Watching the Skies » Flood

West Dallas tornado rated eF-2, six other tornadoes around north Texas

Sean Toner — Thu, 09 Sep 2010 22:59:39 +0000

Tornado damage consistent with an eF-2 tornado was found in West Dallas during a storm survey conducted by the National Weather Service today. The tornado’s path was one half mile in length, causing significant damage to numerous structures in that area. A preliminary track map shows it crossing the Trinity River and its levees, which should debunk any myths people may of had about tornadoes and river crossings… (source: http://www.srh.noaa.gov/fwd/?n=prelimtrackmap) I have included a tornado damage summary provided by the National Weather Service below.

Six other tornadoes were documented around the area, including another which caused moderate damage in southeast Dallas county, to the city of Seagoville. Below is radar snaps of the storm as it looked while producing the tornado in West Dallas. The storm is not overly impressive, when compared to supercells during our spring time severe weather season, but still displays the traditional hook echo and velocity couplet associated with tornadic supercells.

A similar feature is observed with the northeast Ellis/southeast Dallas counties tornado. A noteworthy hook echo and velocity couplet are observed by radar.

Thankfully the next 7 days don’t appear to show any significant tornado threats. Forecast models show marginal chances of thunderstorms Friday night, but I wouldn’t bet on it. Additionally a weak front may move through the area Saturday, then lay stationary across the Metroplex Sunday into Monday. This front has the potential to kick off organized severe development along and to the south of the front, but coverage of storms may be limited. Regardless I would consider storms a possibility Saturday and Sunday. Straight line winds and hail would be possible with stronger storms over the weekend, but the tornado threat will be minimal as environmental wind shearing will be very low. Temps the next 7 days will remain above normal and with high dew points due to the obvious abundance of moisture, our heat indexes will be around 100 to 105.

It would seem summer has not quite left us yet.

Tornado damage survey report by the NWS:

…PRELIMINARY DAMAGE REPORT…

A TOTAL OF SIX TORNADOES OCCURRED ON WEDNESDAY SEPTEMBER 8TH. FOUR
TORNADOES WERE RATED EF0 ON THE ENHANCED FUJITA SCALE. ONE TORNADO
WAS RATED EF1…AND ONE TORNADO WAS PRELIMINARILY RATED EF2. ONLY
TWO MINOR INJURIES HAVE BEEN REPORTED FROM ALL OF THESE STORMS.

THE EF2 TORNADO DAMAGE WAS LOCATED IN THE CITY OF DALLAS NEAR THE
INTERSECTION OF MOCKINGBIRD LANE AND IRVING BOULEVARD. THIS
TORNADO CAUSED MINOR ROOF DAMAGE TO SEVERAL BUILDINGS AND CAUSED
MORE EXTENSIVE DAMAGE TO A WAREHOUSE. AN EXTERIOR NON LOAD BEARING
WALL COLLAPSED…LEADING TO A PARTIAL COLLAPSE OF THE ROOF. THIS
DAMAGE WAS RATED EF2 ON THE ENHANCED FUJITA SCALE WITH WIND SPEEDS
OF APPROXIMATELY 115 MPH. THE LAST TIME THE CITY OF DALLAS HAD A
TORNADO RATED AT F2/EF2 OR HIGHER WAS F2 TORNADO DAMAGE ON APRIL
11 1974. THE LANCASTER TORNADO OF APRIL 25 1994 PRODUCED F4 DAMAGE
IN THE CITY OF LANCASTER BEFORE DISSIPATING WITHIN THE CITY LIMITS
OF DALLAS.

THE EF1 TORNADO DAMAGE WAS LOCATED IN THE CITY OF SEAGOVILLE JUST
EAST OF HIGHWAY 175. AT LEAST THREE APARTMENT BUILDINGS SUFFERED
SIGNIFICANT ROOF DAMAGE. WIND SPEEDS IN THIS TORNADO ARE ESTIMATED
TO BE NEAR 90 MPH.

THE REMAINING TORNADO DAMAGE WAS GIVEN A PRELIMINARY RATING OF
EF0. THESE TORNADOES OCCURRED NEAR LINDSAY IN COOKE COUNTY…NEAR
FERRIS IN ELLIS COUNTY…IN HEATH IN ROCKWALL COUNTY…AND NEAR
BLOSSOM IN LAMAR COUNTY.

