Friday, April 17, 2015

Cold Morning In Spots

Another morning illustrating the difficulties in forecasting low temperatures across a region with complex terrain. Above plot is from MesoWest and shows some of the reported 24-h lows ending at 8:00 am MST this morning - the range in the lows on plot spans 27 F. Here at the house the low fell to 28 F (second coldest morning since back in January). At the observations page on the NWS site I found an additional 6 stations with lows of 32 F or colder - coldest at the RAWS site on Mt. Graham (Columbine) with 19 F. The NWS grid box forecast for where the house is was for 45 F - pretty good for spots a km or 2 north and south of here but way off for the Rillito Wash. I suspect that the algorithms used to adjust the model forecast temperatures for the grids are not very sophisticated - but it's hard to find any technical details.

1 comment:

  1. Anonymous5:41 PM

    Really...a 28F low? That's the most surprised I've been on your low ever, even colder than the usually coldest spots in SE AZ in Cochise County! 45 is my estimate here by UTEP, but 32 most everywhere from Las Cruces W and N.

    I'm not sure an algorhythm can be developed for your area on such nights.

    Is your palo verde tree in bloom, or does that shock it some?