Another element that can arise from severe thunderstorms is the threat of flash flooding. Flash flooding typically occurs when an area that has extremely saturated soil receives heavy rains (or even light to moderate rain over a long period of time). Flash flooding becomes even more dangerous in areas where topography can lead to water moving extremely fast down hill, such as mountain ranges... or the bluffs, ridges, and valleys of our very own Coulee Region.
Flash floods are the number one weather-related killer in the United States. Flash floods are capable of moving boulders, removing trees, damaging buildings and bridges, and can even change the course of rivers and streams! One such event happened in August of 2007 here in the Coulee Region. Parts of La Crosse and Vernon County received between 11 and 15" of rain in about 36 hours. The result was mudslides, rock slides, rapid rises in creeks and streams, road damage, bridges were wiped out and destroyed, and some creeks even changed course. While this was considered a 1000 year event, it can happen anywhere and at anytime.
The best advice is that when a flash flood warning is issued for your area, head for higher ground! Especially if you live along a creek or stream or reside in a valley. And DO NOT DRIVE THROUGH FLOODED ROADS! Turn around, don't drown! The water in a flash flood is moving incredibly fast and you will be swept away before you know it.
Thursday, April 14, 2011
Wednesday, April 13, 2011
Spring and Summer are Severe Thunderstorm Season!
When thunder roars, GO INDOORS! While this saying is commonly used for lightning safety, it's a good rule of thumb for any thunderstorm, especially severe thunderstorms! Severe thunderstorms are thunderstorms that meet one or more of the following criteria: damaging wind gusts in excess of 58 mph, large hail (at least 1" in diameter), or a tornado. Severe thunderstorms are most common during the hours of 3 p.m. and 9 p.m. between April and September, but in reality, can occur at any time of the day.
The strong wind gusts are the most common threat from severe thunderstorms, and are even more damaging if they are in the form of straight-line winds. While a tornado would only affect a relatively small region, straight-line winds can affect entire counties and can even blow at hurricane-force! In the mid to late 90's, La Crosse County was hit with straight-line winds, and the event is still evident today. If you drive south on HWY 35 out of La Crosse and look closely at the north side of a bluff near Goose Island Park, you'll notice many fallen trees from the event laying west to east.
While not considered a criteria for a severe thunderstorm, lightning almost always accompanies them. These electrical discharges from the skies can be hotter than the surface of the sun and are extremely deadly! Lightning, second to flash floods, are one of the major causes for death from thunderstorms. And you don't have to be under the thunderstorm to get struck. Lightning can travel for miles away from it's parent thunderstorm. So basically, when you hear thunder, you are close enough to be struck. So when thunder roars, go indoors!
The strong wind gusts are the most common threat from severe thunderstorms, and are even more damaging if they are in the form of straight-line winds. While a tornado would only affect a relatively small region, straight-line winds can affect entire counties and can even blow at hurricane-force! In the mid to late 90's, La Crosse County was hit with straight-line winds, and the event is still evident today. If you drive south on HWY 35 out of La Crosse and look closely at the north side of a bluff near Goose Island Park, you'll notice many fallen trees from the event laying west to east.
While not considered a criteria for a severe thunderstorm, lightning almost always accompanies them. These electrical discharges from the skies can be hotter than the surface of the sun and are extremely deadly! Lightning, second to flash floods, are one of the major causes for death from thunderstorms. And you don't have to be under the thunderstorm to get struck. Lightning can travel for miles away from it's parent thunderstorm. So basically, when you hear thunder, you are close enough to be struck. So when thunder roars, go indoors!
Tuesday, April 12, 2011
Tornado Facts and Safety
I thought I'd continue on the topic of tornadoes for today and provide you with some commonly asked questions about them, follow by safety tips for when one is headed your way. If you have any questions, please ask in the comment section and I'll get back to you as soon as I can.
How do tornadoes form?
