The following images are provided to illustrate the many different appearances of wall clouds. Click on any image for a larger view.
|Looking west southwest at a wall cloud that was located south of El Dorado, Oklahoma. This wall cloud developed along the flanking line, several miles south of an HP supercell that hammered El Dorado with softball hail. This wall cloud was associated with a doppler radar indicated tornado vortex signature (TVS) and at least baseball size hail.||Looking west at a wall cloud near Snyder, Texas. This wall cloud and associated classic supercell thunderstorm did not result in a visible tornado.||Looking northwest at a wall cloud near Muenster, Texas (west of Gainesville near the Red River). This wall cloud was associated with an LP supercell thunderstorm and produced a brief weak rope tornado and damaging softball size hail.||Looking north at a wall cloud near Plainview, Texas June 5, 1995. This wall cloud and parent LP supercell storm produced multiple tornadoes and a large swath of damaging hail. This storm followed an evolution from LP to classic to HP over its lifetime.||Looking west northwest at an HP supercell wall cloud partially obscured by rain on June 2, 1993. This wall cloud and the parent storm produced large hail. Another wall cloud formed southeast of the precipitation area and produced several tornadoes as the storm moved southeast from Johnson City toward Liberal, Kansas.|
|Looking northwest at a wall cloud near Archer City, Texas on May 8, 1993. This wall cloud produced a tornado, large hail and damaging straight line winds near Lake Kickapoo, southeast of Wichita Falls, Texas. As this wall cloud intensified and the tornado formed, the storm evolved from a classic to an HP supercell structure.||Wall cloud southwest of Gainesville, Texas. This wall cloud and parent classic supercell thunderstorm produced several tornadoes, including parasitic tornadoes on the periphery of the mesocyclone, high straight line winds and large hail.||The wall cloud associated with this HP supercell thunderstorm was located northeast of a heavy precipitation core. It produced large hail and several brief small tornadoes east of Dallas, Texas. This photo was shot looking north from Interstate 20 near Forney, Texas.||Looking down the throat of an HP supercell inflow notch. This storm slowed and became almost stationary as the mesocyclone intensified and produced a brief tornado east of Grand Saline, Texas. It went through a very unusual evolution, evolving from an HP configuration "back" to a classic configuration. Variations in thunderstorm structure, organization and evolution are endless.||Looking west at a wall cloud associated with a classic supercell near Pampa, Texas (1989).|
|Looking southwest at a distant wallcloud under an HP supercell that was located southeast of Guadeloupe Peak in western Texas (1997).||This and the next four images are of the same storm as the wall cloud approached my location. Although the wall cloud was rotating and exhibited rapid upward motion, no debris whirls were seen underneath the wall cloud. However, the terrain was hilly and brief debris whirls could have been out of view. This storm produced a tornado earlier on its western flank as it passed over the Sierra Diablos.|
|Looking west at a developing wall cloud with a dust whirl in the foreground in the right half of the image.||Mesocyclone and wall cloud north of Glen Rose, Texas||Looking west at a wall cloud over the Texas Panhandle||Tornadic wall cloud/mesocyclone near South Plains, Texas on June 5, 1995 - looking north|
|June 5, 1995 near Dickens, Texas - looking north||June 5, 1995 near Dickens, Texas||June 5, 1995 near South Plains, Texas, looking north||June 3, 1995 Looking north over the Red River Valley from Turkey, Texas||June 2, 1995 looking west at a tornadic wall cloud near Tulia, Texas|
|June 2, 1995 near Tulia, Texas||Looking west at a wall cloud and tornado near Vernon, Texas June 9, 1995||Developing wall cloud and rain foot.|
Copyright 1989-1998 - Samuel D. Barricklow - All rights reserved.
SKYWARN spotters and Storm Chasers must be able to recognize wall clouds and be aware of the dangers associated with spotting them.
Wall clouds come in a variety of shapes and sizes. They form under the thunderstorm updraft core. Wall clouds can develop on any flank of a precipitation core. They are typically located within a mile or two of the most intense precipitation. The most dangerous wall clouds, which are associated with mesocyclones and supercell thunderstorm updrafts (updrafts that rotate), have warm moist surface based inflow and produce obvious rapid upward motion and rotation. However, rotation may not always be large scale nor always easily observed. The area of perceived rotation may vary in size from less than a mile in diameter to more than three miles in extreme cases. The most dangerous wall clouds undergo rapid continuous change. Some wall clouds form from a flat rain-free base after a burst of outflow and scud from the precipitation area, while others form before a significant precipitation area is visible. A few produce tornadoes but, most do not. However, you must be suspicious of a storm that produces a wall cloud. Even non-rotating wall clouds often immediately precede the production of large hail and high winds by the parent thunderstorm.
This page will concentrate on spotting wall clouds that are produced by supercell thunderstorms. Currently, supercell thunderstorms are divided into three main categories, low precipitation (LP), classic and high precipitation (HP). The classic supercell is the type most commonly recognized, but after almost three decades of observations by spotters, chasers and research groups, evidence is mounting that the HP supercell and its variations may be the most common stage of supercell evolution.
Low precipitation (LP) supercells produce wall clouds that are usually located southwest or west of the main precipitation core underneath a relatively small rain free base (e.g., less than one mile in diameter). The main precipitation area of LP storms may appear almost transparent. This appearance often hides the fact that many LP storms produce large to giant hail, but little liquid rain! Rarely does precipitation fall through the mesocyclone, with the exception of scattered large hailstones.
While the basic schematic of a classic supercell is similar to that of the LP supercell, there are some significant differences. The classic supercell produces an intense precipitation area that is often dark and foreboding in appearance. Large hail and heavy rain fall northeast or east of the wall cloud/rain free base. Mesocyclones associated with classic supercells often "pull" rain and hail out of the forward flank precipitation area and wrap it around the back side of the wall cloud. This precipitation often resembles a curtain, and may appear to be almost transparent when viewed from the east, but may totally obscure the wall cloud and developing tornadoes when viewed from the west, especially when illuminated by late afternoon sunlight.
High precipitation (HP) supercells are the most difficult to spot. HP supercells produce forward flank precipitation areas similar to classic supercells, but they are characterized by heavy rain and hail northwest, west, southwest and sometimes south of the mesocyclone and wall cloud. HP supercells present a particularly tough problem for storm spotters. HP supercell updrafts are typically located on the leading edge of the storm, ahead of a heavy precipitation core. The best position for viewing HP supercell updrafts is looking west into the inflow notch from a location just south of the "beaver tail" inflow band, adjacent to the forward flank precipitation area. (The "beaver tail" is a low level inflow cloud band that is located along the forward flank precipitation outflow boundary area ahead of the HP updraft.) The wall cloud (and tornado) may not be visible from any other angle.
Be aware that there is a continuous spectrum of storm types. While I have used the LP, classic supercell, and HP stages as examples, most supercell thunderstorms that you see may not fit neatly into one of these molds. And some storms may actually evolve and pass through each of these three stages during their lifetime and at times exhibit characteristics of more than one storm type.
There are other stages of supercell thunderstorm development that I did not describe, such as the bow echo or comma head storms. I've left these out because these two storm types and their variations are extremely difficult for most spotters to recognize visually or to spot effectively and safely.
There's also the left moving supercell that is the mirror image of its right moving parent classic supercell. The "left mover" has its updraft on the left rear flank of the main precipitation area (typically the northwest flank when the jet stream winds are flowing from the southwest). Left movers occasionally, but infrequently produce tornadoes, but are well known by chasers for producing copious amounts of damaging hail. And their mesocyclones (or more properly meso-anticyclones) rotate clockwise, in a direction opposite to that of the "normal" supercell thunderstorm.
The best view of a mesocyclone is normally from a location east of the updraft, looking west. However, getting in position to have this view can place the spotter in significant danger from large hail, the rear flank downdraft winds and potentially, from a tornado. The spotter must have a preplanned escape route to the east, south or southeast. Keep in mind that large hail often falls just east or northeast of the updraft, so north, northeast, northwest or west are usually not good directions for your escape route. If you find yourself in an unfortunate position with no escape, make sure that you have an underground shelter, a sturdy building or as a very last resort, a ditch in which to take refuge.
Also, keep in mind that supercells often move to the right of the direction that other storms move on any particular day, and they can exhibit unexpected deviate motion or produce tornadoes in unexpected ways. Supercells can move in almost any direction, depending on weather conditions. Some tornadic supercells produce "parasitic" tornadoes that develop unexpectedly on the edges of the mesocyclone's circulation or at the leading edge or "nose" of the rear flank downdraft. You could have your attention focused on a tornado located near the center of the mesocyclones circulation, only to have a parasitic tornado develop overhead with little or no warning. Others can produce tornadoes under the flanking line. Some tornadoes become totally rain wrapped or can be obscured by dust, potentially preventing the spotter from seeing a tornado coming toward their spotting location. You must be aware of your situation, not be rigid in your expectations and be prepared to take whatever action is necessary to escape a dangerous situation. I normally get no closer than one to three miles from wall clouds and tornadoes, depending on the strength of the storm. This is a judgment call based mainly on experience. New spotters and chasers should maintain a safe distance based on their level of experience.
On most storms, the observer should set up east or southeast of the updraft. Backlighting from the afternoon or evening sun usually provides good contrast. The most intense mesocyclones produce inflow bands at low and mid-levels. Inflow bands flow toward and converge into the most intense updraft. On rapidly rotating storms, the inflow bands may visibly curve cyclonically toward the updraft core. It is not uncommon with large intense storms for wall clouds to be "tucked" in close to the precipitation area and difficult to see in the dark shadows underneath the tallest storm towers. Inexperienced spotters may be distracted by the ragged underside of the flanking line and as a result, may not see wall clouds that can be hidden in the dark shadows close to heavy precipitation.
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Last revised: February 7, 2007