Long Range Weather Forecast Verification (June 2012)

(Blog Written by Donald Sutherland)

Verfication:

My June 2012 forecast (Message #6) was as follows:

Although past transitions to possible El Niño conditions have witnessed a chilly summer, it appears that the current transition will witness at least the first month of summer turning out warmer than normal across much of North America.

Key Assumptions:
• Neutral ENSO conditions are likely to prevail through much or all of June
• The AO will likely be near neutral (with variability in negative and positive ranges)
• The PNA will likely be predominantly positive (but generally < +1)

The top analog was 1969. Both 1953 and 2009 were close behind.

The charts on which my June idea is based are:

Left: Composite temperature anomalies based on ENSO/Teleconnection Analogs.
Right: Observed Decadal Temperature Change for June

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Some of the greatest warm anomalies in the East occurred during the 6/20-30 timeframe, especially in 1953 and 1969. The leading analogs do not clarify the ENSO situation going foward, but they maintain the theme that odds lean toward the develop of an El Niño. 1953 saw neutral ENSO conditions. 1969 and 2009 witnessed the onset of El Niño conditions.

Based on the combination of the composite teleconnection analogs, observed notable warmth in the Arctic region, and the observed decadal temperature changes, my thoughts for June are as follows:

Much of North America will likely be warmer than normal. A portion of northern Canada could be near to somewhat above normal. Part of the West Coast, probably somewhere in California to perhaps the Pacific Northwest could be cooler than normal.

The June 2012 anomalies were:

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The widespread warmth in June is a strong indication that Summer 2012 will turn out warmer than normal across much of North America. Often, during summers when El Niño events take hold, June’s anomalies do a fairly good job in pointing to the overall summer outcome (especially with respect to possible areas where readings would be cooler than normal). Of course, there are exceptions, but given the continued warmth in the Arctic, any turn to cooler than normal conditions (possible in late August based on the timing of a number of similar El Niño transitions, but not assured), won’t wipe out the warm anomalies that will accumulate prior to then.

Below are some charts comparing the June and summer outcomes for 1976, 2002, and 2009:

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Much of the 2002 scenario is what I expected in my summer thoughts. However, I had expected the Great Lakes region to average near normal. The June outcome provides a strong signal that the summer anomalies in that area will also be warmer than normal (and perhaps much warmer than normal).