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Texas, Oklahoma, Arkansas, and Southern Missouri are under the gun again for some more heavy rainfall and potential (highly likely) widespread flooding. This widespread rain event is caused by three major weather phenomena all coming together at once:
- Strong low-level moisture influx from the Gulf of Mexico
- Strong upper-level moisture influx thanks to Hurricane Sandra in the East Pacific (moving onshore to Mainland Mexico)
- Strong Cold Front pushing out of the Central Plains, but stalling in Central Texas due to strong Gulf flow
These three features characterize heavy rain, and we've seen it before just recently (October 24th-25th with Hurricane Patricia). I expect this event to begin to kick off around nightfall Thursday and persist through Sunday Morning. After the Cold Front passes during the day on Friday, portions of North Texas, as well as Oklahoma, Arkansas, and Missouri will likely see widespread ice pellets (ice storm) and winter-like weather as the temperatures will plummet into the low 30's.
The amount of rainfall expected is significant, especially through Northern Hill Country, North Texas, Oklahoma, and Arkansas may exceed 10 inches. South of the Interstate 10 in Texas, likely only 1-3 inches.
See the attached Weather Prediction Center Outlook.
Obvious Hazards: Flooding (Widespread) and Icy Roads (North Texas/Oklahoma/Arkansas/Missouri)
Stay tuned to the National Weather Service for severe weather updates and local emergency management authorities for more instructions.
Interesting weather satellite image from this evening. Most people are familiar with infrared satellite imagery which colors clouds different colors based on their temperature, even at night when human eyes can't see them. Well, This is infrared water vapor satellite imagery.
What does that mean?
Water Vapor imagery doesn't "see" clouds, it only depicts the amount of water vapor in the middle and upper troposphere and lower stratosphere. It doesn't show any clouds! Granted, we can infer that if there is a lot of water vapor somewhere, there probably are clouds there as well. But clouds are liquid water or ice crystals, not vapor (which is water in it's gaseous state). So what?
What is pointed out in the picture is the Jet Stream. Water vapor imagery is great at outlining the Jet Stream because the Jet Stream causes very dry stratospheric air to mix into the middle and upper troposphere...that's why you see dry air on water vapor imagery at these levels where my arrow point. Generally the more distinct the dry air is, the stronger the Jet Stream. The stronger the Jet Stream, the stronger the storm is that it is pushing along (over the upper Ohio River Valley in this picture).
Now, don't get confused...all dry air on this image is not the Jet Stream...other things can cause dry air to show up...but that's a semester-long course in advanced thermodynamics.
I'm sure y'all have heard of the "Polar Vortex"...a fancy name that someone created during the winter of 2013-2014 for the Jet Stream that becomes very strong and dips well into the southern states. It all starts with Water Vapor Satellite.
Below you can view a loop of model forecast Surface Relative Humidity. The blue colors are high, the yellows, greens, and reds are low. So what can you tell from this? As time progresses, you will notice that the line of blue quickly moves eastward, filled in by lower relative humidifies. This is the outline of the cold front that is passing through Texas tonight.
As you can see, most of the darkest blue indicates areas of potential rainfall...a fast-moving line impacting the majority of the state, but most notably the northern half, and east of the Interstate 35 Corridor.
Most of the severe thunderstorms expected will remain through the Panhandle, North Texas, Oklahoma, and eventually much of East Texas and Louisiana, although much of state of Texas is under-the-gun, even if just slightly. In fact, the majority of West Texas, including all of the Panhandle, as well as the Oklahoma Panhandle and western Kansas are all currently under a Tornado Watch, while East Texas, all of Louisiana, Arkansas, Mississippi, and much of Missouri, Illinois, and Western Tennessee are all poised with a flash flood watch.
Stay tuned to your local news channel and emergency management updates as this system continues to barrel down on the region.
Texas, Oklahoma, and Western Kansas are on the hook for some upcoming severe weather as a storm system barrels down on the Southern Plains. Arkansas, Louisiana, and Mississippi are shortly thereafter, followed by the remainder of the Eastern United States. A fast-moving cold front, which will bring snow to the Inter mountain West (Arizona, Utah, New Mexico, Wyoming, Colorado...) will begin to push through the Texas/Oklahoma Panhandle near sunset Monday evening, bringing severe thunderstorms followed by near-freezing temperatures. By sunrise, the cold front will have blasted through Texas Hill Country and Central Oklahoma/Kansas and will bear down on East Texas, bringing Severe Thunderstorms and potentially heavy rain to much of South-Eastern Texas (Houston Metroplex) and Coastal Louisiana. This will continue through the day on Tuesday, with rain and thunderstorms occurring through the Mississippi River Valley from New Orleans to St Louis. By sunrise Wednesday, expect the cold front ans associated weather to stretch from the Mississippi Gulf to Lake Michigan (wow!)...becoming slightly negatively titled (which is conducive for very bad weather) through the Ohio River Valley. By early morning Thursday, it will hit the Appalachians. At the same time, an additional cold push of air will enter northern Texas, bringing sub-freezing temperatures.
I've attached the Storm Prediction Center's outlook valid from 6am Monday-6am Tuesday. Thunderstorms will occur outside of the shaded areas...this is only their assessment of SEVERE THUNDERSTORM potential. Additionally, this does not account for heavy rain and flooding potential.
***Severe Thunderstorms (as issued by the National Weather Service) include quarter-sized (1-inch diameter) hail and/or wind speeds 58 mph or greater (50 knots). Tornadoes are often a possibility with severe thunderstorms, but the likelihood of a tornado is significantly less than the likelihood of a severe thunderstorm. On average, only about 20-30% of severe thunderstorms are capable of creating a funnel cloud, and even less will create an actual tornado reaching the ground. Nonetheless, the threat exists.
Not a good day to be in Iowa. Multiple reports of severe thunderstorms through the region, including tornadoes in Adams, Pottawattamie, and Ringold Counties (west of Des Moines). Even more recently, Des Moines International Airport Control Tower reported a Tornado on the ground.
It's no surprise to see this, however...meteorologist have been highlighting this area for violent weather for a few days now. As highlighted in the picture below, this storm is fueled by warm, moist air from the Gulf of Mexico, and driven by frigid air from interior Canada. When these two airmasses meet, cold air moves over the warm air, which significantly destabilizes the atmosphere (because warm air likes to rise and cold air likes to sink....but the opposite is happening in this case).
To illustrate how drastic the two airmasses are from each other and how violent the battle can be between the two, Kearney, Nebraska is (when this was posted) 32*F and snowing. 250 miles east-southeast in Kansas City, the temperature is 75*F, with 50mph wind gusts. In fact, outside of damage from tornadoes reported, there have been reports of roofs being blown off structures from these winds.
So why is the wind blowing so hard? Simple....difference in temperature equals difference in pressure.
For example, we all know that when we freeze water in a glass cup, the glass cup will break because the pressure exerted on the glass by the water as it freezes increases. Now we know that pressure changes with temperatures...so how does that make wind blow?
Well, the pressure in your car tire is higher than the pressure of the outside air. That's why when you get a flat tire, the air rushes out, not in (wouldn't that be nice!?). The same happens with weather. Colder temperatures have higher pressure. Warmer temperatures have lower pressure. This causes wind to blow from the cold to the warm. If the cold is really cold, and the warm is really warm, then the wind blows even faster, because the pressure difference is stronger.
And in the case of Iowa and the Midwest today, not only do you have that, but you have an atmosphere that is forcing cold air on top of warm air.....that's like pouring ice water on a hot stove top...the immediate area doesn't like it very much.
You just geeked out for the day....