Chances Increase to 85% Going Into Fall

According to the latest NOAA Climate Prediction Center forecast released May 20, the chances for a return of a La Niña phase in the next three months, following a transition from El Niño to neutral conditions, is about 50%, increasing to 85% in the fall. 

It is interesting to note that during the past four years we had three La Niña events (2020-2022), followed by an El Niño this past year, and now chances are high that we will return to a La Niña phase. It will be the fifth year in a row without a full cycle neutral year. It is not uncommon for a La Niña to follow a strong El Niño like we had this past year. In the past, La Niña followed most of the strong El Niño events including 1972-73, 1982-83, 1997-98, and more recently the 2015-16 strong El Niño.

NOAA-CPC ENSO forecast issued on May 20, 2024, indicating a 49% probability of La Niña returning in the next 3 months (Jun-Jul-Aug). The probability of the La Niña phase in the Fall (Oct-Nov-Dec). increases to 85%.

The El Niño-SouthernOscillation (“ENSO”) phases affect climate patterns in several regions of the world, including the Southeastern US. While every La Niña event is different, they typically bring a warmer and drier winter season to Florida. La Niña is also known to be associated with an active tropical hurricane season since it tends to weaken wind shear over the Caribbean Sea and tropical Atlantic Basin, which enables storms to develop and intensify. 

The combination of La Niña with near-record warm ocean temperatures prompted NOAA to recently forecast above-normal hurricane activity in the Atlantic basin this year. NOAA’s outlook for the 2024 Atlantic hurricane season (June 1 to November 30) predicts an 85% chance of an above-normal season, a 10% chance of a near-normal season and a 5% chance of a below-normal season. The forecast calls for 17-25 named storms, 8-13 hurricanes, and 4-7 major hurricanes. Now is a good time for blueberry growers to review UF/IFAS Disaster Preparation and Recovery resources including Impacts of Hurricane Damage on Southern Highbush Blueberries (https://edis.ifas.ufl.edu/publication/HS1342) and Government Agency Resources for Florida Blueberry Growers (https://edis.ifas.ufl.edu/publication/HS1485).

NOAA 2024 Atlantic Hurricane Season Outlook 

Regarding other potential effects of the expected La Niña weather pattern in the winter, drier weather generally decreases fungal and bacterial diseases, which helps fruit and vegetable growers reduce the number of fungicide applications. Blueberry growers in Florida can track anthracnose risk levels using the web-based AgroClimate Blueberry Advisory System or downloading the mobile phone app available in both the iPhone App or Android Google Play stores. 

High nighttime temperatures (above 65°F) can be a problem for fruit setting with decreased chill accumulation in northern Florida and southern Georgia. A new version of the AgroClimate chill hours calculator will soon be released to help blueberry growers monitor the accumulation of chill hours and chill portions. Chill portions are based on a dynamic model, more appropriate for subtropical climates. Changes in the accumulation of chilling hours and heat units that satisfy dormancy requirements in the deciduous production system and promote flowering and fruit development can also impact the threat from freeze damage during flower and fruit development. 

Typical precipitation deviation from long-term averages during La Niña years showing a reduction of 3.0 to 5.0 inches in  the total precipitation accumulated in Florida from November to March.

CREDIT:
DR. CLYDE FRAISSE, Professor, Agrometeorology, UF/IFAS