climate, weather

Arctic Air Arrives (H. Michael Mogil, CCM, CBM, NWA-DS*)

Apologies to my readers. In my haste to publish this pre-Christmas, I inadvertently omitted the all-important figures. They’ve now been included (1/2/18).

It’s time to kiss the autumnal warmth of the past few weeks across the Central U.S. goodbye, as arctic air arrives in the U.S. with a vengeance. For example, Minneapolis, MN has averaged 5.4 degrees above average through the 22nd of the month, with at least 6 days in double-digit warmth. That is slated for replacement with temperatures some fifteen to twenty degrees below average, including a forecast average of ZERO on Christmas Day.

Tulsa, OK offers similar testimony. After averaging some 6.7 degrees above average through the 23rd of this month (with 9 days in double-digit warmth), look for readings to tumble to some 5 degrees below average this coming week. After New Year’s, an even colder air mass could invade the Central U.S and even the southern Plains.

This transition is linked to a change in the upper level wind pattern from “zonal” (more west to east) flow to “high amplitude” (north and south) wind currents (Fig. 1 and Fig. 2). Notice, in Fig. 2, the formation of a “polar vortex” over Hudson Bay and a wind flow source region from north of the Arctic Circle.

© 2017 H. Michael Mogil

Originally posted 12/24/17; updated 1/2/18 (added omitted figures)

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.