SECC Spring Climate Outlook
Date updated: March 28, 2008
Current Conditions
La Niña not as dry as expected in some areas.For months, both the Southeast Climate Consortium and NOAA’s Climate Prediction Center have been predicting an increased likelihood of drier than normal and warmer patterns for the fall, winter, and early spring seasons in the Southeast, especially in Florida, South Alabama, and South Georgia. The reason is that a moderate to strong La Niña (colder than normal ocean temperatures along the equator in the eastern and central Pacific Ocean) developed this past fall. La Niña is well known to typically bring drier conditions and warmer weather to the Southeast in the colder months (November through March). The threat of a dry winter, when most recharge of surface and groundwater takes place in Georgia and Alabama, did not bode well for any lasting relief in the drought-stricken areas of these states.
Fortunately, this winter has been anything but typical as far as La Niña and rainfall is concerned. January and February saw a pattern that brought frequent storms and low pressure systems along the Gulf Coast. Several heavy rainfall events impacted the Panhandle and North Florida, South Alabama, and South and Central Georgia. The images below show rainfall departures from normal as percent of normal for the last 60 days (left) along with typical patterns associated with La Niña. The recent rainfall has helped bring surface water, groundwater, and soil moisture up sufficiently in these areas that they are now considered to be drought-free according to the U.S Drought Monitor.
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| Rainfall departures from normal for the past 60 days as percent of normal. | Typical February rainfall during La Niña as percent of normal |
In other areas, rainfall has not been so plentiful and drought conditions persist. The hardest hit areas of North Alabama and North Georgia are still experiencing rainfall deficits. Lake and reservoir levels, such as Lake Lanier that supplies Atlanta, are still significantly below normal and have not received as much recharge as hoped during the winter season. Likewise in South Florida, where low Lake Okeechobee levels are dictating water restrictions in South and Southwest Florida.
For more information on the ongoing drought conditions, including a statement by the Georgia State Climatologist, see the following links.
- U.S. Drought Monitor
- Georgia Drought Statement
- Southwest Florida Water Restrictions
- South Florida Water Restrictions
For more detailed information on recent weather, please see the resources below:
- Florida Automated Weather Network
- Georgia Automated Environmental Monitoring Network
- Alabama Office of the State Climatologist
- Southeast Regional Climate Center
- NWS Radar-derived Precipitation Totals
Climate Outlook
La Niña impacts lessen, dryness still a concern. As the season transitions from winter into spring, the typical warm and dry La Niña pattern starts to break down. Looking at historical rainfall measurements from past La Niña episodes, April generally brings a weak tendency for drier than normal conditions over the Florida peninsula, but little change over Alabama and Georgia. Keep in mind, however, that April and early May usher in the spring dry season in the Southeast, where rainfall from winter storms and frontal passages becomes less and less frequent. At the same time, temperatures are on the rise and evapotranspiration rapidly increases with the rising temperatures and greening of deciduous vegetation and planting of crops. Over much of inland Alabama and Georgia, this is the time when evapotranspiration begins to exceed normal rainfall, thus ending most meaningful recharge of surface and groundwater until the following winter. Summer does bring frequent afternoon thundershowers, but the scattered nature of these convective render them insufficient for large scale recharge for the most part. Given that we are entering this critical period with enduring deficits in river flows, lake, reservoir, and groundwater levels, drought will likely remain a critical issue in North Alabama and North Georgia.
Typical April rainfall during La Niña as percent of normal
Typical Junerainfall during La Niña as percent of normal
Looking further ahead, La Niña rainfall patterns can actually reverse themselves over portions of most of Alabama, Western Georgia, and the Florida Panhandle. May and June actually bring patterns that favor more rainfall than normal in these areas, on average from 5% to 10%. While this forecast can be viewed with optimism, there is less confidence in forecasting using La Niña climate shifts at this time of year. Like this current La Niña, sea surface temperatures reach their peak departure from normal in the winter months and have or are in the process of returning to normal by the summer. Also, the active jet stream has migrated north to its summer position, so the tropical Pacific has less influence on it and corresponding weather patterns.
As far as temperatures go, La Niña does not favor any significant shifts in average temperature during the spring and summer seasons. Extreme winter temperature do appear to be tied to the El Niño / La Niña cycle, namely that extreme winter freezes are more likely only when the Pacific Ocean can be considered neutral. Late season freezes are still a risk and do not appear to be connected to the Pacific Ocean. The damaging April freeze of 2007 was a remarkable event and chances are low that this will occur again.
How certain is the forecast? Thus far, much of the discussion has centered around “average” shifts in temperature and precipitation due to La Niña. However, no two La Niña episodes are alike, nor are the climate impacts seen from these events. It is important to consider the range of possibilities that accompanies La Niña episodes rather than counting on climate patterns close to the “average” for La Niña. For more detailed information on El Niño/ La Niña climate shifts in your particular county, please refer to the Climate Risk Tool at AgroClimate:
La Niña is past its peak
More information on El Niño/La Niña
Colder than normal surface temperatures spread over most of the tropical Pacific Ocean in the fall of 2007 consistent with a phenomenon known as La Niña. La Niña can be thought of as the opposite of the better known “El Niño”, where the Pacific Ocean along the equator from the South American coast to the western Pacific turns several degrees C warmer than normal. The colder than normal temperatures continued to spread and intensify during the past fall and winter seasons and the La Niña event grew in magnitude until it was considered a moderate to strong event. The colder ocean temperatures seem to have peaked in February and are now slowly returning closer to normal. However, given the massive area covered by these colder waters and the extent of the cooling, it is nearly certain that La Niña conditions will persist at least through April of this year.
What will happen in the Pacific Ocean later in 2008 is much less certain. While most El Niño/La Niña prediction models show a slow decay of La Niña well into the summer, about half of these are predicting a return of La Niña in the fall of 2008. Multi-year La Niña’s have happened in the past, most recently in 1998-2000. Keep in mind that these long range predictions are quite uncertain, especially at this time of year when the dynamics of the Pacific are not well understood.
Click here for our El Niño Discussion.
Wildfire Season
La Niña is known to bring drier winters and increased wildfire activity to the state of Florida and the Southeast. Fortunately, recent heavy rains across Alabama, Georgia, and North Florida have eased wildfire concerns for the time being. Almost the entire area north of Ocala, FL currently has Keetch-Byram Drought Index (KBDI) values less than 100 corresponding to very moist forest conditions. Southwest Florida is the only area with KBDI values greater than 400 right now, but this is not unseasonably high for this area at this time of year. In spite of the recent rains, there is still a possibility of returning to below-average rainfall for the area as is typical with La Niña. Forest conditions could dry quickly as temperatures and evapotranspiration increase with the progression into spring and early summer. April and early May is also the traditional spring dry season and when wildfire activity tends to peak, especially in Florida. However, the recent rains are certainly beneficial for conditions now and for the short-term future. Going into peak wildfire season with moist forest conditions could lessen the impacts of the spring dry season. For more information on wildfire threat and our forecast of the Keetch-Byram Drought Index pleas reference our wildfire threat forecast.