A classical answer of "Tornadoes form when warm moist air from the Gulf meets cold Canadian air and dry air from the Rocky Mountains" is an extreme oversimplification! Many thunderstorms that form under these conditions never even come close to producing tornadoes. The truth is, we don't fully understand and know why tornadoes form. We do know that the most destructive and deadly tornadoes occur under supercell thunderstorms (massive rotating thunderstorms with a well defined circulation also known as a mesocyclone). The VORTEX program performed over the summers of 2009 and 2010 set out to gather data to better learn how tornadoes actually form. Recent theories and results from the program suggest that once a supercell thunderstorm/mesocyclone is underway, the development of the tornado is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone. However, tornadoes have been know to form without this temperature difference, such was the case with the destructive May 3rd, 1999 tornado that struck Moore and Oklahoma City, Oklahoma. Thus, we're are basically back to square one - we truly do not know. But if you would like more indepth information on theories, just ask me and I can show you some papers from my college years.
Does hail always come before the tornado? How about rain, lightning, or pure silence?
In truth, hail, rain, lightning or that erie silence do not alway come before a tornado. The hail, rain, and lightning characteristics will vary from storm to storm and moment to moment in time. While large hail is a characteristic of a severe thunderstorm and can happen before a tornado, don't always use it as an indicator. All four of these are not reliable predictors of a tornado threat.
Do tornadoes really skip?
I asked this question once myself! I had envisioned a tornado bouncing from hilltop to hilltop in a very cartoon-like fashion. But in reality, they really don't "skip". By classical definition, a tornado must be in contact with the ground. There is currenly a big disagreement among meteorologists over whether or not multiple touchdoens of the same funnel mean different tornadoes.
What happens when two or more tornadoes come together?
This is a very rare occurance, but it has actually been caught on tape. Basically what happens is that the larger and stronger tornado will simply pull in and absorb the smaller, weaker tornado and continue on its course with little change.
What is the Enhanced F-scale?
Most people are somewhat familiar with the classic F-scale (or Fujita scale - named after Dr. Fujita who developed it) but are not familiar with the new Enhanced F-scale (or EF-scale). The EF-scale is a much more precise and robust way to assess tornado damage than the original F-scale. It classifies damage on a scale of EF0 to EF5 by using 28 different types of damage indicators and takes into account the type of buildings/structures, how well they are constructed, and what structures are made of.
Can't we weaken or destroy tornadoes somehow? Like by bombing them or sucking out their heat with a bunch of dry ice?
Wow.... I found this one and I just had to include it! Basically, the main problem is that anything that could possibly stand a chance at affecting a tornado (i.e. a hydrogen bomb!) would be more deadly and destructive than the tornado itself! And the idea of using huge piles of dry ice to destroy temperature differences is very hard to actually deploy in the right place quickly. Basically, the legal ramification of doing either of these things and then inadvertently hurting someone or destroying property dramatically outways the benefits.... so very very bad idea!
How do tornadoes form?
A classical answer of "Tornadoes form when warm moist air from the Gulf meets cold Canadian air and dry air from the Rocky Mountains" is an extreme oversimplification! Many thunderstorms that form under these conditions never even come close to producing tornadoes. The truth is, we don't fully understand and know why tornadoes form. We do know that the most destructive and deadly tornadoes occur under supercell thunderstorms (massive rotating thunderstorms with a well defined circulation also known as a mesocyclone). The VORTEX program performed over the summers of 2009 and 2010 set out to gather data to better learn how tornadoes actually form. Recent theories and results from the program suggest that once a supercell thunderstorm/mesocyclone is underway, the development of the tornado is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone. However, tornadoes have been know to form without this temperature difference, such was the case with the destructive May 3rd, 1999 tornado that struck Moore and Oklahoma City, Oklahoma. Thus, we're are basically back to square one - we truly do not know. But if you would like more indepth information on theories, just ask me and I can show you some papers from my college years.
Does hail always come before the tornado? How about rain, lightning, or pure silence?
