Late summer sunshine

A lovely last day of August at Arctic Village, from the FAA webcam

Return of the Inversion

I was outside at 1230am Sunday and the sky was filled with stars; just a band band of light on the northern horizon (one of the many benefits of outdoor plumbing). Weather-wise, this can only mean one thing: the return of the inversion.
On the left is the temperature plot from the 3AM upper air sounding from Fairbanks, showing a 6.4ºC temperature increase in the lowest 300 meters. The spread in morning low temperatures is of course wider. Lows include: 26ºF at the Salcha River RAWS, 29ºF at the Angel Creek RAWS. 30ºF at Goldstream Creek Co-op, 32F at the Woodsmoke (near North Pole) PWS, up to lows of 50ºF at Clearly Summit and the Nenana Hills RWISs and 48ºF here on Keystone Ridge, making it one of the mildest overnight lows of the month.

Sea Ice Updated

All eyes are on Hurricane Irene now, but here's a quick update on Arctic sea ice coverage, from the folks at the National Snow and Ice Data Center, and as usual, the news isn't good. As of August 25th, total sea ice coverage is just barely above the record low year of 2007. What's interesting about this is that the atmospheric conditions this summer have not been a repeat of 2007. There have been times that it has been similar, but others when it has not been. This shows the impact of the now much thinner ice than was in place in 2007.

Late Season Thunder

There were about 170 lightning strikes in Interior Alaska on Monday, which is a lot for this late in the season. In fact, some of the cells were producing lightning til well after midnight. Here's the view from west ridge of UAF looking southeast about 910pm Monday.

Pot of Gold Found

A 9pm ADT Monday from the FAA webcam at the Ruby airport. Ruby is along the Yukon River about 25 miles upriver from Galena.

It's a Soaker

Fairbanks-land enjoyed a classic August weekend, with something like 3/4 of an inch of rain spread over Saturday and Sunday. The rain was over a long enough duration that it will not impact rivers much. Here's the hydrograph for the upper Chena River (near Mile 40 Chena Hor Springs Road) from the Alaska-Pacific RFC.

There was enough rain to bring monthly totals up to about normal. However, the number of days with rain since late July is above normal, hence the widespread perception that it has been unusually wet.

Close but no Cigar

The mean Sea Level Pressure at Fairbanks bottomed out at 982.1mb at noon ADT Saturday, 1.2mb above the record low pressure for August.

Deep Storm in the Gulf of Alaska

A fairly deep storm for August is churning through the northern Gulf of Alaska. The 330pm ADT GOES infrared image shows a classic cloud structure to the system, with well defined warm, cold and occluded fronts. Unlike most Gulf storms, this one is forecast by all the numerical models to maintain fairly deep pressures as it crosses the Alaska Range on Saturday. In fact, Fairbanks will approach its lowest August sea-level pressure of record on Saturday of 980.9 mb (28.97 inches) set August 5, 1984.

Fire Weather Season About Over

Damp, if not soaking weather persists over most of Alaska, and more than 200 lightning strikes Wednesday not withstanding, the fire season is about over.

According to the Alaska Fire Service, thus far a total of 292,440 acres has burned in Alaska this summer. This number has not changed (or at least been updated by AFS) for more than a week. This is about 27% of the acreage burned last summer. While not the lowest in recent years, it is well below the 20 year median of 681,000 acres.

Like last year, this year was a classic example of how the fire season in Alaska is so completely dependent on warm AND dry weather. Much of Interior Alaska was not especially wet this summer, but after mid-June there was no period of more than a couple days of dry AND warm weather. Here is a plot of the mean July 500 mb height anomalies:



Over land, lower 500mb heights in the summer correspond pretty well with cooler than normal temperatures. This is just what we see over Alaska. A big negative anomaly near the Bering Strait, but with below normal heights extending eastward.

Now here's the same plot for July 2009, which was one of the warmest and driest Julys of record over Interior Alaska, and a big fire year:



A much different picture over Alaska.

