning and advisory criteria for all the Alaska forecast zones. The red dashed lines represent the boundaries between the Fairbanks, Anchorage, and Juneau offices. The differences is advisory numbers as shown in yesterday's post is largely attributable to the different criteria.

Winter Weather Advisory:

This is the snowfall criteria map for a Winter Weather Advisory. 

In addition, all zones have a blowing snow criteria as follows:

When one of the following combinations are forecast to occur for at least 3 hours: 

1. Sustained wind or frequent gusts 25 mph or greater and visibility less than or equal 1/2 mile (but greater than 1/4 mile)

 …OR… 

2. Visibility is 1/4 mile or less, and winds are at least 25 mph but less than 35 mph 

There is also a multiple event criteria for all zones as follows:

Mixed precipitation or multiple winter weather events even if only one precipitation type meets or exceeds advisory criteria, but remains below warning criteria (this may include wind and/or wind chill).

Winter Storm Warning:

Just like the Winter Weather Advisory, there is a rule that applies across all zones. Namely:

Mixed precipitation or multiple winter events, even if only one precipitation type meets or exceeds warning criteria (this may include wind and wind chill) .

Freezing Rain Advisory:

This one is self-explanatory. Any ice amount greater than the amount defined for the Freezing Rain Advisory qualifies as an Ice Storm Warning.


Wind Chill Advisory / Warning:

These should be pretty self-explanatory. Remember that it is not just the wind chill alone but there has to be a sustained wind as well.

Blizzard Warning:

There is no map for the Blizzard Warning. It is standardized across not just Alaska but the entire U.S. The criteria is as follows:

When forecast to occur for at least 3 hours: Blowing snow (with or without falling snow) reducing visibility to < 1/4 mile when accompanied by sustained wind or frequent gusts > 35 mph. 

The text of all the criteria can be found at the following site: http://goo.gl/XAsdJ7#AKClimate

Alaska Winter Advisories 2009-2013

A few days ago Rick pointed me to the Iowa State site that contains NWS advisory archives. I have long been interested in the spatial distribution of weather phenomenon and this archive data set practically begs to be mapped. So, here is a map of total winter advisories for all of Alaska between January 1, 2009, and December 31, 2013 – a five year climatology. The types of advisories include: 1) Winter Storm Warnings, 2) Winter Weather Advisories, 3) Blizzard Warnings, 4) Freezing Rain Advisories, 5) Ice Storm Warnings, 6) Wind Chill Advisories, and 7) Wind Chill Warnings. Watches were not included. Any product with "WSW in the header and NEW, EXA, or EXB in the VTEC line was included.

Note: Many of the differences between adjacent zones are due to the specific criteria for those zones. For example, Cordova's zone does not have a Winter Weather Advisory criteria for snow but Yakutat's zone does. I will have a follow up post with maps of the advisory/warning criteria soon.

Total Number of Winter Advisories/Warnings:

Fig 1. Total number of Advisories and Warnings (all types) between 2009 and 2013.

There are a couple of important things to keep in mind. First, there are three NWS forecast offices in Alaska and they each have different advisory/warning thresholds for the zones in their area of responsibilities. Second, particularly with Winter Weather Advisories, sometimes they are the result of snowfall, sometimes they are the result of blowing snow, and sometimes they are a result of the combination of multiple factors. The same is true for Winter Storm Warnings to a lesser degree. In another post, I will display a series of maps showing the advisory criteria. In the meantime, you can find the Alaska Region text document here: http://goo.gl/XAsdJ7#AKClimate .

Maps of Different Advisory/Warning Types:

Fig 2. Total number of Winter Storm Warnings between 2009 and 2013.

Fig 3. Total number of Winter Weather Advisories between 2009 and 2013.

Fig 4. Total number of Wind Chill Advisories/Warnings between 2009 and 2013.

Fig 5. Total number of Blizzard Warnings between 2009 and 2013.

Fig 6. Total number of Freezing Rain Advisories between 2009 and 2013.

 Fig 7. Total number of Ice Storm Warnings between 2009 and 2013.

