(NEW YORK) -- It's been an unusually cool summer for much of the eastern United States. But does this mean the upcoming winter season will be colder and snowier than normal?
For clues, let's take a look at previous cool summers and how the following winter played out.
For example, Indianapolis averages 15 days per summer of 90 degrees, but through Aug. 20 it had none. Last time this happened was in 2004 when Indianapolis had zero 90 degree days. The following winter was warmer than normal for the city.
Let's look at the Washington, D.C., area for August 2014; at Dulles Airport and Baltimore-Washington International, the first 15 days of August were the third coolest on record. The coolest ever for both reporting locations was 1964; the following winter (1964-65) was near normal.
What about Chicago, which averages 14 or 15 days of 90 degrees and above? So far this summer, only three days recorded temperatures at or above 90 at O'Hare International Airport (at the city's official weather observation station). Also, Chicago had below-normal July and August temperatures. Last time Chicago had a cool summer like that was in 2009 when June, July and August averaged below normal. The 2009-10 winter in the Windy City was colder than normal.
We also have to look at phenomena known as El Niño -- warmer than normal ocean water along the equatorial eastern Pacific Ocean. Usually, El Niño means warmer than normal and slightly wetter than normal winter in the Midwest and the Northeast.
The National Oceanic and Atmospheric Administration (NOAA) is forecasting El Niño to develop this winter.
NOAA says: "In summary, we continue to favor the emergence of El Niño in the coming months, with the peak chance of emergence around 65% (i.e. there is a 35% chance of El Niño not occurring). ENSO forecasters do not expect a strong El Niño (we can’t eliminate the chance of one either), but we are not expecting El Niño to 'fizzle.' In fact, just in the last week, we have started to see westerly wind anomalies pick up near the Date Line. Literally and figuratively, we may be witnessing the start of ENSO’s second wind."
With that said, looking back at warmer than normal winter 2004-05 in Indianapolis, El Niño was present. In the Washington, D.C. area, winter 1964-65 was near normal and there was no El Niño. But in Chicago, 2009-2010 was a cooler than normal winter and had a moderate El Niño.
Each year is unique and many variables could alter the winter forecast in either direction. In the recent years, weather patterns have been slower to move, due to weaker jet streams and lesser temperature contrast between the Arctic and the mid-latitudes. Once you are stuck in one pattern, warm or cold, it seems to continue for months, in some cases even a full year.
So far this year, we have been stuck in a colder than normal weather pattern in the eastern United States and warmer than normal weather in the West. We would need a significant pattern shift to change the current set up.
El Niño could be that trigger mechanism but it would need to be a strong El Niño in order to affect the world weather pattern. With NOAA's Climate Prediction Center not forecasting a strong El Niño, we could wind up with an early fall and colder than normal winter for the Northeast and Midwest.
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