01/12/2021, 9:59 am EST

Cause of the China Cold Outbreak Late DEC/early JAN 2020-21

A December 2020 stratospheric warming event across Northeast Asia spawned a frigid polar vortex stretching from Mongolia to Northeast Asia. Beneath the polar vortex increasingly cold air was generated taking on arctic intensity. In late DEC/early JAN the cold air mass was ejected southeastward into China bringing historic snows and cold.
01/11/2021, 12:29 pm EST

Multivariate ENSO Index (Analog) Suggests La Nina Continues Well Into 2021

The multivariate ENSO index (MEI) for NOV/DEC 2020 was -1.2. This value represents moderate intensity La Nina. The MEI is an excellent ENSO diagnostic as the index measures the reaction of the atmosphere to the cooling waters of the equatorial East Pacific. During the mature phase of La Nina, typically occurring in DEC/JAN for La Nina events since the middle 1990’s a mature phase La Nina MEI of <-1.0 was typically followed by sustained La Nina whereas MEI >-1.0 were more likely to produce La Nina dissipation and possibly El Nino later in the year.
01/10/2021, 10:36 am EST

Heavy Snowstorm for Texas/Louisiana

The more conservative view (by the HRRR model) indicates the heaviest snowfall in west-central Texas (6-10 in.) while GFS is much heavier northwest of Houston area (up to 10-12 in.). Given the strength of the upper trough and rapid cooling of the lower atmosphere late today/this evening the heavier (GFS) totals are favored!
01/09/2021, 10:35 am EST

Diminished Polar Ice Cap Affects Sensible Weather Created By The Major Teleconnection Patterns

The arctic oscillation was -1.7 in December and (traditionally) representative of blocking high pressure in the polar latitudes while a split in the polar vortex southward causes widespread mid-latitude chill. But! December 2020 was mild across most of North America and Europe and only Central Eurasia was (very) cold (about as far away from a maritime influence as possible).