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Summer 2011 forecast verification

Overall I’d give my summer 2011 forecast a B+, a grade worthy of a forecast that used one of the hottest summers on record as its main analog to forecast what ended up being yet another record-setting summer of heat. On a month-to-month scale, I’d give June an A-, July a C and August a B. The one thing that really hurt this forecast was just the sheer extent of the heat, especially over Texas and Oklahoma where extreme drought occurred. Otherwise, the pattern was recognized fairly well, with warm anomalies across the eastern two-thirds of the country and a cooler West Coast.

Summer 2011 (based off of 1971-2000 30-year normals):

The monthly breakdown:




And here’s summer 2010 (left) next to summer 2011 (right)… what I would consider a grade A forecast:

I also must remember to do something like this for last winter, as I managed to completely forget about doing the winter verification.

Enjoy the cooler temps… they’re only temporary

DCA is sitting at +4.0 through the first 12 days of July, with all but two of those days with highs of 91-97. Today was another warm day as temperatures climbed to about 93 before the storms hit.

Tomorrow through Sunday looks to be more seasonal to even slightly below normal, with highs in the mid to upper 80s. While not necessarily cool, it’s certainly a nice period of relief, especially considering what lies ahead.

Another warm up is on the way during the second half of next week, when highs could climb into the 95-105 range (according to the latest model runs and trends). Whether these hot temperatures will verify or not remains speculative since it is still in the medium range, but all of the medium-range signals point to hot, hot, hot weather next week.

So what’s on tap for July?

Waaaaaaay back in February, I made this little number for July:

EDIT: And here’s the updated look for this month:

It looks to be a decent forecast going ahead, with warm adjustments likely needed in the South, Southeast, southern Midwest and southern Mid-Atlantic. The combination of a lingering upper-level ridge and extreme drought conditions in the South/Southeast are the two main attributors to the need for warm changes.

Looking back at the controversial 2010 analog, it did well in capturing some of the extreme heat areas of 2011. However, much cooler temperatures were found in the West and Northeast in 2011 compared to 2010, and obviously the above-normal extremes were not as high as 2010 in most areas. Most of these differences can be accounted for by the strong -AO/-NAO combination we had in 2011, whereas 2010’s AO/NAO values were close to normal overall. When 2010 is coupled with some of the ENSO analogs (strong Niña in the winter that weakened to neutral conditions in the early summer) and drought is accounted for, the June 2011 map appears.

For the Mid-Atlantic, July should be another warm month as the teleconnections seem to indicate a similar pattern to June in the eastern U.S., yielding temperatures of around 2.5-3.5 degrees above normal. So long as we see a continued -AO/-NAO/-PNA pattern to go along with the more long term -PDO/+AMO signals, we should see similar anomalies appear in July.

As for the rest of the country, one of the bigger risks is going to be where the upper-level ridge settles once we head into the middle of the month. We’re already seeing hints of the ridge wanting to move either into the mid-country or into the West going into this weekend. Should the ridge linger out west, it would cause the Northern Plains to be warmer than my July forecast and/or could make the mountain West warmer than expected.

January analogs using Niña winters and strong blocking

Januarys with a moderate/strong Niña in NDJ (-1.0 or lower) and the corresponding January AO and NAO values 1950-present:

Year (AO, NAO)

1951 (-0.085, +0.08)
1955 (-1.163, -1.84)
1956 (-1.204, -0.22)
1965* (-1.046, -0.12)
1971* (-0.163, -1.13)
1974** (+0.232, +1.34)
1976 (+0.034, -0.25)
1985 (-2.806, -1.61)
1989* (+3.106, +1.17)
1999** (+0.110, +0.77)
2000 (+1.270, +0.60)
2008** (+0.819, +0.89)

* Years where the previous winter had a weak El Niño
** Years where the previous winter had a mod/strong El Niño

Using the four highlighted years, which indicate a mod/strong -AO during January (no weak -AO cases), we get this composite for January, using 1971-2000 normals:

1965, the ONLY analog from 1950-present with a mod/strong -AO coming out of any sort of Niño to mod/strong Niña transition year:


And here is more along the lines of what people were thinking, with years coming off of a mod/strong El Niño (much like this year):