Severe Weather Risk in Texas & Oklahoma #TXwx #OKwx

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An active severe weather afternoon is forecast to develop across much of Central Texas, into Central and South Oklahoma.  All severe hazards are possible, with the highest risk coming from large hail. Some wind is possible. Also, a tornado or two can not be ruled out.

refcmp_uh001h-us_sc

We are expecting thunderstorms to develop later this afternoon across the region. While the coverage is not expected to be widespread, a supercell or two is not out of the question. We will continue to monitor the situation through the remainder of the afternoon and evening.

Severe Weather Risk 1/2/2017

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As we start the new year, the severe weather risk will be increasing. New Year’s Day will feature a risk back in Texas. For this particular post, we will be focusing on the risk for Monday across much of Louisiana, Mississippi, and the adjacent states.

12z-nam-dewpoint-21z-january-2

One of the first things we look at for a severe risk is the quality of moisture available. Dewpoints shown here Monday evening are forecast to rise well into the 60s. This will be especially true down in southeast Texas, along with southern portions of Louisiana, Mississippi, and Alabama.

12z-nam-sbcape-21z-january-2 crossover-us_se

When one normally looks at the Surface Based Convective Available Potential Energy (SBCAPE), they may think it does not look overly impressive. However, since we are in the Winter season, it does not take much to do so. The higher SBCAPE values (greens and yellows) are located in the areas included in the slight risk for Monday.

The crossover map indicates in general the wind direction at the surface, 850 mb (5,000 feet above ground level), and 500 mb (18,000 feet above ground level). Surface winds are generally south to southeast. The winds at 850 mb  and 500 mb are more to the southwest. That indicates potential for rotation in any severe thunderstorm that does develop.

12z-nam-500-wind-21z-january-2 12z-nam-surface-wind-21z-january-2 12z-nam-850-wind-21z-january-2

While not overly impressive, the amount of wind shown here (surface, 850 mb, 500 mb) will be more than sufficient for any severe thunderstorm to tap into.

12z-nam-0-1km-helicity-21z-january-2 12z-nam-0-3km-helicity-21z-january-2

The amounts of 1km helicity (100 units or more) and 3km helicity (250 units or more) for Monday evening are forecast to be more than sufficient for updrafts to become sustained in any severe thunderstorm that does develop. Areas at higher risk look to be down along the Gulf Coast in Louisiana, Mississippi, and Alabama.

12z-nam-6km-shear-21z-january-2 12z-nam-1km-shear-21z-january-2

While the amounts of shear in the lower 1km to 6km for Monday evening, the amounts look to be more than sufficient for any severe thunderstorm to develop supercell characteristics.

12z-vorticity-generation-parameter-21z-january-2

The Vorticity Generation Parameter indicates where the best tornado potential will be for a certain location. Areas in the yellows, oranges, and reds along the Gulf Coast in Louisiana, Mississippi, and Alabama indicate that the highest tornado potential looks to be located along that region.

However, all of the areas in the slight risk will be running the risk for possible tornado activity. Also, damaging straight-line winds will be a risk. While the hail risk will not be particularly high, some reports of large hail are a distinct possibility. We will continue to monitor the situation for you in the next couple of days. Stay tuned.

Heating Up in the Plains This Weekend

day5prob

It has been quiet out in the Plains, severe weather wise, for much of this week. However, that looks to change this weekend. While there is a severe weather risk Saturday just east of the Rocky Mountains, this blog post will focus more on the severe weather risk for Sunday. That area stretches from Southwest Texas north into central Nebraska. For this blog posting, we will be using the data from this afternoon’s 18z GFS model run.

18z GFS Dewpoint Hr 102

As with most severe weather setups in the Spring on the Plains, this setup features what is called a dryline. The areas in brown indicate dewpoints generally below 30° to 40°F. The dark green colors indicate where dewpoint temperatures range above 60°F. Areas in the green color are more at risk for seeing potential severe thunderstorm development.

