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Some basic abreviations used for direction: (ese = east southeast) (nnw = north northwest) (sw = southwest)....etc. I use those often throughout the site.   When looking at storms it is good to have an understanding of height. Often the terms low-level, mid-level, and high-level(or upper-level) will be used to broadly describe something. First off, height of a storm doesn't always indicate severity as I believe thunderstorms in the tropics will often reach really high levels, yet not be as severe as a big storm on the plains. But to give an idea of storm height I know 70,000 feet is VERY rare on the plains. I'm not sure I've chased one yet that was that tall. The tallest storm I know of chasing was July 12, 2004 in central Nebraska. Radar indicated heights of 65,000 to 70,000 feet. It was simply a massive supercell. As you can see on the below image the top of the scale is 70,000 feet. Look for the light grey area south of O'Neill and you'll see this storm's top and see the scale on the bottom showing the associated level.   So that is a level to consider and think of visually. 70,000 feet is VERY rare(anything near 65,000 could be considered very rare too I guess). I'd guess 50,000 to 60,000 feet is still considered a big storm. 50,000 to 55,000 is more typical for a decent storm. Time of year contributes to the height quite a bit. Storms earlier in the year are generally shorter storms(same for late in the year/fall)...generally.   Now back to low-level, mid-level, and high-level(or upper-level). If you hear of the term the low level jet(I often just type LLJ for it) it is considered to usually be around 6,000 feet. The mid-level jet(a JET is just a core or strong winds) is basically around 18,000 feet. And the upper-level jet is pretty much 30,000 feet or higher. So to me when I say low-level I'm thinking 9,000 feet and lower. Mid-level and I'm thinking 9,000 feet to say 25,000 feet. Upper-level and I'd say 25,000 feet on up. It isn't like one needs to be very specific with it but that is a general idea of height.

Towering Cumulus Rising updraft of air which condenses forming clouds. The towering cumulus is the stage of growth before it becomes a Cumulonimbus. Cumulonimbus Basically it becomes a cumulonimbus when it starts producing an anvil.
Anvil The anvil is the top flat portion of a storm. The updraft gets up so high and the moisture it is carrying upward freezes forming small ice crystals. They are then carried outward with the winds aloft. The production of an extensive anvil sheild depends on the strength and duration of the uprdaft producing it. Before this shot this updraft was a potent supercell storm. It was going for a good couple hours anyway. I got to it and it died. It shrank away into nothingness. This of course halts the production of this anvil. When that updraft is completely gone you are left with what is called an Orphan Anvil. The anvil can cover a lot of ground quick because it is high up in the stronger winds. It will often spread out away from your storm quite quickly. So if you are to the east a good ways and have no data and see an anvil streaking over all the sudden you can know something fired somewhere to the west. It sucks when you then make the drive only to find you are chasing an Orphan Anvil which no longer has a storm attached to it.
Updraft/Thunderhead/Convection/Cloud Tower/Cumulonimbus.....etc: They all refer to the big cloud you see that contains rising air. To the right is an updraft from the November 12, 2005 chase. This is pretty much where severe weather starts. The view here is looking straight east. Looking east(or viewing on the west side) enables you to see the updraft tower itself the best. If you were on the other side looking west at it it gets harder and harder to see the updraft towers like this as the storm develops. Rain will start to block the view of the billowing and the storm will also become structured on that side(smoothed or striated...etc)....also from the west you'll likely have the sun shining on it more.
Overshooting Top/Anvil Dome An overshooting top or dome is a protrusion of the updraft extending above the anvil level. Generally the larger and the higher one is the more intense the updraft producing it is. This is from a short chase July 6, 2003. Backshearing Anvil This is when the anvil cloud spreads upwind against the stronger flow aloft. In this picture the winds aloft are blowing from left to right(west to east, looking north). It can indicate a stronger updraft much like the dome can. The one thing to consider is how strong are the winds aloft. If they are weak(which they were this day) then backshearing avils really do not mean a whole lot. If you know the winds aloft are strong and you see one, then you likely have an intense updraft. So far they are of little use to me as I'm often east of the storms unable to see any of this. They love to produce mammatus clouds however and those can be a real treat.
