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Active Weather returns by Thursday & Friday
Beginning February 1, 2012 we will begin to produce a daily weather video. This video will feature the same content as these blog posts, except be on a daily basis. It’s our hope that these videos will explain the weather for the upcoming days by discussing weather data you don’t normally see on TV broadcasts. That being said, we’ll also keep the discussions simple enough for the non-weather weenies to understand.
- We’ve had pretty tranquel weather across Texas, and frankly most of the United States, since our severe weather event last Wedensday. A strong cold front pushed through the region which brought in very dry air. It takes several days for the Gulf of Mexico to recover after a strong cold front pushes through. We don’t normally see moisture just surge back northward. Indeed, that is the case with a dewpoint of 56° here at my house in Duncanville (just southwest of Dallas) five days after the event. That being said, a lack of moisture is usually why we don’t get potent severe weather events during the cool season. Still, we do get enough moisture from time to time and you saw last Wednesday what the results can end up being. So keep in mind that we need good moisture in place to support severe weather, and more specifically surface-based convection. For those that don’t know what surface based convection means… That would be a thunderstorm that is rooted in the boundary layer (Thunderstorms that break the cap) that can pull in the warm, moist air at the surface and possibly become quite severe with tornado potential. Convection that is not surface-based is elevated, or above the cap. That means there is no tornado potential, but there is still a risk of hail and damaging winds. What does all that have to do with this blog post? Well absolutely nothing since I’m not going to be getting that detailed with this post, but hey, now you can say you learned something about weather!
0Z NAM: Surface dewpoint values and surface winds at 6 PM Thursday
Speaking of surface moisture, this graphic comes from the 0Z NAM (North American Model) and is 72 hours out, otherwise known as 6 PM Thursday. The bright yellow line represents the 50° isotherm for dewpoints. That’s pretty much the lowest value you can get substantial severe weather. There are exceptions to that rule, but those won’t apply to this situation. Notice the less evident line across Central Texas, which is the 60° isotherm line for dewpoints. The 0Z NAM has the higher moisture values (50°> dewpoint values) are being pulled northward ahead of a storm system developing across Colorado. As this storm system begins to develop on Wednesday, we should see moisture begin to surge northward in response to southeasterly surface winds. As I’m going to stress several times in this discussion, we’re still over three days away from Thursday and nothing is set in stone. As you’ll see when I show you the 500 millibar graphics, weather models are still differing pretty significantly on the overall setup. The point of me showing the surface moisture chart is to show that we will have higher moisture values surging northward ahead of our next storm system.
0Z NAM: Most Unstable Instability (MUCAPE) at 6 PM Thursday
Since the weather models are still differing quite a bit on the whole setup, there’s no point in digging down and looking at specifics like instability values and low level wind patters. However, I will show you this graphic which shows the most unstable instability values off the 0Z NAM. Anything over 1,000 joules per kilogram is pretty substantial for late February. As you can see, the NAM has a fairly large instability pool across West Texas at 6 PM on Thursday. That’s one of the reasons why I’m already talking about this setup because those are pretty good instability values for a cool season event. I won’t dig any further into that, but keep those in mind for future discussions.
0Z NAM: 500 millibar winds at 6 PM Thursday
Lets take a look at the mid-level setup of this upcoming storm system. This graphic is also from the 0Z NAM at 6 PM and is for 500 millibars, which translates to about 18,500 feet above sea level. The 0Z NAM has a positive tilt trough digging through Utah and Colorado with the base of the trough and right-entrance region located over New Mexico. For organized thunderstorms, I want to see values at or above 35 knots. Generally speaking, the NAM values above 50 knots across most of the Texas Panhandle and northern cap-rock. If we had a piece of energy swing through that trough and move across the panhandle at the right time, that would help initiate thunderstorms and with the overall setup shown above, we would likely see a few organized thunderstorms, maybe even supercells depending on how much forcing was present. However, lets take a look at a different weather model for the same time…
0Z GFS: 500 millibar winds at 6 PM Thursday
This graphic comes from the 0Z GFS (Global Forecast System) and shows the same graphic as the one above and applies at 6 PM Thursday. Notice anything different? First off, the GFS has the system running slower and further south. Instead of Utah and Colorado like the NAM shows, the GFS has the base of the trough located over Arizona and New Mexico. Still, it has a good southwesterly flow in place over the Panhandle, although its a bit further south then the NAM. Keeping this model variability in mind, lets take a look at Friday.
