NOAA has issued an El Nino Advisory, confirming the development of El Nino in the tropical Pacific. This climate phenomenon is expected to strengthen to moderate or strong levels by fall 2023. Forecasts indicate a 63% probability of sea surface temperatures in the Nino-monitored area exceeding 2.0°C, a threshold that qualifies as a “very strong” El Nino.
Understanding El Nino
El Nino, which means “little boy” in Spanish, is identified when equatorial Pacific temperatures rise 0.5°C above average for several consecutive months. NOAA observes atmospheric conditions as well, particularly the Walker Circulation. This east-to-west airflow is impacted by temperature and pressure differences between warmer western and cooler eastern ocean areas. A breakdown in the Walker Circulation and an eastward movement of warmer water towards South America signals the onset of El Nino.
Impact on U.S. Weather
El Nino typically has the most significant effects during the winter months, particularly in the Northern Hemisphere. It often alters the jet stream over the North Pacific, leading to:
- A southward shift in the storm track, increasing storm activity across the Southern U.S.
- Drier conditions in the Northern Rockies and parts of the Ohio and Tennessee valleys.
- Warmer-than-average winters in the northern regions of the United States.
“Each El Nino event is unique, leaving its own mark on weather patterns,” stated Ken Graham, director of NOAA’s National Weather Service. Advanced monitoring has improved the ability to predict these patterns, allowing better preparation for potential impacts.
Potential Effects of El Nino
- Stronger upper-level winds may reduce storm and hurricane activity in the Atlantic Basin.
- Increased storminess with higher chances of rain and snow in the Southern U.S.
- Higher risks of tidal flooding, especially along the West Coast.
- Shifts in fish migrations and marine life behavior due to warmer ocean temperatures.
- Potential increases in harmful algal blooms along the U.S. West Coast.
Enhanced Monitoring of ENSO
In February 2023, NOAA adopted the Relative Oceanic Nino Index (RONI) for more accurate monitoring of sea surface temperatures. Unlike the traditional Oceanic Nino Index (ONI), which relies on a static 30-year dataset, RONI adapts monthly, making it a more reliable tool for forecasting El Nino and La Nina events.
Since implementing RONI, NOAA’s ENSO team has tracked both RONI and ONI, determining that RONI better aligns with changes in the Walker Circulation. This provides vital insights for weather experts, emergency managers, and the public.
