Executive Summary: Winter 2017-18 wind was driven by a weak La Nina which opened the door for non-ENSO climate influences including stratospheric warming causing a January arctic outbreak followed by a powerful Pacific Madden Julian oscillation bringing high wind to California and causing record warmth downstream east of the Continental Divide. The strongest anomalous monthly wind regime of the 5-month period was across Florida in January and California during California. Normally, highest anomalous wind speeds would extend from northern California to the Upper Midwest U.S. during a La Nina winter.
November 2017 wind: A strong Pacific jet stream enabled anomalous high wind speeds in the Coastal Northwest while high pressure to the south lent lighter than normal wind in California. Wind across the far northern U.S. were stronger than normal.
Fig. 1-2: U.S. average wind speed and wind speed anomalies observed in November 2017.
December 2017 wind: A mild pattern was beginning to break down later in the month. Highest wind speed compared to normal was across the Midwest U.S. growing stronger late month as arctic air began to pool in Canada and started delivery to the Midwest/East-Central U.S. after Christmas.
Fig. 3-4: U.S. average wind speed and wind speed anomalies observed in December 2017.
January 2018 wind: Above normal wind speeds affected most of the East due to frequent surges of arctic air from Canada followed by mild strong Pacific influence later in the month. Interestingly, Florida observed an unusually windy month. The Northwest was windy while southern California winds were lighter than normal, typical of La Nina. La Nina was in the mature phase.
Fig. 5-6: U.S. average wind speed and wind speed anomalies observed in January 2018.
February 2018 wind: Madden Julian oscillation intensified in the equatorial Pacific Ocean propelling an El Nino-like climate across the U.S. for late winter. Very windy conditions emerged in California. The strong Pacific influence lost its moist character crossing the Rocky Mountains and warmed east of the Continental Divide causing breezy and mild weather to finish winter.
Fig. 7-8: U.S. average wind speed and wind speed anomalies observed in February 2018.
March 2018 wind: A polar vortex pattern emerged due to another stratospheric warming event. Above normal wind speeds were observed along the southern periphery of the polar vortex from the Continental Divide east to the Mid-Atlantic States.
Fig. 9-10: U.S. average wind speed and wind speed anomalies observed in March 2018.