0Z GFS: 500 millibar winds at 6 PM Friday
Fast forward twenty four hours and we see the setup at 6 PM on Friday. This is using the same parameters as the 500 millibar graphic above. It looks like the GFS wants to go negative tilt with the trough and shortwave with it much stronger then it was on Thursday. Winds in the base of the trough exceed 90 knots and overall, the GFS has a strong system in place by Friday evening. It takes a lot more then a strong shortwave to create organized severe weather. It takes instability, low level wind shear, and rich moisture to create a severe weather event. That being said, there is some indication that we could be dealing with another severe weather event on Friday across parts of East Texas out into Dixie Alley (Arkansas/Louisiana). That’s four days out and with models not behaving particularly well, we won’t make speculation at this point. However, this is something we need to keep an eye on. Stay Tuned!
Beginning February 1, 2012 we will begin to produce a daily weather video. This video will feature the same content as these blog posts, except be on a daily basis. It’s our hope that these videos will explain the weather for the upcoming days by discussing weather data you don’t normally see on TV broadcasts. That being said, we’ll also keep the discussions simple enough for the non-weather weenies to understand.
What happened to Winter?
Snow Cover (February 10, 2011)
Snow Cover (January 27, 2012)
While we have experienced some brief cold spells, most folks across Texas are asking what happened to winter. It’s not just us in Texas that are wondering, but most of the United States. Take these two snow cover graphics for example, the first graphic is from February 10, 2011 (about a week after our major winter storm and coldest spell in 20 years in Texas). A majority of the United States, east of the Rockies, have snow on the ground. In fact, the snow cover extended south to the Interstate 20 corridor from Texas all the way into Alabama. Even Houston had some snow! Fast forward about 50 weeks and you have the second graphic. You’re hard pressed to find any snow across the Country. Sure, you have a few inches on the ground in the Dakotas east to Wisconsin, but this time last year they had almost two to three feet on the ground!
So why the major difference this year? We remain in La Nina conditions, similar to last winter, so what gives? It’s actually pretty simple and can be attributed to one specific parameter. For the meteorological definition, we differ to the Climate Prediction Center. For more detailed information on the NAO, visit the CPC at http://www.cpc.ncep.noaa.gov/data/teledoc/nao.shtml
“The NAO consists of a north-south dipole of anomalies, with one center located over Greenland and the other center of opposite sign spanning the central latitudes of the North Atlantic between 35°N and 40°N. The positive phase of the NAO reflects below-normal heights and pressure across the high latitudes of the North Atlantic and above-normal heights and pressure over the central North Atlantic, the eastern United States and western Europe. The negative phase reflects an opposite pattern of height and pressure anomalies over these regions. Both phases of the NAO are associated with basin-wide changes in the intensity and location of the North Atlantic jet stream and storm track, and in large-scale modulations of the normal patterns of zonal and meridional heat and moisture transport (Hurrell 1995), which in turn results in changes in temperature and precipitation patterns often extending from eastern North America to western and central Europe (Walker and Bliss 1932, van Loon and Rogers 1978, Rogers and van Loon 1979).” (Source 1).
Now that we have the official, wordy definition out of the way, let me explain it in a way most of you will be able to understand. When the NAO is in a positive state; very cold air often has great difficulty making it to the Southern United States. In order for cold air of arctic origin to make it south into the United States, the jet-stream must originate from a high latitude and then dive south, known as a trough. That type of setup is commonly associated with a negative NAO. Cold air can still make it into the United States, but not the bitterly cold, arctic air that can cause several days of freezing weather in Texas with sub-zero temperatures across northern US. During a positive NAO, we generally have a warmer pattern across the country. We definitely can get cold snaps, but not to the extremes or duration as we would get with a negative NAO. During a positive NAO, we generally have above average temperatures across the southern US.
North Atlantic Oscillation from September 30, 2011 through January 27, 2012
Now that I’ve explained the basics with the NAO, lets take a look at what it’s been showing over the past few months. This graphic shows the North Atlantic Oscillation from September 30, 2011 to January 27th. The red lines are model guidance for the next 14 days, we’ll talk about that in a minute. Over the past few months, we have not seen any major negative trends in the NAO, which is why we have not had any major cold spells or winter storms across the Country as a whole. Now there have been localized events, especially in Iowa/Wisconsin/Illinois, but they’re at a higher latitude and have localized features (The Great Lakes) that can help enhance their events. Until we see the NAO go negative, we will not see a major cold spell. Looking in the next two weeks, there really is no sign of the NAO going negative. We’re actually pretty close to neutral right now, but the NAO will head back up into the positive territory as we get into February.