THE ENHANCED FUJITA SCALE RATES TORNADO DAMAGE.

ENHANCED FUJITA SCALE APPROXIMATE WIND SPEED RANGE

EF0 65-85 MPH
EF1 86-110 MPH
EF2 111-135 MPH
EF3 136-165 MPH
EF4 166-200 MPH
EF5 200 MPH OR GREATER

Tropical Storm Hermine & it’s effects

Sean Toner — Thu, 09 Sep 2010 02:08:59 +0000

Tropical Storm Hermine, a remarkably impactful storm for the DFW Metroplex which sits 550 miles north of the storm’s initial landfall. The storm has brought severe flooding to a 300 mile stretch of central and north Texas, along the I-35 corridor. The worst flood effects are being felt in San Antonio through Austin. Flash flooding has even occurred in the Metroplex, the most notable being numerous homes and trailers flooded in the cities of Lewisville, Arlington, and Fort Worth. The heavy rains brought over 12 inches of rain near Austin as of 8am today (9/8/10) and 4 to 6 inches of rain in the Metroplex. (source: CoCoRaHS) My CoCoRaHS gauge captured 4.01 inches of rain in the 24hr period from 8am 9/7/10 to 8am 9/8/10. Another several inches have been observed since that time, with even more rain on the way. Below is radar estimated total rainfall from the FWS dopplar radar. An even more accurate and complete picture region wide view is available from the National Weather Service at http://www.srh.noaa.gov/ridge2/RFC_Precip/.

As if the flooding rainfalls weren’t enough, Hermine brought the risk of tornadoes to the region with several damage reports in Dallas, Highland Park, Seagoville, Ferris and Trumbull. Tornadoes embedded within the outer rain bands of tropical systems aren’t uncommon to coastal regions in the Gulf, but it is fairly unusual to get those type of tornadic storms this far away from the Gulf. Tornadoes in this type of environment tend to develop without warning and are difficult to detect with current radar technology, but are very brief and usually weak. The Dallas Morning News reported ripped up roofs in Cockrell Hill, Oak Cliff, West Dallas, and the Love Field areas. (source: Dallas Morning News) A Tornado Warning was also issued for a storm 4 miles south of Hebron at 5:37pm. The warned area included Frisco, Plano, and The Colony. The storm showed rotation on radar, and storm spotters observed a rotating wall cloud within the storm. Thankfully no tornado damage has been reported with this storm. Its center of circulation traveled north along the Denton/Collin county line, passing over Highway 121 and Plano Parkway, then dissipating. I got the pleasure of evacuating to our work’s ‘shelter’ area which amasses to little more than an open hallway, without access to my computer with accurate radar data.

A Tornado Watch still remains in effect for the entire DFW Metroplex, southeastern Oklahoma and western Arkansas until 1am. Another rain band is approaching from the west, with an approximate ETA of around 11pm to midnight tonight to Frisco/Plano/The Colony. Rain chances will continue Thursday, however nowhere near the levels observed the past two days. Hot and humid conditions should be expected the remainder of the week and weekend as the sun comes out and starts evaporating the abundance of water on the ground.

Lastly ill end with a quote from the local weather forecast office regarding the heavy rains the last two days…

DFW AND WACO HAVE BOTH SET CALENDAR-DAY PRECIPITATION RECORDS TODAY (SEPT 8). FOR BOTH SITES…THE 24-HR TOTALS (SEPT 7-8) WILL RANK AMONG THE TOP 10 ALL-TIME. PRECISE NUMBERS WILL BE AVAILABLE THURSDAY MORNING.

AT THE PRESENT TIME…THIS MONTH WILL RANK AS THE 4TH WETTEST SEPTEMBER ON RECORD FOR BOTH DALLAS/FORT WORTH AND WACO.

Flash Flooding around the entire DFW Metroplex

Sean Toner — Wed, 08 Sep 2010 14:08:07 +0000

Hey group… its been awhile but the weather conditions today merit an email… By now we are all aware of the heavy rainfall affecting the region, but may not be immediately aware of the flash flooding occurring around the region. Right now, several flash flood reports have come in from the area, including Plano, Dallas, Fort Worth and Saginaw. Major intersections in Plano near the George Bush Turnpike are submerged, low water crossings in Dallas are under several feet of water, and intersections around Fort Worth are impassible due to water. All stations in the area show at least 3 inches of rain with some showing 6 to 7 inches in the last 24 hours, which easily surpasses the criteria needed for flash flooding conditions. Below is radar estimated total rainfall. You can see Fort Worth is showing a large swath of 7 to 8 inch estimates so far. Stay safe everyone, and do not attempt to drive into submerged intersections!

Tropical Storm Ida nearing landfall in Mobile, AL

Sean Toner — Tue, 10 Nov 2009 06:13:54 +0000

Looks like the storm has lost most of its strength after heavy upper level wind shearing and cooler water temperatures in the gulf. The storm has already created about 5 feet of storm surge in eastern New Orleans, areas outside the hurricane flood control systems. The storm will continue to weaken and make a hard right turn just after landfall, impacting south Alabama, south Georgia, and the Florida panhandle.

Heavy rain impacts around the Metroplex

Sean Toner — Mon, 26 Oct 2009 05:17:18 +0000

Now that the heaviest rains are beginning to exist the Metroplex as they move east, I will send a brief update on tonight’s severe weather impacts. Only a few reports of high winds around the area, none of them reporting any damage so far. Several large hail reports in Parker, Tarrant, Denton and Cooke counties. One report of lightning striking a home in Trenton, 30 miles NE of Frisco, though damage is unknown at this time. Flooding impacts however are notable… several high water rescues have been reported in Fort Worth due to flooding rains stranding motorists or entering houses. Extreme north Collin county shows an estimated 6.24 inches of rainfall in the last 5 hours! The city of Celina, just 12 miles north of Frisco is embedded in a swath of the heaviest rains, reporting flood waters entering houses as well. There are also some road closures due to high waters south, and west of McKinney.

Attached is rainfall estimates since 6:22pm Sunday 10/25. You can see the area 2.5 miles north of Weston, or extreme north Collin and south Grayson counties showing up to 6.24 inches of rain. This is a result of several thunderstorms training across this area. Frisco by comparison is estimated around 1.17 inches, and only 19 miles south of the heaviest rainfall.

Rainfall totals much higher than normal for north Texas!

Sean Toner — Fri, 23 Oct 2009 04:00:55 +0000

Since moving to Frisco Texas a year ago I have seen the terminology ‘In Texas it takes a flood to end a drought’ used quite a few times, now I understand why that phrase is quite accurate. So far for the month of October DFW Airport has recorded 7.09 inches of rainfall, placing us 4.12 inches above normal. Currently this October is ranked the 8th rainiest and we still have 8 calendar days left to go. The number 1 rainiest October beats all others by a very large margin at 14.18 inches in 1981 so we are likely not to break this record. However we are in striking distance of the number 2 spot which is 9.44 inches set in 1919. With at least two to three more rain days in the forecast this month we very well make the number two spot. On a side note, average temperatures this month are below normal with the October 2009 average being 65.0 and the October normal temp of 68.4. I will try to find out cloud cover percentages of this month vs normal and vs records later on… its a bit harder to find that info.

Precipitation totals for the year are also well above normal… At this time precipitation is at 36.32 inches since Jan 1, or 7.87 inches above normal. Normal annual rainfall is 37.05 inches so if we received no additional rainfall the rest of the year, we would be only 0.73 inches below normal.

The rainfall from Wednesday made up a significant portion of this month’s totals with the National Weather Service office in Fort Worth receiving the most rain at 5.81 inches. Most locations received 3 to 4 inches of rainfall during Wednesday. Some river and stream flooding is still occurring at this time including the Trinity River in Dallas, and the Denton creek near Justin. The Trinity River in Dallas is currently sitting at 36.4 feet, or 6.4 feet above flood stage.

Regarding the drought conditions in central and southern Texas… the recent rainfalls have made significant improvements to lessening the drought impacts to our south, and virtually eliminated drought conditions in all of north Texas. A small area of coastal south Texas around Corpus Christi is still in the ‘Exceptional’ drought classification, the highest possible. This area however is very tiny, in comparison to just 3 months ago when over 20% of Texas was in an Exceptional drought status. With current climate forecasts showing the weak El Nino conditions persisting throughout winter and thus above average precipitation for our region, I would expect nearly all drought in Texas to be wiped out in the next few months.

