Friday, December 7, 2012

Daytime High Temperatures


Weather the past several weeks over Interior Alaska has been dominated by surface high pressure, with clear skies much of the time. Also, during the past couple weeks winds have not been able to break through the inversion. As a result, temperatures have remained strong elevationally stratified. Here is a plot of daytime (7am-7pm) daily high temperatures (based on hourly data) since Thanksgiving Day at eight weather stations in the greater Fairbanks area. The stations are:

WODA2=Woodsmoke PWS (near North Pole), elevation 500' MSL
GCSA2=Goldstream Creek CWOP elevation 577' MSL
PAFA= Fairbanks Airport, elevation 435' MSL
FAOA2=UAF West Ridge, elevation 597' MSL
CLGA2=College Hills PWS (near the top of Baline Hill) elevation 751' MSL
NHPA2=Nenana Hills RWIS (Parks Highway between Fairbanks and Nenana), elevation 1398' MSL
KERA2= Keystone Ridge, elevation 1600' MSL
WICA2=Wickersham Dome, elevation 2230' MSL

The comparative gap in the middle is a function of the narrow elevational band that is intermediate between "valley" and "hill" and there happens to be few weather stations in that band (there is at least one other PWS, that is in the intermediate band at 1100' MSL, CW6333, but it has reported only a few days in the past two weeks). That is too bad because many of the residences in the "hills" are only a few hundred feet above the valley floor. 

10 comments:

  1. Hello Rick from Gary in Fairbanks. Discovered your WX Blog today and want to compliment you on the fine product. Been here almost 48 yrs working, recreating, and flying around the state, so weather has become a necessary hobby.

    I have many weather sites bookmarked that I read daily, but have yet to find one with this perspective. Your work, both here and up on the hill is appreciated.

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    1. Thanks for stopping by Gary.

      Rick

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  2. Why did CPC/NCEP's ENSO models shift so quickly to a cooler winter forecast for Alaska? I know the ENSO went neutral/cool water temps than expected. Any cause the change that you've come across?

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    1. Gary,

      Do you mean the December outlook from CPC?

      http://www.cpc.ncep.noaa.gov/products/predictions/30day/off15_temp.gif

      The final December-February outlook has increased chances of significantly below normal on the Gulf of Alaska coast and increased chances of significantly above normal on the North Slope, and no forecast in-between.

      I can't speak to exactly why CPC makes the forecast they do in any particular case, but in this case, for December, I would guess that 1) the short range numerical guidance showed the cold pattern locked in for the first week of December, 2) the Climate Forecast System version 2, which is a short-term numerical climate model has been doing quite well (not perfect) in the two to eight week forecast in this part of the world over the past year, 3) sea surface temperatures remain below normal along the northwest North American coast, which favors below normal temperatures near the coast and 4) ENSO neutral has no correlation with seasonal mean temperatures in this part of the world, so it is not a useful tool (i.e. other things potentially are more important drivers).

      Does this help?

      Rick

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  3. Thanks Rick for the fill. This summer/fall they predicted (via their predictive model suite) above normal temps for Interior/Northern Alaska per a weak El Nino.

    I watched it unfold until about October when they went ENSO neutral, and the models (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf) pp. 25-27 called for a colder regime change.

    I'm curious what changed. I assume it was the ENSO temps.

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    1. My sense is that it may have been some bleed over from the North Slope too, but the change in ENSO was probably a factor. Actually though, weak ENSOs, which is all that was ever forecast, do not have much correlation with Interior temps. It's the moderate to strong events that have a much better correlation.

      Rick

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  4. They discuss the current lack of "driver teleconnections" here: http://www.ncdc.noaa.gov/sotc/synoptic/

    Now to explain the persistent ridging over northern Alaska. I read somewhere (?) it may be due to warmer ocean temps lingering into winter. An effect of Global Warming?

    Before I drive you completely mad I'll leave it at that and enjoy your Blog

    Gary

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    1. ENSO neutral would be a "lack of driver teleconnections", teleconnections being nothing more than reoccurring mid-level flow patterns.

      I'm suspicious (in general) of ascribing large scale patterns, which is what the persistent ridging has been to local causes without a solid physical mechanism. So increased intensity of summer storms in the Arctic can be directly tied to the declining summer sea ice. However, sea surface temps have been normal across the Arctic until the past few weeks but the ridge has been strongly centered along the dateline. I'll post the graphic.

      Thanks for reading,

      Rick

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    2. Gary, in looking at the anomaly plot I need to rethink my previous statement. That's a huge area of significant positive anomaly across nearly the entire Arctic.

      Rick

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  5. Whenever I see one or more "H's" rimming the northern continental coastal boundaries in winter I turn up the house heat and check the jetstream progs. Seems like the H's keep the warm air to the south at bay, and if the upper air flow ~300 mb can't penetrate the H-wall, or slows, loops, flows over Siberia, and drops over us...well I'm glad I turned up the heat.

    I can see the cold Siberian H forming over Yakutia. But why have they formed so strongly (it seems) recently in November over North America?

    All I remember is the fall/winters of 1975 (cold), and 1976 (in contrast amazingly warm). Even the old timers remarked how unusual it was at the time.The PDO was active of course. Now with the Internet's resources, I like to look for driving mechanisms as an amusement.

    I'm not a meteorologist, but like many in Interior Alaska, weather affects my life in many ways.

    Gary

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