That generally means we won’t likely see any long-duration cold spells in the near future. We’ll have cold fronts come through once in a while that will cool us back down to our average temperatures across Texas, but the duration of those cool spells won’t last long.
6-10 Day Temperature Anomaly Forecast
As would be expected with the positive NAO, much of the country will be experiencing above average temperatures for the next two weeks. This graphic comes from the Climate Prediction Center and shows that they expect much of the country has a good chance of experiencing above average temperatures over the next two weeks. While the Continental US will be warm, take a look at Alaska. With the positive NAO, the colder air is being bottled up north so they will likely experience colder then average temperatures for their neck of the woods. One thing we’ll have to watch for in February is that cold air to push south. It’s been bottled up north for a while now and we rarely make it through a winter without one cold spell. Let me remind you that many of our biggest winter storms have been in February, so just because it’s been warm so far, don’t think we’re going to get through the rest of winter without a major cold spell. We’ll keep an eye on things as we head into February, but I hope you’ve learned a bit about what we look for when forecasting cold spells across the USA.
Just to recap…
Positive NAO = Average/Above Average Temperatures Possible
Negative NAO = Below Average Temperatures Possible
Source 1: Climate Prediction Center Internet Team. "North Atlantic Oscillation (NAO)." Climate Prediction Center. National Weather Service, 10 Jan. 2012. Web. 27 Jan. 2012. <http://www.cpc.ncep.noaa.gov/data/teledoc/nao.shtml>.
January 25, 2012 – Tornado Surveys
NOTE: Storm Surveys are still on-going and additional events will be added to this page as they are received.
Austin, Texas Tornado
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX 251 PM CST WED JAN 25 2012 ...PRELIMINARY STORM DAMAGE SURVEY FOR NORTHEAST AUSTIN TX... A NATIONAL WEATHER SERVICE STORM DAMAGE SURVEY WAS CONDUCTED THIS MORNING IN THE AREA ALONG SPRINGDALE ROAD IN NORTHEAST AUSTIN. THE FOLLOWING HAVE BEEN DETERMINED... EVENT DATE: JANUARY 25 2012 EVENT RATING: AWAITING FINAL DATA ESTIMATED PEAK WINDS (MPH): AWAITING FINAL RATING INJURIES/FATALITIES: 0 EVENT START TIME/LOCATION COORDINATES: 30.3221/-97.6536 AT 258 AM EVENT END TIME/LOCATION COORDINATES: 30.3381/-97.6551 AT 305 AM DAMAGE PATH LENGTH (IN MILES): 1.14 DAMAGE PATH WIDTH (IN YARDS): 50 THE TORNADO PATH BEGAN AT THE INTERSECTION OF COMMERCIAL PARK DRIVE AND OLD MANOR ROAD...WITH RADAR INDICATING A TOUCHDOWN TIME NEAR 2:58 AM. DAMAGE CONTINUED NORTH THROUGH AN INDUSTRIAL PARK...THEN ACROSS U.S. 290...BEFORE ENTERING THE WALNUT PLACE SUBDIVISION. FURTHER DAMAGE OCCURRED TO HOMES ON THE WEST SIDE OF HAPPY TRAIL... WITH TREES ON THE EAST SIDE OF HAPPY TRAIL LAYING DOWN TOWARD THE WEST AND CONVERGING WITH THE DAMAGE TO THE HOMES. DEBRIS WAS NOTED ALONG FERGUSON LANE...WITH THE TORNADO PATH ENDING JUST WEST OF THE INTERSECTION OF FERGUSON LANE AND SANSOM ROAD.;
Courtesy of City of Austin Homeland Security and Emergency Management – Tornado Track Map
San Antonio, Texas Tornado
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX 331 PM CST WED JAN 25 2012 ...PRELIMINARY STORM DAMAGE SURVEY FOR SOUTHWEST SAN ANTONIO TX... A NATIONAL WEATHER SERVICE STORM DAMAGE SURVEY WAS CONDUCTED THIS AFTERNOON IN THE AREA ALONG DEER PARK (STREET) IN SOUTHWEST SAN ANTONIO. THE FOLLOWING HAVE BEEN DETERMINED... EVENT DATE: JANUARY 25 2012 EVENT RATING: AWAITING FINAL DATA ESTIMATED PEAK WINDS (MPH): AWAITING FINAL RATING INJURIES/FATALITIES: 0 EVENT START TIME/LOCATION COORDINATES: 29.4556/-98.6645 AT 415 AM EVENT END TIME/LOCATION COORDINATES: 29.4545/-98.6603 DAMAGE PATH LENGTH (IN MILES): 0.27 DAMAGE PATH WIDTH (IN YARDS): 30 THE TORNADO PATH BEGAN AT THE INTERSECTION OF DEER PARK AND RICHLAND HILLS DRIVE...AND CONTINUED ALONG DEER PARK TO THE INTERSECTION OF DEER PARK AND LEANDER. THE PRIMARY DAMAGE WAS A CARPORT BEING THROWN INTO A HOME AND CAUSING SUBSTANTIAL DAMAGE.