Signs of Autumn

Signs of autumn are starting to show in the vegetation. Here's a photo of the front yard Tuesday afternoon. The dogwood has gone purple and the Spiraea is turning yellow and red. Not much color in the birch and aspen yet but it will not be long.

Oh yeah, yesterday was the first day since July 23rd with zero precipitation here at Keystone Ridge. The 23 days is the longest streak of consecutive days with some precipitation in 15+ years of record here. However, total rainfall during this time was only slightly above normal. A lot of days with trace, 0.01 or 0.02 inches of rain. Output from the solar panels though is way down from the past few years.

Arctic Ice Update

Here's the Alaska-centric view of sea ice coverage in the Arctic as of August 15th. As as been the case for a couple weeks, this summer's coverage is just above the record low year of 2007. There is about another month of retreat left; it looks certain that this year will have either the lowest or second lowest summer ice minimum coverage in the satellite era (since 1979).

Soaker in Denali

The western half of Denali National Park has received a lot of rain in the past couple days. Eielson Visitors Center as received 2.53 inches of rain since late Friday night.
Other amounts include:
Kantishna: 1.60 inches
Toklat: 1.40 inches
Wonder Lake: 1.17 inches

Even this much rain does not normally produce flooding problems in the Park. Freezing levels are lowering and as of Sunday morning are down to about 4500' MSL.

Update: steady rain has ended, as this photo from the NPS at Wonder Lake shows

Snow on the Mountains

I was in Tok Wednesday and Thursday: grey and rainy. Snow level about 5000' MSL Wednesday, and a bit lower Thursday. This photo is of the Sheep Mountains from just east of the Robertson River rest stop on Wednesday.

Warm Weather Frequency

With the Tanana Valley Fair in full swing and a bout of cooler weather the last few days, it reminds me of how quickly temperatures drop off in Interior Alaska, climatologically speaking.

Here is a plot of the frequnecy, by week, of daily high temperatures of 75F or warmer (Data 1905-2010). There are a couple of interesting things here. First, from late May to late June there is a basically linear increase in the frequency, then a plateau the first half of July. The decline is not quite so linear from mid July to early August, but close. Thereafter days with high temperatures 75º or warmer become increasingly unusual. The latest date with a temperature so warm is Sept 21, 1995 during a spectacular chinook.

Fresh Snow in the Brooks Range

FAA webcam photo from Chandalar DOT camp on the Dalton Highway at 1220pm Saturday. Looks the fresh snow level is at about 4500' MSL.

It was NOT 97 degrees at Northway in July

Okay, I guess have have to say this: It was NOT 97 degrees at Northway in July.

There is a news story going around about record highs in all 50 states in July, including 97F at Northway on July 11th. 97F would be an all-time record high for Northway.

Except that the high temperature on July 11th at Northway was 77F.

The 97F high temperature was encoded in an observation, but the temperature sensor was bused (probably the aspirator fan failed). The FAA observers did correct the daily max temp after the original observation went out to the world.

Other high temps that day were in the upper Tanana Valley region were in the upper 70s and lower 80s.

Moral of the story is the same as always: constant vigilance.

Not Much Frost

Skies were never able to clear overnight so there was not much in the way of freezing temperatures in the Fairbanks area. The low at the airport was 44F, but even Goldstream Creek only got to 36F, which is nothing for there (they had 4 days in July with a min temp of 32F or less). Eielson AFB also got to 36F. The coop site at Mile 42 Steese Highway did report a low of 30F. To the north of Fairbanks there were less clouds, and Livengood RAWS reported a low of 28F, and 31F at Seven Mile, just north of the Yukon River on the Dalton Highway.

Now That's a Front

You say it must be getting on towards autumn when Rick starts putting up upper air plots? Well…

A well marked but essentially dry cold front moved through the Fairbanks area Friday mid-morning. We don't often see temperatures this time of year cooler at the surface at 3pm than at 3am in the absence of rain. The 850mb temperature was right at freezing at 3pm, not quite a record but still impressively cool for the first week of August.

