NOVEMBER 2016/WINTER 2016-17 WEATHER UPDATE
Fall temperatures in the lower 48 states have continued an overall warmer than normal trend. September
temperatures were above normal in all but some western parts of the nation and for the contiguous U.S. this past
September ranked as the 9th warmest since 1895. The seven-month period from March through September of this
year was the 2nd warmest such period since 1895, ranking behind only 2012. October temperatures have
averaged above normal so far in much of the lower 48 states, with significant areas of below normal readings
confined to some northwestern and far western parts of the nation. For lower 48 states, as a whole, October 2016
will go into the record books as yet another warmer than normal month. October precipitation showed wide
variability from one side of normal to the other in the northern one-half the Plains and in the Midwest. Larger
areas of below normal amounts in areas farther south lead to worsening drought conditions in many areas. Below are
maps from the High Plains Climate center showing departure from normal temperatures and percent of normal precipitation
for much of October. This precipitation map does not include some of significant rain that fell in Midwest on October 25 and
26.
Sea surface temperature departures from normal in the NINO3.4 region of the Tropical Pacific have continued to
average below normal recently, with temperature departures in the -0.3 to -0.9 degrees C. range since July.
These temperature departures were around the threshold values for weak La Nina or in the weak La Nina category.
The latest weekly value was -0.6 degrees F. These temperatures are measured near the equator, and since sea
surface temperatures cooled below normal the Equatorial Region this past summer, there have continued to be
areas the Pacific Ocean farther north and farther south in which sea surface temperatures have remained warmer
than normal. Below is a graph from the U.S. Climate Prediction Center showing the trend in sea surface
temperature departures from normal in the NINO3.4 region.
Sea Surface Temperature Anomalies for NINO 3.4 Region in Degrees C.
Latest indications are that major additional cooling is not likely to occur in the Tropical Pacific into late this year. Most
models keep conditions in the weak La Nina or in the negative neutral range into late 2016 and some indicate a trend
for some warming overall early next year. Average conditions into winter will likely be weak La Nina or strong negative
neutral conditions.
Another notable trend in the weather of 2016 was the trend for above normal overall growing season precipitation in
the area defined as the primary corn and soybean producing region of the U.S. by the U.S. Climate Prediction Center.
The seven-month period of March through September ranked as the 5th wettest such period for this region since 1895,
even though there were shorter periods of time when below normal rainfall was concern for some locations. This
combination of wetter March through September conditions in the corn and soybean areas, and warmer than normal
conditions in the contiguous U.S. had some overall similarity to the past years of 2015, 2011, 2010, 1998 and 1977,
however each of these years also showed differences when looking at smaller geographic areas or shorter periods of
time. In these years, there was tendency for above normal October and November temperatures for the lower 48
states as whole, with 1977 being the coolest. Average winter temperatures for nation showed more variability in these
years. In 1998 and 2010 we had significant El Nino conditions early in the year transitioning to La Nina later in the
year, somewhat similar to trends of this year, but in both of these cases the La Nina was considerably stronger than is
expected for this season. The winter of 1998-99 was warmer than normal for the lower 48 states as whole, while the
winter of 2010-11 was cooler than normal.
In looking for other trends for winter weather I continued to look at years in which there was a transition from EI Nino
to negative neutral or weak La Nina conditions, with these conditions then continuing into winter. Some of these years
continue to be 1954, 1964 and 1995, years that I have been looking at the previous few months. No consideration was
given to past weather in these years or in the strength of the previous El Nino. Some other years that could be
included, with somewhat less favor however, would be 1966, 1983 and 2005. Winter seasons in these years also show
variability from one side of normal to the other for winter temperatures as whole for the lower 48 states. The current
winter outlook is based on composites of weather from these years, as well as from general trends for all winters with
weak La Nina conditions or strong negative neutral conditions in the Tropical Pacific. The November updated outlook is
more strongly based on current mid-range forecasts and climate model trends
October 26, 2016
Dan Hicks/Meteorologist
Freese-Notis Weather
515-282-9310
[email protected] IM: weathertrader89 Twitter: @freesenotis