Heavy Rain, High Winds, and Isolated Tornadoes Possible!

A strong cold front will be moving into East Texas Early Friday morning and along and ahead of this front, there is a chance of severe storms, including isolated tornadoes. The image above is of a forecast radar image for 7AM tomorrow morning. Instead of seeing a straight line of storms we see more of a wavy pattern. This is called a line echo wave pattern and in many cases this type of storm system will produce very gusty winds and isolated tornadoes. Many East Texas tornadoes occur in patterns such as the one moving through East Texas tomorrow morning.

In addition to a slight risk of severe weather, heavy rain will be a concern. The amount of moisture available for thunderstorms is unusually high for this time of the year thanks to a strong southerly flow off the Gulf this afternoon. As the cold front moves into East Texas, it will force this warm moist air up and over the front producing widespread heavy rain behind the main line of storms. Some places, mainly north of I-20, could see 2 to 4 inches of rain tomorrow. The image below shows the storm total precipitation that is forecast. Notice the heavy rain forecast across the northwest counties of East Texas, where flooding was a problem in September. We also see a bulls eye of heavy rain across our southeastern counties however, we have not seen as much rain here over the past 30 days so flooding is not as great of a concern.




Now most of the dynamic energy needed for severe weather will move north of our area but there are a few features that jump out at me that could lead to gusty winds and isolated tornadoes. The image below is from a short range high resolution forecast model which shows the amount of instability available as the line of storms enters East Texas tomorrow. Most of East Texas is colored in pink which indicates surface based lifted index values less than -6°C. This is more than enough instability for intense thunderstorm updrafts.



The next image shows there will be lots of moisture available as the dark blue colors indicates dew point temperatures in the low 70. You will also see a couple of small low pressure areas, or mesoscale lows, indicting areas of backed winds leading to low level rotation. With the amount of moisture available, cloud bases will be very low increasing the threat of isolated tornadoes.



There will also be moderate amounts of energy to help with thunderstorm development. The image below shows the amount of surface based CAPE. A large area of East Texas has CAPE values over 2000 J/kg out ahead of the storms, providing additional energy for thunderstorm updraft. What is not shown is much of that energy is confined to the lowest levels of the atmosphere, where there is more spin available. This could help in developing low level mesocyclones which could produce an isolated tornado.



In the final image, the amount of 0-1km storm relative helicity, or the amount of low level spin in the atmosphere, is shown. Most of East Texas is at or above 160 which is enough when you combine the amount of CAPE to produce an isolated tornado. You can also see areas of enhanced 0-1km helicity near the mesoscale low pressure areas. This could really enhance the possibility of isolated tornadoes as the line moves through.


So as this line of storms moves through tomorrow morning, we could see some wind damage and isolated tornadoes. Overall I believe the main threat will be flooding rains but we will be monitoring the situation very closely.

Today's Severe Weather Threat

A strong cold front will move into East Texas this afternoon and evening bringing with it the possibility of strong to severe thunderstorms. Right now the main threat of severe weather appears to be strong gusty winds and hail up to the size of pennies. This morning, a layer of warm air just above the surface is putting a lid on thunderstorm development until immediately behind the front. This trend will continue until temperatures this afternoon reach the middle to upper 80s across East Texas. Once these temperatures are reached we will see air lifted ahead of the cold front increasing thunderstorm development. Winds throughout the atmosphere ahead of the cold front are out of the southwest limiting the amount of turning of the winds with height, a big factor needed in tornado development. However, with any additional daytime heating this afternoon, enough instability could form to compensate for the lack of vertical wind shear so we can’t rule out an isolated tornado, especially over the northeaster parts of East Texas.

In addition to severe weather, parts of East Texas today with come close to having dangerous heat index values. Tremendous amounts of Gulf moisture are in place across East Texas and as temperatures approach 90 degrees, especially across our southwestern counties, heat index values will range between 100 and 105 degrees this afternoon. Across most of East Texas heat index values will reach the middle to upper 90s, something we have not experienced in a while across East Texas. Please use caution later this afternoon with any strenuous outdoor activities.

