Seasonal Updates

    Chris Coleman, ERCOT Meteorologist

    November 29 Update: December will start out quite warm. However, it's likely ERCOT will transition to a much colder pattern beginning December 5-6. And there's potential for this pattern to hang on for quite a while. This could make a mild, above-normal December difficult to achieve. It also puts into question how much impact this will have on the winter as a whole. At this point, the one takeaway from the original forecast below would be to emphasize that this winter is not likely to be as warm as either of the past two winters.

    2017-18 Winter Temperature Outlook: Last winter was the warmest winter on record for the state of Texas, dating back to 1895. The winter prior was the 8th warmest on record. You have to look back to the winter of 2013-14 for the last winter that was truly colder-than-normal in Texas (2013-14 was the winter when the term, "polar vortex" became popularized). Only three of the past 29 winters have ranked in the coldest third of all historical winters. Meanwhile, 15 of the past 29 have ranked in the warmest third. We’ve had a lack of truly cold winters in recent decades.

    2003-04, 2004-05, and 2006-07 are the top three historical winters being applied to the winter of 2017-18. None of those winters ranked in the top third coldest based on mean temperature – though 2006-07 was close. Based on minimum temperatures, all three winters were on the warm-half of the historical rankings. There’s also still some lingering similarities with last year. However, the next tier of historically similar winters were all cold – 1958-59, 1960-61, and 2009-10. Thus, a colder-than-normal winter cannot be completely discounted.

    We are currently (as of November 1) in neither an El Niño nor a La Niña. This is considered a neutral phase (UPDATE: as of mid-November, we are now in a La Niña). The trend over recent months has been in the negative or La Niña direction. But it hasn’t quite achieved it yet. The projection for this winter is for a weak La Niña to develop. This will not be a strong event. And unlikely it will reach moderate intensity. As a result, this La Niña is not likely to be a significant player in shaping the winter weather patterns in North America, including Texas. Though it could have some impact.

    Winter 2017-18 Temperature Map

    The forecast for this winter in Texas is warmer-than-normal. But likely not as warm as either of the past two winters. In fact, it may be a much more variable winter than we’ve seen in a while, which would suggest several cold fronts -- and some potentially strong. But the warm periods should outnumber the cold periods. Some regions within ERCOT may not be clearly above-normal.

    Portions of the Coast, South, and West Texas have opportunities for winter temperatures to average very near normal or a bit below. But the majority of the state is not likely to fall below-normal for the winter season, on average – especially for the minimum temperatures (overnight temperatures/morning lows). There will be potential for cloud cover and precipitation to limit daytime heating, however.

    A point of emphasis … winter is the most changeable season. We can experience periods of extreme cold in a mild, warmer-than-normal winter. In fact, this just happened last winter. The January 6-7 period was the coldest in Texas since February 2011. Yet, it was our warmest winter on record. Don’t let your guard down when you read or hear a forecast for a warm winter. Because many times, that warm winter will be accompanied by periods of quite cold air.

    For interests outside of ERCOT, it’s unlikely this will be a winter of widespread below-normal temperatures across North America. The most likely region for a colder-than-normal winter is the Canadian Maritimes. It’s possible some of this below-normal regime spreads into New England. And the eastern third to quarter of the U.S. may be more susceptible to cold outbreaks than any other part of the continent. The best bet for above-normal temperatures this winter will be over the Northern Plains into portions of the Upper Midwest. Much of the middle half-to-third of the country could see a relatively mild winter – from the Rockies to the Mississippi River Valley.

    2017-18 Winter Precipitation Outlook: Drought has not been a significant, widespread concern since the flooding rains in the spring of 2015. And though 2017 has had periods of dry weather, there have been enough (or in Hurricane Harvey’s case – more than enough) wet periods to minimize drought concerns. Some portions of Northeast, West, and South Texas show some limited drought concerns. It’s possible some of those same regions remain concerns through the winter months. But in general, this is not forecast to be a widespread, extremely dry winter. And most of West Texas is forecast to be wet this winter. Drought is not expected to strongly develop over the winter months.

    Winter 2017-18 Temperature Map


    Update on October 5, 2017: Recent trends suggest this fall may be drier than the forecast below. Especially for West Texas. Temperatures still look above-normal warm, though. Possibly even warmer than forecast. November looks to be more above-normal than October.


    The fall weather outlook extends from October 1 through November 30. (The summer outlook remains available below – scroll down.)

    The historical fall seasons being applied to the 2017 fall forecast are: 1994, 2003, 2004, 2006 and 2016. At this point, 1994 is being treated as the primary historical match.

    Fall 2017 Temperature Outlook

    Fall 2017 Temperature Map

    While much of the second-half of the summer has lacked periods of above-normal temperatures, do not expect this trend to continue through the majority of the fall season (October and November).

    The forecast for the fall is above-normal across all of ERCOT. Portions of North and West Texas (and the Panhandle) may be closer to normal. All of the large cities (Dallas-Fort Worth, Houston, San Antonio, and Austin) are forecast to experience a warmer-than-normal fall. In some cases, much above-normal. November shows greater potential to be much warmer-than-normal than does October. Thus, October may serve as a bit of a transition month toward a very warm November.

    Fall 2017 Precipitation Outlook

    Fall 2017 Temperature Map

    This fall should see a generally wet pattern continue. The bulk of ERCOT has recorded normal to above-normal rainfall both this summer and 2017 to-date. The dry exceptions being over portions of South Texas through the Edwards Plateau (West-Central TX/Hill Country).

    The bulk of the state – including the cities of Dallas-Fort Worth, Houston, Austin, and San Antonio are forecast to see 125 to 175% of normal precipitation. The Rio Grande Valley is the only region forecast to record below-normal rainfall (only slightly-below – with some wetter potential). Some historical similar years suggest this fall could be wetter-than-forecast.

    And remember, the hurricane season continues through the entire fall season. In what has been a very active season in the tropics – including Hurricane Harvey’s devastating impacts in Texas – another tropical cyclone is not out of the question.