Chris Coleman, ERCOT Senior Meteorologist
Summer 2019 Weather Outlook (published 5/8/19)
Summary/Highlights for Summer 2019:
- El Niño will likely still play a role, at least through the first half of the summer.
- Summer 2019 will not be as hot as summer 2011.
- Summer 2019 is not expected to be as hot as summer 2018 for the season as a whole. Summer 2018 ranks sixth hottest.
- Using the nine previous summers this decade for a comparison, summer 2019 is unlikely to rank with the top three hottest years for mean temperature (2011, 2018, 2010) or the top four hottest years for max temperature (2011, 2012, 2018, 2013).
- 2015 ranked the fifth hottest of nine summers this decade, which is a reasonable expectation for this summer. However, there is a better chance that summer 2019 will be cooler than summer 2015.
- Summer 2019 could rank in the mildest third of summers this decade, yet rank in the hottest third of summers all-time.
- Early summer 2019 is less likely to be hotter than normal than late summer.
- West Texas has the greatest chance for a hotter-than-normal summer, followed by Central Texas.
- Forecast indicators are limited for the summer precipitation forecast, but no extremes are expected.
- Widespread, extreme drought is not expected, but there may be some regional concerns in the West-Southwest.
- The hurricane season forecast is 15 total named storms, 7 of those as hurricanes, 4 of those 7 as major hurricanes -- category three or greater. This is a bit more active than normal. There are no early indications of an active Texas Gulf Coast, but only short-range forecasts can determine specific paths and landfalls.
The summer of 2019 weather patterns will largely be shaped by the El Niño that is still in place, as well as reservoir levels, soil moisture and recent weather patterns.
Last summer was hotter than normal. It was the sixth hottest summer of all time, dating back to 1895, with the hottest anomalies occurring during the first half of the summer.
Since last summer, seasonal mean temperature anomalies have been significantly cooler. The past six months (October – March) have been cooler than normal — and only twice in the past 10 years have those months been colder (2009-10 and 2013-14). Only four of the past 20 October – March periods have been colder than the current period. This is even more pronounced when examining max (high) temperatures. Only one such period has been colder than the current year over the past 10 years, and that was 2009-10.
Here is a monthly breakdown:
October: Below normal. Coolest since 2009.
November: Below normal. Coolest since 2014.
December: Above normal. Only 2017 has been cooler over the past five Decembers.
January: Above normal. Second warmest of the past five Januarys.
February: Above normal, but coolest of the past five Februarys.
March: Below normal. Coolest since 2014.
April: Below normal. Only two of the past nine Aprils have been cooler.
Summer 2019 Temperature Outlook:
The summer 2019 outlook is for near-normal temperatures. Based on the most recent 10- to 15-year period of weather, this summer could be slightly more mild than average, taking into account that there have been a lot of hot summers this decade. Based on a longer-term period to define normal, this summer will likely end up slightly on the hot side of normal; however, it will not be a repeat of 2011.
Although no two summers are exactly alike, there are historical summers that are similar to what is expected this summer, with 2015 being the closest match from this decade. 2015 was also in an El Niño heading into the summer season. A very wet spring was followed by a very dry summer that year, and a brief flash drought impacted lawns and vegetation for a few months. Summer 2015 was the 18th hottest on record, ranking it the sixth hottest since 2000 for mean temperatures and seventh hottest for max (daytime high) temperatures. ERCOT anticipates this will likely be the hottest possible scenario for summer 2019.
Three summers from the last decade – 2003, 2004, and 2005 – are good references for summer 2019. Of those three years, 2003 is the most similar, and it was a relatively cool summer. 2005 was the only one that was on the hot side of normal – in a range similar to 2015.
Years 1958, 1960, and 1969 can also be used for comparison. 1958 and 1960 were both hotter than normal, but not quite as hot as 2015. 1960 was right around normal. Basically, the historical matches do not have strong correlations to one another, and there is nothing to suggest temperatures will be hotter than 2015 or 2011.
For the past couple of summers, the first half of summer was hotter than the second half. In recent years, weather and load were lower in August due to cold fronts and Hurricane Harvey. For the majority of summers, ERCOT’s peak load typically occurred during the month of August. However, the system-wide peaks occurred in July during the past two summers. The summer of 2019 shows more support for the second half of the season being hotter (or at least relative to normal) than the first half. While forecast ability lessens with monthly projections more than a month out, there are early indications that September has the most above-normal potential of the summer months. June, July, and August all show more mixed messages, but each offers some below-normal potential for parts of the state.
There’s a better than 50/50 chance the mean temperature will rank higher (hotter, compared to historical summers’ mean temperatures) than the maximum temperature compared to historical summers’ max/high temperatures. This would indicate higher humidity, cloud cover and possibly more than typical rain chances, which would keep the overnights and mornings warmer but limit the heating in the afternoon/evening timeframes.
There will likely be some regional differences. West Texas, especially the Far West zone, has the highest potential for a hotter-than-normal summer. The South zone has the lowest potential for a hotter-than-normal summer. Central and North Texas could go in either direction, with Central Texas having a bit more above-normal potential than North Texas.
On a national level, the Western U.S. has the best opportunity for a hotter-than-normal summer, especially interior Northwest and Great Basin. The Southeast U.S. and portions of the Midwest, especially the southern half, have the most potential for a cooler-than-normal summer.
Please note that a four-month summer seasonal forecast uses a broad brush. It will not capture the peak load period as well as a short-range forecast will (not more than 7-10 days in advance). But in most cases, if a summer is hotter than normal, load peak records are broken. If the summer is mild, load peaks have less opportunity to be broken.
Summer 2019 Precipitation Outlook:
Precipitation was lacking during the first quarter of 2019, tracking as the driest for the state, on average, since 2014. However, substantial April and May rains are rapidly changing the setup. Drought concerns are expected to be localized, minimal or both heading into the summer season. The majority of reservoirs continue to operate at high levels. Additionally, an El Niño is still in effect and will continue to impact summer weather patterns. El Niños do not support extended periods of drought, and drought plays a significant role in extreme summer heat.
As with the temperature outlook, the rainfall forecast for the summer season is not extreme in either direction, wet or dry. There is potential for a wet spring to turn into a dry summer. But drought concerns will still likely be minimal, as most reservoirs are full or close to full. If there are some regional drought concerns, parts of West and northwestern South Texas are the areas of most concern.
2019 Hurricane Outlook:
El Niño is not typically conducive to an active hurricane season. However, there are exceptions. It is possible the current El Niño will weaken significantly or be non-existent by mid-summer, having little impact on the hurricane season. Historical comparisons suggest this coming Atlantic hurricane season will range from slightly below normal to very active. The least likely scenario is a very quiet season. The current forecast for the 2019 hurricane season is 15 named storms, 7 hurricanes, and 4 major hurricanes, which is more active than normal. It will require a shorter-range forecast window to determine paths, but similar historical patterns lean slightly in the less-active direction for Texas.