Thursday, November 20, 2014

A Little Cooler

The air mass over interior Alaska has cooled some in the past few days, but above-freezing temperatures still persisted at about 1100' above Fairbanks in this morning's balloon sounding.  Every sounding since 3pm on November 8 has recorded above-freezing temperatures aloft, which is the longest stretch on record in the winter months of November through March.  The new record of 26 consecutive above-freezing soundings compares to 25 straight in late March 1998; the previous November-February record was 21 straight soundings.

The above-freezing temperatures have come to an end (for now) at 850 mb and 925 mb, and November-March records were easily broken at both levels for the duration of the warmth; here are the top events in the 1948-present history:

850 mb:
16 soundings ending 3 am Nov 19, 2014
12 soundings ending 3 pm Jan 28, 2014
12 soundings ending 3 pm Jan 6, 1995
12 soundings ending 3 pm Feb 16, 1980

The 850 mb record also ties the November-April record (16 soundings ending 3 pm April 27, 1994).

925 mb:
20 soundings ending 3 pm Nov 19, 2014
16 soundings ending 3 pm March 25, 1998
15 soundings ending 3 am Jan 30, 2014

Here's a time-height cross-section of the temperature departure from normal since October 1 in the lowest 3 km; the magnitude and persistence of the recent anomalies are, to say the least, striking.

I'll note here for future reference that the Chena and Tanana rivers still show a considerable quantity of flowing water, which is remarkable for the date.


  1. Ducks everywhere too. They still fly from the open rivers to the University's fields of standing grain daily to feed. They are particularly abundant in the field east of the Georgeson Botanical Garden below the Butrovich Building. We have to enjoy it while it lasts.

    But folks in rural Alaska need ice and snow to travel, gather firewood, and trap fur bearers. That'll happen soon enough.


  2. Do we have dates when any river totally freezes over? Is this possible? I'm still amazed that the Chena downtown hasn't frozen over as that cam capture shows. Especially with the Chena freezing over where I live near the airport.

    1. Eric, There is a freeze-up database on the APRFC website, but I haven't explored the data. There must be a certain amount of subjectivity in the dates because as you note the early ice coverage can vary greatly depending on location.

      I wonder if high streamflows from the excessively wet summer are delaying freeze-up compared to normal.

    2. Good suspicion regarding the summer's rain impacting flow in the water table. I'm not sure where to look, but here's one source.

      Look and select a year's worth of info for soil moisture in the upland and floodplain datasets:


    3. I meant to add soil temps (particularly at 200cm) as well...just select that option.


    4. I found the following database for Chena River streamflows.

      It appears the October 1-20 mean flow was 2140 cf/s, compared to a long-term normal of 1190 for the month of October and 2160 for September.