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CONTACT: David F. Zierden, State Climatologist of Florida
(850) 644-3417; This email address is being protected from spambots. You need JavaScript enabled to view it.
October 30, 2013
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Weather patterns this year for the upcoming winter are prone to be more variable, with swings between warmer, colder, wetter, and drier periods throughout the season. The reason is that the Pacific Ocean is currently in the neutral phase; meaning sea surface temperatures near the equator in eastern and central Pacific Ocean are close to normal. Winter weather and climate patterns in Florida and the Southeast are heavily influenced by the El Niño/La Niña cycle, where ocean temperatures in the tropical Pacific swing between warmer than normal and colder than normal every 2 to 7 years.
El Niño refers to periods when the sea surface temperatures near the equator from the coast of South America all the way to the central Pacific turn unusually warm for a period of 6 to 12 months. The presence of this warm water tends to set jet stream patterns in place that usher frequent storms and rain to the northern Gulf Coast, Florida, and the Southeast Atlantic coast along with cooler temperatures. The opposite phase, or La Niña, describes a colder than normal sea surface in the same region of the Pacific Ocean. La Niña brings a pattern of warmer and drier winters to the Southeast, often leading to the development of drought.
With neither El Niño nor La Niña in place this year, the jet streams are freer to meander over North America, leading to greater variability in temperature and rainfall from week to week. When looking at the winter as a whole, the seasonal temperature and rainfall is likely to be close to normal. Instead of the odds being heavily tipped towards wetter and colder or drier and warmer, all possibilities are equally likely in a neutral winter.
(click on the header to expand)Sea surface temperatures along the equator near the coast of South America cooled slightly in the summer months, yet remained well within the "normal" range. Near normal sea surface temperatures in this area of the Pacific is known as Neutral conditions. Historically, neutral conditions occur roughly half the years while El Niño and La Niña each occur about a quarter of the time. Neutral conditions have prevailed since April of 2012, including last fall, winter, and spring, giving us the first "neutral" year since 2007.
Current East Pacific SST Anomaly Analysis (degrees C)
Neutral conditions are likely to continue through the remainder of 2013 and into spring of 2014. In spite of the recent cooling in the far eastern Pacific, temperatures in the central and western Pacific remain very close to normal. Deeper water temperatures along the whole equator are actually somewhat warmer than normal, lending little support any continued cooling at the surface. In addition, surface trade winds over the western and central Pacific are near normal giving little dynamic support for additional cooling. Most projections from both dynamical and statistical ocean models support the continuation of neutral conditions through the winter and spring of 2013.
Florida (and the Southeast) can expect freezing temperatures nearly every winter as far south as Lake Okeechobee. Some years, however, see severe freezes and Arctic outbreaks that devastate citrus and vegetable production in the State of Florida. These "impact" freezes occur on average every 10 to 20 years. A dozen or so of these "impact" freezes have struck since 1894, including several in the very cold decade of the 1980's. Of these harsh freezes, nearly every one has occurred during the neutral phase of the Pacific Ocean.
Probability (in percent) of reaching 25 degrees or cold at least once in the upcoming winter
During years with El Niño or La Niña, the jet streams seem to lock into preferred positions that block the intrusions of the coldest Arctic air masses. In neutral winters, the jet streams are freer to meander and possible amplify into the dramatic dip over the eastern U.S. that can usher in the frigid Arctic air. The neutral phase does not guarantee that we will experience on of these damaging freezes this winter, just that the odds are twice as likely than in other phases of the Pacific Ocean.
The rain this summer has been frequent, widespread, and heavy at times. From South Florida to the Panhandle and Southeast Alabama and even western and central Carolinas, both the month of July and the three months of June through August rank among the wettest ever with many stations setting records. Even in the parts that have received a little less rainfall, saturated soils and standing water were a huge problem. Many locations recorded over 30 inches of rain in the three months, over half the annual average. The rainfall was not only heavy and widespread, but also frequent occurring nearly daily. In the month of July, many locations in Florida, Alabama, and Georgia recorded rainfall on 25 of the 31 days in the month.