18z GFS  SBCAPE Hr 102  18z GFS SBCIN Hr 102

While the surface based instability Sunday evening is more than sufficient for thunderstorm development, the amount of surface based inhibition is there that could initially hinder storm development. However, that particular amount is not enough that it will totally hinder it either.

18z GFS 6 km Shear Hr 102 18z GFS 1 km Shear Hr 102

The amount of 1 km and 6 km shear, shown here, are more that sufficient for supercell thunderstorm developing Sunday evening. Just to point out, the 6 km shear is really up there, as noted in the darker yellows and oranges.

18z GFS 1 km Helicity Hr 102 18z GFS 3km Helicity

There is also plentiful amounts of helicity in the lowest one and three kilometers for Sunday Evening. When we see these values, that usually signals the distinct possibility of robust updrafts within any severe thunderstorm that does develop.

18z GFS Surface Winds Hr 102 18z GFS 850 mb Wind Hr 102 18z GFS 500 mb Wind Hr 102

Plenty of wind is noted as well at the surface, 850 mb (5,000 feet above ground level), and 500 mb (18,000 feet above ground level). Also to note, notice on each level there how the wind direction changes with height. That will allow any thunderstorm that develops to potentially sustain rotation during its life cycle. With the strong south to southeast winds at the surface, transporting of low level moisture looks to be a non-issue as well.

18z GFS Vorticity Generation Parameter Hr 102

With all those storm ingredients noted above, we now come to the final piece of the puzzle. The Vorticity Generation Parameter. Values above 0.2 indicate an environment where tornado producing thunderstorms are a possibility.  The darker yellows there in central and eastern Oklahoma indicate an even higher potential for tornado activity Sunday evening.

BOTTOM LINE : The forecast models continue to come into general agreement of severe thunderstorm activity on Sunday evening across the Plains. All severe weather hazards look to be in play (Damaging Straight-Line Wind, Large Hail, Tornadoes). We will keep you updated with the latest. Stay tuned.

Severe Weather Threat Brewing

day7prob

The severe weather has steadily increasing over the last week to ten days across the Southern Plains. However, the first major severe weather issue of the season is a distinct possibility.  As a result, The Storm Prediction Center has highlighted much of Oklahoma, SE Kansas, N Central Texas, and Far NW Arkansas for the risk of severe weather the middle of next week (Tuesday). This is a day seven outlook. While not uncommon, it is relatively rare to get a risk area defined this far out.

For this particular blog posting, we will focus on the threat in Oklahoma for Wednesday of next week. Model data for this post will come from the 0z GFS run late this Wednesday Night.

SBCAPE Surface Dewpoint

This particular setup looks to be a classic southern plains severe weather setup. On the surface dewpoint map above, notice the brown area (dry air) in far west Oklahoma and the Texas Panhandle. Also, notice the green/aqua area (Central and East Oklahoma). That is a dryline setup. When you add the plentiful amounts of surface based instability across much of Oklahoma Tuesday evening, the potential is there for supercell thunderstorm development.

Surface 850mb 500mb

Here is another thing that is of much concern. Notice how the surface winds are south to southeast, the 850 mb winds are more south to southwest, and the 500 mb winds are mainly southwest. This is a classic recipe for any supercell thunderstorm to gain rotation within it.

Lowest 3 km Lowest 1 km

Another aspect of this that is impressive is the amount of helicity in the lowest one and three kilometers Tuesday evening. The areas in yellow and orange look to have the highest potential for sustained updrafts with any thunderstorm that develops.

0-6 km 0-1 km

One aspect that will not be lacking is the amount of shear in the lowest one and six kilometers Tuesday Night. Both amounts of shear (shown above) are more than sufficient to help sustain supercell thunderstorms for a longer period of time.

LCL Heights SBCIN

With the Lifted Condensation Levels projected to be below 1000 meters across much of central and eastern Oklahoma Wednesday Night, that area will see higher potential of tornadic supercell thunderstorms.  There is some surface based inhibition in Central and Eastern Oklahoma for Tuesday Night. However, given this potential setup, that inhibition could be broken easily.

