An Early Look at 2008-09 Winter Possibilities
Reader Morgan wanted to know if we were likely to see some relief from the drought and any changes to the climate patterns we’ve been seeing over the past few years. While I wish I was as prescient as he makes me appear, let’s take a look at what might happen this winter.
We’ll start with the three month outlooks from the Climate Prediction Center. The three month outlook from October through December calls for equal chances of above or below normal temperatures and precipitation for the period east of the Mississippi River. Note this doesn’t mean a ‘normal’ fall season–it’s more like the indicators they are using for the outlook don’t point strongly one way or another.
For the winter proper, from December, 2008 through February 2009, the CPC says we’re likely to see warmer than normal temperatures for most of the US, and drier than normal conditions in the southeast, including Georgia. Based on what I’ve seen in the past, this prediction is likely to become the ‘official’ winter outlook that the Weather Service will release in Mid October. You’ve got to take these outlooks with a grain of salt. In their Winter 2007-08 outlook, they predicted a warm and dry seaon, while in actuality, the results show we did have above normal temperatures in Georgia, but we also had above normal rain.
Another way of trying to predict future weather is through the use of analogs. The theory here is that you look at previous years with similar weather conditions to the current year, and examine what follows. For the upcoming winter, good analog years would be those that had above-normal Atlantic hurricane seasons coming off an La Nina winter that led to neutral conditions. Kirk Melhuish of WSB Radio is suggesting that we should look at 1976, 1985, 1989, 1996, 2000 and 2005 as analogs. I’ve heard 1985 as a possible analog year from other forecasters as well.
I dont’ have handy access to weather records prior to 1991, which makes it hard to compare 1985, although I found a map of precipitation from October-March that showed drier than normal conditions in North Georgia. For the years I do have records, in Atlanta the 1996-97 winter had 54% of normal precipitation, for 2000-01, 66% of normal, and only for 2005-06 did we see normal precipitation from December through February, with 102%.
So, based on this evidence, it doesn’t look like we’re going to be seeing a huge change in the drought situation through Spring. However, the proof of the pudding is in the eating, and ultimately, the weather will tell us what happens.
Side Note: No rain was reported at Atlanta Hartsfield yesterday or today, so it looks like we’re going to be short on precipitation for Septermber, with .75 inches or 18% of normal. Some folks got lucky, though. I was talking to a friend tonight with a reliable rain gauge who told me that he recorded 1.5 inches in about 20 minutes last night during a popup storm at his location between Snellville and Loganville. “I was so glad to see some rain, I went outside with my hands up,” he said. “That’s the first rain I’ve seen since Fay came through with four inches last month.”
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September 30th, 2008 at 11:14 pm
How does this September compare with other Septembers by your data and the other data (ie, Hartsfield, etc.) with regards to temperature and rainfall?
October 1st, 2008 at 7:49 pm
Kathy,
Unfortunately, the monthly rankings that are provided by the National Climate Data Center aren’t available until about the 10th of the month. Those are the ones that tell us that Sept. 2008 was the xxth warmest or yyth driest in the last 114 years. I spent some time digging around to see if I could find this information elsewhere, but while I could find data that would tell me the year each day of September was the warmest/coldest/had the most rain, there didn’t seem to be a good source for monthly comparisons with previous years, without spending a bunch of money buying the complete daily data set for each year and then working it out somehow.
That being said, I do know that September 2005 was the second driest September ever for Atlanta, and I found a blog post I made at the time listing the top ten driest Septembers. We know that .069 was the 11th driest Atlanta September in 1927, so I would think that this year’s .75 inches is probably within the top 20 driest. That post also noted that we went sixteen days without rain that month, the longest dry spell since 2001. We are now at 14 days without rain at Hartsfield, which is getting pretty close to that record, and no rain is forecast for the rest of the week.
Temperature wise, I think we were about normal. While Atlanta was 1.2 degrees above normal, much of that can be attributed to the heat island effect causing warmer nights in the city as opposed to the suburbs. I recorded an average temperature 2.8 degrees lower than Atlanta, which is more in line with the normal September temperatures for Gainesville and Athens.
In any case, I’ll keep an eye out for the official September rankings, and will post them when available.
October 2nd, 2008 at 8:13 am
If found information on Atlanta Temperature and Precipitation by month since 1950. Going back for the last 58 years, Atlanta had its 16th warmest September, with a mean temperature of 74.5 degrees. and its 5th driest September, with .75 inches of rain.