Will a Warm 2016/2017 Winter Result in a Hotter-than-Normal Summer 2017?

Despite this March bringing a last hurrah to winter in the Midwest and East, it comes at the tail end of a warm winter. The November to March period (actuals through the 15^th and 15-day forecast) is on track to be one of the top three warmest winters since 1950 on a Heating Degree Day (HDD) basis. This follows right on the heels of a record 2015/2016 winter, which was the warmest on record since 1950 on a gas-weighted HDD (GWHDD) basis.

As winter winds down and we look forward to summer, will a warmer-than-normal winter correlate to a warmer-than-normal summer?  

Available data from EarthStat shows that, since 1950, nine out of the 10 warmest winters have indeed produced hotter-than-normal summers. The table below shows those winters and the impact on average summer temperatures.  If this current winter comes in at 2,289 GWHDD, cooling load is likely to be at least 900 and could exceed 1,000 population weighted Cooling Degree Day (PWCDD).

Finally, it is worth noting that the current 10 year normal for summer temperatures would now be the eighth warmest summer on record.

Source: Earthstat

As we look ahead to summer 2017, what are some of the drivers that could dictate a hotter-than-normal summer? One hint is the progression or regression of current drought conditions.  Dry ground tends to dry out more in hotter than normal conditions and this can lead to daytime highs coming in at the upper end of a forecast range or exceeding it. Conversely, higher soil moisture content in the ground in summer months can provide a natural cooling effect as the sun dries out the ground. Current drought conditions are shown below with increasing dry conditions in the Northeast, Southeast and Mid-Continent regions. Current snowpack in the Northeast will help alleviate some dry conditions, but not in the Southeast where spring rainfall could be key.

Source: United States Drought Monitor & NOAA

Another key driver of summer 2017 weather could be around how (and if) El Niño conditions (warmer than normal temperatures off the equatorial Pacific) develop over the coming months along with its strength. Long-term weather models are forecasting an El Niño to emerge from the current “neutral” state that we are currently in. Yet the intensity of the El Niño is uncertain at this time. The graph below shows current El Niño-Southern Oscillation (ENSO) conditions at -0.2 C currently, but how it progresses from here is a key factor. Meteorologists have looked at past summers and seen two distinct trends:

• Fast development tends to lead to cooler summers, as storminess tends to be active, bringing more rainfall and keeping soil moisture levels higher. This can provide a natural cooling effect.
• Slow development tends to lead to hotter summers, which keeps a cap on storminess.

Source: NOAA

Initial summer forecasts from the National Oceanic and Atmospheric Administration (NOAA) for June through August shows the impact of a slower developing El Niño on a hotter-than-normal summer for most of the Lower 48 with heat concentrated in the Southwest from Arizona through the Gulf Coast. Texas has experienced a lot of rain this winter, which could be an offsetting factor.

It is important to mention that not all models are in agreement. The current American model predicts a rapidly developing El Niño, which would translate into a cooler-than-normal summer. The ENSO trend is away from cooler towards warmer water temperatures. How El Niño develops between now and May will likely be a key driver of summer temperatures.

To learn more about this summer’s weather outlook from team of experts who monitor the market, register for our upcoming Energy Market Outlook Webinar on April 19^th.