0-1 km Vorticity Generation Parameter

This is what concerns us. The 0-1 km Vorticity Generation Parameter is off the scale across much of Oklahoma, and especially true in north central Oklahoma. That red (and purple area) indicate where tornado potential is highest for Wednesday Night.

SUMMARY : A severe weather episode looks to be a distinct possibility Tuesday Evening and Night across much of Oklahoma. All modes of severe weather are in play (Damaging Straight-Line Wind, Large Hail, and Tornadoes). We will keep you up to date with the latest.

Mid Week Severe Weather Threat

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The active start to the severe weather season looks to continue on Wednesday. A risk for severe weather has been noted by the Storm Prediction Center. Areas included in the risk are Northeast Texas, Far Eastern Oklahoma, Southwest Missouri, Western Arkansas, and Far Northwest Louisiana.

capesc capesc (1)

For this particular blog post, we will use a blend of this morning’s runs of the 12z NAM and 12z GFS. The amount of surface based instability is more than sufficient for thunderstorms to develop late Wednesday afternoon and evening.

12z NAM 03srhsc 12z NAM 01srhsc 12z GFS 03srhsc

Also to note, the amount of helicity in the lowest one and three kilometers are not the greatest. However, these helicity values look to be more than sufficient for sustained updrafts in any thunderstorm that does develop.

12z NAM sfctdsc 12z GFS sfcsc

The winds at the surface…

12 NAM 850mbsc 12z GFS 850mbsc

…850 mb (about 5,000 feet above ground level)…

12z NAM 500mbsc 12z GFS 500mbsc

…and at 500 mb (about 18,000 feet above ground level) do indicate some turning of the wind with change of height. While this portion of the setup is not overly impressive, some of the thunderstorms that do form will have the potential to rotate.

12z NAM lclsc 12z GFS lclsc

The amount of the Lifted Condensation Level (LCL) in place for Wednesday evening currently appears to be low enough that an isolated tornado threat can not be ruled out.

12z NAM cinsc 12z GFS cinsc

There looks to be hardly any surface based inhibition Wednesday evening. That will allow thunderstorms to develop fairly quickly across the region.

12z NAM Southeast Oklahoma Hr 84 12z NAM Dallas Fort Worth Hr 84

These two soundings that I pulled up for Wednesday evening are from the Dallas/Fort Worth Metroplex, along with areas in Southeastern Oklahoma. Note where the two circles are located at. Those areas indicate where the freezing level is at. Basic rule of thumb. The lower the green (dewpoint) line when it crosses 0°C, potential increases for large hail. Both soundings in this instance indicate such.

In summary, here are the severe threats that we are looking at for Wednesday…

  • Large hail (some potentially larger than golf ball size)
  • Isolated Tornadoes
  • Damaging Straight-Line Winds (lower of the three potential hazards)

We will keep you posted on the developing weather situation for Wednesday. Stay tuned.

Tuesday Severe Weather Risk Across Dixie Alley

day5prob

This relative lull in the weather pattern so far this week will be coming to a screeching halt come next week. A dynamic storm system is forecast to affect much of the Lower 48 east of the Rocky Mountains on Monday and Tuesday. For this particular blog entry, we will be focusing on the severe weather potential for Tuesday. Areas from far southern Ohio to the Louisiana/Mississippi Gulf Coast are at risk.

sfctdse

One of the first basics we look at is the dewpoint temperature. Plenty of moisture will be available Tuesday afternoon and evening across Dixie Alley. Dewpoint temperatures and the actual air temperatures are forecast to be only separated by about five to seven degrees Tuesday afternoon and evening.

lclse

As a result, the Lifted Condensation Levels are forecast to be plenty low across Mississippi Tuesday afternoon. This is forecast to move into Alabama by Tuesday evening. When the LCL heights are forecast to be this low, tornado formation is more likely.

capese

The Surface Based Convective Available Potential Energy (SBCAPE) Tuesday afternoon is forecast to peg just below 1,000 J/kg across much of western Mississippi. At first, you would think it is not that much. Given this is the Winter season, it is more than enough for any thunderstorm development to feed off of.

sfcse 850mbse 500mbse

Notice the wind direction at the surface (south to southeast), at 850 mb (5,000 ft. above ground level) (southwest), and at 500 mb (18,000 ft. above ground level) (west to southwest). Winds in this instance are backed at the surface. That is one favorable factor for tornadic supercell development. In addition, the winds at 850 and 500 are screaming.