Thursday's Storms

Well, as forecast a line of strong storms developed out ahead of a fast moving cold front Thursday evening. The severity of the storms was not quite as strong as I thought they would be but none the less, most of East Texas was given a spectacular lightning display with heavy rain and gusty winds. Yours truly drove all over East Texas with my chase partner Paul Lachowsky looking for places to take lightning photos. Unfortunately from all the angles we approached the storms, the lightning was hidden from us by very heavy rain and small hail. We got hundreds of illuminated sky capes but very little in the way of actual lightning bolts. A few of our viewers had better luck just staying at home. Tim Ogrodnik was again lucky in capturing a few lightning shoots and was kind enough to send them my way. The shoot of the actual bolts is from him, I need to take lessons.

For the most part the severe weather remained west of our viewing area last night however, there were many large trees blown down and power outages reported across western Upshur County. As for hail, I can vouch for pea size hail in a few locations as the loud ting of hail hitting Paul’s truck greeted us in a few locations.

A couple of interesting photos I took last night included a look at the back edge of the storms with clear skies immediately behind the line. I love seeing the back edge of a thunderstorm with stars all around.



The second photo was a tree that was struck by lightning last night in front of Bullard High School. The tree was still smoldering as you can see the orange glow of the trunk and the rest of the tree smoldering on the ground to the left. Wish I could have seen the bolt hit.

Today's Severe Weather Threat

We have been discussing the possibility of severe weather today since the beginning of the week and it looks as though everything will come together to produce a widespread, gusty wind event. A strong cold front to our northwest will move into East Texas along the I-30 corridor this evening and sweep through all of East Texas by Friday Morning. The main threat with this line of storms will be gusty winds however, temperature decrease a good deal in the mid levels of the atmosphere so I can’t rule out large hail with this line of storms, especially along and north of I-20. All of East Texas has been outline for a slight risk for severe weather with the greatest chance across North East Texas. Right now it appears the line of storms should form along the I-30 corridor around 7PM, enter the I-20 corridor around 10PM, and the Lufkin Nacogdoches area around 1AM. By Sunrise tomorrow the front should be through all of East Texas and drier cooler air will move in.


We could also see a few isolated storms develop this afternoon out ahead of the squall line. If temperatures can reach the middle to upper 80s we will see enough surface based instability for robust thunderstorm updraft development. Enough wind shear will be present this afternoon for any storm to take on supercellular characteristics. A south southwesterly flow at the surface will minimize the tornado threat but we could see large hail and high winds with these storms as well. So until the front moves through your neighborhood, severe weather is a possibility.

Thursday's Severe Weather Possibilties Tue PM Update

The GFS has slowed down the frontal passage (Fig 1) by about 150 miles and is coming more in line with the NAM and WRF (Fig 2). We still do not see a dry line forming on the GFS solution so we would be looking mainly at a squall line event Thursday evening. The NAM still shows a dryline and develops a secondary surface low, much like the GFS was hinting Monday morning, causing backing winds over north central TX and south central OK (Fig 3). This will aid in low level mesocyclone development which could lead to a tornado or two developing during storm initiation. I still like the northern target better for the possibility of tornadoes but the 12Z NAM has a better potential for tornadoes in the Southern Plains. Looks as though there could be a significant tornado or two late Thursady into Friday in eastern OK and north west AR but the chase terrain here is not the greatest. As of now I will probably head out Thursday after Midday and wait to see what happens.

Fig 1

Fig 2

Fig 3

Thursday's Severe Weather

We are still looking at a threat of severe weather developing Thursday across the Central U.S. but depending on which forecast model you go by, there is a very different result. The image above shows the forecast for Thursday evening at 7PM CDT. Notice the cold front is much farther east than the forecast for the NAM (see below). The scenario forecast by the NAM would be much more conducive for supercell and tornado development Thursday afternoon and evening so this will be the model of choice to discuss, since the GFS shows a fast moving squall line with mainly a gusty winds small hail event.



