Autumn Creep

From the train station at Denali National Park 755AM Thursday

Cooling Down up North

Here's the 4pm AST Tuesday (00 UTC Wednesday) surface analysis from Environment Canada. We're finally starting to see some subzero temperatures in far northwest Canada, with a low temperature of -5F this afternoon at Isachsen, NU (78N, 104W). Nowhere else in the northwest Canadian Arctic has been quite that cold thus far, but with a decent snow cover now and open water freeing up, it will not be long.

First Freeze

Most valley locations that had yet to have a freeze finally got one this morning. The low temperature of 32F at Fairbanks International Airport ties for the second latest first freeze of record. The low of 30F at UAF West Ridge is the third latest of record (since 1949). Here on Keystone Ridge, close, but no cigar, so far. Low was 34F, with some frozen rain on the car. However, the first freeze here has been later than September 25th three times since 1996.

Barrow Finally Below Freezing

Late on Friday evening, September 23, Barrow dipped below freezing for the first time since June 29th. The streak of 85 days is 17 days longer than the previous record set in 2009.

Blast Furnace from the Past

With temperatures headed back toward something like normal over Interior Alaska this upcoming weekend, this seems a good time to look back at one of the greatest autumn chinooks of record.

It was mid-September back in '95, when sustained strong southerly flow brought six straight days with highs of 70F or higher to Fairbanks. Here is the NCAR reanalysis for 4am ADT Sep 20th:



Remarkable in itself, but this was topped off by one of the most anomalous temperature records in the 100+ years of weather observations here. On September 20th, a very mild airmass and strong southeast winds that remained up all kept the daily low temperature to an unbelievable 65F. Here's a plot of the upper air observations from Fairbanks for 4am ADT Sep 20th, courtesy of the Plymouth State Weather Center. Note that the near surface is well mixed thanks to the winds:



The low of 65F is not only, by far, the highest daily minimum temperature of record in September, its higher than any daily min temperature in August. This is a stunning 4.6 standard deviations above the long term mean daily minimum temperature for the three days centered on September 20th. This "standardized departure" is the largest daily positive anomaly in the Weather Bureau/NWS era of observations (1930-present) in Fairbanks.

Barrow no-freeze

Amazingly, Barrow STILL has not been below freezing. The low Tuesday Sep 20th was 32F, and there was 0.3 inches of snow in the early morning. The streak of temperatures at or above 32F now stands at 83 days. Wow.

The Beat Goes on

Overnight low temperatures:

Fairbanks International Airport: 35F
UAF West Ridge: 33F

Barrow: 34F

Monday morning guidance (technically, MOS) actually does not have Fairbanks IA with a low of freezing or below for the next week, though two days have a low of 33F. Far be it from me to put much faith in this, but clearly this could go on for some time to come: since it almost certainly will not get to freezing in the next few days, this will be one of the latest of record, and continuing the now six year long streak of very late first freezes. The latest "first freezes" at Fairbanks IA are:

1. Sep 27 1974
2. Sep 25 2006
3. Sep 23 2009
Sep 23 1982
4. Sep 22 2010
Sep 22 1978
Sep 22 1973
5. Sep 21 2008
Sep 21 2007

More on No freeze

Continuing on the topic of first autumn freezes, here's a plot of the date of first freeze at Fairbanks Airport.



Obviously, the date of first freeze has not been consistently so late in September anytime in the past 60 years. Also note the increased frequency of very late dates since 1997. Suspiciously, this corresponds to the advent of the switch to the ASOS. However, this can only be (at most) part of the story, as this plot of the date of the first freeze at the College 5NW co-op site shows:



College 5NW is the longest climate time series we have for the Fairbanks area hills: it is about 450' MSL above Goldstream Creek. This is not quite an apples to apples comparison: in a few years the date of first freeze at the airport is from the temperature dropping to or below freezing in the late evening, while College 5NW has had an observation time around 8am for most of the period of record. Still, while College 5NW has sometimes had late dates through its period of record, the consistently late dates since 2006 again stand out as unprecedented.

Still no Freeze

It's a lovely morning for the Equinox Marathon, with temperatures around 40F for the start of the race. Runners have had to slog through snow on Ester Dome in some years, but not this one.

Between 1952 and 2005 the first freeze of the autumn at the Fairbanks Airport was September 20th or later five times (in 54 years). Since 2005, the first freeze has been September 20th or later EVERY autumn. The low temperature so far has been 36F, and both the overall pattern and numerical guidance suggests this year will continue that strong trend.