In truth, hail, rain, lightning or that erie silence do not alway come before a tornado. The hail, rain, and lightning characteristics will vary from storm to storm and moment to moment in time. While large hail is a characteristic of a severe thunderstorm and can happen before a tornado, don't always use it as an indicator. All four of these are not reliable predictors of a tornado threat.
Do tornadoes really skip?
I asked this question once myself! I had envisioned a tornado bouncing from hilltop to hilltop in a very cartoon-like fashion. But in reality, they really don't "skip". By classical definition, a tornado must be in contact with the ground. There is currenly a big disagreement among meteorologists over whether or not multiple touchdoens of the same funnel mean different tornadoes.
What happens when two or more tornadoes come together?
This is a very rare occurance, but it has actually been caught on tape. Basically what happens is that the larger and stronger tornado will simply pull in and absorb the smaller, weaker tornado and continue on its course with little change.
What is the Enhanced F-scale?
Most people are somewhat familiar with the classic F-scale (or Fujita scale - named after Dr. Fujita who developed it) but are not familiar with the new Enhanced F-scale (or EF-scale). The EF-scale is a much more precise and robust way to assess tornado damage than the original F-scale. It classifies damage on a scale of EF0 to EF5 by using 28 different types of damage indicators and takes into account the type of buildings/structures, how well they are constructed, and what structures are made of.
Can't we weaken or destroy tornadoes somehow? Like by bombing them or sucking out their heat with a bunch of dry ice?
Wow.... I found this one and I just had to include it! Basically, the main problem is that anything that could possibly stand a chance at affecting a tornado (i.e. a hydrogen bomb!) would be more deadly and destructive than the tornado itself! And the idea of using huge piles of dry ice to destroy temperature differences is very hard to actually deploy in the right place quickly. Basically, the legal ramification of doing either of these things and then inadvertently hurting someone or destroying property dramatically outways the benefits.... so very very bad idea!
Tornado Safety Tips
- In a house with a basement, avoid all windows and get in the basement and under some kind of sturdy protection. Know where very heavy objects are on the floor(s) above and do not go under them - if the floor weakends, they could fall through and crush you.
- In a house without a basement. again, avoid all windows. Go to the lowest floor of the home and in a small interior room, under a stairwell, or in an interior hallway with NO windows. Crouch as low as possible to the floor, facing down and cover your head with your hands (like you practiced in school!). Even in an interior room, try to cover yourself with some sort of thick padding (i.e. a mattress, blankets, etc.) to protect yourself from debris.
- In an office building or hospital: Go directly to an enclosed, windowless area in the center of the building and stay away from glass. If you can, get on the lowest floor possible. Then crouch down and cover your head. Interior stairwells are usually good places to take shelter, and if they are not crowded, get to the lowest level possible as quickly as possible. And avoid elevators!
- In a mobile home: Get out! Even if your home is tied down, you are more likely to be safer outside! If your community has a tornado shelter, get there fast. If there is a sturdy permanent building within easy running distances, seek shelter there. Otherwise, lie flat on low ground away from your home and protect your head. If possible, use open ground away from trees and cars which can be blown onto you.
- At school: Follow the drill! Go to the interior hall or room in an orderly way and do as you are told. Crouch down, head down, and protect the back of your neck with your arms. Stay away from windows and large open rooms like gyms and auditoriums.
- In a car or truck: If the tornado is visible, far away, and the traffic is light, you may be able to drive out of its path by moving at right angles to the tornado. Otherwise, park your vehicle as quickly and as safely as possible and out of traffic lanes. Get out and seek shelter in a sturdy building. If in the open country, run to low ground away from any cars. Lie flat and face-down, protecting the back of your head with your arms. AVOID SEEKING SHELTER UNDER BRIDGES & OVERPASSES!
- If outdoors: If possible, seek shelter in a sturdy building. If one is not available, lie flat and face-down on low ground, protecting the back of your head with your arms. Get as far away from trees and cars as you can!
