Author: Jason Cooley

#WeatherWednesday – Hurricane Ike

Happy #WeatherWednesday everyone! This weekly blog has taken a brief hiatus as Texas was being affected by Hurricane Harvey and Florida by Hurricane Irma. Our thoughts and prayers go out to everyone affected by these tragic storms. Things have settled down for now, just in time to discuss a piece of Texas weather history. Today is the 9th anniversary of Hurricane Ike’s landfall in Galveston, TX. Before 2017, Ike was the third most costly Atlantic tropical system. It likely won’t hold this placement after the official cost assessment of recent Hurricanes Harvey and Irma is announced. Ike really messed up Haiti and killed 74, cost a lot of damage in the US and killed 113, and overall killed 195 people. Here is the path with color-coded intensities: Ike made landfall in Cuba as a Category 4. On this day at 2AM 9 years ago, after a trip through the Gulf of Mexico, Ike made landfall in Galveston as a high end Cat-2 with 110mph winds! Ike didn’t dissipate until it blew past the Great Lakes and well into Quebec on the 15th. It affected the Houston/Galveston metro, the Ozarks, and the Lower Ohio Valley/Great Lakes with damaging winds and dangerous flooding. This wind damage actually tied the Xenia tornado outbreak as the costliest storm event in Ohio (1.1 billion USD). Canada also had record setting flash flooding from Ike....

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#WeatherWednesday- Derecho

Hello everybody and happy #WeatherWednesday! Last week we discussed the concept of the monsoon. Today we will talk about a type of storm called a “derecho”. The word is Spanish for straight and it has to do with straight line winds! A derecho isn’t the most common storm, but it’s definitely dangerous. These storms occur several times per year in the USA. They are storm systems associated with high surface winds from storm outflow. The longevity and elevated forward speed of the damaging storm are primary defining factors. This means more area liable to be damaged by a storm moving faster than normal. Many derechos propagate at 35-65mph. Storms can produce locally high winds and damage anytime, but derechos produce high winds for hours over a great length and width. A squall line on the other hand usually produces sporadic wind damage at various parts of the storm. A squall is similar in structure but is only considered a derecho if there have been 60mph+ winds on the storm front for at least 6 hours. A serial derecho can commonly be identified as a bow echo or backward C on radar reflectivity during its lifetime. Visually, a shelf cloud normally develops on the leading gust front where the temperature gradient from colder outflow and warm inflow exists. Derechos occur in the summer most of the time when warm air...

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#WeatherWednesday – The Monsoon Season

Happy #WeatherWednesday everyone! I hope the lesson on RFD cleared up any confusion you had about its meaning! We will return to talking about supercell characteristics at a later time. With the recent weather business going on in the southwest USA, I would like to talk a bit about it. This isn’t unusual for the interior southwest. Places like Arizona, New Mexico, Nevada, Colorado, California, Utah, and sometimes Trans-Pecos (Texas) experience numerous storms virtually daily around this time every year. It’s called a monsoon! The North American Monsoon usually starts in July and lasts into mid-September. The rain and...

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#WeatherWednesday – RFD

Hello and happy #WeatherWednesday everyone! I hope you found the last write-up about atmospheric instability and stability useful and interesting. To change things up we will switch to a mesoscale meteorology lesson today. We are going to discuss what the term “RFD” means! As many of you know, a supercell is what we call a storm with a sustained, rotating, and tilted updraft. The most frequent severe weather is caused by supercell thunderstorms. One of the biggest defining features of a supercell is the presence of RFD, or rear-flank downdraft. On radar, this is visualized by a “hook echo”,...

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#WeatherWednesday – CAP versus CAPE

Happy #WeatherWednesday guys and gals! Have you always wondered what the meteorologists on TV or weather websites really mean when they say the atmosphere is stable or unstable? We will discuss what that means and how “the cap” or “CAPE” relate to these descriptors. A stable atmosphere is characterized by ¬†air that is warmer aloft than the theoretical temperature of an air parcel that is vertically displaced from the surface. This warmer air can be a variety of thicknesses and magnitudes. In this context, the stability is stronger as this temperature differential between the atmosphere and the surface parcel increases and/or the as thickness that differential exists grows. This layer is called the cap. Colder air is denser than warm air and will SINK in the fluid atmosphere. Warm air RISES. Since you need air displacing upward to trigger thunderstorms, a cap will prohibit vertical motion and storms unless a “lifting mechanism” is strong enough to force air to erode the cap due to momentum and cooling effects of evaporation. So what’s the opposite of stability and a cap? It is instability, or CAPE (Convective Available Potential Energy). This is the potential energy for a surface air parcel to accelerate **opposing gravity** upward until it reaches stability again. Here is where the environment is colder than the theoretical surface parcel temperature allowing the relatively warmer air to continue rising...

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