Statewide precipitation rankings for summer of 2013 (June - August)
The map above shows that the states of Florida, Georgia, and South Caroline all experienced their wettest summer since records began in 1895. The map also shows that the rainy conditions affected the entire eastern U.S, with New York also having its rainiest summer ever and many other states ranked in the top five or top ten.
Surprisingly, nearly all of this rainfall has not come from tropical depressions or storms. Tropical storm Andrea has been the only system to impact the state so far this year, brining 1-2 inches of rain over central Florida and higher amounts to north Florida and the Big Bend.
Instead, a recurring pattern of high pressure ridging over the Western U.S. and troughing or lower pressures over the central and eastern U.S. set itself up time and time again this summer. The subtropical or "Bermuda" high has been pushed further eastward over the Atlantic Ocean, allowing a very moist southerly flow of tropical humidity over the region. Add to that an unstable atmosphere and stalled frontal boundaries over the northern Gulf Coast, showers and thunderstorms have been numerous, frequent, and widespread
Fortunately, the arrival of fall brought a drying trend to the Southeast. Fall is usually one of the drier seasons in the Southeast, barring a hit from a tropical system or hurricane. Since September 1st, rainfall is running only 50% of normal over most of most of the Southeast, with the exception of the Florida west coast.
Percent of normal precipitation for the last 60 days (from Oct. 30) from radar estimates (Courtesy NWS)
This drier weather has been generally good for crops, with the plentiful sunshine and warm temperature allowing crops to reach maturity. The dry weather can also be favorable for harvest, though some peanut fields are getting too hard and dry to dig.
With the drier pattern, drought is once again starting to threaten parts of the Southeast. The latest U.S. Drought Monitor has "abnormally dry", or D0, starting to reappear over Southeast Georgia and Northeast Florida, the Georgia-South Carolina border, and Central Alabama. We anticipate normal rainfall over the interior of Georgia and Alabama this winter and spring, which should provide the needed recharge of surface and groundwater than normally happens in the winter and spring.
Latest U.S. Drought Monitor showing "abnormally dry", or D0, developing in parts of the Southeast
CONTACT: David F. Zierden, State Climatologist of Florida
(850) 644-3417; This email address is being protected from spambots. You need JavaScript enabled to view it.
March 14, 2014
Download report in PDF format or read the report below
After a summer of record-setting rainfall across much of the Southeast and near-normal winter rainfall, surface water, groundwater, and soil moisture are all in good shape as spring approaches. The States of Florida, Georgia, and South Carolina all experienced the wettest summer on record (since 1895) and many others were in the top five or top ten. The map below shows statewide precipitation rankings since 1895. Cold season rainfall was close to normal, with some locations like south Georgia and northwest Alabama being a little on the dry side, with other locations being a little wet. Overall, winter rainfall was close to normal and provided sufficient recharge of surface water, groundwater, and soil moisture.
While our neighbors to the north in the Midwest and Northeast experienced a rather severe winter with cold temperatures and frequent snowstorms, temperatures in the Southeast were not too unusual. The snow and ice storms that impacted the Southeast on January 29th and February 13th made it seem like a severe winter, but historical temperature rankings indicate a mixed bag. Some weather stations in western Alabama ranked among the top five or top ten coldest, while south Florida ranked as 2nd or 3rd warmest. In between temperatures were close to normal. Florida citrus, fruit, and vegetable growers did not endure a damaging freeze this year.
According to the U.S. Drought Monitor, the Southeast remains relatively drought-free as spring approaches. There are a few spots of D0 (unusually dry) in Alabama and Georgia where they missed some of the winter rain, but D0 does not indicate any drought impact, just areas to watch closely. So far the state of Florida has had a fairly quiet wildfire season, but the peak of the season has not arrived yet. Keetch-Byram Drought Index values range from very moist across north Florida and the Panhandle to over 500 in South Florida. However, high values occur in south Florida every year at this time due to the prolonged dry season.