Well... I hope you enjoyed these facts about tornadoes and know the safety tips. They could save your life! Tomorrow, I'll be talking about a different subject about severe weather, so check back sometime tomorrow!
Monday, April 11, 2011
Common Tornado Myths!
Ah yes.... one of my favorite subjects. Tornado myths. There are so many out there, but here are some of my favorites and explainations as to why they are indeed myths and not fact.
Tornado Myth #1: Highway overpasses are a safe place to take shelter if you are on the road when you see a tornado approaching.
This myth stems from an interview with a man who survived the Wichita Falls tornado of 1979 by parking his car and running up underneath an overpass crossing the highway. Luckily, he managed to survive. In the early 1990's, a television crew was on their way back from covering a story when they spotted a tornado approaching them. When they realized that they couldn't outrun it, the parked their vehicle and took shelter under an overpass with several other people. A weak tornado was heading straight for them, but eventually passed just to the south of their location. However, what the people experienced was very intense and the crew caught it on tape and has been seen by millions and millions of people worldwide.
Since that tape aired, most of the public have assumed that an overpass is indeed a safe shelter since the news crew and the others survived. But the truth is, any time you deliberately put yourself above ground level during a torando, you are putting yourself in harms way!
Now why is this myth a myth? Well.. when a tornado approaches an overpass, the intense winds of the tornado also funnel underneath the overpass - only, they may speed up! Basically, the rise in the embankment adjacent to the highway places you in a wind tunnel with nothing to hang onto and exposing you to the tornado and flying debris! And any large debris can easily be lodged into the overpass itself, making them a collection area for debris and a very dangerous place to be during a tornado. So please, stay away from the overpasses during a tornado!
Tornado Myth #2: The southwest corner of a basement is the safest location during the passage of a tornado.
I heard this myth first-hand growing up from my father! He told us that if we were ever to see a tornado, that we were to go to the southwest corner of the basement (or barn if we were milking cows). In reality, the truth is that the part of the home towards the approaching tornado (which is often, but not always, the southwest) is the least safest place in the basement (also true for above ground as well)! During most tornadoes, more homes will be shifted than be blown down completely free of the foundation. And homes "attacked" from the southwest tend to shift northeast. Thus, the unsupported part of the house (which is then the SW corner) may collapse into the basement AND/OR pull over part of the foundation. Several studies from the 60's and 70's have proved this to be true. As a general rule, being under a stairwell, heavy table, or work bench in the basement will afford even more protection then being in any corner!
Tornado Myth #3: Tornadoes never strike big cities.
There is a sliver of truth to this. While big cities rarely get hit, they do in fact, get hit! The reason why this myth arose is because of the fact that big cities rarely get hit. It's just that big cities account for a very small land mass (when one thinks of big city, they think of sky scrapers and large office buildings) making it a very small target. The tornadoes are more likely to hit the city's boundaries and suburbs then the "big city". And it should also be noted that very few "big cities" exist in tornado alley. But one of them, St. Louis, has had a long history of tornadoes in it's central area!
Tornado Myth #4: Openning windows in your house to equalize air pressure will save a roof, or even a home, from the destructive forces of the tornado.
YIKES! This one is just a scary thought and a waste of precious time! The thought of moving a thin plane of very breakable glass is going to protect your home from one of the most violent force of mother nature is crazy! This idea is basically wishful thinking. In reality, openning windows is a dangerous and useless waste of time! As a tornado passes through, the debris flying around it and the sheer strength of the winds will blow more than enough vent holes in the building to equalize any pressure differences. Basically, the best advice is to leave those windows alone and head for cover in a basement or shelter as fast as possible! One should not think about the house roof first, but the impact of one's death on their family or being seriously injured!
Tornado Myth #5: Some towns are "protected!"
