Synoptic DiscussionJanuary 2023

Note: This Synoptic Discussion describes recent weather events and climate anomalies in relation to the phenomena that cause the weather. These phenomena include the jet stream, fronts and low pressure systems that bring precipitation, high pressure systems that bring dry weather, and the mechanisms which control these features โ€” such as El Niรฑo, La Niรฑa, and other oceanic and atmospheric drivers (PNA, NAO, AO, and others). The report may contain more technical language than other components of the State of the Climate series.


Overview

Key Drivers

Monthly Mean

The January mean circulation was dominated by a trough along the West Coast and a ridge near the Northeast. This circulation was associated with teleconnections from the ongoing La Niรฑa, a positive NAO, and a positive WPO. The trough was associated with repeated atmospheric rivers that brought heavy precipitation to California. It also fed unusually active severe weather and tornadoes for January in the Southern Plains and Southeast. Meanwhile, the ridge was associated with warm temperature anomalies for the Northeast, particularly early in the month. These patterns moderated during the second half of January when the trough shifted eastward.

Submonthly Evolution

500-mb height mean (contours) and anomalies (shading) for the North America

Average Temperature Departures

Average Temperature Percentiles

Percent of Average Precipitation

Precipitation Percentiles

January 1-7

January began with a trough along the West Coast and ridge along the East Coast. The trough maintained a string of atmospheric rivers that made landfall in California that caused extreme precipitation and landslides. Temperatures were generally near normal over the western half of the country with this trough. Two extratropical cyclones in the subtropical jet brought wet conditions to the Southeast and an unusual January tornado outbreak to the Southern Plains and Southeast. The ridge near the East Coast was associated with record warmth for the Northeast, which would dominate the January mean temperatures for the region.

January 8-17

During the middle of January, the ridge shifted westward towards the Great Plains. This shift spread the warm conditions across most of the country and also suppressed precipitation for the Southern Plains. However, the trough along the West Coast continued directing atmospheric rivers to California.

January 18-31

The second half of January featured a very different circulation pattern as the negative AO, positive WPO, and positive EPO all transitioned to their opposite phases. The regime shift brought a ridge to the Gulf of Alaska and an end to the atmospheric rivers for California. The trough shifted eastward to the Rockies and brought widespread cool anomalies to the western U.S. Meanwhile, a ridge along the East Coast maintained warmer-than-normal temperatures for the Northeast. The primary storm track also shifted northward away from the subtropical jet.

Atmospheric Drivers

500-mb height mean (contours) and anomalies (shading) for the Northern Hemisphere

ENSO: El Niรฑo Southern Oscillation

MJO: Madden-Julian Oscillation

  • Description: The MJO is the biggest source of subseasonal (31-50 day) tropical variability. It typically develops as a large envelope of tropical thunderstorms over the Indian Ocean that then moves eastward. Like ENSO, the MJO's effects on tropical rainfall is so strong that it can alter the atmospheric circulation around the globe. The thunderstorms decay when they cross the Pacific, but the associated winds can often continue across the Western Hemisphere to initiate the next MJO in the Indian Ocean. The MJO is episodic, meaning that it is not always active. Most indices for tracking the MJO identify both the MJO's amplitude and the longitude of its strongest rainfall, usually described as one of eight phases.
  • Status: The MJO index began January over the Western Pacific (phases 6/7) and moved across the Western Hemisphere to the Indian Ocean (phase 3) by the end of the month.
  • Teleconnections (influence on weather): During January, MJO phase 6 is typically associated with warm and wet conditions near the Tennessee Valley. These were observed at the beginning of January (temperature and precipitation) when the MJO was in phase 6.

PNA: Pacific/North American Pattern

AO: Arctic Oscillation

NAO: North Atlantic Oscillation

WPO: West Pacific Oscillation

EPO: East Pacific Oscillation


Citing This Report

NOAA National Centers for Environmental Information, Monthly Synoptic Discussion for January 2023, published online February 2023, retrieved on July 31, 2025 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/synoptic/202301. DOI: https://www.ncei.noaa.gov/access/metadata/landing-page/bin/iso?id=gov.noaa.ncdc:C00768