Chris Coleman, ERCOT Meteorologist
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
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
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.
Summer 2017 Weather Outlook
The past seven seasons, beginning with the summer of 2015, have all ranked warmer-than-normal for Texas. Last fall was the warmest fall season on record (dating back to 1895). Last winter was the warmest winter in Texas history. The six-month period, October 2016 through March 2017, was the warmest October through March on record. That's an incredible stretch of record-breaking, above-normal temperatures.
Should we expect to see this very warm, above-normal temperatures to continue through the summer season? Possibly. But unlikely to the record-breaking levels we've been seeing
Summer 2017 Temperature Outlook
Update on May 31, 2017 to temperature outlook: The region of the U.S. most likely to see above-normal temperatures this summer will be the Western U.S. That doesn't mean the rest of the country couldn't also see an above-normal summer, but there appears to be a greater number of milder opportunities from the Front Range of the Rockies to the East Coast -- including the ERCOT region.
The summer 2017 temperature outlook shows an average Texas forecast of slightly-above-normal temperatures for the summer season as a whole. The forecast calls for near-normal to slightly below-normal temperatures for the Panhandle and Far West Texas. Near-normal temperatures for portions of the Coast. The rest of ERCOT is forecast to see near-normal to slightly-above normal temperatures. Best potential for above-normal temperatures will be over North Central and Northeast Texas.
Last summer ranked the 21st hottest since 1895. The summer prior (2015) ranked the 17th hottest. This summer's forecast is not strongly hotter than either of the past two summers, based on mean temperatures. While last summer ranked 21st hottest (mean temperature), the maximum temperature (afternoon highs) only ranked 53rd. There is greater-than-average potential for this summer to rank hotter than last summer's 53rd ranked maximum temperatures.
Along with the potential for hotter afternoons (especially Dallas to San Antonio), there is a good chance for more 100-degree days than the prior two summers (chances may be slightly greater in Dallas than Austin or San Antonio.)
A reoccurrence of the summer of 2011 is highly unlikely. The primary reasons are the much wetter ground and significantly fuller reservoirs currently compared to this point (leading into the summer) in 2011. In fact, 2015-2016 combined was the wettest two year period in Texas weather history. In other words, we are currently far from a widespread, extreme drought. And drought feeds extreme heat.
We do still have some lingering characteristics with 2016. Also, there are some noteworthy correlations with 2006 and 2012 (though both of those years were drier than the current year). Many other past summers with similar characteristics to now were relatively mild summers.
Even though the forecast is for slightly above-normal temperatures, on average, for the June through September period, there is greater potential for a milder summer than forecast rather than hotter. Above-normal is possible, as is a greater number of 100-degree days than we’ve observed the past couple of summers. But 2011 levels will not be met.
While forecasting individual months within a seasonal forecast has significantly lower skill, there is a forecast lean toward the first-half of the summer having greater above-normal temperature potential than the back-half.
Summer 2017 Precipitation Outlook:
The summer precipitation forecast is for mostly normal to above-normal rainfall. Best bet for above-normal is West Texas. There could be an area of below-normal rainfall over portions of North Central and Northeast Texas, but widespread below-normal precipitation this summer is unlikely.
The summer 2017 rainfall forecast suggests drought conditions are not likely to be an increasing concern for Texas as a whole. There could be some regional concerns, however. Portions of Northeast and North Central Texas may need to be monitored -- though that part of the state has improved this spring. Probably also worth keeping an eye on the Rio Grande Valley. But widespread, extreme, hydrological drought is highly unlikely to develop this summer. Only some possible regional concerns -- and mostly agricultural-related, if at all.
Update on May 25, 2017 to hurricane outlook: There are increasing indications of a greater number of tropical storms and hurricanes than currently forecast. The updated, revised number is 14 total named storms, 7 of those hurricanes, and of the hurricanes, 4 are forecast to be major (category 3 or greater). We have already recorded Tropical Storm Arlene in mid-April. There is still some upside potential (greater numbers) to the hurricane outlook.
Last year was the most active hurricane season for the Atlantic Basin since 2012. 15 total named storms, seven of those were hurricanes, and three of those hurricanes were major hurricanes (category 3 or greater). There were four named storms in the Gulf of Mexico last year, but none made Texas landfall. The last hurricane to make landfall on the Texas Gulf Coast was Ike in 2008. We are currently one year shy of a tie with 1990=98 for the longest span of years minus a hurricane landfall in Texas since 1900.
The forecast for this hurricane season is 12 named storms, 5 of those will be hurricanes, and two of the hurricanes will be major. Last year had four named storms in the Gulf. 3 to 4 is the forecast for this year -- but too soon to project Texas landfall or not. In other words, this season is forecast to be slightly less active than last.