With any drought or unusual dryness you have to consider large fire impacts as well… With the abundant rainfall in the late growing season for Texas, vegetation will sprout new growth before going dormant after the first hard freeze. The hard freeze tends to dry out plant life and create excellent fuel for large wildfires during the winter and early spring. However the above average rainfall forecast for this Winter should dampen any wide spread fire impacts. Due to this, the winter looks to present a relatively low hazard for wildfires.

This information is considered ‘preliminary’ from the National Weather Service, and obtained directly from the website for NWS Fort Worth at http://www.srh.noaa.gov/fwd/

Flash Flooding across the Metroplex

Sean Toner — Thu, 22 Oct 2009 03:20:20 +0000

Several Flash Flood Warnings are issued for Tarrant, Denton, Collin, Grayson, Cooke and other counties around the area. A band of very heavy rainfall has fallen creating flooding conditions most notably around Fort Worth where several high water rescues have been taking place after motorists get stranded in high waters. Additionally the Trinity river at Dallas is surpassing flood stage at this time, and is forecast to exceed flood stage by 4 feet. At 34 feet several low water crossings will flood. This heavy rainfall will continue for a few more hours at least until the cold front passes through Thursday before sunrise. The rain will likely come to an end sometime around 3am to 5am I am thinking. Until then, plan for continuous heavy rain and flash flooding potential.

Here is the storm total rainfall amounts so far, this is since 1:21am Wednesday morning. Blue areas are reaching up to 5.8 inches of rainfall. The green polygons indicate current Flash Flood Warnings, the green and blue FFL icons indicate reports of Flash Flooding including road closures and high water rescues.

Flash Flooding around North Texas!

Sean Toner — Tue, 13 Oct 2009 15:15:26 +0000

A band of moderate to heavy rainfall is sitting stationary just south and east of the DFW Metroplex, prompting Flash Flood Warnings and even a high water rescue in the city of Terrell. Rain totals in these areas since 6 pm Monday are around 2.25 inches estimated, showing that the soil is so heavily saturated and unable to absorb any more rainfall.

Below is radar estimated rainfall since 6pm Monday, you can easily see the areas where rainfall is most concentrated… the Green FFL icons indicate reports of Flash Flooding, the green polygons show current Flash Flood Warnings.

Heavy rainfall estimates and upcoming weather

Sean Toner — Fri, 09 Oct 2009 14:47:57 +0000

Rainfall is coming to an end for today as the cold front sinks further to the southeast. Flooding isn’t as wide spread or severe as anticipated likely due to the lack of rainfall during the day Thursday, as had been previously forecast. Temperatures for the next several days will be significantly cooler, including lows in the mid 40s the next two nights! Saturday and Sunday look to have partly cloudy skies, highs in the mid 60s and lows from mid 40s to low 50s.

Radar estimated rainfall totals so far. A healthy portion has received rainfall estimated over 2 inches (yellow), and some areas estimated to 3.5 inches (orange).

Severe weather and flash flooding possible Thursday

Sean Toner — Thu, 08 Oct 2009 13:38:37 +0000

Heavy rains and Severe Thunderstorms are probable during the afternoon and evening hours of Thursday. The entire region is still under a Flash Flood Watch with around 2.5 inches of rain forecast the next 36 hours. Additionally the SPC in Oklahoma has our area under a ‘Slight’ severe storm risk with the main risk being severe winds. The local weather service noted in their forecast discussions that this is an event to take seriously. Flooding potential with this storm is quite high.

COPIOUS MOISTURE FOR THE SYSTEM TO
WORK WITH. IN MY MEMORY…I HAVE NOT SEEN PWAT/S THIS
HIGH…ESPECIALLY IN FALL…WITHOUT SEEING THE OCCURRENCE OF
FLASH FLOODING. FEEL THAT THIS IS AN EVENT TO BE TAKEN SERIOUSLY.

At this time we are in a 30% severe wind, 15% severe hail, and 2% tornado risk. The most likely time for these storms appears to be just before or around midnight. Thunderstorms are possible during the afternoon hours today as well, but the bulk of the severe activity is set around midnight… this is subject to change however.

Again flash flooding is a very likely possibility over the next 36 hours… flooding may be as bad or worse than any event we have seen since moving out to Texas a year ago.