January State Record Temperature in Port Alsworth

Rick noted today that the Alaska January temperature record of 62°F was tied yesterday (1/27) at the CRN station in Port Alsworth. This is quite a fortuitous observation. The CRN network was established to create a baseline of data for future climate change studies. The sites were selected to represent a  variety of ecological settings without the urbanization, land use, and equipment changes that may affect long term temperature measurements. Highly reliable equipment is used at CRN stations.

Port Alsworth is located on the southeast shore of Lake Clark approximately 170 miles southwest of Anchorage. Looking at recent VIIRS and Modis imagery, there appears to be no snow cover in the vicinity of the station (see second image below). Also, there is a state airport weather station in Port Alsworth (PALJ) and a RAWS station. The chart below shows the 15-minute observations from the CRN station plus the few airport and more numerous RAWS observations. Quite clearly, the airport and RAWS data support the CRN data. Finally, since the 62°F reading was one of the 15-minute observations, there is a chance that a higher reading occurred between the 15-minute readings.

Fig 1. Temperature plot of CRN, airport, and RAWS temperatures on 1.17/14.

Fig 2. Suomi NPP Landcover image from 1/28/14 showing the lack of snow cover in the region. Cyan is snow and brown indicats no snow. White indicates clouds (not snow). Port Alsworth is at the lower left end of the yellow line. Anchorage is at the upper right end of the yellow line. Click on image for a closer look.

Record Warmth Aloft in Barrow

You wouldn't know it from the surface conditions (4 °F and breezy), but this morning's balloon sounding from Barrow observed record warmth aloft for the time of year.  A temperature of +9.0 °C was measured at about 3500 feet above ground, which is more than 1 °C warmer than the previous highest temperature measured at any height above Barrow in January or February (data back to 1948).  The temperature of +7.0 °C at 850 mb broke the January-March record for that pressure level by a wide margin (previous record +4.2 °C).  Barrow has never measured an 850 mb temperature above 5 °C between December 2 and April 28 - until today.

The chart below shows this morning's temperature profile (blue line) along with the historical soundings that were previously the record-holders for temperature at any height (red line) and at 850 mb (green line).  The square markers indicate the 850 mb level in each sounding.

Record Winter Warmth in Nome

Nome airport is basking in warm midwinter sunshine this afternoon and reporting a temperature of 50 °F at 1 pm AKST, which is a new all-time high temperature record for January and for the period of December through March; historical temperature data in Nome go all the way back to 1907.  There appears to be little chance that today's measurement is erroneous, as nearby Golovin is also reporting 50 °F.

If the temperature rises any higher, the November-March record will also be broken (50 °F on November 1, 1928).  Nome has never before observed a temperature above 50 °F between October 17 and April 9.

[Update 4 pm AKST: The temperature has reached 51 °F, so it is unequivocally a new winter record.]

Record Freezing Level at Fairbanks

The 12Z (3 a.m.) balloon sounding launched from the Fairbanks International Airport this morning set some quite impressive records.

1) The 850 mb temperature of 9.4°C is a January record and is also at or above any temperature measured in November, December, March or April; but not February.

2) The 700 mb temperature of 1.4°C is a record for any month between November and March.

3) The 1000-500 mb thickness of 5545 meters is also a  record for any month between November and March (from Rick).

4) The 850-500 mb thickness of 4202 m appears to be a record for November through April (from Richard).

5) The interpolated freezing level of 3,229 m is a January and seasonal record. The previous record was 3,217 m on Jan 18, 1963.

The chart below shows today's 12Z sounding and the 1/18/63 (12Z) sounding side by side. If you discount the very shallow surface inversion where temperatures were below freezing (~24m), you have to ascend another 10,000+ feet to drop back below freezing. For comparison, the 3,229 m freezing level was only slightly lower than the 3,395 m at Bermuda and the 3,329 m at Lake Charles, Louisiana.