It's not just the airport either, as Fairbanks Midtown, University Experiment Station and UAF West Ridge Co-op sites have all yet to see a freeze, and none of the hill sites have been close to freezing. The cooler valley spots have of course, although the low of the season thus far at KJNP in North Pole (the oldest of the Co-op sites in the North Pole area) is just 29F.

Summer Arctic Sea Ice Minimum

It looks like the minimum Arctic Sea Ice coverage has been reached. The National Snow and Ice Data Center reports a coverage of 4.33 million square kilometers on September 9th, with coverage having increased slightly since then. Here is the Alaska-centric view from September 14th from the University of Illinois Polar research group. Notice how far beyond the coast the ice edge is:



If this is the minimum (and there is some chance that the coverage could yet decrease), this would be the second lowest of the satellite era and four percent above the minimum coverage of 2007. Here is the comparison from NSIDC:



The University of Bremen made the news earlier this week with the report that sea ice coverage was lower than 2007. NSIDC and Bremen use different procedures and datasets (the Bremen data has higher horizontal resolution than NSIDC). However, the main point is not whether 2011 was just above or just below 2007. The message is that summer and autumn sea ice coverage continues to rapidly decline and that 2007 was not some "fluke", the result of some rare combination of weather.

Pretty Evening

A pretty Monday evening at Chandalar DOT at Mile 239 Dalton Highway. Snow level is about 3500' MSL. Photo from the FAA.

What no sea ice means

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
240 PM AKDT MON SEP 12 2011

THE TEMPERATURE AT BARROW...THE NORTHERNMOST CITY IN ALASKA...
HAS NOT BEEN BELOW FREEZING...32 DEGREES...SINCE JUNE 29TH. THIS
74 DAY STREAK IS BY FAR THE MOST CONSECUTIVE DAYS THAT BARROW HAS
EVER HAD WITHOUT THE TEMPERATURE DROPPING BELOW FREEZING. THE
PREVIOUS RECORD OF 68 DAYS WAS SET TWO YEARS AGO.

THE TEMPERATURE IS NOT EXPECTED TO GO BELOW FREEZING AT BARROW FOR
AT LEAST A FEW MORE DAYS.

$$
RT SEP 11

This is a direct result of the pack ice being 150 miles north of Barrow and nearshore water temperatures in the 40s.

Autumn

A cloudy Saturday over most of northern Alaska.; polar orbiter image from NWS Alaska Region. Here in Fairbanks-land, rain and temperatures in the 30s and 40s. Snow level is above most of the terrain: at 3pm ADT temperature was 35F at both Munson Ridge (3100' MSL) and Caribou Peak (2500' MSL), 39F here at Keystone Ridge (1600' MSL). Rainfall amounts so far mostly in the tenth to quarter inch range. Combined with the golden foliage, it really seems like autumn, though warmer weather is on tap for early next week.

No urban heat island here

Here is the plot of temperatures for the past year at Eureka, Nunavat, from the Climate Prediction Center. Eureka is on the Fosheim Peninsula, on the north-central side of Ellesmere Island at 80N. Unlike other northern Canadian weather stations in the high Arctic, Eurerka is set back on a deep fjord, so has a less maritime climate that other sites. The middle plot shows the 30-day running mean, which smooths out the day to day variation in "weather", though as the top plot shows, temperatures have been monolithically above normal since early May.

Arctic Sea Ice Seond Lowest of Record

The National Snow and Ice Data Center has released their August analysis of sea ice cover in the Arctic. The mean ice coverage for the month of 5.52 million sq km is the second lowest of the satellite era (since 1979). There is the plot of NSIDC of the August mean coverage: the trend is stunning.



The press release also notes that as of September 5th the coverage had fallen below the minimums measured in both 2008 and last year, guaranteeing that 2011 is at least the second lowest minimum coverage of record. Here is the coverage plot for September 6th from the University of Illinois Polar Research group.



The ice melt season has about two weeks to go, and is certain to be very close to the 2007 record minimum. The implications for Alaska weather and climate are, of course, large. The fact that Barrow has not had a temperature of freezing or below since July 9th is directly attributable to the lack of near shore sea ice and the "warm" waters offshore (as of Seep 6th the NWS Anchorage Marine Ice program had sea surface temperatures of about +6C near Barrow).

Here comes ex-Talas

Here's the surface analysis for 10am ADT Monday from the Ocean Prediction Center. The 956 mb low southeast of Kodiak Island is the remains of tropical storm Talas, and is making for a pretty windy wet day on the Gulf coast. Kodiak has had gusts to around 50 mph and Middleton Island about 65 mph.

