The outlook for Autumn of 2011 and winter of 2011-2012 is based on a constructed analog approach using the long-term patterns of BOTH Pacific and Atlantic Ocean patterns, solar cycles, global volcanic activity, and teleconnection indices from both the Northern and Southern hemisphere. Recent behavior of USA spring and summer weather is salted in and related. A variety of GCM climate models are also consulted. When looking at ENSO the SOI, SST, and MEI are all considered. South American weather signals were also considered.
Global SSTA patterns show a cold or negative PDO with a warm or positive AMO, and the expectation of another cold or negative ENSO (La Nina, possibly East based) in the winter after being neutral through at least October, a tendency for high latitude blocking since 2007 (negative AO/NAO), and a QBO in a negative state.
Low arctic sea ice levels possibly related to low solar activity in the 11-year sunspot cycle is factored in as well and may point to the high latitude blocking and the reason for the predominance of –AO/NAO. The National Climate Prediction Center has issued an official LA NINA WATCH.
NOTE THAT 30-YEAR CLIMATE NORMAL HAS CHANGED from 1971-2000 last year to now 1981-2010 as NOAA/NCDC updates these on a rolling basis.
As always the 3 month period may capture nature better than the monthlies. Analogs will no doubt be sorted by November and change for the final winter outlook based on behavior of the hurricane season, fall weather, and teleconnection indicators at that time.
The complete list of current analogs being looked at for the autumn of 2011:
1883, 1893, 1904,1917, 1918, 1933,1934, 1950, 1951, 1952,1953, 1954, 1955, 1962, 1963, 1966, 1968, 1971, 1974, 1976,1980, 1985, 1986, 1988, 1989, 1991, 1995, 1996, 1997, 1999, 2000, 2003, 2005,2007, 2008.
Filtering to most common matches in the research yields the temperature anomaly maps for the 3-month period. Most departures from normal look rather modest, but I suspect the SW and Southern Plains to western Dixie will be warmer than the analogs show due to the dry ground positive feedback loop. These analog years will be revised for the winter forecast based on trends over the next 90 days.
The autumn trend is the heat of summer lingers in the South but closer to normal through September, with a slow but steady step down across most of the nation for October and then some early chill in November East of the Rockies, but mainly East of the MO River. The greatest autumn above-normal region will tend to be where it has been hottest in the summer, the southern plains and western Dixie. The greatest below-normal zone for fall will be from Idaho to Michigan.
FOR GEORGIA THE BIG THEMES ARE that the summer heat will continue into the first part of fall but fade to near-normal by the middle, then a colder than normal November follows. The entire period remains drier than normal unless a tropical system or two hit.
The hurricane season is still expected to be above-normal, but a high number does not guarantee they will strike the U.S. Last year was very active but they did not hit America, as 95% of hurricanes stay off the East Coast on average. This year we do expect at least several hits on the U.S. mainly the Eastern Gulf and the East Coast.
There have already been 9 tropical storms. We expect at least 3 more including a couple more strong hurricanes.