Thursday, November 13, 2014

Exceptional Warmth

The intense high-pressure ridge over northwestern North America has brought extremely unusual warmth to interior and northern Alaska in recent days.  In Kotzebue, which has been much warmer than normal for most of 2014, the temperature hasn't been below freezing since Sunday - this will probably be the fourth consecutive day with a minimum temperature at or above 32 °F.

In the context of the historical data, this is remarkable.  It's unusual to see any day in November (or December) with a minimum temperature of 32° or above; there have only been 15 cases since 1930 prior to this year, and all but four of these were before November 10.  The only remotely comparable event was in 2003, when the first 5 days of the month remained at or above 32 °F.

Extreme warmth has also been seen at McGrath, where the temperature reached 50 °F yesterday; this breaks the all-time record for November.  Previously the latest date in the year that 50 °F was observed was October 22, 1980 - more than 3 weeks earlier in the year.  Judging from the FAA webcam image this afternoon, there is little or no snow cover left at McGrath.

The upper-level high pressure system is the dominant feature in this morning's 500 mb analysis, see below.  The 500 mb height and temperature at Fairbanks were measured at 5670 m and -16.5 °C, both of which are above the normal values for the peak of summer.  Remarkably, the 1000-500 mb thickness was 5502 m, which is the same as the normal value in late June or mid-August; so it is no exaggeration to say that the average column temperature in the lower half of the atmosphere is as warm as in summer.

The evolution of the temperature profile in the past several days over Fairbanks is shown below.  Today's 850 mb temperature of +9.0 °C is the highest on record for November, and the temperature of +10.0 °C at 3900' AGL is the highest temperature measured at any level in a Fairbanks sounding between November 2 and January 14 inclusive.

Update November 14: Yesterday afternoon's Fairbanks sounding recorded even more impressive warmth, with the 850 mb temperature reaching 9.8 °C and a new all-time high freezing level for the winter season (November-March).  The 500 mb height reached 5690 m and the 1000-500 mb thickness was 5530 m.


  1. Thanks for this incredibly informative blog, it's like crack for weather-obsessed geeks (such as myself). Regarding your latest post about the recent dramatic, unprecedented warmth. This seems actually quite frightening to me. Does it strike you the same way?

    1. Thanks for reading. I certainly didn't intend for the information to come across as alarming, so I apologize if that was the effect. Personally I find this event fascinating, as with all extreme weather; and it provides the impetus for many lines of scientific inquiry.

  2. Richard,

    I know there was discussion in the media last year about the recent tendency of blocking to set up in the long wave pattern (polar vortex, blah blah blah). No report I saw really illustrated if there has actually been a historical shift toward more blocking. Have you looked at any datasets that might suggest if this is happening? I know that El Nino and positive-phase PDO promote a deeper Aluetian low and ridging over western Canada, and the resulting warm advection into Alaska, but the event we are seeing is remarkable both for the intensity and the duration.

    1. Andy,

      There is debate in the scientific community about the magnitude and significance of changes in blocking. It seems the answer might depend on how you perform the analysis; there are many ways of looking at the problem. Here's a brief summary of the issue from UAF's John Walsh:

      Here on the blog, I looked at changes in the frequency of cut-off lows and highs:

  3. I am new to the blog, and first wanted to express my gratitude for the effort it takes on your part for its existence.

    Although in a former life I was directly involved in what used to be termed "synoptic meteorology" at both the instructional and research levels, I no longer have the time to investigate daily evolution of the global atmospheric environment. This is one of the reasons I appreciate your blog so much.

    In that light, if you'll please forgive what might seem obvious to anyone else that is not looking at this from a cold start, what role did Nuri play in pumping the "climatological" (climatological in terms of temporal scales - and in a mean sense, the spatial location as well) ridge within a background set-up by this season's PDO warm event-appearing SST anomaly pattern (realizing of course the PDO operates on time-scales of several decades rather than single seasons)?

    1. David,

      Thanks for reading. I very much enjoy putting together the blog posts and wish I had more time to do more serious research! I feel like we just scratch the surface of every issue we look at.

      Your question about building the ridge appears similar to reader Gary's question earlier in the week, so I'll direct you to the comments on last Saturday's post:

      Let me know if this isn't clear.

    2. Thanks Richard. Sorry for the redundancy in my question. My cold start is now warning up!

  4. The inconsistencies in Los Angeles weather are evident, when it is 113°F yesterday in Downtown (110.8°F here in Monrovia) and today we did not even break 100°F and now have a chance of thunderstorms. Only in Southern California!

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