Monday, December 26, 2011
A Clear Boxing Day
Skies cleared in the Fairbanks early Monday morning, allowing for strong valley cooling. Here is the NOAA-19 polar orbiter infrared image taken about 4am AST Monday, courtesy of the NWS Alaska Region, showing the clear skies and cold valleys in the middle Tanana valley. Temperatures cooled 20+ degrees in the valleys, while in the hills temperatures fell only a few degrees. At 10am Monday, Fairbanks area temperatures vary from the mid 20s below in the cooler valley spots to 0 to 5 above at higher elevations. Here on Keystone Ridge (1600' MSL), the top of the inversion is close by, with temperatures mid-morning swinging between -4F and +3F in a matter of minutes.
My post from last Wednesday, Winter to Return, demonstrates the difficulties the numerical models have been having recently. On Wednesday both the GFS and the ECMWF, two major mid-range models were both forecasting deep cold by Monday (today). As it turned out, the observed 1000-500 mb thickness this morning at Fairbanks was 5038 gpm, an error of nearly 120 meters. That is a very large error and the result is temperatures zero to 20 below instead of 20 to 40 below.