Heat Burst in Yukon Territory

Yesterday afternoon brought a remarkable weather event to Burwash Landing, on the shores of Kluane Lake in the southwest Yukon Territory.  Kluane Lake and Burwash Landing lie just northeast of Kluane National Park and Reserve, which includes Mt Logan, the highest mountain in Canada; the St Elias mountain range forms a high barrier between the Pacific Ocean and the interior Yukon.  Yesterday a brief period of downsloping flow from the mountainous terrain brought dramatic warming to Burwash Landing and broke some longstanding temperature records.

Here are the hourly observations from Burwash airport yesterday from 9 am to 6 pm local time:

Hour (UTC)	Temperature (°C)	MSLP (mb)	Wind Speed (knots)	Wind Direction (°)
17	8	1010.0	31	140
18	8	1010.9	26	140
19	8	1011.2	25	150
20	8	1011.9	17	160
21	9	1012.4	16	150
22	16	1012.4	10	190
23	16	1013.1	12	230
00	9	1015.2	4	250
01	7	1017.7	10	330
02	5	1019.5	9	270

Here is the topographic map of the area, courtesy of Google; Burwash Landing is indicated with the purple marker.  Note the prominent valley running from southeast (Haines Junction area) to northwest; the Alaska Highway follows the valley for many miles.

In the morning, strong southeasterly winds were blowing along the valley, accompanied by extraordinarily warm air for the time of year (8 °C or 46 °F); wind gusts of 45 knots were measured at Burwash airport.  The pressure was rising steadily as low pressure over the Alaskan interior was weakening while the ridge over British Columbia was building northwest.  The chart below shows the surface analysis at 18 UTC and indicates a strong pressure gradient over the southwest Yukon, along with a front approaching from the west.

In the afternoon hours, the winds at Burwash airport veered to the south (2 pm), then southwest (3 pm) and eventually northwest (5 pm), and for two hours the reported temperature jumped up to 16 °C; the maximum temperature was reported as 16.5 °C (62 °F).  The surface analysis at 4 pm local time (below) shows a weak low pressure center very close to Burwash Landing.  By 4 pm the temperature was back down to 9 °C with rapidly rising pressure, indicating that the front/low had passed, and in the subsequent hours the temperature continued falling while the pressure kept rising.  It is also noteworthy that the visibility was reported as 30 miles throughout the day until 4 pm, when it dropped to 9 miles and remained there; the sudden change is also evidence of the arrival of a different air mass.

Is it plausible that the temperature could have exceeded 60 °F in the Yukon Territory in January?  I believe so: the chart below shows the 00 UTC sounding from Yakutat, the closest upper-air station, which is indicated with a green marker on the terrain map above.  Very warm air was observed aloft, with temperatures only slightly below freezing at 700 mb.  Note that the winds (indicated by the barbs on the right) were blowing from the southwest above about 800 mb, i.e. perpendicular to the coastal mountain range.  Therefore when the surface winds at Burwash Airport veered to the south and southwest in the early afternoon, the surface flow became aligned with the upper flow and the warm air aloft was able to descend the lee slope of the high terrain, undergoing strong warming during its descent.

A simple calculation reveals that the air would have had to descend from about 750 mb, or about 2400 m above sea level, to reach 16 °C at the altitude of Burwash airport.  Perhaps not coincidentally, this is just about the height of the terrain immediately to the southwest of Burwash Landing.  Physically, then, the observations at the airport seem to make sense.

Assuming that the temperature measurements were accurate, the high temperature yesterday was by far the highest ever recorded in January in Burwash Landing; historical data are mostly complete back to 1967.  The previous January record was 49 °F.  Yesterday's event is also the warmest ever observed in winter (November-March) there, the previous record being 57 °F.  It is possible that the event is a record for January in the Yukon Territory; I don't have complete historical data for all Yukon stations, but the highest January temperature at any of the 26 Yukon stations that have 1981-2010 normals is only 10.1 °C (50 °F).