Early August Sea Ice

According to the analysis of Arctic Sea Ice coverage by the National Snow and Ice Data Center, ice coverage for July was the lowest of record, even lower than 2007. However, during the last couple weeks of July the rate of ice loss decreased, and as of August 3rd the total coverage is no longer lower than the same date in 2007.



This is potentially good news, but the slower loss may not last. Figure 4 of the analysis, below, shows that there is a lot of first year ice that is still vulnerable to loss in the six or seven weeks that remain of the ice loss season.

Darkness

2am Thursday in Fairbanks: darkness at night, a novel idea.

Wind Clouds

Pretty view of lenticular clouds from Delta Junction Wednesday evening. Surface winds gusted to nearly 50 mph at Fort Greely on Wednesday, which is pretty unusual for this time of year even in Delta.

July Narrative Summary

Public Information Statement
National Weather Service Fairbanks Ak
1211 Pm AKDT Mon Aug 1 2011

...Fairbanks Weather Summary For July...

Weather in July was fairly typical for an Interior Alaska mid-summer...with no extremes of temperatures. Rainfall…as is often the case this time of year...was highly variable.

At the Fairbanks Airport...the average high temperature was 71 degrees and the average low was 52 degrees. The average temperature of 61.8 degrees was 0.7 degrees below normal. The highest temperature for the month was 81 degrees on the 22nd. the low for the month was 45 degrees on the 17th and 20th.

Rainfall was highly variable in the area. At the Fairbanks Airport...the total July rainfall was 1.70 inches...almost exactly the normal of 1.73 inches. Measurable rain fell on 16 days during the month...three days more than normal. Thunder was hear at the airport on three days in july...which is also about normal. However...Eielson AFB measured monthly rainfall of 1.39 inches...just barely half of normal. In contrast…the College Observatory cooperative station on UAF West Ridge recorded 2.18 inches of rain in July…which is a tenth of an inch above normal.

Other July rainfall totals include...

University West..........2.84 Inches
Aurora.........................2.68 Inches
Goldstream Creek.......2.63 Inches
Gilmore Creek............2.12 Inches
East Farmers Loop.....2.01 Inches
Keystone Ridge...........1.90 Inches
Fort Wainwright..........1.33 Inches
North Pole..................1.31 Inches
Salcha River At Bridge...0.95 Inches

Much more rain fell in the uplands well east of town...which caused the Chena and Salcha rivers to rise to near flood stage on July 6th. The cooperative weather station at 43 mile Steese Highway recorded 5.53 inches of rain for July...while the automated station near Angel Creek in the upper Chena basin recorded 4.83 inches. Along the Salcha River...an automated gauge about 20 miles above the bridge recorded 4.54 inches of rain.

A couple of wildfires started mid-month on the flats south of Fairbanks...and the Bonnifield #1 fire grew to over 6000 acres by months end. This fire brought smoke at times to the area...which
on a couple of days was thick around North Pole and Eielson AFB.

Looking ahead to august...normal temperatures start to decline noticeably. The normal high temperature falls from 70 degrees on the first to 62 by the end of the month. Normal low temperatures fall from 51 degrees on the first to 43 on the 31st. In the past 106 years...august temperatures in Fairbanks have ranged from a high of 93 degrees in 1994 to a low of 21 degrees in 1922. Low lying areas usually have the first frost of the season in August.

Normal rainfall is 1.88 inches. Snow is very rare at valley level in August...though it has occurred a few times. Accumulating snow has occurred in town just once in August. On August 29th
1922...three inches of snow accumulated in Fairbanks.

Possible sunshine declines by more than three hours...from over 18 hours on the first to less than 15 hours on the 31st. Darkness returns to Fairbanks skies for the first time since late
April...and the first northern lights of the season at often spotted during the last ten days of the month.

$$

RT Aug 11