500mbrelvortse

Pay attention to these two arrows here. These two arrows represent a difluent wind pattern. When this occurs, it is a strong indicator that tornado activity is a definite possibility. That will allow thunderstorm development to be rather explosive.

03srhse

The amount of helicity in the lowest three kilometers on Tuesday will be more than enough for supercell thunderstorm development across Dixie Alley. Values in excess of 200 units are quite prevalent across Dixie Alley.

03ehise

The Energy Helicity Index values Tuesday afternoon are pegging over one unit across much of Mississippi. This will transition into Alabama during the later afternoon and evening hours. Those values would represent a tornadic supercell threat.

IN SUMMARY : A very active severe weather day on Tuesday looks likely across much of Mississippi and Alabama. Make sure you have multiple ways of receiving warnings in case your area is affected by severe thunderstorms.

Dixie Alley Severe Weather Threat

day4prob

The overall weather pattern has been very quiet across much of the US, east of the Rocky Mountains here recently. However, the potential is there for severe thunderstorm activity across parts of Dixie Alley. While the Storm Prediction Center has highlighted parts of Arkansas, Louisiana, and Mississippi for Wednesday, the area at risk looks to be larger in size. That could easily include portions of Alabama and Tennessee.

sfctdse

Dewpoints look to not be lacking with this particular setup. Ample amounts of moisture will be in place across Dixie Alley Wednesday afternoon and evening. The surface temperatures Wednesday Afternoon look to be in the lower 70s. When combined with these dewpoint values in the middle 60s, the lifted condesation levels will be low enough that would allow a higher potential of tornado activity.

capeshearse

The winds at the surface (in red), along with winds at 850 mb (5,000 feet) and 500 mb (18,000 feet), do indicate that the wind is forecast to turn with height. When we say turn with height, the wind at the surface is forecast to be south to southeast. At 850 mb and 500 mb, the wind direction is mainly from the west and southwest. That will allow any thunderstorm that does develop to have potential to rotate. In addition, CAPE values in excess of 500 J/Kg are widespread across the region.

0z NAM 6km Shear Hr 69 0z NAM 1km Shear Hr 69

No shortage on the amount of shear in the lowest one and six kilometers is noted on tonight’s run of the North American Model (NAM). In the lowest one kilometer, 25 to 30 knots of shear are noted. In the lowest six kilometers, shear amounts in excess of 40 knots is noted. These values are more than sufficient for supercell thunderstorm activity to development.

01srhse 03srhse

Also, there is no shortage on the amounts of helicity in the lowest one and three kilometers. In the lowest one kilometer, helicity values in excess of 200 units are noted especially across northern Mississippi and northern Alabama.  Three kilometer helicity amounts in excess of three hundred units are noted across the same region. That will allow tornado potential to increase with any thunderstorm activity that does develop.

scp255sestpse

When we combine all the data above, it is easy for one to see that the Supercell Composite and the Significant Tornado Parameter are getting up there in value. Supercell values higher than 4 are noted across much of the region Wednesday afternoon. That would bring about the chance for sustained supercell thunderstorms. The significant tornado parameter values are higher than one unit across Dixie Alley as well on Wednesday afternoon. These areas would be at an increased risk for tornado activity.

Overall, the potential is on the board for severe thunderstorm activity across Dixie Alley Wednesday Afternoon and Wednesday Night. We will continue to monitor the situation for you. Stay tuned.

Severe Weather Threat for Saturday

day4prob

The quiet weather pattern that has occurred across much of the U.S. the last couple of weeks looks to get more active. A severe weather risk area has been defined for Saturday and Saturday Night by the Storm Prediction Center. Areas included in the risk area includes much of eastern Texas, southeast Oklahoma, west Arkansas, and far west Louisiana. For this particular blog post, two things are noted. We will be using the 12z GFS run from today. Also, we will focus on Saturday’s severe weather risk.

