A recent headline should
have caught your attention if you’re looking forward to fall-like weather as
well as the upcoming winter season. NOAA
recently issued a “La Nina Watch” for an increased chance that La Nina
conditions will develop this winter. The
opposite of “El Nino,” La Nina features cooler than average ocean water in the
tropical east Pacific (west of Mexico).
Not all La Nina winters
are alike as there can be varying intensities of La Nina. More often than not, La Nina winters have had
below average snowfall in the Nation’s Capital.
Some of the snowiest winters on record in the Nation’s Capital have occurred
during the last 25 years, during both El Nino and La Nina. For example, while the 1995-1996 winter
season (46” of snow) occurred during a weak episode of La Nina, the 2002-2003
(40.4”) and 2009-2010 (56.1”) winters featured a moderate episode of El Nino. All three of these winters were colder than
and much snowier than average (15.4”) in Washington, D.C. and ranked among the
Top 5 for snowiest inters on record (dating back to 1888).
The presence of El Nino
or La Nina is just one of several factors that scientists look at when issuing
seasonal forecasts for the winter season.
Some other factors scientists consider are the North Atlantic
Oscillation (NAO) and the Pacific-North American Pattern (PNA).
More recently, the
2015-2016 winter season is remembered for two things. December 2015 was the warmest on record in
the Nation’s Capital and the first snow of the 2015-2016 winter season didn’t
occur until January 12, 2016. That set a
new record for latest first snowfall. However,
later that month, Washingtonians had a major winter storm that tied for fourth
largest snowfall on record. The 17.8”
that occurred on January 22-23, 2016 made up more than 80% of the snow that
fell during the entire winter. Despite
the warm start and late first snowfall, the 2015-2016 winter finished snowier
than average (22.2”).
There was a very strong
El Nino event during the 2015-2016 winter season. By comparison, 27.6” of snow fell in the
Nation’s Capital during another very strong El Nino winter in 1982-1983. Similar to the 2015-2016 winter that saw most
of the seasonal snowfall in one storm, more than half the 1982-3 snowfall
occurred on February 10-11, 1983 (DC’s 7th largest snowfall with
16.6”). This underscores the fact that
storm track is a variable that remains independent of large scale seasonal factors like
La Nina or El Nino. The 1997-1998 winter
also featured a very strong El Nino but Washingtonians only saw 0.1” of snow
during that entire winter.
While a winter season
could be warmer than average, one significant snow event could also make it
snowier than average. That’s what
happened in the 2015-2016 winter where the unusual December warmth caused the
seasonal winter temperature to finish at 42° - significantly above the average
of 38.2°. We will see if La Nina
develops, know it only takes one big storm to turn seasonal predictions upside
down. Whether you love or loathe the
snow, most people know the right set of ingredients has to come together only
once to create a memorable winter storm.
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