Sharp Negative Phase North Atlantic Oscillation/Scandinavia Index

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Fig. 1: Negative NAO and Scandinavia Index propel Northeast U.S. storm and following cold plus Eurasia chill.

Fig. 2-3: 12Z GFS temperature anomaly forecasts for the medium-range with annotated highlights/changes.

Discussion: The negative North Atlantic oscillation (-NAO) is impressive…surging toward -3.00 later this month. Implied is storminess and following cold into the East. The 12Z GFS has less of a storm for next week in the Northeast. However, the -NAO pattern is sufficiently strong to foreshadow another intense storm forecast by ECM later this afternoon and the GFS returning to that solution and a possible second storm last weekend of the month. The Scandinavia Index drops to -4.00 to -6.00 which indicates an unusually cold trough for Northwest Eurasia which will include cold temperatures and snow for that region. The (very) warm West U.S. forecasts have been too warm.

Of note at 12Z is the returning colder HDD values for Nov. 26-Dec. 2 now very close to normal after yesterday’s brief warmer change.

DatesHDD Forecast12-Hr Change24 Hours Ago10-Year NML30-Year NML
Nov. 12-18118.4-0.6118.1130.4129.2
Nov. 19-25147.4-1.9153.5143.9145.2
No. 26-De. 2151.0+8.3139.5154.9160.6

 Table 1: The 12Z GFS gas population weight HDD forecast compared to the 30-year/10-year normal and 12 and 24 hours ago.