Humboldt Current Weakening as Waters off the West Coast of South America Turn Warmer

Top Concern with Incoming Polar Vortex is Extreme Wind
12/20/2022, 5:57 am EST
Stratospheric Cooling, Alaska Ridge Bridge, and the December 2022 U.S. Cold Outbreak
12/23/2022, 1:27 pm EST
Show all

Fig. 1-2: The 12Z GFS 15-day percent of normal rainfall and temperature anomaly forecast for Argentina and Brazil.

Discussion: Today’s trend across Argentina is drier in the latest GFS 15-day forecast (Fig. 1). Wet weather is patchy but where rainfall is present heavy amount is likely in Brazil. The wet weather in Brazil suppresses heat risk (Fig. 2). However, in Argentina a hotter 15-day outlook is indicated. The cool risk forecast by ECM for the 6-10-day period from early this week is removed. So anomalous heat is present much of the time in Argentina subtracting moisture from already drier than normal soils.

In a development likely related to ENSO, the cold Humboldt Current off the West Coast of South America appears to be weakening and possibly shutting down. The past 30 days have produced much warmer ocean surface temperatures in this region (Fig. 3). Also implied is weakening of the La Nina pattern.

Fig. 3: The 30-day SSTA change analysis in the South Pacific basin.

An activated Madden Julian oscillation (MJO) across Maritime Continent is attributed to the very wet 15-day forecast for the northern portion of Australia (Fig. 4). Eastern Australia misses the heavy rainfall. In Europe, the outlook shifts much warmer into early January (Fig. 5).

Fig. 4-5: The CMC ENS 15-day percent of normal rainfall forecast and GFS 15-day temperature anomaly outlook.