Mammatus These are protrusions hanging down from the anvil cloud. They are rather common around severe storms and are not dangerous themselves. They form from turbulent sinking air motions. They like to form upwind of the updraft more than they do downwind. The updraft is trying to force the clouds into the stronger winds aloft and essentially forces this to happen.
Fuzzy Anvil The appearance of an anvil can tell you a bit about the updraft strength. This updraft is obviously starved and pathetic and you can see what this does to the anvil. You get a pretty fuzzy anvil that you can largely see through. The edges of it are also soft and not crisp. If your updraft is weak it will not be able to create a more crisp anvil, so looking at the anvil from a distance can tell you something about the updraft creating it. Fuzzy anvils don't mean the storm won't later strengthen. Often you can note this right around initiation as towering cumulus struggle to become cumulonimbus and occasionally produce anvil clouds.
Thick/Sharp Anvil If the anvil edge is sharp you can be pretty certain your updraft is moving some serious air. The thickness of it can say alot too, like when you get mammatus forming downstream of the updraft like here. This view is looking straight up next to an updraft tower(June 23, 2003 in Aurora NE the day after Aurora broke the record hail size). This is the east side of the updraft and so this is not the view of a backsheared anvil(since it is the downwind side this day).
Rounded Anvil Here is a case showing a very powerful updraft. I marked the edges of the updraft with the arrows. Note how rounded the anvil is around the back(right side). It is as nice as they come basically(well there are some extreme examples of upside down convection in the backsheared anvil). I'm looking to the southeast and this is the direction of the winds aloft, so this anvil is backsheared nicely. What is the most impressive about it was the powerful upper jet it was backshearing into. This was June 13, 2004 se of Omaha as the storm reformed. It was tornado warned at this time.
Updraft Base   The updraft base is pretty obvious what it is. It is the bottom of the storm you are viewing. Now on this view I'm looking straight west as this storm moves east. Instead of being able to see the billowing updraft towers above the base you get to see structured cloud material, often smoothed or layered. Supercells will have a rounded look to their base. Rain-free Base(RFB) Simply an updraft base free of rain/precipitaion. A chaser doesn't like seeing rain falling back through the updraft and wants a nice rain-free base. This is from the May 28, 2004 chase in northeast Nebraska.
Downdraft A downdraft is also what it says it is, sinking air or precip. If you have air going upward something has to be moving downward somewhere. This is where your rain or hail falls. The rain or hail will bring air/wind down with it. It is best to have this downdraft seperated at least a bit from the updraft base. In this case it is nicely seperated. Winds aloft are tilting the updraft a bit and making sure the downdraft it is causing is away from its base. This way the base is free to keep entraining warm unstable air. If the winds aloft are light the updraft goes up and the rain it creates comes straight back down, killing the updraft. That is what popcorn or garden variety summer storms do, which is why they don't last long. They go up and come right back down. Supercells need the winds aloft to be long-lived thunderstorms.
Types of Downdrafts: Forward-flank Downdraft(FFD) This is the main drowndraft of the storm which is downwind of the updraft and rain-free base. The image above is showing the FFD, as is the one to the right. It is quite clear in both. Most of the precipitation falls in this region. This is from the June 13, 2004 chase near Alvo Nebraska..
Here is a radar image of the storm above around the same time. Note the strong looking hook appearance. Notice where I drew in where I think the updraft would be located. If you look back and forth between the two images it should be clear how this works, or at least somewhat(the storm/updraft is often not right where the precip is on radar but next to it). The picture is looking straight west. The storm was moving ese(east-southeast). The radar image is aligned with the top of it to the north. As this updraft/storm moves ese it leaves the majority of its precipitation on the north or northeast side of the updraft's path.
Rear-flank Downdraft(RFD) This is an important term to understand. How this area acts can tell you a lot about a storm. Basically all it means is the sinking air behind a storm, any storm. So you have sinking air and precipitation in the forward-flank downdraft area ahead of the storm, or nearly ahead(often left of the storms path when looking in the storm's moving direction). You also have this area BEHIND the updraft where there is sinking air, sometimes containing precipitation. It is called the RFD or Rear-flank Downdraft. The image to the right is shot just behind a supercell looking to the northeast. You can see the wall cloud with this storm and the storm base around it. You can also see clearing or brighter white cutting in and wrapping around this wall cloud(wall cloud is the big low object here). That clear notch forming is called an RFD notch. It is simply the notch forming from the RFD.
This is the same storm moments later but looking straight north now. The white cloud is obviously the updraft, but you can see it here thanks to the RFD behind the storm clearing the area out. This visual RFD notch preceeds most all tornadoes. Sometimes it isn't as easy to make out however(most cases it is very clear).
Still the same storm a few more moments later. I'm now looking northwest at it. It is still the same storm so you can see how the view changes as you move east of it. The clear area right behind the storm can basically be called the RFD everytime. All of the above three images were shot August 26, 2004 in sw IA.
Flanking Line A flanking line is a line or row of towering cumulus clouds leading up to the main updraft tower. Basically their destination is to become the main updraft tower at some point. It is like a conveyor of towers rising up and being directed towards the main updraft position by the winds aloft. Remember that RFD behind the storm? That sinking air acts as a front to get new updrafts gong. It is called the Gust Front. These towers making up the flanking line are forming on that boundary. To get storms going up in the first place you usually need convergence of winds at the surface(a front). If the wind is coming together it will want to go up. This is the push these new updrafts need. Shot June 29, 2005 in sw MN.
Meso or Mesocyclone A meso or mesocyclone is basically a rotating updraft. Only a radar can detect a mesocyclone(the size, duration, and speed of rotation must meet a certain criteria) but in many cases it is visually obvious the storm likely contains a mesocyclone. In order for a storm to be a supercell it must contain a mesocyclone. Mesocyclones and supercells are responsible for most severe weather as well as the most intense kinds of severe weather, including tornadoes, very large hail, and high winds. The storm to the right here was shot May 22, 2004 and likely has a mesocyclone at this time. The view is looking ese as it moves due east. Note the very large hail falling. This storm produced baseball hail and high winds along highway 30 east of Columbus NE.
Supercell A thunderstorm with a persistent rotating updraft(a mesocyclone). This is what we chasers are after. These are the tornado producers as well as the big hail and high wind producers. They come in all sorts of shapes, colors and intensities. The one thing they must all have in common is a single rotating updraft with a mesocyclone. Shot May 10, 2005 near Grand Island NE. There are 3 general classifications of them. LP-Low Precipitation Supercell HP-High Precipitation Supercell SC-Supercell Classic(classic supercell)
LP-Low Precipitation Supercell These are just as they sound, lacking much in the way of precipitation. They are prolific hail producers however. This is why they often just seem like there is no precip, because it consists largely of hail and appears to be clear when it really isn't. LP supercells are inflow dominant supercells. This just means there is little in the way of downdraft and the whole storm is mostly inflow. Often there isn't much of a flanking-line with these storms. LP supercells are not prolific tornado producers. The rare occasion they do the tornadoes are usually small and short-lived. This LP actually does produce a small tornado within a minute or two of this image. I believe it also produces 5 inch diameter hail after the tornado. This was June 7, 2005 in sw SD.
HP-High Precipitation Supercell HP supercells are the most difficult to chase because precipitation is all around the storm hiding possible tornadoes. This makes them the most dangerous storms to chase as well. Unlike LP supercells, HPs are outflow dominant. This heavy precip and cold air in the RFD is really driving this storm and where it goes. It surges outward lifting up new updrafts over and over as it goes along, so it is outflow dominant. Most tornadoes with these will also be short-lived. The view on this one is looking to the southwest, June 2, 2005 in eastern Colorado. Small hail is falling in my location at this time.
SC-Classic Supercell Classic supercells are what we chasers are really looking for. These produce the big tornadoes. They are inflow and outflow balanced storms. They have a dominant forward-flank downdraft. Their RFDs can often be quite powerful and often lack much precipitation until the tornado's disipating stage when it can become full of rain and wrap the tornado...hiding it from view. This balance is required to produce not only the larger and longer-lived tornadoes, but also mulitple tornadoes. Classics producing multiple tornadoes are refered to as cyclical tornadic supercells. The balance required to do this is pretty amazing. Watching one and how it works is a real treat. Often as the tornado wraps in rain and disipates a new one is forming near or just north of the apex of the RFD notch. Shot June 9, 2005 near Hill City KS.
Wall Cloud This is one of the better examples of a wall cloud I have. They are lowered areas ATTACHED to a storm base. They usually aren't long objects, but more short abrupt lowerings. Notice how vertical the left side of this lowering(wall cloud) is. The precip is to the northeast(the direction of the photo) and the lowered side is leaning down towards the precip. This is a good way to determine if something is a wall cloud. Wall clouds mark areas of focused low-level inflow into the storm's updraft. Rotating Wall Clouds When a wall cloud is rotating it is not something that requires any imagination to see. It is often very obvious. They rotate on a vertical axis, not a horizontal one.
Beaver Tail A beaver tail is often shaped like, well, a beaver's tail. It forms along the boundary created by the rain or forward-flank downdraft. The area where it is raining is cool but the area se of the storm is warm, so this cloud will form where the two meet and mark it out very nicely. Some confuse tail clouds and beaver tails. The beaver tail will be found attatched to the north side of supercells and will be attaching to the area near the storm base, but not lowerings below the base, like wall clouds. Tail Cloud This is a nice example as you can see a tail cloud along with a beaver tail. The tail cloud sticks out and is attached to the wall cloud. Beaver tail attatched to storm base area and tail cloud attached to the wall cloud lowering.
Here is another example of a tail cloud attached to a wall cloud. It is an interesting example in that neither of them would be considered typical examples and it shows there are often hybrid examples of about any form of storm structure. This wall cloud isn't typical in my opinion but I believe one would call it a wall cloud. It is rather long and largely flat along the botton but still a wall cloud. This tail cloud also looks a lot like a beaver tail, but it is very low to the ground and attaching to the wall cloud. The actual storm base is quite a bit higher. This storm really has no beaver tail at this time.
Another example of a wall cloud and tail cloud. This is looking to the southwest. The rain or forward-flank downdraft area is to the right of the picture(north). Notice how the side of the wall cloud closest to the precip is the lowest. It leans downward towards the precip area and is ATTACHED to the storm base. This storm had the most insane tail cloud I've ever seen. At several points it takes on the shape of an aligator head. It is from the June 9, 2005 Hill City KS chase.
Bear's Cage This is the area below a wall cloud. It is called the Bear's Cage because it is the likely area you'll get a tornado to form. You play in the bear's cage at your own risk.
The Bear This came out to play from the above storm. June 9, 2005 near Hill City KS.
Vault This is the visually clear area north of the updraft between the updraft and forward-flank downdraft/rain core. Often large hail can be found falling in this region allowing it to still appear as if it is clear of precipitation. This is also a popular area for lightning strikes. Image from June 13, 2004.
Inflow Bands There are several forms of inflow bands including ones like on the top of the picture here which are some mid-level inflow bands which take on striated forms. A beaver tail is also a form of inflow band...as is a tail cloud. Storm from June 2, 2005 eastern CO chase.
Feeder Bands These are attached to the south or southeast side of an updraft base and point southeast or south. The top example is from November 12, 2005 near Woodward Iowa, seconds after a tornado hits the town.   July 12, 2004 Example: The bottom picture is a video capture from the 65,000 foot + tall supercell. I saw the supercell get this kind of inflow band twice this day. I'm looking southwest and it is attached to the se side of the updraft and pointing southeast.   These aren't terribly common. A flanking-line can trail off like this sometimes but this is not the flanking-line as the flanking-line in these continues on around and west while this protrudes off of it to the se or south.
Supercell Overview A cyclonic supercell's rotation will be left to right when looking at it. If you look down and draw the motion on the ground it is counter-clockwise(looking up at the motion and it'll be clockwise...best to remember left to right when looking at the storm). This image is looking to the southwest at the Hill City tornadic supercell. The tornado had lifted and was coming back down again. There was a big wide funnel(big V shape) always there just off the ground with ground circulation below it. Note the bottom arrows going off the left side of the image. The structure is often quite large. That is the flanking-line curling back around and to the southwest. It comes clear east and around and north before going back to the west and wrapping on down into the tornado. The RFD is behind this storm base and flanking-line. It is that big notch that is cutting in south of the tornado. Tornadoes form north of these notches the most frequently. So if you note the rfd notch you should be watching the area to the north of it.
Another shot but before the above image by a few minutes. The tornado is alot more obvious in this one. You can still see the same objects/features but without all the text over it.
Scud Low ragged cloud material which should not be confused with wall clouds. It is really simple to know what is scud and what is a wall cloud. The scud is not attached to a storm base...a wall cloud is. Scud is not dangerous. Scud is formed as rain cooled air surges outward and encounters the warmer air, forming clouds. If you breathe onto cold glass it will fog up. This is similar. This is from the September 18, 2005 chase.
Shelf Cloud These are common and form along a storm's gust front, which is created by the rain-cooled air from the storm. They come in many various forms. The atmosphere has cold air aloft and is warmer at the surface. There is often a lid or cap several thousand feet off the ground where the temperature raises breifly. This holds the warmer air near the surface, keeping it from rising into storms. A front can help lift the warm air above this cap. This is basically what is going on in this picture. As the rain-cooled air surges outward it acts as a wedge to force the warm moist air ahead of it upward. This creates new updrafts which create new precipitation which creates more cold air surging out which lifts more warm air up over it which again creates more updrafts....on and on. The cycle will die off when the storm encounters cooler surface temperatures/instability and lifts it creating less in the way of convection and less in the way of precip....basically. Other factors can come into play but that is a quick overview of how a shelf works or even an MCS(mesoscale convective system). Image from August 16, 2002 chase.
Cloud to Cloud Lightning This is exactly what it says it is, just like the following examples. August 5, 2003 chase.
Ground to Air Lightning Electrical discharge that visually goes from the ground upward. They are fairly rare, but not super rare. They often can be seen going up from a radio tower. I don't shoot much lightning and am really lucky I got this one. I saw it happening on a drive home one night and got setup and got the 3rd one I saw. I saw no more after this one. I believe it is also refered to as 'reverse lightning'.
Cloud to Air Lightning August 5, 2003 chase. I haven't seen this very often. Often there will be an anvil there for it to appear in contact with. This storm was in a pretty chilly environment and had not backsheared anvil.
Cloud to Ground(often called a CG)
Anvil to Ground This is a video capture from July 26, 2002. I'd say these are the most dangerous lightning bolts as they can occur well away from precipitation. They are often highly branched and sometimes stacato bolts(extremely short duration flashes/discharges).
Anvil Crawler These can be seen running along the underside of an anvil. They can be quite long and very dramatic looking. They basically won't come down to the ground except for back near the updrafts and precipitation. Often you'll see a cg and then these racing outward under the anvil. Sometimes the crawling will preceed the cg back near the storm complex. I haven't seen very many good anvil crawler shows. The real good displays are somewhat rare.
Dry Microburst Instese downdraft which contains little to no precipitation. They are often associated with virga(precipation not reaching the ground). In this case to the right it is associated with a broken line of storms. Rapid clearing was noted in the clouds(see the bright area in the center) preceding a very strong dust plume which raced upwards to the cloud base. Microburst was from a chase on May 17, 2005. Wet Microburst Similar to dry microburst but is an intense downdraft of air containing precipitation.
Virga Simply precipitation that is drying up/evaporating before it reaches the ground.
Rain Foot Here is an ok example of a rain foot. It is the area of rain that can be seen stretching outward horizontally. They indicate intense straight line winds as the precip is being forced outward by them.
F-Scale Rating System	The F-Scale is a damage scale not a direct wind scale. The given wind speeds are simply what is thought needed to create the damage given at each level. It is important to remember that this scale is nothing but a damage assesment scale.
F0 Gale tornado: 40-72 mph	Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.
F1 Moderate tornado: 73-112 mph	Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.
F2 Significant tornado: 113-157 mph	Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated.
F3 Severe tornado: 158-206 mph	Roof and some walls torn off well constructed houses; trains overturned; most trees in forest uprooted
F4 Devastating tornado: 207-260 mph	Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.
F5 Incredible tornado: 261-318 mph	Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 300 feet; trees debarked; steel re-inforced concrete structures damaged.
F6 Inconceivable tornado: 319-379 mph	These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies