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Tornado Watch issued for DFW Metroplex

Sean Toner — Sat, 23 Oct 2010 17:38:08 +0000

Tornado watch issued for the entire DFW metroplex at 12:05pm. A line of strong thunderstorms, with some severe, is approaching from the west. Conditions are favorable for a couple of tornadoes today, so keep an ear to your weather radios and keep watching the skies *chuckle*.

URGENT – IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 704
NWS STORM PREDICTION CENTER NORMAN OK
1205 PM CDT SAT OCT 23 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

SOUTHEAST OKLAHOMA
CENTRAL AND NORTHERN TEXAS

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1205 PM UNTIL
800 PM CDT.

TORNADOES…HAIL TO 1.5 INCHES IN DIAMETER…THUNDERSTORM WIND
GUSTS TO 70 MPH…AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES NORTH OF PARIS TEXAS
TO 65 MILES SOUTH SOUTHEAST OF BROWNWOOD TEXAS. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU4).

REMEMBER…A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION…THIS TORNADO WATCH REPLACES SEVERE
THUNDERSTORM WATCH NUMBER 703. WATCH NUMBER 703 WILL NOT BE IN
EFFECT AFTER 1205 PM CDT.

DISCUSSION…TSTMS SHOULD CONTINUE TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON ALONG RESIDUAL OUTFLOW ASSOCIATED WITH
DECAYING NOCTURNAL MCS AS LARGE-SCALE FORCING INTENSIFIES AHEAD OF
MIDLEVEL TROUGH. CONSIDERABLE CLOUDS AND PRECIPITATION WILL TEND TO
LIMIT THE POTENTIAL FOR MORE WIDESPREAD AND STRONGER AIR MASS
DESTABILIZATION. HOWEVER…THE PRESENCE OF A MOIST BOUNDARY LAYER
COUPLED WITH POCKETS OF STRONGER HEATING WILL STILL YIELD AFTERNOON
MLCAPE VALUES APPROACHING 1000-1500 J/KG. THIS INSTABILITY COUPLED
WITH SUFFICIENTLY STRONG LOW AND DEEP-LAYER SHEAR FOR STORM
ORGANIZATION/ROTATION INDICATES A THREAT FOR EMBEDDED SUPERCELLS
CAPABLE OF DAMAGING WINDS…HAIL AND A COUPLE OF TORNADOES.

AVIATION…TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24030.

Severe storm risk Friday and Saturday

Sean Toner — Fri, 22 Oct 2010 01:01:49 +0000

Texans, looks like die-hard Rangers fans will be watching the ALCS in the rain down in Arlington this weekend as several rounds of thunderstorms appear likely over the next 7 days.

First off, overnight tonight and into Friday morning some thunderstorms may push eastward from the panhandle and soak the metroplex. Best guess on timing to the metroplex is around 7am, but rain is possible as early as 4am. Latest computer models would indicate this line of storms may weaken as it approaches the metroplex, so storm coverage and strength is up for debate at this time.

Afterward, there appears to be a difference in opinion between the local weather forecast office and the Storm Prediction Center.
According to the local forecast office, a brief shot of subsiding air moves through the area during late morning to mid-afternoon and would prevent thunderstorm activity. However because of this subsiding air, a strong low level jet channeling moisture from the gulf will get trapped under it and create heavy low level cloudiness during the day Friday. The heavy cloudiness will prevent sunlight from destabilizing the atmosphere and restrict widespread severe storms from developing in the evening.
The Storm Prediction Center indicates there may be some clearing in the afternoon in proximity to a cold front, allowing diurnally driven instability in the area and thus supporting a linear storm mode in the evening with widespread severe potential.
Either way, the forecast calls for a second round of thunderstorms to occur late afternoon to evening across the metroplex with severe wind, hail, and tornadoes possible. Best guess on timing for these storms is 7pm to 10pm.

Then on Saturday afternoon, a shortwave trough will move through the area, triggering another round of thunderstorms with the best possibility of severe weather north of I-20 and east of I-35. Low level wind shearing will exist, so tornado chances may be slightly elevated, along with hail and wind risks.

Sunday afternoon brings the next round of thunderstorms, where a narrow window of opportunity exists for storm development. The weather service indicates a time frame of about 1pm to 7pm local time where storm development is possible. Strong mid-level lapse rates and good wind shearing aloft would support organized severe thunderstorms with an elevated severe wind risk. Storms should quickly end after 7pm as stable air moves in behind.

Monday brings warmer temps with gusty southwest winds, but should remain rain free. Tuesday has a small chance of storms along with a cold front according to one computer model, while another does not indicate any chance of storms.

The next notable weather system will hit next Thursday, with a cold front passing through the area. This system is still 7 days out, but it appears this cold front will be fairly strong and bring much cooler temperatures. Next Thursday's highs appear to be only in the mid 60s!

Take care this weekend everyone.

Thunder & cooler temps on the way

Sean Toner — Thu, 23 Sep 2010 20:09:00 +0000

I say its about time! Computer models have identified a cold front set to move through the region late in the day Friday, bringing scattered showers and thunderstorms. Conditions associated with the front will be favorable for some organized severe activity, but the specific severe risks have not been outlined by the weather service yet.

After the frontal passage on Friday evening, scattered thunderstorms will still spread the entire region, through late Saturday at least. Sunday should bring about cooler and breezy conditions under clear to partly cloudy skies. Highs in the low 80s, lows in the upper 50s. Sunday looks to be a great day for outdoor activities this weekend, including the Texas State Fair!

Temperatures finally close to normal appear to be in store for the rest of the forecast period, through next Thursday. Highs low to mid 80s, lows around 60, and lower humidity.

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!

Brief funnel clouds possible around DFW today

Sean Toner — Fri, 25 Jun 2010 17:29:34 +0000

An interesting statement from our local weather forecast office… funnel clouds are possible this afternoon due to favorable atmospheric conditions. Tornadoes are not likely however.

…Brief funnel clouds will be possible this afternoon…

A cluster of strong thunderstorms across the area are in an
environment favorable for the formation of brief funnel clouds.
These funnel clouds are usually short-lived and typically do not
reach the ground. However…residents should remain alert when
thunderstorms are in the vicinity.

Heavy rains and flooding possible Wednesday and Thursday

Sean Toner — Tue, 08 Jun 2010 14:07:50 +0000

A low pressure system feeding a very rich band of tropical moisture from near the equator will pass over north Texas the next two or three days. This system will very likely bring heavy rainfall, and some flash flooding may be possible. The low pressure interestingly enough evolved from a small cluster of thunderstorms which developed last week over the Texas caprock. The low has meandered around Texas since then, catching a hold on rich tropical moisture. Rainfall estimates for the DFW Metroplex range from 2-3 inches likely, with pockets of 4 inches possible.

The rainfall will be very much welcomed, after our below average May rainfall. With the onset of La Nina coming this summer, we can use all the rainfall we can get right now. The heaviest rain will occur Wednesday and Thursday likely during the night time. However rainfall will be possible all day on both days.

Severe weather outbreak for DFW Wednesday!

Sean Toner — Wed, 19 May 2010 03:57:49 +0000

You wont see me use the word 'outbreak' very often, especially when it is in reference to a forecast. Tomorrow's severe weather potential however has good likelihood to become a severe weather outbreak, with the SPC already issuing a 'Moderate' risk for the northern half of DFW, through central Oklahoma. Very large hail is forecast, along with a very favorable environment for tornadoes. The storm mode is expected to begin as discreet or semi-discreet supercells along NW Texas and SW Oklahoma, which could eventually converge into a broken line of severe thunderstorms along the Red River. Current forecasts show the best tornadic potential right along the Red River, however favorable tornado conditions exist around the entire region including DFW.

Above shows the SPC's Day 2 outlook. You can see the moderate risk area encompasses the DFW metroplex as well as portions of Oklahoma.

I will actually be storm chasing this weather event, so I may not be very forthcoming on local weather updates. Keep an eye on the news or an ear to your weather radio on Wednesday.

Strong thunderstorms and heavy rains

Sean Toner — Fri, 14 May 2010 17:48:48 +0000

Hey folks, sorry I have not been to forthcoming on weather information as of late… I am in the midst of moving, which takes up every ounce of free time I have. A round of strong to borderline severe storms are moving through the metroplex right now, with one of these strong storms headed through Lewisville on its way towards Frisco. These storms have very high winds approaching 55mph, which is nearly at the severe criteria. After the initial batch of strong storms, expect moderate to heavy rains to continue throughout the day. 2 inches of rain today can be expected, with some isolated spots receiving up to 5 inches.