Estimated Tornado Track (This was created using the damage survey. This meant to only be an estimation of the exact track of the tornado.)
Pearland, Texas Tornado
Pearland, TX Damaging Wind and Tornado Track (From NWS Houston)
THE SURVEY TEAM FOUND A SWATH OF STRAIGHT LINE WIND DAMAGE BEGINNING AROUND HATFIELD ROAD AND EXTENDED EAST NORTHEAST AROUND 2 MILES WHICH CONSISTED OF FENCES BLOWN DOWN AND SPORADIC TREE DAMAGE. THE DAMAGE SWATH WAS BETWEEN 1/10 AND 1/4 MILE WIDE. WITHIN THAT SWATH IT WAS DETERMINED THAT A SHORT LIVED TORNADO ALSO TOUCHED DOWN AT HIGHWAY 35 AND PLUM STREET. A CHEVRON STATION HAD ITS ITS GAS PUMP AWNING DESTROYED AND THE BUSINESS TO THE SOUTH OF PLUM STREET HAD ITS ROOF PEELED BACK. TORNADO PATH WAS APPROXIMATELY 200 YARDS LONG AND WAS 75 YARDS WIDE. IT WAS RATED AN EF-0 WITH 65 TO 85 MPH WINDS.
Brenham, Texas Tornado
STRAIGHT LINE WIND DAMAGE WAS OBSERVED WITHIN THE TOWN OF BRENHAM EXTENDING TO AREAS ALONG AND EAST OF FM 50 TO NEAR INDEPENDENCE. THIS EVENT WAS FROM APPROXIMATELY 700 AM TO 725 AM. WINDS WERE ESTIMATED BETWEEN 60 AND 75 MPH WHICH DOWNED POWERLINES AND NUMEROUS TREES. THE DAMAGE WAS SPORADIC AND NOT CONTINUOUS. THE ASSOCIATED LINE OF STORMS ALSO DROPPED A TORNADO DOWN WEST OF COUNTY ROAD 50 JUST TO THE NORTH OF BRENHAM MUNICIPAL AIRPORT AND TRAVELED EASTWARD TO THE INTERSECTION OF FM262 AND COUNTY ROAD 65. THIS TORNADO DESTROYED SEVERAL METAL OUTBUILDINGS AND REMOVED THE ROOF FROM A BARN. IT ALSO PRODUCED MINOR ROOF DAMAGE TO A HOUSE AND SNAPPED NUMEROUS LARGE TREES. THIS TORNADO WAS RATED AN EF-0 WITH ESTIMATED 85 MPH WINDS. DAMAGE PATH WAS 2.5 MILES LONG AND 50 YARDS WIDE.
Caldwell, Texas Tornado
EVENT TIME…6:43 AM
EVENT TYPE…EF1 TORNADO
ESTIMATED PEAK WINDS (MPH)…90 to 100
INJURIES/FATALITIES…0
AN EF1 TORNADO CUT A DAMAGE SWATH THAT EXTENDED FROM JUST NORTHEAST OF DEANVILLE TO JUST SOUTHEAST OF CALDWELL. DAMAGE APPEARED TORNADIC ALONG THE SOUTHERN PORTION OF THAT AREA WITH NUMEROUS TREES SNAPPED OR UPROOTED. ONE HOUSE WAS PUSHED OFF A CINDER BLOCK BASE THEN DRAGGED ALONG A CURVED PATH FOR ABOUT 100 FEET. A FEED TRAILER WAS LIFTED OVER A FENCE THEN ROLLED ABOUT 150 FEET. SEVERAL SHEDS AND BARNS WERE DESTROYED. STRAIGHT LINE WIND DAMAGE ALSO FOUND IN THE AREA.
