TEXAS WILDLAND FIRE POTENTIAL WINTER/SPRING 2018/2019

Transcription

1 TEXAS WILDLAND FIRE POTENTIAL WINTER/SPRING 2018/2019 Texas A&M Forest Service Predictive Services Prepared December 12 th 2018 Brad Smith Luke Kanclerz Scott Breit Tom Spencer Mike Dunivan

2 2 Fire Potential Outlook for the 2018/2019 Dormant Season Freeze cured grass is the catalyst for the dormant fire season. A combination of short term drying (2-4 days) and moderate fire weather is a recipe for wildland grass fires. Initial attack fires that occur with this recipe trend to the low end of the fire spectrum and have low resistance to control. But if extended drying/drought, widespread above normal grass loading and high impact fire weather become part of the recipe, then significant fires that trend to the upper end of the fire spectrum and are highly resistant to control become more likely. This outlook examines the three fire recipe elements to identify areas that have the potential for fires on the upper end of the fire spectrum.

3 Dormant Season Fire Potential Considerations Drought Trends Emerging, Persistent or Improving Fine Fuel Condition Grass Production or Grass Loading in Grass Dominant Regions Seasonal Temperature and Precipitation Trends El Nino Southern Oscillation (ENSO)

4 Emerging drought was the trend prior to the 2018 dormant season. Drought improvement is the current trend and forecast for the upcoming dormant season Drought trends have improved significantly since this time last year. Most of the improvement has occurred over the last three months. One year ago 28% of the state had no level of drought. Three months ago only 20% of the state had no drought. Currently 96% of the state has no drought according to the U.S Drought Monitor. 4

5 Seasonal Drought Forecast for Texas is for Drought Improvement The Climate Prediction Center s (CPC) Seasonal Drought Outlook has drought removal likely listed for the two remaining areas in Texas through February Couple this drought outlook with CPC s outlook for above normal chances for rainfall during the March through May period and it is difficult to forecast any emerging drought in Texas through May (see precipitation outlooks in weather trend section) 5

6 2018 Grass Production or Grass Fuel Loading 6 28 of the 30 largest fires in Texas history occurred during the dormant season in grass dominant fuel beds. Most of these burned in years that supported widespread above normal grass loading. The 2008, 2011 and 2017 dormant seasons followed growing seasons with high levels of grass production on the western Plains. Above normal grass stocking or loading facilitates the ignition and spread of wildland fires. The increased grass loading increases fire intensities and spread rates which in turn increases a fire s resistance to control. We use growing season rainfall and random site inspections as guidance to subjectively characterize grass loading as below normal, normal, and above normal. Land ownership in Texas is mostly private. Grazing practices from one ownership to the next will impact the grass loading at any given location.

7 2018 Growing Season Percent of Normal Rainfall (May-September) Growing season rainfall provides guidance for grass production for the grass dominant regions in the state. Above normal rainfall can promote above normal grass production. Above normal grass loading provides a continuous, robust grass fuel bed that enhances the ignition and spread of wildfires. 2008, 2011, and 2018 supported widespread above normal grass loading. 7 The growing season rainfall anomalies shown here are heavily weighted to the wet September we experienced. There was little grass production in September for the northern half of the state. The cooler September temperature anomalies or prior drought conditions might have muted an expected surge in grass production here. For whatever reason the above normal September rainfall did not increase grass production in the northern half of the state

8 Percent of normal rainfall during the growing season (previous slide) was heavily weighted to September. Our thinking is that above normal rainfall in September north of I-20 did not produce above normal grass loading. Localized above normal grass loading north of I-20 can be located on the May through August where 125% of normal are shown. May Through August September 8 September rainfall south of I-20 did increase grass production. Above normal grass loading is very likely in locations where above normal rainfall anomalies from both maps align.

9 Above Normal Grass Production in Andrews County (left) and Motley County (right) 9 Here are examples of localized above normal grass loading on the grass dominant Texas Plains. Both locations saw repeated monthly occurrence of above normal rainfall during the 2018 growing season. Above normal grass production is the exception and not the norm this year on the grass dominant Texas Plains.

10 Normal grass loading in Northwest Roberts County (High Plains) on Pats Creek road just off the Caprock in the Canadian River drainage. This area received near normal rainfall from May through August. Roberts County Percent of Normal Rainfall for May through August 10

11 These pictures were taken at the same location in King County just south of Guthrie. (Same two Juniper are present in both photos from different angle) You can see the above normal loading that was present for the 2017 dormant season and the normal to below normal loading that is present for the current 2019 dormant season. November November 2018 A combination of 25-50% of normal growing season rainfall deficits here in 2018 and grazing has produced the current grass load. Some of the current grass loading may actually be leftover from the 2017 growing season.

12 Grazing impacts seem to be magnified this year with generally lower grass production across the western Plains. The examples shown here are from Hartley County (High Plains) on the left and Nolan County (Rolling Plains) right. Last year, grazing would reduce the widespread above normal loading to a normal loading. This year, any level of grazing seems to reduce the grass to below normal loading as seen in these examples. 12

13 Seasonal Precipitation and Temperature Trends 13 Most forecast models and forecasters are predicting an El Nino episode to develop and persist through at least April Past El Nino episodes have shown a strong correlation to wetter than normal conditions in Texas. Though El Nino is not the only consideration for seasonal precipitation trends, the Climate Prediction Center (CPC) appears to be weighting the forecast EL Nino episode heavily for the Spring precipitation trend with monthly outlooks through April favoring above normal precipitation. The official CPC temperature outlook as of 11/15 is favoring above normal temperatures. This temperature outlook is not consistent with past El Nino episodes that generally favor below normal temperatures. This is not a consensus forecast as many forecasters favor normal to below normal temperatures during the dormant season.

14 It is likely (80% chance) that El Nino conditions will exist through February. There is a 65% probability that El Nino conditions will persist through April. 80% thru February 65% through April 14

15 15 Climate Prediction Center Precipitation and Temperature Forecast for December through February

16 16 The CPC February through April outlook favors above normal precipitation (left) and above normal temperatures (right) for Texas

17 17 The CPC March through May outlook favors above normal precipitation (left) and above normal temperatures (right) for Texas

18 Above normal precipitation was observed in Texas during previous El Nino episodes The blue colors in Texas represent above normal precipitation anomalies that occurred from January through April in previous El Nino episodes. The years of previous El Nino episodes included here are 1992, 1993, 1995, 2005, 2007, 2010 and Past El Nino episodes correlate well to above normal precipitation during the dormant season in Texas. 18

19 2018/2019 Dormant Season Fire Potential Summary Most of the Texas Plains will carry normal to below normal grass loading into the upcoming dormant season. There are localized areas on the Plains supporting above normal grass loading. No drought development is expected through the dormant season. No high impact or Southern Plains Outbreak fire weather events are anticipated. Above normal chances for rainfall are outlooked from December through April.

20 /2019 Dormant Season Fire Potential Summary (Cont.) Below normal fire activity is forecast for the upcoming dormant season. Fire activity will be associated with short term drying in cured grasses centered around dry frontal passages. Significant fires are possible but not likely. Most fires will fall into the initial attack or large fire (300 to 3000 acre) category with low to moderate resistance to control.