Seasonal Updates

Chris Coleman, ERCOT Senior Meteorologist

Winter 2018-19 Weather Outlook (published 10/31/18)

Winter 2018-19 Temperature Outlook:

12 of the 30 hottest summers have occurred since 1998 (POR = 1895-2018), including this past summer. Of the 11 historical (before this year’s summer), seven were followed by a warm winter (upper-third in ranking of all winters). One was followed by a normal winter (middle-third). Three were followed by a cold winter (bottom-third). However, only two of those historically hot summers since 1998 were accompanied by an El Niño – 2009 and 2015. 2009-10 was a very cold winter. 2015-16 was a very warm winter. In other words, there is very limited historical reference for the type of pattern we are currently experiencing (hot summer followed by an El Niño winter).

The winter 2018-19 temperature outlook will go against the statistical odds outlined above, with a colder-than-normal forecast for ERCOT. This is also colder than the preliminary forecast, released in September.

Summer 2018 Precipitation Map

This winter has a better chance than not of being colder than last winter. To note, last winter was only the 75th coldest winter, dating back to 1895. However, it was colder than the previous two winters and mid-January 2018 was the coldest period since February 2011. A cold forecast for the winter season does not necessarily foretell an extreme cold period that is similar to January 17, 2018 or February 2, 2011 – or worse. Extreme cold events can occur in otherwise mild winters. Colder-than-normal winters sometimes lack extreme cold periods, but generally experience more persistently below-normal temperatures.

There are indications this coming winter’s temperatures will be significantly influenced by clouds and precipitation. That means daytime/afternoon temperatures will be suppressed by cloud cover and precipitation more so than nighttime and morning temperatures. This is typical with the El Niño event that will be impacting weather patterns this winter. The polar vortex may not be as active with this pattern. Or if it is, it will be more common over the Eastern U.S. So the extreme cold morning lows should be limited in ERCOT this winter. But it only takes one brief period of extreme cold over the entire winter (mild or not) to approach record peaks. So that can never be completely ruled out in a long-range forecast. Regardless, I believe this winter’s temperatures will be influenced more by clouds and precipitation limiting daytime heating than by bitterly cold air plunging southward from the Polar Regions.

The Southeastern third of Texas is the region most likely to experience a colder-than-normal winter. This would include Houston, the Rio Grande Valley, San Antonio, and Austin (in that order of likelihood for a relatively cold winter). The rest of ERCOT is forecast to be either normal or a bit colder-than-normal. Best chance for normal temperatures this winter will be over the Far West. A widespread warm winter seems unlikely for ERCOT as a whole – not completely impossible – but if it does turn warmer, better chances North and West than the rest of the state. Highly unlikely this winter will approach the warm winters of 2015-16 and 2016-17.

I do apply historical references to the forecast. The winter of 2002-03 is my preferred match – although no winter will be an exact match with this winter. It should also be noted the winter of 2009-10 does show some matches worth keeping an eye on. That winter was the coldest this century – colder than the polar vortex winter of 2013-14. At this point, I’m not seeing enough similarities to go with that over the winter of 2002-03, but a colder winter than I currently have forecast cannot be ruled out.

Winter 2018-19 Precipitation Outlook:

Regarding El Niño’s impact on Texas this winter, a continuation of the wet pattern that set up in autumn is likely to continue through the winter months. Drought concerns are minimal thanks to significant rainfall during September and October. Drought shouldn’t be expected to make a return this winter.

Summer 2018 Precipitation Map

This winter’s forecast is for all but possibly a small portion of Northwest Texas to record above-normal precipitation. The best bet for the heaviest precipitation compared to normal will be over Far West Texas.

While forecasting snow and ice is best done in a short-term forecast, the type of weather pattern expected this winter is more conducive than average for frozen precipitation. There is a very good chance that Dallas-Fort Worth breaks it’s "snow drought" experienced over the past three winters.

One final note regarding the El Niño pattern for the winter season. This is likely to be a Central-Pacific-based El Niño. That means the water temperatures near the South America coast (along/near the equator) won’t be as anomalously cold as those west over the Central Pacific. This El Niño is also not likely to be strong. Both the intensity and the location of the warmest water temperatures in the Pacific drive the temperature patterns. And the expected El Niño scenario for this winter typically allows for a colder third-to-half of the U.S. The Southeastern U.S. is the region with the highest likelihood for a colder-than-normal winter under this scenario – but it oftentimes impacts a much larger region. The Western U.S. (especially the Pacific Northwest) tends to be quite mild/warm with this type of El Niño.

As the winter gets underway in December, if there’s any changes to the weather pattern, this forecast will be updated. Again, note the opening paragraph, which points out the lacking number of historically similar weather patterns. This does create a potential for forecast adjustments.

Fall Outlook Update (10/26/18)

October started warm and will finish warm -- but the bulk of the month in-between was quite chilly, leading to a below-normal first-half of the fall season.

There are indications suggesting November's weather pattern will be similar to October -- colder-than-normal -- and colder than other long-range forecasts I've seen. This would result in a below-normal autumn, which would be colder than the initial forecast.