This myth actually stems from Native American origin. The Osage Indians, native to the central plains, told settlers that tornadoes will not strike between two rivers near the point where the rivers join. Well.... this one has been shown to be indeed a myth! Emporia, KS, located between the Cottonwood and Neosho Rivers, was "protected" for over a century in native Osage territory. Then a tornado struck the town on June 8th, 1974, killing 6 and causing $20 million in damage. Another twister hi on June 7th, 1990 and caused only $6 million in damage.
The idea of a town being "protected" is basically the cause of wishful thinking, short memory, the rarity of tornadoes, and a distorted sense of here or there. Geological features such as rivers, ridges, and valleys have little to no effect on mature tornadoes. Tornadoes have passed over mountain ridges and have crossed the mighty Mississippi River. Topography may have a bit of influence, but definely not protection. Weak tornadoes will damage hilltops, but mature tornadoes can actually stretch down into valleys and intensify! During this stretching, the tornado becomes narrower and will spin more rapidly!
Basically, tornadoes go where they want, no matter what is in the way!
I hope you enjoyed some of these myths. There are plenty more out there, but I don't want this posting to go on forever! See you tomorrow!
Tornado Myth #1: Highway overpasses are a safe place to take shelter if you are on the road when you see a tornado approaching.
This myth stems from an interview with a man who survived the Wichita Falls tornado of 1979 by parking his car and running up underneath an overpass crossing the highway. Luckily, he managed to survive. In the early 1990's, a television crew was on their way back from covering a story when they spotted a tornado approaching them. When they realized that they couldn't outrun it, the parked their vehicle and took shelter under an overpass with several other people. A weak tornado was heading straight for them, but eventually passed just to the south of their location. However, what the people experienced was very intense and the crew caught it on tape and has been seen by millions and millions of people worldwide.
Since that tape aired, most of the public have assumed that an overpass is indeed a safe shelter since the news crew and the others survived. But the truth is, any time you deliberately put yourself above ground level during a torando, you are putting yourself in harms way!
Now why is this myth a myth? Well.. when a tornado approaches an overpass, the intense winds of the tornado also funnel underneath the overpass - only, they may speed up! Basically, the rise in the embankment adjacent to the highway places you in a wind tunnel with nothing to hang onto and exposing you to the tornado and flying debris! And any large debris can easily be lodged into the overpass itself, making them a collection area for debris and a very dangerous place to be during a tornado. So please, stay away from the overpasses during a tornado!
Tornado Myth #2: The southwest corner of a basement is the safest location during the passage of a tornado.
I heard this myth first-hand growing up from my father! He told us that if we were ever to see a tornado, that we were to go to the southwest corner of the basement (or barn if we were milking cows). In reality, the truth is that the part of the home towards the approaching tornado (which is often, but not always, the southwest) is the least safest place in the basement (also true for above ground as well)! During most tornadoes, more homes will be shifted than be blown down completely free of the foundation. And homes "attacked" from the southwest tend to shift northeast. Thus, the unsupported part of the house (which is then the SW corner) may collapse into the basement AND/OR pull over part of the foundation. Several studies from the 60's and 70's have proved this to be true. As a general rule, being under a stairwell, heavy table, or work bench in the basement will afford even more protection then being in any corner!
Tornado Myth #3: Tornadoes never strike big cities.
There is a sliver of truth to this. While big cities rarely get hit, they do in fact, get hit! The reason why this myth arose is because of the fact that big cities rarely get hit. It's just that big cities account for a very small land mass (when one thinks of big city, they think of sky scrapers and large office buildings) making it a very small target. The tornadoes are more likely to hit the city's boundaries and suburbs then the "big city". And it should also be noted that very few "big cities" exist in tornado alley. But one of them, St. Louis, has had a long history of tornadoes in it's central area!
Tornado Myth #4: Openning windows in your house to equalize air pressure will save a roof, or even a home, from the destructive forces of the tornado.
YIKES! This one is just a scary thought and a waste of precious time! The thought of moving a thin plane of very breakable glass is going to protect your home from one of the most violent force of mother nature is crazy! This idea is basically wishful thinking. In reality, openning windows is a dangerous and useless waste of time! As a tornado passes through, the debris flying around it and the sheer strength of the winds will blow more than enough vent holes in the building to equalize any pressure differences. Basically, the best advice is to leave those windows alone and head for cover in a basement or shelter as fast as possible! One should not think about the house roof first, but the impact of one's death on their family or being seriously injured!
Tornado Myth #5: Some towns are "protected!"
This myth actually stems from Native American origin. The Osage Indians, native to the central plains, told settlers that tornadoes will not strike between two rivers near the point where the rivers join. Well.... this one has been shown to be indeed a myth! Emporia, KS, located between the Cottonwood and Neosho Rivers, was "protected" for over a century in native Osage territory. Then a tornado struck the town on June 8th, 1974, killing 6 and causing $20 million in damage. Another twister hi on June 7th, 1990 and caused only $6 million in damage.
The idea of a town being "protected" is basically the cause of wishful thinking, short memory, the rarity of tornadoes, and a distorted sense of here or there. Geological features such as rivers, ridges, and valleys have little to no effect on mature tornadoes. Tornadoes have passed over mountain ridges and have crossed the mighty Mississippi River. Topography may have a bit of influence, but definely not protection. Weak tornadoes will damage hilltops, but mature tornadoes can actually stretch down into valleys and intensify! During this stretching, the tornado becomes narrower and will spin more rapidly!
Basically, tornadoes go where they want, no matter what is in the way!
I hope you enjoyed some of these myths. There are plenty more out there, but I don't want this posting to go on forever! See you tomorrow!
Monday, April 4, 2011
Severe Weather is Coming..... Are You Ready?
Hey everyone! As spring kicks into high gear here in the Upper Midwest, so does another weather aspect..... severe weather! While the violent wrath of mother nature can be exciting (or terrifying) to watch, you should always be ready when severe weather threatens your life and property! Coming up next week is Severe Weather Awareness Week in Wisconsin & Minnesota (it's in Iowa this week) and I'll be having a post everyday on various aspects of severe weather! But before that, it's important to start making a severe weather survival kit to have ready for when severe weather strikes (and as Southern Wisconsin found out last night, the season has begun!).
A severe weather kit may seem like something you don't even want to think about, but it can be a major life saver in the event that you are impacted with the wrath of mother nature! So here is a list of items everyone needs to have ready in a severe weather kit this season:
The Basics:
Gloves - for protection for your hands
Pliers - to shut off gas and water lines in need be.
Playing cards - keeps your mind off of things
Now, this list can obviously be added too depending on the individual needs of you and your family. But having this basic kit on hand will be a useful tool should severe weather strike in your neck of the woods.
A severe weather kit may seem like something you don't even want to think about, but it can be a major life saver in the event that you are impacted with the wrath of mother nature! So here is a list of items everyone needs to have ready in a severe weather kit this season:
The Basics:
- 1 gallon of water per person per day - to keep you hydrated.
- An emergency non-perishable food ration - high energy bars work great for this. Also, avoid salty foods as these will make you thirsty!
- 2 Emergency Blankets - to stay warm or shield you from debris.
- 1 Multi-purpose tool - like a Swiss Army knife... something that will come in handy!
- 4 - 12 Hour Light Sticks - so you can see and others can see you!
- Several Plastic Bags - for sanitation purposes if your trapped!
- Pocket Tissue
- Ponchos for every member of your family.
- First Aid Kit - for any wounds you may receive!
- Whistle - so you can let others know where you are.
- Prescription Drugs - so you don't run out when you need them!
- NOAA Weather Radio - Important so you know when the storm has passed and it's safe to leave your safe place.
Gloves - for protection for your hands
Pliers - to shut off gas and water lines in need be.
Playing cards - keeps your mind off of things
Now, this list can obviously be added too depending on the individual needs of you and your family. But having this basic kit on hand will be a useful tool should severe weather strike in your neck of the woods.
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