12z GFS Surface Based CAPE Hr 90

With the amount of Surface Based Instability shown here (less than 1,000 J/kg), it may not seem like it is enough. Now that we are into the month of December, it usually does not take much surface based instability to cause a ruckus.

12z GFS Surface Dewpoint Hr 90

One thing we always look for in particular is the available amount of moisture. With this setup, plenty of moisture is available for thunderstorm development. Note the dewpoints in the 40s Saturday Night across central and west Texas. Also, note the dewpoints well into the 60s across eastern Texas. This will prove to be the zone for the severe weather potential.

12z GFS 850 Winds Hr 90 12z GFS 500 Winds Hr 90 12z GFS Surface Winds Hr 90

Note the surface winds to the south and southeast, while compared to the 850 mb (5,000 feet above ground level), and 500 mb (18,000 feet above ground level). While there is not a significant amount of difference in the changing of the wind direction, it is more than sufficient for any thunderstorm that develops to produce damaging straight-line winds, along with a tornado threat.

12z GFS 1km Helicity Hr 90 12z GFS 3km Helicity Hr 90

The amount of helicity in the lowest one (greater than 100 units) and three kilometers (greater than 250 units) Saturday Night are more than sufficient for any thunderstorm, whether along the squall line, or ahead of it, to have some tornado potential.

12z GFS 1km AGL Shear Hr 90 12z GFS 6km AGL Shear Hr 90

Plenty of shear in the lowest one kilometer (noted in the yellow), along with the lowest six kilometers (in the yellows and oranges), are noted on this run of the GFS. When combined with the amount surface based instability being forecast, this has the looks of a low CAPE/high shear setup.

12z GFS SBCIN Hr 90

This particular run of the GFS does not indicate any of the Surface Based Inhibition (also known as the “cap”) late Saturday Night. Storms that do develop will have a better opportunity to sustain themselves Saturday Night.

12z GFS 1km VGP Hr 90 12z GFS 1km EHI Hr 90

While the one kilometer Energy Helicity Index and Vorticity Generation Parameter are not particularly high, that in itself can be deceiving. This particular storm setup is a cool season type setup, which is more typical for this time of year.

SUMMARY : The potential is there for severe thunderstorms Saturday Night across the risk area. While damaging straight line winds will be the main severe weather hazard, a tornado risk can not be ruled out either. We will keep you up to date with the latest. Stay tuned.

Severe Weather Threat for Next Week

day5prob

The active weather pattern we are currently in will continue to move right along. While this next storm system will most likely be a multiple-day weather event, we will focus our attention on the Monday threat. This threat includes all of eastern Texas, along with the adjacent states.

12z GFS Hr 108 500mb Absolute Vorticity

That bowling ball feature you see there over Arizona will be the main driving force in the severe weather threat for the first portion of next week across the south. It will begin to take on more of a negative tilt (that is to the left). As a result, severe weather is a definite possibility.

12z GFS Hr 108 Surface Dewpoint 12z GFS Hr 108 SBCAPE

With the storm center in the past couple of days that was lacking moisture, this particular setup will not. Also, the surface based convective available potential energy (SBCAPE) was lacking some. With this particular setup, there is more than sufficient SBCAPE across eastern Texas.

12z GFS Hr 108 Surface Wind 12z GFS Hr 108 500 Wind 12z GFS Hr 108 850 Wind

As was the case with the storm center that caused the severe weather issues in Iowa and Missouri, you have south-southeast to southeast winds at the surface. Going to 850 mb (5,000 feet above ground level), and 500 mb (18,000 feet above ground level), there is changing of wind direction with height. That will aid any thunderstorm development to gain rotation.

12z GFS Hr 108 0-3 km Helicity 12z GFS Hr 108 0-1 km Helicity

The areas you see there in the yellows and oranges feature areas where the helicity in the lowest one kilometer and three kilometers indicate higher potential for more organized updrafts. That would aid in the development of severe thunderstorms with potential to produce tornado activity.