Madison County, Texas Tornado
EVENT TIME…8:00 AM
EVENT TYPE…EF0 TORNADO
ESTIMATED PEAK WINDS (MPH)…65 to 85
INJURIES/FATALITIES…0
DAMAGE PATH LENGTH… 1/3 MILE
DAMAGE WIDTH… 50 YARDS
TREES SNAPPED OR UPROOTED ALONG A NARROW PATH. BARN DESTROYED WITH TIN FROM ROOF FANNED OUT IN DIFFERENT DIRECTIONS AND THROWN IN SOME CASES ABOUT 200 YARDS. MINOR ROOF DAMAGE TO HOME. STRAIGHT LINE WIND DAMAGE ALSO FOUND IN THE AREA.
Huntsville, Texas Tornadoes
EVENT TIME…9:06 AM
EVENT TYPE…EF0 TORNADO
ESTIMATED PEAK WINDS (MPH)…65 to 85
INJURIES/FATALITIES…0
DAMAGE PATH LENGTH… 0.36 MILES
DAMAGE WIDTH… 50 YARDS
TORNADO TOUCHED DOWN AT CAR DEALERSHIP, LIFTED METAL AWNING AND MOVED IT 100 YARDS AWAY ON TOP OF TWO CARS. THERE WAS MINOR DAMAGE TO THE TWO CARS.
EVENT TIME…9:10 AM
EVENT TYPE…EF0 TORNADO
ESTIMATED PEAK WINDS (MPH)…65 to 85
INJURIES/FATALITIES…0
DAMAGE PATH LENGTH… 50 YARDS
DAMAGE WIDTH… 25 YARDS
TORNADO BRIEFLY TOUCHED DOWN IN A RESIDENTIAL SECTION OF HUNTSVILLE CAUSING SIGINIFICANT TREE DAMAGE. ONE OF THE TREES DID FALL ON A NEARBY HOUSE CAUSING SOME ROOF DAMAGE. TREES IN THE AREA WERE BLOWN DOWN IN DIFFERENT DIRECTIONS GIVING INDICATION OF A STRONG CIRCULATION IN THE AREA.
ADDITIONAL WIDESPREAD STRAIGHT LINE WIND DAMAGE WAS FOUND IN THE HUNSTVILLE AREA WITH NUMEROUS TREES DOWN THROUGHOUT THE CITY. THERE WAS ONE INJURY AT SAM HOUSTON STATE UNIVERSITY FROM A FALLING TREE LIMB.
Houston NWS: Huntsville, TX Tornado Track
Damage Photos from Anderson County
These photos were sent to us by Jeremy Davis from Palestine, Texas. He writes that he took these photos just north of Palestine, Texas near the Cayuga/Bethel area. He also says to disregard the camera’s date, that it was incorrect.
North Texas Lakes Rising!
- National Weather Service in Fort Worth: Graphical representation of rising lake levels.
This information comes from the National Weather Service in Fort Worth…
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
350 PM CST WED JAN 25 2012
....NORTH TEXAS LAKES ARE ON THE RISE...
THE WIDESPREAD HEAVY EVENT OF THE PAST 24 HOURS HAS BROUGHT SOME
SIGNIFICANT RECHARGE TO THE LAKES IN NORTH TEXAS. RAINFALL TOTALS
AVERAGED 3 TO 5 INCHES ACROSS THE AREA FROM MIDDAY TUESDAY THROUGH
NOON WEDNESDAY.
LAKE LAKE ELEVATION GAIN THROUGH 3PM WEDNESDAY
GRAPEVINE 3.1 FEET
LEWISVILLE 1.8 FEET
JOE POOL 2.7 FEET
LAVON 2.5 FEET
RAY HUBBARD 1.4 FEET
RAY ROBERTS 1.5 FEET
ARLINGTON 5.4 FEET
EAGLE MOUNTAIN 2.2 FEET
BRIDGEPORT 1.3 FEET
POSSUM KINGDOM 1.2 FEET
GRANBURY 3.6 FEET
BARDWELL 2.2 FEET
RICHLAND CHAMBERS 0.5 FEET
CEDAR CREEK 0.5 FEET
WHITNEY 1.5 FEET
Chase Status
This shows the probability of a storm chase within the next 5 days.
By roczag
By weatherworm