tropical threats 8/20/23

Gulf Disturbance Could Increase Fire Danger

(11AM 8/20/23 and updated at 7PM) Here’s something you don’t often see – a tropical disturbance that could increase fire danger more than flood risk.

The 8am 7-day tropical outlook from the National Hurricane Center shows that Tropical Storm Emily has formed in the Atlantic. Separately, a disturbance lingering over the Bahamas has finally crossed over Florida and moved into the Gulf. However, the latter storm will likely miss Houston as it veers south into the lower Texas Coast and northern Mexico. That means…

8AM update on Aug 20, 2023 from NHC

Twelve hours later, another tropical storm formed in the Atlantic – Franklin. And NHC increased the chances for formation for the two orange disturbances to 70%.

8PM update on Aug 20, 2023 from NHC

High winds from the storm combined with the lack of rain and dry vegetation could actually increase fire danger north of I-10.

Jeff Lindner, Harris County Meteorologist

Rainfall Chances for North Houston Area Slight

Unfortunately, the still unnamed Gulf disturbance will likely bring little rain to the Houston area. The 72-hour cumulative prediction from the National Weather Service shows about a quarter inch of rain south of I-10 and a tenth of an inch north of it.

As of Sunday morning, the disturbance is centered south of the Florida panhandle.

That big clear area over the southern plains and Texas is the high pressure system that has dominated our weather for the last month. It forms a barrier that will likely block the lower pressure system in the Gulf from moving north toward Houston.

High Winds, but Little Chance of Flooding

Jeff Lindner, Harris County meteorologist predicts that tropical moisture will begin to arrive along the Texas coast on Monday with offshore scattered activity increasing through the day.”

Lindner believes that I-10 will be a good dividing line between higher coastal rain chances and lower inland chances late Monday into Tuesday.

Said Lindner, “There will likely be a strong south to north rainfall gradient over the region … with rain chances in the 50-60% range near the coast, 30-40% along I-10, and generally less than 30% north of I-10. 

Lindner expects wind gusts up to 30 knots on Monday and Tuesday as the storm passes. He also predicts that seas will build 5-9 feet for most offshore waters. He also predicts that tides will be elevated late Monday into Tuesday, but he doesn’t expect them to reach critical thresholds or cause any issues along the coast or in the inland bays.

Inland winds will increase Monday into the 15-20 mph range with higher gusts. Ironically, the biggest threat from this storm may be fire.

Lindner predicts that the high winds inland along with low humidity and critically dry vegetation will support an enhanced fire danger for those areas along and north of I-10. “Fires could quickly spread in these conditions,” warns Lindner.

Red Flag Warnings

At 2:39 PM, Lindner announced that red flag warnings had been issued for most counties in SE Texas including Harris, Montgomery and Liberty.

Potentially dangerous fire weather conditions will exist on Monday as the tropical system approaches. It will increase the pressure gradient across much of SE TX. Humidity values will decrease through Monday and reach below 30% during the afternoon and early evening hours.

Fuels loads are critically dry over the region, said Lindner. “Small fire will grow rapidly. Fires continue to exhibit aggressive behavior in pine areas and winds on Monday.Ccanopy crown runs will make containment lines challenging.

Fire conditions have deteriorated to those similar to August and September 2011 when several large devastating fires occurred over portions of SE and central Texas.   

Extreme Drought Conditions Persist

In fact, the U.S. Drought Monitor shows that the Lake Houston Area is in Extreme Drought.

What have temperatures and rainfall been compared to the 30-year average?

Temperatures so far this year have been consistently above the average for the last thirty years (green line compared to yellow line). Rainfall (blue and red bars) has been both above and below average. April and May were both above average. But June, July and August have been far below.

According to the Harris County Flood Warning System, the West Fork San Jacinto gage at US59 last received rain on July 23rd – four one-hundredths of an inch!

Obviously, this is not the time for outdoor burning! In fact, the Texas A&M Forest Service shows that most Texas counties currently have burn bans.

Posted by Bob Rehak on 8/20/2023

2182 Days since Hurricane Harvey