Update: As of 5pm ADT, Middleton Island has had winds 63 gusting to 78 mph. The Cape Cleare buoy (46076), a little southwest of Middleton Island has reported similar winds with seas of 26 ft.

Update 2: My old colleague Stu Ostro, who works as a Senior Meteorologist at the Weather Channel, pointed out to me that this storm is not really the remains of Talas, though some of energy may be from Talas. I hang my head. Still though, a deep storm for Labor Day.

Chilly Morning

Autumn is in full swing across Interior Alaska. Here's a photo from Livengood Monday morning (from the FAA) showing the golds of September.

It was completely clear Sunday night/Monday morning, with an aurora through in for good measure. Throw in a seasonable airmass and not much wind, and it's no surprise that Monday was the coolest morning thus far this early autumn, with a fairly widespread frost or freeze in the valley.

Lows reported thus far include:

Goldstream Creek: 25F
Chena Hot Springs: 28F
Woodsmoke PW: 28F
Eielson AFB: 31F
UAF West Ridge: 35F
Fairbanks Airport: 37F
Keystone Ridge: 41F

In the hills this was not the coolest night of the season; here on Keystone Ridge it was the coolest night in almost a month.

Talas Coming to Alaska

Tropical Storm Talas made landfall on southern Japan early Saturday and will move over the Sea of Japan later today. From there the storm will head north and then northeast, and will be a deep storm in the northern Gulf of Alaska by Monday evening. At the right is the 12UTC GFS forecast for 10pm ADT: a 958mb low in the Gulf of Alaska this time of year is quite unusual, but this is a way to do it. The storm will bring plenty of rain and wind to the coast. Here in the Interior, the main impacts will be to produce some wind and keep it reasonably mild. A bigger impact comes with the eventual evolution of the cyclone: ex-tropical systems historically give numerical models fits, especially in the mid range. So will this storm pump-up a ridge over western North America, or spin down in isolation over the Gulf? Time will tell.

Arctic Sea Ice update

Looks like the September 1st total Arctic sea ice coverage is now right at the coverage at this date during the record low 2007 season. Amazingly disturbing but utterly unsurprising. Image from the National Snow and Ice Data Center.

End of Summer

With the foliage now rapidly turning to autumnal reds and yellows, thoughts turn to the end of summer in Interior Alaska, and the question arises, are summers ending later than in years gone by? Of course, I have a chart for this question.

Since a couple of cool days does not autumn make, I've defined the end of summer as the last day in the season when the 7-day centered running mean is 55F or higher. From the plot at the left, it is clear that at least until very recently, there was no trend at all. However, the gray line is the 4 year running mean, and it has, just in the past few years, popped up to the highest value in the century of instrumental records. Through September 1, this summer is already beyond the mean date for the past 40 years, and if the forecast for the next few days works out, this will push this year's "end of summer" later still.

It is very tempting to pin this recent and dramatic change on the loss of sea ice near Alaska, though we need some modeling of this idea.

August Weather Summary

What I did on my vacation…

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1216 PM AKDT THU SEP 1 2011

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

...FAIRBANKS WEATHER SUMMARY FOR AUGUST AND A REVIEW OF THE SUMMER...

AUGUST WAS A FAIRLY CLOUDY MONTH WITH FREQUENT BUT MOSTLY LIGHT
RAINFALL. THE MONTH ENDED ON A DRIER NOTE THROUGH...WITH A STRING OF
RATHER SUNNY DAYS HIGHLIGHTING THE BEGINNINGS OF THE AUTUMN
COLORS AND A COUPLE OF LATE NIGHT AURORA DISPLAYS.

AT THE FAIRBANKS INTERNATIONAL AIRPORT...THE AVERAGE HIGH
TEMPERATURE IN AUGUST WAS 67 DEGREES AND THE AVERAGE LOW WAS 48
DEGREES. THE MEAN TEMPERATURE OF 57.2 DEGREES WAS 1.1 DEGREES
ABOVE NORMAL. THE HIGH FOR THE MONTH WAS 76 DEGREES ON THE 4TH AND
THE LOW WAS 40 DEGREES ON THE 8TH. THE COOLEST OF THE NORMALLY
COOLER OUTLYING AREA DID HAVE ONE OR MORE MORNINGS WITH FREEZING
TEMPERATURES...INCLUDING 27 DEGREES AT GOLDSTREAM VALLEY BOTTOM ON
THE 30TH AND 31 DEGREES AT WOODSMOKE...NEAR NORTH POLE ON THE
29TH.

