Sunday, September 15, 2013

September 1992…Round One Done

By late on September 15th, the snow was pretty much done in Fairbanks-land. There were widespread power outages as the heavy snow bent and brought down trees across power lines.
The rapid evolution of the upper level pattern can be seen in the 12 hourly 500mb height and anomaly plots from the NCEP/NCAR reanalysis (4pm AKDT Sep 14, 1992 right, 4am Sep 15 center, 4pm Sep 15 right):

NCEP/NCAR Reanalysis 500mb Heights & Anomalies 00Z Sep 15 (left), 12Z Sep 15 (center) and 00Z Sep 16, 19 (right)

The deep cold low that had been north of Barrow two days below sent one piece of energy southeast across the northern and eastern Interior, with a second center remaining in the Beaufort Sea.This resulted in rapid end to the precipitation over the central Interior during the day on the 15th.

The snowfall amounts from the 12th through the 15th were truly remarkable in the central Alaska Range and also in the Fairbanks area:
  • Denali National Park Headquarters: 38.1"
  • Healy coop: 24"
  • Two Rivers coop: 17.8"
  • Fairbanks IA: 16.8"
  • College 5NW coop: 16.4

Here are a couple of plots of most of the snowfall amounts and liquid equivalents I could find, done shortly after the event. The locational plots are primitive but it's what we had to work with in 1992:
A few comments: the site labled "Goldstream is actually the College 5NW cooperative observation, and the snow amount at Eielson is too high because the observers were doing hourly snowfall measurements (this happened there throughout the early 1990s). The amount at North Pole is probably slightly too low. Note that the 10" at Chatanika though is real: there was definitely  less snow there. The site labeled 9NE is the only higher elevation observation available, unlikely the heavy snows in May 1992, this one in the Fairbanks area did not have much elevation dependency. The impact of the warm air push on the 13th is evident at Nenana, where some rain fell on the 13th, so overall there was much less snow with far more liquid.

Here's a similar clunky-looking plot from the time for the Delta Junction area:

Here the main item of interest is the dramatic drop-off in precipitation south of Fort Greely. The accuracy was of these observations were confirmed at the time with the met team at Fort Greely, who reported at the snow on the ground south of Bolio Lake went to very little in just a couple miles.

1 comment:

  1. Rick,

    Remarkable and fascinating - thanks. It's interesting that the snow:water ratios were pretty high, over 15 at some Fairbanks-area locations. In the lower 48, out-of-season snows with marginal temperatures tend to have low ratios, usually under 10 ... wet heavy stuff.