Two questions spring to mind in regard to this event: first, if it's possible to bring warmth to the Yukon interior by this downsloping flow, why was yesterday's event so far beyond the previous January records?  I suggest that this event involved a very unusual set of circumstances that allowed the warm air aloft to reach the surface at Burwash Landing: the boundary layer was already thoroughly mixed and destabilized by extremely warm conditions and strong winds earlier in the day, so there was no surface-based inversion to scour out.  Also, the passage of a frontal disturbance very close to the area created additional vertical mixing that allowed warm air from aloft to descend.  I suspect that it is very rare to get deep vertical mixing all the way to the surface over the Yukon interior in winter, because snow cover, radiative imbalance, and pre-existing cold air in place so strongly favor low-level inversions.

The other question is, has a similar temperature ever been observed before in winter in the Yukon Territory?  If so, we might have more confidence that yesterday's temperature report was not erroneous.  The answer is yes: the all-time winter (Nov-Mar) record high temperature for the 26 Yukon stations mentioned above is 18.9 °C (66 °F) on February 4, 1941, at Carcross (indicated with a red marker on the terrain map above).  On the same day, Mayo, in the central Yukon, recorded 51 °F, a near-record for February.  The map below shows the estimated sea-level pressure and 700 mb height on that day in 1941; while not identical to yesterday's pattern, it was fairly similar with deep flow from the south crossing the coastal range and bringing strong chinook warming to the interior northwest.  To put the event in context, Anchorage recorded 45 °F on February 3, 1941, and Fairbanks reported 42 °F on the 4th.

What Might February Look Like

Several people have asked me if the rest of the winter will be as warm as the last several weeks have been. While there is no way to tell for sure, it is helpful to look back at February's that follow exceptionally warm January's. To do this, I looked at all of the GHCN data from NWS and COOP stations (no RAWS) and organized them by climate division according to Bieniek et al (citation at the end of the post). Then, each climate division was weighted according to the proportion of the state that the division encompasses. Between 1940 and 2013, here are the ten warmest and coldest January's.

What I wanted to know was not only how those ten January's looked (first map below) but more importantly, how the February's afterward looked. To my surprise, the February's were essentially normal. In one sense, the temperatures always tend to drift toward normality; however, I expected the forcings that caused the warm January's to have a residual effect in February too. The ESRL database that I used to generate the maps has data beginning in 1948 so any years from the top 10 list that fell between 1940 and 1948 was substituted with the next year down on the list. Unfortunately the ESRL database that goes back to the beginning of he 20th century is temporarily out of order.

Bieniek, Peter A., and Coauthors, 2012: Climate Divisions for Alaska Based on Objective Methods. J. Appl. Meteor. Climatol., 51, 1276–1289.

Eagle Record Warmth

Update January 24: the airport temperature data from Eagle yesterday was incorrect, as the ASOS aspirator has failed (information courtesy of Rick).  The high temperature at the COOP station was "only" 42 °F - still a record for the date, but not for the month.  However, with warmth aloft intensifying over the next few days, many more temperature records will undoubtedly fall.

Original post:
This post will need updating when the final data is in, but the current [noon AKST] temperature of 54 °F at Eagle airport appears to be the highest January temperature on record for any observing station in Eagle, the previous January record being 50 °F in 1981.

Today's temperature is also higher than any temperature recorded in November, December, or March in Eagle; the only higher temperature in the winter season was 57 °F on February 10, 2006.

Sunrise in Barrow

The sun rose in Barrow today for the first time since November 19th last year (64 days). It was up from 1:29 p.m. to 1:51 p.m. Below is the FAA webcam picture looking south at 1:31 p.m. – 2 minutes after sunrise. Here is the only METAR from when the sun was up: 

Site M/A Day Time Sky Conditions           VIS Weather Temp DP Wind(kt)  Alt  RH  Chill Peak

PABR  MP 22 1349  OVC055                     3 BS-       0  -8 06018     997  68% -22    

(PABR 222249Z 06018KT 3SM BLSN OVC055 M18/M22 A2997=)

Rain in Nome

Unseasonably warm air over western Alaska brought rain to Nome yesterday - both the freezing kind and just plain rain.  The temperature reached 36 °F at the surface - not quite a record for the date - and 37 °F was measured a few hundred feet above the surface in the afternoon.

