Football has started and fall is right around the corner and people are already asking about this winter. Will it be cold, will it snow... will we even have a winter this year? After the non-existent winter last year, any winter would be welcome for me. Some forecasters and meteorologist have started making their winter forecast and so far most are predicting a return to winter this year.
There is a gentleman in Savannah known as GaWx (he prefers to keep it that way!) that keeps very detailed climate records for Georgia and the southeast. As some of you may know, we are headed toward (or slightly in) a weak El Nino, as opposed to the La Nina that we've been in for the last several years. GaWx compiled some very interesting statistics regarding Atlanta winters during weak El Nino's, and he has given me permission to reprint those here. My comments are italicized. If you like winter... read on!
"As we move along and get closer, the chances for there being a weak El Nino this fall/winter (ONI peak of +0.5 to +1.0 and five trimonths in a row of +0.5+) continue to increase. The weak El Nino has historically lead to the coldest winters on average by a good margin for KATL and much of the SE of any of the ENSO phases. One additional key is to attain a -NAO (North Atlantic Oscillation) for DJF (Dec-Jan-Feb) to go along with it although that isn't 100% necessary as the very cold 1904-5 would indicate. It also helps very much to have a +PDO (Pacific Decadal Oscillation) for DJF, even during a -PDO regime although it seems as if there may be a chicken-egg issue with it (the +PDO may tend to follow from the +PNA pattern bringing the cold). All of the coldest winters had at least a neutral PDO and most had a +PDO. 1968-9 was a pretty rare cold winter, though not one of the coldest, that actually had a -PDO in DJF. Also, the chances of a cold winter seem to be enhanced when El Nino follows La Nina. Well, that would be the case this year, which is quite encouraging for cold chances.
Weak El Nino winters following La Nina's for KATL (Atlanta in chronological order):
1) 1904-05 (3rd coldest winter on record; 1" S/IP and 2 major ZR's )
2) 1911-02 (cold winter; 5.2" S/IP and a major ZR )
3) 1939-40 (7th coldest winter on record; 8.3" S/IP and a major ZR )
4) 1951-02 (only warm winter (warmest of 16 weak Nino's by far though 3.9" of S/IP still fell; most -PDO of weak Nino's by good margin and NAO was +)
5) 1963-04 (6th coldest winter on record; 3.6" S/IP )
6) 1968-09 (cold winter; 2.2" S/IP)
7) 1976-07 (COLDEST winter on record; 1.0" S/IP)
9) 2009-10 (I added this one since it was the 9th coldest and most recent cold winter here)
So, a very impressive 4 of the 7 coldest winters were in this little group of 7! By the way, what isn't shown are weak Nino's that didn't follow La Nina. The 2nd, 10th, and 11th coldest winter spots were taken up by those. So, weak El Ninos as a whole took up a very impressive 7 of the 11 coldest spots!! There have been only 16 weak Ninos in the last 133 years, the total length of records for ATL, or about one of every eight winters. So, only about 1-2 of the 11 coldest would be the “expected value” if there were no bias of weak Nino’s toward either warm or cold versus the 7 on the list! To better put this stat in perspective, 2009-10 was the 9th coldest Atlanta winter.
Regarding S/IP (Snow/Sleet), 25.2" fell for the 7 winters, which is 3.6"/winter or nearly double the long term avg. of ~2"/winter. Regarding ZR (Freezing Rain/Ice) events, there were 4 of them in the 7 listed winters versus only 1 every 4.4 winters overall, or about double the longterm average frequency.
In summary, ASSUMING WE GET A WEAK NINO PEAK THIS FALL/WINTER (looking increasingly likely), the stats strongly suggest that things are looking up for a very interesting SE winter in 2012-3 (whether it's cold, above normal wintry precipitation, or both), especially since it would be following La Nina . Out of the 7 listed, 6 were cold and 4 were very cold. The only warm one still had major S/IP at KATL (twice the norm). Only one had below normal for both S/IP and ZR and that was the coldest of all time! Although we obviously could still have another boring winter in terms of both temperature's and wintry precipitation, even with a weak Nino following a La Nina, since nothing is set in stone. I'm about as optimistic as I can possibly be in August that that won't occur in 2012-2013 for the SE as a whole. We'll see!"
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