Odds for La Niña Development this Fall Have Increased Slightly. - LCRA Odds for La Niña Development this Fall Have Increased Slightly. - LCRA


In a discussion released Thursday, forecasters at NOAA’s Climate Prediction Center indicate the odds for the development of La Niña this fall have increased to approximately 60 percent.

CPC forecasters noted that during August, sea surface temperatures (SSTs) in the equatorial Pacific, from the Date Line to the west coast of South America, were observed to be below average.  The four Niño indices were negative during the latest week, with the Niño-3.4 and Niño-3 indices at -0.6°C.

In addition to cooler than normal surface waters, water temperatures below the surface in this same region which had warmed some during June and early July, began cooling again in mid-July.  In early August, below-average subsurface temperatures re-emerged in the east-central equatorial Pacific.  Observations during July showed low-level wind anomalies were easterly across most of the equatorial Pacific while upper-level wind anomalies were westerly over portions of the far western, central, and eastern Pacific.  Tropical convection was suppressed over the western and central Pacific, and was near average over Indonesia. Putting all of these factors together, the combined oceanic and atmospheric system remains consistent with ENSO-neutral.  (Neither El Niño nor La Niña).

CPC forecasters noted the latest long-range climate models are split between La Niña and continued ENSO-neutral conditions (Nino-3.4 index between -0.5°C and +0.5°C) for the fall and winter.  However, the models slightly favor La Niña from the August-October through the November-January seasons.  Based largely on dynamical forecast model guidance, the forecaster consensus favors La Niña development during the August-October season, lasting through winter 2020-21.

In summary, the Climate Prediction Center is calling for a ~60% chance of La Niña development during Northern Hemisphere fall 2020 and a ~55% chance for La Niña to continue through winter 2020-2021.

La Niña Nina’s typically bring a drier than-normal and milder than-normal weather pattern to much of Texas during the fall and winter months.  The latest Climate Prediction Center rainfall outlook for this fall and winter calls for increased odds rainfall will average below normal through both seasons.

Stay tuned for additional updates.

Bob