Highlight: 12Z GFS delivers a cold 6-10-day forecast into the East AND lingers the chill days 11-15.
Fig. 1-2: 12Z GFS medium-range temperature anomaly forecast.
Discussion: The midday 12Z GFS maintained an unusually cold pattern across eastern Ontario/western Quebec extending to the Northeast U.S. in the 6-10-day forecast (Fig. 1) while (also) keeping the West warm. The eastern chill is well-supported by a strong negative phase North Atlantic oscillation (-NAO). In the 11-15-day forecast, the model is much cooler Central and East U.S. (Fig. 2). To validate the much cooler change, the -NAO pattern needs to extend through the 11-15-day period which is not indicated. Consequently, the 11-15-day forecast is too cool although early in the period the cool pattern lingers.
A pattern change is indicated next week in Europe. For 2-3 weeks Europe has been mostly mild and very dry while the Black Sea region (including Ukraine) cold and snowy. Next week, the Scandinavia index flips negative and a ferocious upper trough pushes much cooler air across the northern half of Europe coupled with an impressive storm track across U.K. and into Western Russia including Ukraine (Fig. 3).
Springtime severe weather is most plentiful and intense when the Gulf of Mexico is warmer than normal. Currently, the northern and western Gulf have cooled-off while the southern half of the Gulf is somewhat warmer than normal (Fig. 4). The Gulf has warmed slightly during the past 7 days.
At midday the 12Z GFS gas population weight HDD forecast indicated slightly colder forecasts for late March/early April (Table 1).
Fig. 3: Pattern change ahead for Europe/Western Russia next week.
Fig. 4: The current sea surface temperature anomalies across the Gulf of Mexico.
|Dates||HDD Forecast||12-Hr Change||24 Hours Ago||10-Year NML||30-Year NML|
Table 1: The 12Z GFS U.S. population weight HDD forecast compared to 12 and 24 hours ago.