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.

Erika Could Form Today.

The tropical Atlantic looks to become active again as Erika will probably begin to form today. Satellite shows a fairly well organized system moving into an area favorable for development. Our mid range tropical computer models vary with the strength on this system. It does appear we will at least see a strong tropical storm if not a hurricane by the Thursday or Friday. A weakness in between two areas of high pressure, one in the central Atlantic and the other over the U.S., could steer this system into the Atlantic. There is a chance this system could move south of this weakness and this could steer this system into the Gulf of Mexico. Stay tuned for the latest information.

Remembering Katrina

Four Years ago today the Gulf Coast was changed forever and the city of New Orleans was about to go under water. Scientists’ worst fear, a category 5 hurricane, was about to make landfall on the City of New Orleans. The catastrophe that followed was unimaginable just 24 hours earlier to most but, the Nation Weather Service in New Orleans put out a couple of statements that really made you feel the severity of what was about to happen. The first statement is a special weather statement issued by the national weather service on the morning before Katrina made landfall. The second is the afternoon forecast discussion hours before Katrina made landfall. Just Chilling!

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1011 A.M. CDT SUN AUG 28 2005
...DEVASTATING DAMAGE EXPECTED...
.HURRICANE KATRINA...A MOST POWERFUL HURRICANE WITH UNPRECEDENTED STRENGTH...RIVALING THE INTENSITY OF HURRICANE CAMILLE OF 1969.
MOST OF THE AREA WILL BE UNINHABITABLE FOR WEEKS...PERHAPS LONGER. AT LEAST ONE HALF OF WELL CONSTRUCTED HOMES WILL HAVE ROOF AND WALL FAILURE. ALL GABLED ROOFS WILL FAIL...LEAVING THOSE HOMES SEVERELY DAMAGED OR DESTROYED.
THE MAJORITY OF INDUSTRIAL BUILDINGS WILL BECOME NON FUNCTIONAL. PARTIAL TO COMPLETE WALL AND ROOF FAILURE IS EXPECTED. ALL WOOD FRAMED LOW RISING APARTMENT BUILDINGS WILL BE DESTROYED. CONCRETE BLOCK LOW RISE APARTMENTS WILL SUSTAIN MAJOR DAMAGE...INCLUDING SOME WALL AND ROOF FAILURE.
HIGH RISE OFFICE AND APARTMENT BUILDINGS WILL SWAY DANGEROUSLY...A FEW TO THE POINT OF TOTAL COLLAPSE. ALL WINDOWS WILL BLOW OUT.
AIRBORNE DEBRIS WILL BE WIDESPREAD...AND MAY INCLUDE HEAVY ITEMS SUCH AS HOUSEHOLD APPLIANCES AND EVEN LIGHT VEHICLES. SPORT UTILITY VEHICLES AND LIGHT TRUCKS WILL BE MOVED. THE BLOWN DEBRIS WILL CREATE ADDITIONAL DESTRUCTION. PERSONS...PETS...AND LIVESTOCK EXPOSED TO THE WINDS WILL FACE CERTAIN DEATH IF STRUCK.
POWER OUTAGES WILL LAST FOR WEEKS...AS MOST POWER POLES WILL BE DOWN AND TRANSFORMERS DESTROYED. WATER SHORTAGES WILL MAKE HUMAN SUFFERING INCREDIBLE BY MODERN STANDARDS.
THE VAST MAJORITY OF NATIVE TREES WILL BE SNAPPED OR UPROOTED. ONLY THE HEARTIEST WILL REMAIN STANDING...BUT BE TOTALLY DEFOLIATED. FEW CROPS WILL REMAIN. LIVESTOCK LEFT EXPOSED TO THE WINDS WILL BE KILLED.
AN INLAND HURRICANE WIND WARNING IS ISSUED WHEN SUSTAINED WINDS NEAR HURRICANE FORCE...OR FREQUENT GUSTS AT OR ABOVE HURRICANE FORCE...ARE CERTAIN WITHIN THE NEXT 12 TO 24 HOURS.
ONCE TROPICAL STORM AND HURRICANE FORCE WINDS ONSET...DO NOT VENTURE OUTSIDE!
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS LA
452 PM CDT SUN AUG 28 2005



.UPDATE...TO ADD TORNADO WATCH #752.