Rain with above-freezing temperatures is obviously unusual at this time of year in Nome, but it has happened many times before in the climate record.  The first chart below shows the number of January days with plain rain reported in the hourly observations since 1936 (red columns); note that there is a big gap in the data from 1947 to 1972.  Also, a number of years have incomplete or missing data in the early years (marked with asterisks).  The blue columns show the frequency of above-freezing temperatures (with or without rain) in the hourly data.  The second chart shows the same information for the December-February period each year.

 

The climate shift in 1976 with the change to a positive Pacific Decadal Oscillation stands out very clearly, as the frequency of warm and warm-rainy days appears to have increased dramatically.  For the winter as a whole, above-freezing and plain rain events have been less common in the past decade than in the first decade of the positive PDO regime; this reflects the shift back towards the negative PDO phase (see the PDO time series chart below; image credit: http://en.wikipedia.org/wiki/File:PDO.svg).  However, in January plain rain has now occurred in 9 of the past 13 years, which is a higher annual rate of recurrence than earlier in the climate record.

Fairbanks Warming Event

Fairbanks briefly experienced above-freezing temperatures at the airport on Friday afternoon for the first time since November 14, and even warmer conditions were observed in favored locations in the southern interior of Alaska.  An interesting aspect of the event in Fairbanks is that the valley-level wind was out of the north or northeast throughout the warming.  Of course, the warm air mass was coming from the south, as winds were out of the south less than 1500 m above ground, but the wind aloft was not particularly strong and did not mix down to the surface.  In this sense, I'm not sure whether it's right to call this a "chinook" event in Fairbanks.

The chart below shows the hourly observations of temperature and wind speed and direction at the airport, along with the twice-daily measurements of temperature at 850 mb.  Temperatures rose in tandem with the low-level northerly wind speed, but as soon as the wind died away, the temperature dropped back to its former level.

Surface observations from across Alaska at the peak of the warmth in Fairbanks show an impressive temperature gradient both across the entire state and in the central interior, as temperatures remained much cooler to the north and west of Fairbanks.

Jan. 16, 2009, Revisited

Today is the 5-year anniversary of perhaps the warmest day ever recorded in Alaska during the month of January. On January 16, 2009, the high temperature in Fairbanks was 52°F – a daily and monthly record. In Anchorage, the high temperature of 50°F was the second highest on record for January and the low of 37°F and the daily average temperature of 44°F were the warmest on record for any day in the month of January. Many other stations recorded daily and monthly records. It was the third day in a multi-day Chinook event.

Here are three maps that show how remarkable it was. The maps show, 1) the actual high temperature on January 16, 2009, 2) the normal high temperature on January 16, 2009, and 3) the departure from normal of the high temperature on January 16, 2009. As you can see, there were pockets of areas a full 50°F above normal and at least half of the state was more than 35°F above normal.

Here in Anchorage the snow depth dropped from 17" down to 5". All of the snow disappeared from the roofs in town and many shingles were blown off. I spent several hours replacing missing shingles in the middle of January!

Weak Inversion

The brief cold spells in interior Alaska over Christmas and earlier this week brought strong low-level temperature inversions to the Fairbanks area, as is typical for the time of year; but since the beginning of the climatological inversion season (October 19), far more days have had weak or non-existent inversions than strong inversions.  The chart below shows the daily inversion strength based on the daily mean temperatures at Keystone Ridge and Fairbanks International Airport.  (Note the missing data from Keystone Ridge in early December.)  Remarkably, there were seven consecutive days in December with a positive mean temperature lapse rate (no inversion); the average number of such days in December is only two.

Looking at the mean inversion strength from October 19 through January 13, this winter so far has the weakest mean inversion since records began on Keystone Ridge in 1996 (see chart below).  Over the same dates, airport temperatures have averaged 4.7 °F above normal while Keystone Ridge has been 1.8 °F above normal; and so the inversion has been 2.9 °F weaker than normal.