Strongest –PNA on record beneath a historic cold polar vortex causes record West U.S. cold in February. Related to solar minima?

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The cold and snow in the West U.S. is becoming extreme. HDD projections indicate a colder February than 1989. A likely historic negative phase (for February) of the Pacific North America index is partially to blame.

Discussion: The West U.S. cold is increasingly extreme and favored to remain so through most of February. The projected HDD for Seattle (820), Portland (795) and Sacramento (530) each exceed the previous cold (since 1980) set in 1989 (Fig. 1). Burbank FEB-19 HDD is projected at 345 falling just short of the 2001 cold (353). The super cold is blamed on what may be the strongest negative phase of the Pacific North America (PNA) index (since 1950). The FEB-19 PNA is projected at near -2.0 (Fig. 2) exceeding the previous record 0f -1.86 (1990).

Fig. 1: The West Coast is in for one of the coldest February’s on record. Seattle, Portland and Sacramento eclipse the previous coldest HDD month (1989). Burbank is just shy of the 2001 HDD record for February.

Fig. 2: February 2019 is likely to produce the strongest negative phase of the Pacific North America (PNA) index in the 1950-2019 climatology. –PNA patterns are correlated to cold upper troughs over western North America.

Of interest (concern?) is the potential coldest high level polar vortex on record in early February (Fig. 3). Temperature anomalies approach -30K at 10 MB (about 19 miles above earth surface). As stated by climate scientists late last month speculated is a piece of the polar vortex has broken from its core and descended through the atmosphere bringing historic cold to the Midwest last week and the West U.S. this week and shortly Russia.

Fig. 3: Possibly a record cold polar vortex to begin February 2019.

A likely cause of the super cold polar vortex is the re-entry of the 11-year solar cycle into solar minimum (Fig. 4). The previous solar minimum mid-to-late last decade was unusually intense and lengthy in duration. The following solar maximum in 2012-14 was choppy in character about one half the strength of the previous 10 solar maximum’s dating back over 1 century. In 2019 an intense solar minimum has returned. Speculated by some scientists is a possible Daulton Minimum observed in 1800-1830 when an inactive sun was present.

Fig. 4: Solar cycle of the past 10 years.