12z GFS Hr 108 0-6 km Shear 12z GFS Hr 108 0-1 km Shear

With shear in the lowest one kilometer exceeding 20 knots shown here, along with the six kilometer shear exceeding 40 knots, that will aid in any thunderstorm’s potential to become supercelluar in nature, and the ability to potentially produce tornado activity.

12z GFS Hr 108 SBCIN

Warm air inversion should not be of particular concern with this setup. The areas in the white and light blue indicate areas where there is basically no cap. As a result, thunderstorms should easily develop.

12z GFS Hr 108 Vorticity Generation Parameter 1km 12z GFS Hr 108 0-1 km Energy Helicity Index

With the Vorticity Generation Parameter shown here, it indicates which locations are at highest risk for possible tornado activity. Values over 0.2 indicate the highest potential for such. Much of eastern Texas is at or well above 0.2, nearing 0.4 to 0.5. Those values indicate tornado activity is very much a possibility.

Also to note, the zero to one kilometer Energy Helicity Index is depicting values over one unit across much of eastern Texas. With those values, the chances are higher of strong damaging tornadoes with any discrete supercell thunderstorm that does develop.

We will continue to monitor this developing storm situation for you here at Velocity Storm Chasing. Stay tuned.

Veterans Day Severe Weather Potential Next Week

day5prob

The weather currently is fairly quiet across the US. However, as we move towards the middle of next week, severe weather looks to be a definite possibility across areas from the Southern Plains eastward to the mid-south. Let us get into the details of this particular threat. The forecast model run we will look at for this blog post is this morning’s 12z GFS.

12z GFS 2m Dewpoint 7 PM Wednesday12z GFS SBCAPE 7 PM Wednesday

One factor that we look at is the amount of moisture available. With this particular storm setup, the amount of moisture should not be a factor at all. The amount of surface based Convective Available Potential Energy shown here is a bit deceiving, given the other parameters shown below…

12z GFS Surface Wind 7 PM Wednesday 12z GFS 850mb Wind 7 PM Wednesday 12z GFS 500mb Wind 7 PM Wednesday

With this particular setup, the wind fields are very impressive. In one aspect, note the changing of the wind directions from the surface, to 850 mb (5,000 feet), and 500 mb (18,000 feet) above ground level. The other aspect is the magnitude of the winds. This aspect looks to be supportive for potential supercell thunderstorm development.

12z GFS 6km Shear 7 PM Wednesday 12z GFS 1km Shear 7 PM Wednesday

The amount of shear being forecast in the lower 1 kilometer and 6 kilometers are more than sufficient for potential supercell thunderstorm development. When you see the reds and purples on the 6 km shear map shown here, this particular aspect would indicate the atmosphere is very unstable.

 

12z GFS 3km Helicity 7 PM Wednesday 12z GFS 1km Helicity 7 PM Wednesday

Another aspect to look at is the amount of storm relative helicity in the lowest one kilometer and three kilometers. The areas showing in the orange and grey colors are areas which have the highest amounts of helicity. These amounts are far more than sufficient for supercell thunderstorm development, and possible tornado activity.

12z GFS 3km Energy Helicity Index 7 PM Wednesday 12z GFS Lifted Condesation Level 7 PM Wednesday

The Lifted Condesation Level (shown above) indicates areas which would see the best potential for tornado activity. As one can plainly see, the areas in light grey from the lower Great Lakes down to the mid south look to have the best potential for tornado activity. Also, the Energy Helicity Index highlights the same general area for Wednesday Evening’s severe weather potential.

12z GFS 1km Vorticity Generation Parameter 7 PM Wednesday 12z GFS SBCIN 7 PM Wednesday

Two more parameters we look at here are the Vorticity Generation Parameter (VGP), along with the Surface Based Convective Inhibition (SBCIN). With the VGP, it indicates which areas see the best chances for tornado activity. Areas from the mid-south to the lower Great Lakes see such potential. With the SBCIN values shown above, that indicates storm development should not be hindered that much.

We will continue to monitor this particular situation for you here at Velocity Storm Chasing. Stay tuned.