Wednesday, February 02, 2011

Cold Forecast By ECMWF Definitely More Accurate Than GFS!

Chicago Lake Shore Drive during "rush" hour last evening - credit: Brian Cassella, Chicago Tribune.

Photo at top just one of many from the Midwest last evening and this morning of the show-stopping blizzard.
Last Saturday I noted in a post that the ECMWF 120-hour forecast for 1200 UTC tomorrow morning was much different than, and VERY much colder than, the NWS GFS forecast for same time. That ECMWF forecast is playing out to have been much more accurate, perhaps even a bit conservative, as very cold air overs the West this morning (Wednesday February 2nd). It looks as if the 120-hour GFS forecast may have missed the 1000-500 mb thickness near Tucson for tomorrow morning by around 250m! The middle two panels show the NCAR RAP analyses of the 1200 UTC observations at 500 mb and 850 mb this morning. The 500 mb height analysis indicates a closed low near the Four Corners, while the observed winds indicate an open short-wave still, with temps of -38C near Grand Junction (note the very cold surface temperatures in northwest Colorado). The 850 mb analysis captures the extreme temperature gradients over the Southwest. Coldest arctic air remains east of the Continental Divide, but it is also spilling southward from the Great Basin. A weak inverted trough still extends south-to-north just along and west of the Continental Divide. The weakening, blizzard cyclone in the Midwest is now centered near Detroit.
The 7 am surface data plot from NCAR RAP is the bottom graphic - one of the more wintery charts I've ever seen for Aziona and New Mexico. Observations of note: Guadalupe Pass, Texas, -2F with snow and east-northeast wind gusts to 41 mph; El Paso and Deming, New Mexico, both 9F with snow; Nogales, Arizona, 17F; here at house 7 am temperature was 20F (looks like low was 19F a bit after 7 - airport was still dropping at 8 am with 26F). Will tomorrow morning bring all time record lows?

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