TOTAL RAINFALL IN AUGUST AT THE AIRPORT WAS 1.60 INCHES...WHICH
WAS 0.28 INCHES BELOW NORMAL. SOME RAIN FELL ON 22 DAYS AT THE
AIRPORT...FOUR MORE THAN AVERAGE...BUT ON ALMOST HALF OF THOSE
DAYS THERE WAS JUST A TRACE OF RAIN. THE 12 DAYS WITH MEASURABLE
RAIN IS ONE DAY LESS THAN AVERAGE. THERE WERE THUNDERSTORMS IN THE
AREA ON SEVERAL DAYS DURING THE MONTH...THOUGH NONE WAS HEARD AT
THE AIRPORT. AS IS OFTEN THE CASE...RAINFALL WAS SIGNIFICANTLY
HIGHER AT NEARLY ALL OTHER WEATHER OBSERVING LOCATIONS IN THE
GREATER FAIRBANKS AREA. THESE INCLUDE...

AURORA.................1.96 INCHES...0.17 INCHES BELOW NORMAL
EIELSON AFB............2.04 INCHES...0.31 INCHES BELOW NORMAL
UAF WEST RIDGE.........2.18 INCHES...0.10 INCHES ABOVE NORMAL
NORTH POLE.............2.19 INCHES...0.17 INCHES ABOVE NORMAL
FORT WAINWRIGHT........2.35 INCHES
EAST FARMERS LOOP......2.43 INCHES
FAIRBANKS MIDTOWN......2.74 INCHES...0.62 INCHES ABOVE NORMAL
KEYSTONE RIDGE.........2.76 INCHES...0.36 INCHES ABOVE NORMAL

SMOKE FROM THE BONNIFIELD FIRE ON THE FLATS SOUTH OF FAIRBANKS WAS
EVIDENT ON SEVERAL DAYS EARLY IN THE MONTH.

FOR THE SUMMER AS A WHOLE...THE AVERAGE TEMPERATURE OF 59.8 DEGREES
AND TOTAL RAINFALL OF 5.07 INCHES ARE BOTH CLOSE TO NORMAL.
HOWEVER...EXCEPT FOR THE LAST WEEK OF MAY...THERE WAS A DISTINCT
LACK OF HOT WEATHER. THE TEMPERATURE REACHED 80 DEGREES OR HIGHER
NINE DAYS...BUT FIVE OF THOSE DAYS WERE IN MAY. THE HIGHEST
TEMPERATURE THIS SUMMER AT THE AIRPORT WAS 88 DEGREES ON JUNE
25TH. ACCORDING TO THE ALASKA FIRE SERVICE...JUST OVER 292
THOUSAND ACRES BURNED IN THE STATE THROUGH THE END OF
AUGUST...WELL BELOW THE AVERAGE OF RECENT DECADES. TWO FIRES
THOUGH THAT STARTED DURING THE WARM WEATHER OF MAY WERE OF MAJOR
CONCERN TO THE FAIRBANKS AREA....THE MOOSE MOUNTAIN FIRE ABOVE
GOLDSTREAM VALLEY AND THE HASTINGS FIRE NORTHEAST OF MURPHY DOME.

LOOKING AHEAD TO SEPTEMBER...THIS MONTH TYPICALLY FEATURES MILD
TEMPERATURES AND BRIGHT AUTUMN COLORS EARLY ON FOLLOWED BY A TASTE
OF THE WINTER TO COME BY THE LAST DAYS OF THE MONTH. THE AVERAGE
HIGH TEMPERATURE DROPS FROM 62 DEGREES ON THE FIRST TO 46 DEGREES
ON THE 30TH. THE AVERAGE LOW TEMPERATURE DROPS BELOW FREEZING ON
THE 25TH. IN THE LAST 106 YEARS...TEMPERATURES IN FAIRBANKS HAVE
RANGED FROM A HIGH OF 84 DEGREES IN 1957 TO A LOW OF 3 ABOVE IN
1992. PRECIPITATION AVERAGES 1.10 INCHES. MOST...BUT NOT
ALL...SEPTEMBERS SEE THE FIRST SNOW OF THE UPCOMING WINTER...AND A
SMALL ACCUMULATION IS NOT UNUSUAL DURING THE LAST WEEK OF THE
MONTH. TOTAL SEPTEMBER SNOWFALL HAS EXCEEDED SIX INCHES JUST FOUR
TIMES IN THE PAST CENTURY...BUT THREE OF THOSE YEARS WERE IN THE
1990S.

$$
RT SEP 11