Looking at the forecast map for the NAM for 0Z Friday ( 7PM CDT Thursday Evening) you see an area of low pressure with a warm front extending east through central Illinois and a cold front draped across central Kansas and northwestern Oklahoma. Out ahead of the front a dryline sets up and would be the focusing mechanism for thunderstorm development if this scenario unfolds. There are two areas that seem favorable for supercell development which could lead to isolated tornadoes late Thursday.

The first area that seems likely a few supercells could develop is along and east of I-35 in central Oklahoma south into North Texas north of Dallas. A large area of low level helicity will combine with moderate instability and moderate CAPE across these areas. 0-1km storm relative helicity are between 100 and 250 from the Dallas Forth Worth area through the Eastern third of Oklahoma (Fig 1). This should provide adequate low level turning of height to help produce low level meso cyclones as thunderstorms develop. In the same area surface based CAPE is on the order of 1500 to 2000 J/kg (Fig 2), not extreme but enough to have robust updraft strength in this area of low level helicity. Finally the surface based lifted index is around -4 in this same area providing moderate levels of instability (Fig 3).

Fig 1

Fig 2

Fig 3


The second area of supercell development and in my opinion may be the big winner when it comes to tornado development is out ahead of the surface low across southeast Nebraska, southwestern Iowa, eastern Kansas, and northwestern Missouri. An area of higher instability, CAPE and strong low level helicity will combine for the development of scattered supercells along the dryline/cold front. The images below show the surface based lifted index and CAPE for 4PM CDT Thursday Afternoon. LIs approach -5 (Fig 4)with CAPE approaching 2000 J/kg (Fig 5) in southeastern Nebraska. This area will also be experiencing very strong low level relative helicity, approaching 250 (Fig 6). For chasing Thursday I really like the northern option out ahead of the surface low for tornado development.

Fig 4

Fig 5

Fig 6

Again the following forecast is based on the NAM forecast model. I feel the GFS may be bringing this system through too fast as the water vapor imagery shows the 500mb vort max is moving into the Pacific Northwest slower than the GSF advertised on the 0Z run. I will issue another update later this afternoon after analyzing the 12Z model runs.

Thursday's Severe Weather Possibilties Update

A quick update to share what the 12Z model runs are showing. The GFS continues to move the cold front rapidly through the Southern Plains. The 12Z run speeds up the frontal passage and puts it near the I-20 corridor by 7PM Thursday evening.(See image below) I feel this may be a little too fast. The instability forecast is also much lower on the 12Z run decreasing the severe threat.


The 12Z NAM is now in the forecast time frame and is showing a much slower and better severe weather set up than the GFS. The NAM is forecasting a dryline to set up Thursday afternoon across central Oklahoma and hangs the actual cold front across northwest Oklahoma Thursday evening. This will allow for plenty of Gulf moisture to move in across the Southern Plains(See image below).



Below is the forecast for CAPE (convective available potential energy) for the NAM Thursday evening. Notice the energy is pooling along the dryline in central Oklahoma.



With the much faster GFS solution CAPE is confined to East Texas and is no where near as much as advertised by the 0Z GFS.(See image below) This solution would still produce storms and with the shear available, we could see a line of storms with gusty winds across the Southern Plains.



Overall I feel the GFS is too fast and the NAM is a bit too slow. Both models do not point to a significant tornado threat as wind shear will be mainly unidirectional. However, if a secondary low develops as the 0Z GFS advertised, we could see an enhanced tornado threat along and just north of the low. This system still bears watching and may be a worthwhile chase for me later this week.

Severe Weather Possible Late Thursday

A strong storm system is forecast to move into the middle of the country Thursday and drag a cold front through the Southern Plains. Current forecast models are coming to an agreement on the position and strength of this system. There is a possibility of severe weather along and ahead of the cold front from eastern Nebraska into Texas late Thursday through Friday morning. Right now the main threat with this line appears to be strong winds and hail but, I can’t rule out a possible tornado or two late Thursday, especially near the Oklahoma Texas state line north of Dallas.