.DISCUSSION...
SOUTHEAST LOUISIANA SEEMS POISED FOR A DATE WITH DESTINY AS CATEGORY 5 HURRICANE KATRINA CONTINUES TO KEEP A BEAD ON BARATARIA BAY AND THE GREATER NEW ORLEANS AREA. THE GFS MODEL CONTINUES TO BE SUPERIOR IN ITS HANDLING OF THE SYSTEM INASMUCH AS TO BASE THE CONVENTIONAL FORECAST PARAMETERS WITH GOOD INTEGRITY AND IN AGREEMENT WITH NHC ADVISORIES.

NEEDLESS TO SAY...THE WORST CAN BE ANTICIPATED AND URGENCY IS BEING STRESSED IN ALL PRODUCTS AS A WORST CASE HURRICANE SCENARIO FOR THIS VERY FRAGILE AND VULNERABLE STRETCH OF U.S. COASTLINE. THE EYE IS EMERGING ON THE KLIX LONG RANGE LOOP AND BANDS ARE EXTENDING TO LAKE PONTCHARTRAIN AT THIS TIME. THINGS WILL BE DETIORATING STEADILY FROM THIS POINT FORWARD FOR THE NEXT 24 HOURS.

WILL MAINTAIN ALL WARNINGS AS ALREADY POSTED AS WELL AS THE FLASH FLOOD WATCH. STORM PREDICTION CENTER HAS ADVISED THAT THE FIRST TORNADO WATCH OF THE EVENT WILL LIKELY BE ISSUED FOR THE REGION EARLY THIS EVENING...PROBABLY RIGHT AFTER SUNSET.

MOST ATTENTION WITH THIS PACKAGE WAS DAY 1-2 WITH LITTLE IF ANY CHANGES MADE BEYOND DAY 3. GOOD LUCK AND GODSPEED TO ALL IN THE PATH OF THIS STORM.

There has been much discussion on whose fault and why we saw so many deaths from Katrina. Without getting political let me say I hope we have all learned a valuable lesson and when a catastrophic storm heads towards the coast again, residents get out.

Wednesday's Pop Up Storms.

Wednesday afternoon and evening saw some very strong to severe storms develop across parts of East Texas. I decided to head to the lookout off highway 69 north of Jacksonville in Cherokee County to watch a developing storm move west. The visibility was good from the high elevation looking east at the developing storm. The storm which later became severe formed on top of two intersecting outflow boundaries from earlier morning storms. This allowed for some rotation in the lower levels of the storm producing the funnel cloud you see in the photo below.
I took around 300 photos of this storm alone trying to catch a daytime lightning strike, not one. Trust me, there was plenty of lightning, I just need to work on my reflexes. This storm eventually moved into Anderson County and was showing signs of a huge hail core. Thankfully not too much in the way of large hail was reported, doesn’t mean it did not fall somewhere.
I drove north to the Bullard First Baptist Church and tried my luck at a few lightning shots. Once again I was unsuccessful but I did catch an amazing shot. The photo below is of a developing storm west of the church as the sun sets behind it. Notice the crepuscular rays streaming across the top of the storm, beautiful.


Once the sun set the atmosphere released the last bit of instability with a dramatic lightning display over southwestern Smith County and eastern Henderson County. This display of lightning was one of the best I have seen in years. Of course with my luck, I did not have a good view of the storm from my house so I had to get in the car and drive to where I had good visibility. Unfortunately for me, the best lightning shot I have seen from last night was not from my camera. Tim Ogrodnik of Altra Federal Credit Union was nice enough to send me some photos he took of the storm. In a word, amazing!



By the time I made it to my destination the storm was beginning to die down. I was able to catch a few nice shots but nothing near the quality of Tim. I hope you enjoyed the photos. Hoping for a little lightning photography tonight, we shall see.

Tropical Storm Danny

Tropical Storm Danny has formed in the Atlantic Ocean this morning. Hurricane hunter aircraft report top winds with Danny are 45 mph. Danny is forecast to become a hurricane and eventually turn to the north and northeast. The question is when will Danny make the turn? Most tropical forecast models turn Danny out to sea in plenty of time and miss the United States East Coast. However, a couple of our short range and long range forecast models show Danny becoming a major hurricane hitting the Outer Banks of North Carolina and then riding up the East Coast. Stay tuned for the latest.