(click on the header to expand)Sea surface temperatures along the equator near the coast of South America cooled slightly in recent weeks, yet remained well within the "normal" range. Near normal sea surface temperatures in this area of the Pacific is known as Neutral conditions. Historically, neutral conditions occur roughly half the years while El Niño and La Niña each occur about a quarter of the time. Neutral conditions have prevailed since April of 2012, including last fall, winter, and spring, giving us two "neutral" years in a row. Neutral conditions will continue at least for the next several months.
Current East Pacific SST Anomaly Analysis (degrees C)
The Pacific Ocean may be in a period of transition right now. Since late December, westerly wind anomalies have been present on and off in the western Pacific along the equator. It is these changes in the trade winds that excite Kelvin waves, which travel eastward to the South American Coast and begin the warming process of surface waters. A very strong Kelvin wave is making its month long trek across the Pacific Ocean right now. In addition, many of the models that predict sea surface temperatures are now forecasting the development of El Niño over the summer. Because of the recent events in the Pacific and the prediction models, NOAA has now issued an El Niño watch, meaning there is a greater that 50% chance of El Niño developing this summer. However, this is a notoriously difficult time of the year to predict the Pacific Ocean, and it takes more than one Kelvin wave to build a full-blown El Niño. We will have to wait and see how the next few months unfold before we know with any certainty that El Niño is on the way.
Weather patterns for the early spring are prone to be more variable, with swings between warmer, colder, wetter, and drier periods throughout the season. The reason is that the Pacific Ocean is currently in the neutral phase; meaning sea surface temperatures near the equator in eastern and central Pacific Ocean are close to normal. Winter and spring weather and climate patterns in Florida and the Southeast are heavily influenced by the El Niño/La Niña cycle, where ocean temperatures in the tropical Pacific swing between warmer than normal and colder than normal every 2 to 7 years.
With neither El Niño nor La Niña in place this year, the jet streams are freer to meander over North America, leading to greater variability in temperature and rainfall from week to week. When looking at the winter and spring as a whole, the seasonal temperature and rainfall is likely to be close to normal. Instead of the odds being heavily tipped towards wetter and colder or drier and warmer, all possibilities are equally likely in a neutral spring.
While the El Niño/La Niña cycle gives us a good deal of predictability in the cold months, its impact on our summer climate is much weaker. One reason that there is not much of an ENSO signal in the Southeast is that the sea surface temperature (SST) anomalies in the tropical Pacific are usually weaker or in transition during the summer months. But, even when stronger anomalies exist (even stronger than the 0.5 degree El Nino/La Nina threshold), the coupling with the atmosphere is also much weaker during the summer.
Our conceptual model is that El Niño /La Niña cause preferred jet stream patterns over North America. In the winter, the jet stream is more active and farther south and more of a direct driver of storm tracks and climate and weather patterns. In the summer, the jet stream retreats much farther north where 1) it is less affected by the tropical Pacific, and 2) less of player in our weather patterns here in the southeast.
Last summer, the Pacific Ocean was firmly in the neutral phase and we ended up with one of the wettest summers on record. This unusually wet pattern could not have been predicted by looking at the Pacific Ocean and was not predicted by NOAA's climate prediction center.
With all of that being said, rainfall patterns may be normal to above normal this summer whether or not the Pacific Ocean transitions into El Nino. The map below shows summer (June through August) rainfall departures from normal in years where there was a transition from neutral to El Niño. On average during these years May through July have been wetter than normal for much of the Southeast. However, these kind of composites or analogs have to be taken with a grain of salt because one or two unusual years can greatly influence the results.
Summer temperatures are highly correlated with rainfall across the Southeast. Frequent rainfall and cloud cover (like last summer) will keep temperatures below normal. Dry clear days are when we see higher afternoon temperatures. Temperatures across the region the last two summers have generally been below normal, corresponding to above normal rainfall.
If El Niño does develop as forecast this summer, one of the first impacts could be on the Atlantic hurricane season. It is well-known that El Niño tends to suppress hurricane formation in the Atlantic basin by creating an environment of unfavorable vertical sheer, or winds changing with height. Sheer will tear a developing storm apart before it has a chance to grow into a strong hurricane. If an El Niño forms, look for fewer hurricanes this year. Keep in mind that landfall from a hurricane or destructive tropical system is still possible, even in relatively quiet years, and that plans should be ready every year to deal with a possible storm. The figure below shows the probability of hurricane landfalls in the three phases of the Pacific Ocean. The probability of two or more hurricanes making landfall in the United States is only half as great during El Niño as with the other phases.
