Severe weather chances increase as we move into spring

Taken from the CASE website

Now that spring is here and warmer, more humid air is entering the US, severe weather and tornado chances are increasing across the country.  There is an excellent animation that shows how the region of severe weather occurrence moves around the country at the NOAA Storm Prediction Center.   The area of most likely severe weather moves north and south with the area of greatest temperature contrast and most active storm track as the sun’s angle changes over time.

The Weather Channel has also provided a series of bar graphs which show the monthly probability of tornadoes for over 40 cities around the country (link).  From the graphs you can see that the Southeast has a split severe weather season, with the major peak in spring and a secondary peak in late fall.

For answers to every question you can ask about tornadoes, check out the tornado FAQ from the Storm Prediction Center.

And make sure you have access to real-time severe weather warnings via smartphone app or NOAA weather radio, especially if you are working outside on high-risk days.



When do we expect the last frost?

Taken from the CASE website and written by Pam Knox, University of Georgia Agricultural Climatologist

Now that March is upon us and the atmospheric pattern has shifted into something that is bringing more spring-like weather to the Southeast, it’s time to think about planting.  And that means thinking about the last frost of the winter.

AgroClimate has a tool which shows the last frost date by county for the Southeast.  The 50 percent map shows the average date for the last frost, while the 10 percent map shows the date that one in ten years will see a frost, and the 90 percent map shows the date for which in just one out of ten years the last frost will come early (or in other words, in 9 out of 10 years the last frost will come later than this date).  The maps below show the dates for 32 F.  You can find the tool at


If you need the information for a different temperature threshold, then a good source of information is the Southeast Regional Climate Center.  You can go to their web page and pick “Historical Climate Summaries” from the “Climate Data” menu at the top.  Pick your station and then look for “Spring Freeze Probabilities” on the left menu.  Here is the graphical output for Tifton, GA.


What this shows is that for Tifton, for a temperature of 32 F (orange line) at the 50th percentile (for the average date), the date is about March 10.  You can click on the link for tabular data to get a table of numbers instead of the graph shown here.  Keep in mind that this is for the period of record for the station, and that last dates for spring freeze have been trending earlier in the season in recent warm years.  If you have a different source of freeze information that you like to use, please let us know!

Lawn and Garden Moisture Index

Information taken from the Climate and Agriculture in the Southeast (CASE) newsletter.

Do things seem really dry where you are?  How much should you water your lawn or irrigate your crops?  There are a number of commercial products out there that can help you determine this, but one simple method that is available for free is the Lawn and Garden Moisture Index, a daily map put out by the Alabama State Climatologist based on estimated rainfall from radar.  This map tells you whether your lawn and garden have enough moisture or if more needs to be added.  This is one of a number of useful products available on, a website developed by the Southeast Climate Consortium, a group of eight universities around the Southeast.


This map shows the areas with surplus water in greens (no need to water or irrigate there) and areas with a water deficit in oranges and reds.  The darkest red areas are almost 2 inches short of water, including a large portion of Georgia.  If this situation continues, then the Drought Monitor is likely to add D0, abnormally dry conditions, to the next weekly Drought Monitor map.  Areas with deficits of an inch or more should be irrigated to help alleviate the dry conditions and keep lawns and gardens healthy.

Climate Outlook for 2014 Growing Season and Winter 2014-15

Pam Knox, UGA Climatologist

Taken from Climate and Agriculture in the Southeast (CASE)

Following a very wet 2013, this year has gotten off to a drier than usual start, although generally soil moisture has been very good until recently. In the last few weeks, abnormally dry conditions have started to creep into the mountains in northeast Georgia as well as scattered locations in the west central and southwest parts of the state.  However, a major drought is not expected to develop this growing season.

Short-term forecasts out to two weeks indicate that some dryness may continue in southern Georgia but north Georgia is likely to be wetter. In the one to three month period that includes April through June, there are equal chances for below, near, and above normal rainfall, since accurate predictions are very hard in neutral conditions when no El Nino or La Nina are occurring. However, following recent climate trends, temperatures have an increased chance of above normal conditions for the next few months.

NOAA has now issued an El Nino watch for the potential development of an El Nino in the eastern Pacific Ocean by mid to late summer. When an El Nino occurs, we commonly see wet and cool conditions in south Georgia associated with the persistent presence of a subtropical jet stream above the earth’s surface which directs weather systems right across Georgia.

At this time, NOAA is predicting a 50 percent chance of an El Nino developing by midsummer.  If one does occur, then we can expect next winter to be cooler and wetter than normal in 2014-2015. Some scientists believe that this is likely to be a stronger than usual El Nino based on current ocean temperatures. If that happens, the cool and wet conditions will extend throughout Georgia instead of just affecting the southern part of the state.

One impact of El Nino on Georgia’s climate is a reduction in the number of hurricanes in the Atlantic Ocean. However, even in a quiet season, a single direct hit by a hurricane or tropical storm can cause significant damage to the area it passes over. Most other effects of El Nino are seen in the winter when the El Nino is strongest.

Other impacts from El Nino include excessive cloudiness, which reduces solar radiation and increases drying times for hay as well as enhancing the development of fungal diseases. Low-lying areas are likely to be soggy and hard to work due to the persistent rain. Cooler temperatures and high humidity may also affect the development of pecans and Vidalia onions, reducing pecan yields as well as the average size of the onions. In general, El Nino winters are not associated with unusually late frost dates, however.  Runoff may also increase, leading to increased erosion or movement of surface applications into streams.

You can find more information about the impacts of El Nino on climate patterns and crop yields at