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Heading for a strong El Nino

In his briefing for the Appalachicola-Chattahoochee-Flint River stakeholder group today, Florida State Climatologist David Zierden noted that the eastern Pacific Ocean is nearly at the threshold for a strong El Nino now and should pass that threshold in the next month.  He presented some information about what to expect from a strong El Nino based on composites of weather information from the strongest El Nino events.  His summary slide is shown below.

Based on composites from the strongest El Nino years, May and June (top map) were expected to be wetter than normal in Texas and Oklahoma as well as the Southeast.  The composite-predicted rainfall has been very accurate for the southern Plains, although not as good for the Southeast, where we are close to normal. In July and August (bottom map), the composite suggests that a pattern shift may occur and that most of the South, including all of the Southeast, could go into a dry spell.  Often those dry spells are associated with above normal temperatures.  They may also be related to tropical seasons with lower than average activity in El Nino summers.

Since El Nino typically brings rain to most of the Southeast in the winter, David was asked when the change from the late summer dryness to fall and winter wet conditions might occur.  He noted that it has occurred as early as early October in 2002, but in most years it is late October into November before the Southeast returns to rainy conditions.  Once the transition occurs, however, rainy weather may continue so farmers should watch for those conditions in the fall to help plan harvesting schedules.

zierden strong el nino impacts