Below is the forecast position of the 500mb Vorticity maximum late Thursday by the GFS forecast model. Along with this strong area of vorticity, this image shows diffluent heights across Ozark Plateau and Southern Plains. This will aid in the lift for the formation of strong storms late Thursday.



This storm system is still too far out to show on the short range NAM model run for Thursday evening however, it is showing up Thursday morning on this model and is a very similar position to the long range GFS forecast model. The next two images show the comparison between both models. Not much difference.





There also appears to be plenty of Gulf moisture available for this upcoming storm system. By Thursday morning both forecast models show a large area of dewpoints over 70°F along the Texas Gulf Coast with the GFS showing a larger supply of moisture.





By Thursday evening the GFS is showing plenty of deep moisture with mid 60 dewpoint temperatures being pulled into the storm system across the Southern Plains and 70+ degree dewpoints across southeast Texas.



Now the GFS is hinting at a smaller secondary surface low (shown below) developing somewhere near the Oklahoma Texas state line. This is an important feature because along and to the north of this secondary low, surface winds will have an easterly component, or what we call backing. This will increase the threat of tornadoes with any storm that can develop in this area.



We also see plenty of instability with this system. Surfaced Based lifted index in south central Oklahoma are approaching -8, more than enough for strong to severe storm development. (See image below)





There is a maximum of CAPE (Convective Available Potential Energy) near the maximum of instability in south central Oklahoma.(See image above) This will allow for stronger thunderstorm updrafts aiding in the possibility of large hail. Now, if the best instability and energy develop in the area just northeast of the developing secondary low pressure, the chances of tornadoes will increase, especially during initial thunderstorm development. The GFS is showing this threat with the 0-1km EHI (Energy Helicity Index) of 4 (Values greater than 2 have been associated with significant tornadoes) or greater near Lake Texoma. (Image below)



Other experimental severe weather indices are pointing to a possible severe weather event as well. The two images below the Craven Significant Severe weather index and the Supercell Composite Parameter. The second image is showing a bulls eye near the same area of increased instability and CAPE.





So will we see an outbreak of tornadoes? Well we won’t know for sure until we get closer to the forecast event however, the last image shows a long line of enhanced 700mb vertical motion, or lift. This indicates the storms that form will quickly form into a squall line so the best chance of isolated supercell thunderstorms will be during the early evolution of storms late Thursday afternoon. With the associated shear anticipated Thursday evening, this line of storms will more than likely take on a line echo wave pattern (LEWP). This will allow for a few isolated supercells to be embedded in the squall line increasing the threat for strong winds and an isolated tornado. I will have an update once the NAM forecast model is in the forecast timeframe.

High Water Mark for the Historic 1945 Flood

The National Weather Service will unveil two high water mark signs commemorating the historic April 1945 flood in Jefferson, Texas, on Tuesday September 22, at 11 a.m. One of the signs will be installed on the front of Henderson’s Auto Parts Store at 218 Polk Street. A second sign will be installed on the Jefferson Jimplecute building at 205 West Austin Street. This historic ceremony will be held at Henderson’s Auto Parts Store, and the public is welcome to attend.
Armando Garza, Meteorologist In Charge of the Shreveport Weather Forecast Office said, “The High Water Mark sign at Jefferson is the first such sign in the State of Texas. We live in an area where heavy rainfall can cause havoc and flooding is still a very real threat to our communities.”
Other signs are planned in south and central Texas in early 2010. The National Weather Service Forecast Office in Shreveport will also work to plan additional installations over north Louisiana next year. The signs not only document major historical floods, but more importantly convey the potential impact that floods have had and could have again on communities. Floods are one of the most deadly and most costly natural disasters, and more people lose their lives in floods than due to lightning or tornadoes. The signs are a good reminder to maintain our vigilance and evaluate our preparedness for floods.
The peak of Jefferson’s record flood occurred on April 2, 1945 when the Big Cypress Bayou rose to a stage of 30 feet, inundating parts of the town with more than five feet of water. This flood led to the United States Congress passing the Flood Control Act of 1946. This piece of legislation eventually established the many flood control reservoirs in the Red River Valley across Northeast Texas, including Lake O’ the Pines a few miles upstream of Jefferson. The flood also caused the city to abandon the developed areas on the south bank of the river.
The National Weather Service office in Shreveport, the Lower Mississippi River Forecast Center (LMRFC), the Marion County Historical Commission, and Jefferson City Officials cooperated on this project. The LMRFC creates forecast guidance of river levels and flows for over 200 points in the southern U.S. including the Big Cypress Bayou at Jefferson. The National Weather Service used US Army Corps of Engineers and US Geological Survey data since they maintain a real-time hydrologic monitoring network of stage, streamflow, and rainfall gages that are a crucial component of the NWS’s river forecast and flood warning programs.

Winter Comes Early to Colorado

Another cut off low has formed across the country this week. This one is a cold core low bringing rain and even snow to parts of the High Plains and Rockies. Ahead of this low is a cold front that is slowly moving through Texas this morning. Cooler slightly drier air will move in behind this front but, we will still see a chance of showers in East Texas thanks to weak disturbances swinging around the upper low to our northwest.

Temperatures this morning across the great state of Texas ranged from 34°F in Burleson to 85° in Port Aransas. Temperatures in East Texas will drop into the lower 60s tonight with the possibility of seeing a few upper 50s in our western counties, closer to the much colder air that will spread across West Texas over night.

Remembering Ike

One year ago yesterday at 2:10AM CDT, hurricane Ike made landfall on Galveston Island. Ike was a strong category 2 storm that covered a tremendous amount of area in the Gulf of Mexico. Because of this, Ike produced a catastrophic storm surge one would expect from a Category 4 or higher storm. Ike will probably go down as the third costliest natural disaster in U.S. history behind Hurricanes Katrina and Andrew.
Ike began as a tropical wave off the African Coast and became a tropical depression on the morning of September 1st. Later that same afternoon Ike strengthened into a tropical storm. The rapid intensification of Ike continued over the next 72 hours with Ike reaching a category 4 status by the evening of the 4th with top winds of 145mph. On September 7th Ike hit the island of Great Inagua near the Curks and Caicos followed by western Cuba that evening. The higher terrain of Cuba helped weaken Ike to a top wind speed of 100 mph as he entered the Gulf of Mexico. However, the amount of real estate Ike possessed was tremendous. Just look at the size of Ike when the center of the storm was a few hundred miles south of Galveston.

He nearly takes up the entire Gulf of Mexico. It was Ike’s large area that enabled it produce such a large storm surge as water was funneled into the shallow waters of the Galveston Bay and Sabine Lake in the Northwest Gulf of Mexico. According to the National Hurricane Center the highest water mark from Ike’s storm surge was 17.5’ above mean sea level 10 miles inland across Chambers County. 20 lives were lost across the Gulf coast from Ike and another five lives were lost in Arkansas due to high winds. Right now the official damage total is around $19 billon making Ike the fourth costliest storm in U.S. history but once all insurance claims are taken care of, Ike will more than likely move up to number three on the list.



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The Great Galveston Hurricane of 1900.

On the evening of September 8th, 1900, Galveston Texas was struck by a category 4 hurricane estimated wind speeds of up to 135 mph and a storm surge of 15 to 20 feet. After the storm had past, up to 8000 lives were lost and the coast line was changed forever.


The origin of the “Great Hurricane” remains unclear due to the limited observation ability 109 years ago. It is believed the storm originated as many powerful Atlantic Basin hurricanes do off the west coast of Africa. On August 27th an area of “unsettled weather” 1000 miles east of the Windward Islands was reported by a ship (source Neil L. Frank). This area of disturbed weather developed into a tropical storm and moved over the Island of Cuba and entered the Florida Straits as either a strong tropical storm or a weak hurricane on September 5th. The storm continued to move west northwest until making landfall on Galveston Island on the night of the 8th. The destruction was unbelievable. For more information on this catastrophic storm click the following photos:

Galveston Tornado

Sunday evening a rapidly developing thunderstorm developed off the Galveston Coast. The storm developed over two intersecting outflow boundaries from earlier storms. The result was a waterspout which moved on shore to become an EF-1 tornado. Here is the official report from the National Weather Service in Houston:
...NWS STORM SURVEY RESULTS FOR GALVESTON TORNADO...

AT AROUND 948 PM ON SUNDAY...AUGUST 30TH...A WATERSPOUT MOVED
ONSHORE ON GALVESTON ISLAND NEAR THE INTERSECTION OF 29TH STREET AND
SEAWALL BLVD. THE TORNADO THEN PRODUCED AN INTERMITTENT DAMAGE PATH
FOR ABOUT ONE THIRD OF A MILE TO THE NORTHWEST...ENDING NEAR THE
INTERSECTION OF 31ST STREET AND AVENUE R. SEVERAL STRUCTURES WERE
DAMAGED INCLUDING THE DOLPHIN WORLD SOUVENIR SHOP...WHERE WINDOWS
WERE SHATTERED AND MOST OF THE METAL ROOF WAS PEELED OFF. A
GALVESTON POLICE DEPARTMENT PATROL CAR HAD ITS WINDOWS BLOWN OUT IN
THE SAME AREA. HEADING FURTHER INLAND...THE TORNADO PUSHED OVER A
HOME ON STILTS AND REMOVED MOST OF THE ROOF OF A MOBILE HOME.
ANOTHER HOME AT THE INTERSECTION OF 31ST STREET AND AVENUE Q 1/2 HAD
ITS ROOF COMPLETELY REMOVED. BEYOND THIS LOCATION DAMAGE WAS LIMITED
TO SMALL TREE LIMBS AND SOME SHINGLES REMOVED FROM ROOFS.

THE OBSERVED DAMAGE SUGGESTS WIND SPEEDS IN THE 80 TO 90 MPH
RANGE...WITH MAXIMUM WINDS LEADING TO AN EF-1 RATING ON THE ENHANCED
FUJITA SCALE. DAMAGE PATH LENGTH WAS AROUND ONE THIRD OF A
MILE...WITH A WIDTH OF AROUND 100 FEET. THERE WERE THREE INJURIES
REPORTED. TWO POLICE OFFICERS...WHO WERE IN THE PATROL CAR WHEN ITS
WINDOWS SHATTERED...WERE TREATED AND RELEASED. ANOTHER MAN...WHO WAS
THROWN AGAINST A WALL...REMAINS HOSPITALIZED AT UTMB.
Most waterspouts form under developing cumulus towers along sea breeze and land breeze fronts where the surface vorticity can be stretched in the vertical under the developing cloud updrafts. These so called “fair weather spouts” are usually short lived and remain off shore. Every once in a while one of these spouts will make land fall becoming officially a tornado but rarely producing more than EF-0 damage. The water spout that formed Sunday night appears to have formed in the same way the Beaumont Tornado formed earlier in August. By looking at the radar data from Sunday night we can see that two outflow boundaries were interesting each other just off the coast of Galveston.

At this intersection a new storm cell rapidly developed indicating an area of strong vertical growth. This rapid upward movement was able to stretch the surface vorticity located over the intersection allowing for the waterspout to form.


Thanks to the amount of low level energy available(08/31/09 OZ RUC 0-3km CAPE over 200 J/kg off shore) for storm development, a strong updraft was able to form translating to a stronger wind speed in the tornado as it moved on shore, producing EF-1 damage. Below are a couple of radar loops of the develop storm which spawned the tornado. In the first you can see the two boundaries with the cell rapidly developing over the intersection. In the second loop you can see the rapid vertical development showing signs of a strong updraft over the intersecting boundaries.