From AgroClimate.
Date updated: July 6, 2009
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| Current East Pacific SST Analysis | Current East Pacific SST Anomaly Analysis |
| Click on image for a full-size version. | |
Ocean temperatures in the past month have warmed rapidly in the eastern and central tropical Pacific Ocean and are now above the 0.5 C threshold that commonly designates El Niño conditions. This warming completes the transition from a weak La Niña in March of 2009 through several months of neutral conditions in April, May, and June, to impending El Niño for the remainder of 2009. El Niño refers to a periodic (every 2-7 years) of the tropical Pacific Ocean along the equator from the coast of South America to the central Pacific. Weakened trade winds over the central Pacific and abundant warm water beneath the surface indicate that surface temperatures will continue to warm in the next few months. Modeling centers around the world that predict El Niño/La Niña agree that waters will continue to warm and result in a weak to moderate El Niño over the next 3-6 months. NOAA's Climate Prediction Center issued an "El Niño watch" in early June, meaning that the development of El Niño conditions are likely in the next 1-3 months.
If El Niño fails to develop as forecast, then neutral conditions will be the other possibility. There is virtually no chance for a return to La Niña in 2009.
The development of El Niño could have dramatic impacts on the climate of the Southeast for the remainder of 2009. First, El Niño hinders hurricane development in the Atlantic basin and leads to less active seasons. El Niño events that develop this early in the summer can lead to drier than normal conditions across Alabama and Georgia in the late summer and early fall. El Niño has its strongest impacts on the Southeast in the colder months, bringing wet, stormy, and cool winter and spring seasons to the Southeast. For more detailed information on climate impacts in the Southeast, see the latest climate outlook.
The SECC tracks the temperatures of the Pacific Ocean using the JMA index. For more information and current JMA values, see the following link:
Below are links to El Niño/La Niña forecasts from other centers in the U.S. and worldwide. Caution: the SECC may not agree with their forecasts and/or classification criteria.
From AgroClimate.
Date updated: November 13, 2009
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Current East Pacific SST Analysis |
Current East Pacific SST Anomaly Analysis |
| Click on each image for a full-size version. | |
Ocean temperatures in the past few months have continued to warm in the eastern and central tropical Pacific Ocean and are now over 1.0 degree C warmer than normal over a large area. Sea surface temperatures in this region of 0.5 degree C warmer than normal are the commonly used threshold to designate El Niño conditions. El Niño refers to a periodic (every 2-7 years) warming of the tropical Pacific Ocean along the equator from the coast of South America to the central Pacific. Once surface temperatures warm to over 1.0 degrees C the El Niño is considered moderate in strength (the three classifications are weak, moderate, and strong). This warming began in May and has continued through the summer and fall months. The development of this El Niño follows the typical life cycle of building in the summer and fall months before reaching peak strength in mid winter.
Weakened trade winds over the central Pacific and abundant warm water beneath the surface indicate that surface temperatures will continue to warm in the next 1 to 3 months. Modeling centers around the world that predict El Niño/La Niña agree that waters will continue to warm and result in at least a moderate El Niño during the winter and spring months. There is a small chance that the El Niño will reach the strong category. There is no chance of La Niña returning in the near future and very little chance of neutral conditions.
The development of El Niño could have dramatic impacts on the climate of the Southeast for the remainder of 2009. First, El Niño hinders hurricane development in the Atlantic basin and is largely responsible for the relatively quiet season thus far. El Niño has its strongest impacts on the Southeast in the colder months, bringing wet, stormy, and cool winter and spring seasons to the Southeast. For more detailed information on climate impacts in the Southeast, see the latest climate outlook.
The SECC tracks the temperatures of the Pacific Ocean using the JMA index. For more information and current JMA values, see the following link:
Below are links to El Niño/La Niña forecasts from other centers in the U.S. and worldwide. Caution: the SECC may not agree with their forecasts and/or classification criteria.
From AgroClimate.
Date updated: July 7, 2009
The Pacific Ocean is transitioning into the El Niño Phase. Ocean temperatures in the past month have warmed rapidly in the eastern and central tropical Pacific Ocean and are now above the 0.5 C threshold that commonly designates El Niño conditions. This warming completes the transition from a weak La Niña as late as March 2009 through several months of neutral conditions in April, May, and June, to impending El Niño for the remainder of 2009. El Niño refers to a periodic (every 2-7 years) warming of the tropical Pacific Ocean along the equator from the coast of South America to the central Pacific.
Sea surface temperature departures from normal (degrees C) over The Pacific Ocean as of July 1.
Weakened trade winds over the central Pacific and abundant warm water beneath the surface indicate that surface temperatures will continue to warm in the next few months. Modeling centers around the world that predict El Niño/La Niña are in good agreement that waters will continue to warm and result in a weak to moderate El Niño over the next 3-6 months. NOAA's Climate Prediction Center issued an "El Niño watch" earlier in June, meaning that the development of El Niño is likely in the next 1-3 months. If El Niño fails to develop as forecasted, then neutral conditions will be the other possibility. There is virtually no chance for a return to La Niña in 2009.
What does El Niño mean for the rest of the summer? When an El Niño develops this early in the summer (they usually form in the fall and reach peak strength in the winter months), it has the potential to lead to drier than normal weather patterns across the Southeast in the second half of summer and in early fall. This tendency towards drier weather is strongest over Alabama, north Georgia, and the Carolinas where rainfall averages 10% to 20% less than normal in July and August during El Niño.
Average changes in precipitation (percent change from normal) for August during El Niño episodes
Over much of inland Alabama and Georgia, this is the time when evapotranspiration normally exceeds rainfall, meaning soil moisture, surface water, and groundwater levels usually decline until the following winter. Summer does bring frequent afternoon thundershowers, but the scattered nature of these convective rains render them insufficient for large scale recharge for the most part. With even drier conditions expected in the next 1-3 months due to the developing El Niño, there is the potential for drought conditions to re-emerge.
Over Florida, the summer rainy season should continue as usual. In general, the second half of the season is a little drier than the first half in south Florida, but more rainfall hits north Florida and the Panhandle. Any drying impacts from El Niño at this time should not greatly offset the summer accumulation of rain. Also, expect Gulf coastal areas to receive more frequent thunderstorms, as Gulf water temperatures are now warm enough to support nocturnal convection.
The recent heavy rains across North Florida, South Alabama, and South Georgia have saturated soils and filled area lakes, ponds, and rivers. This should provide sufficient moisture for planting field crops and greening of pastures for the next month or more. Standing water or saturated soils could hinder field preparations.The tropical season greatly affects rainfall amounts and coverage during late summer and fall in the Southeast. One or more tropical systems, whether a hurricanes, weak storms, or depressions, can bring beneficial rainfall that is a normal component of the climate. Tropical storm Faye brought torrential rainfall to the state of Florida last year and beneficial rains to Georgia and Alabama. El Niño lessens tropical activity in the Atlantic, Caribbean Sea, and Gulf of Mexico, so the threat of hurricanes or damaging tropical storms should be lower through the remainder of the season.
Looking ahead to the fall/winter. Once we shift seasons into the colder months, the more widely recognized impacts of El Niño in the Southeast begin to set in. Starting in November, El Niño affects the jet stream pattern in a manner that leads to frequent winter storms and frontal systems, cooler temperatures, cloudier skies, and much above average rainfall. In December through March El Niño typically leads to rainfall 40% to 50% greater than normal over the peninsula of Florida and up to 30% greater than normal over coastal Alabama, South Georgia, and coastal North and South Carolina. These winter impacts of El Niño are generally stronger than any other time of year and more consistent among past El Niño events; therefore the winter forecast can be viewed as more reliable.
For more detailed information on El Niño climate shifts in your particular county, please refer to the Climate Risk Tool at AgClimate:
