Professional Pilot, May 2017

A cluster of echoes is a certain indicator of local instability In the USA the cell at the south end of a line like the one in this picture is normally the most dangerous as it has less competition for moisture water vapor coming up from the Gulf of Mexico Note that there is a Mae West couplet at the south end of this line Air mass storms shown on a radar screen PROFESSIONAL PILOT May 2017 79 This image shows multiple signs of extreme hazards That finger sticking out upper left indicates the possibility of an intense hail shaft Also observe the extremely steep gradients across the top On the right side theres a deep notch often caused by a vertical shaft of wind so intense that its lifting all the precipitation out of the area On the lower left flank a detached echo suggests a developing Mae West formation And at the bottom the pronounced counterclockwise hook strongly suggests tornado development ed destination The FO was flying and drug out the touchdown long enough that the captain finally urged him to Put it down A flooded runway and a delay in getting spoilers out led to hydroplaning The aircraft overran the runway into a ravine and broke up Fortunately all passengers escaped successfully Should the crew have known that the Mae West shaped echo indicated extreme danger Yes Emphatically The Mae West echo was recognized 45 years ago by thunderstorm researchers at the USA National Severe Storms Laboratory Occasionally a storm cell begins to build which Echoes shaped like a frying pan with a handle are bad That handle could be a hail shaft or perhaps it is a horizontal tornado which sometimes extend out from a mother cell In any case its a finger of detectable precipitation sticking out for some abnormal reason It deserves caution at first may be just an air mass little cell But if theres enough water vapor in the air plus lift along an outflow line it blossoms up into a 35000 to 40000 foot tall monster It will still have the outward appearance of a common thunderstorm that normally will grow up rain out then dissipate However as this storm dissipates its own outflows may spread out and kick off another baby storm adjacent to it And as it continues to dissipate its outflows feed more and more into the exploding baby storm The 1st storm will be gone within minutes and the new storm will grow into a vicious overblown monster feeding off those outflows Its during this conversion that the Mae West shape becomes evident on the radar When you see one dont tempt it Just stay far far away About 20 to 30 nm from all parts of it should be adequate Other storm shapes to be wary of In addition to storms with a Mae West shape there are several other storm echoes that should grab your attention as potential hazards Simple air mass storms as illustrated in the photo below are typically round or oblong side to side The gradients between the colors are symmetrical and each is centered The more an echo varies from that classic round shape the greater should be your caution A U shaped echo indicates a rapidly growing cell Note the magenta here Shapes seen on NEXRAD are also meaningful This bowed line of storms is a classic It is indicative of a fast moving danger in the atmosphere If the bow is downwind from winds aloft thats very bad In this image winds are left to right Normally the most dangerous storms will be to the left of winds aloft Archie Trammell is President of Radar Training Systems He holds CFII A P and A P Ground Instructor licenses