AOPA Pilot Magazine - June 2022 - 89

With the approach of many cold fronts in the warmest months of the year, a thermal ridge
(shaded) of southerly winds ahead of the front builds warm, humid flows that ultimately
create the fuel for thunderstorms.
and move slowly. Warm fronts typically
move at a blistering 10 to 15 knots, if that,
and stationary fronts, well, as the name
implies, don't move much at all. Maybe
five knots on average. They tend to languish
for as much as a day or two-or until
another system comes along and blows
them apart. Same thing with an occluded
front. The adverse weather associated
with these slow-movers can cover several
states, and generally moves to the north
and east. These fronts are well-advertised
in forecasts, so experienced and current
instrument pilots flying more capable airplanes
are more likely to take them on.
Day-VFR pilots know enough to stay away.
Cold fronts are different beasts. They
move comparatively quickly, at groundspeeds
as high as 50 knots or more, to the
southerly and/or easterly quadrants of the
compass. A pilot who received a weather
briefing, then drove an hour to the departure
airport, might be surprised to notice
that a cold front's clouds, precipitation, and
turbulence may well have moved closer
than expected to a route originally anticipated
to have good VFR weather.
Of course, in the summer months cold
fronts are apt to produce thunderstorms,
and the gust fronts, outflow boundaries,
squall lines, and icing that can precede them.
In worst cases, tornadoes can occur. These
happen when upper air patterns create the
right amount of wind shear to allow lowlevel
air columns to rotate and become
ingested into supercell thunderstorms. For
all this mayhem, it's a thunderstorm's turbulence
that often causes accidents-because
of in-flight breakups.
As for flying near cold fronts bear in
mind the warnings to maintain visual separation
(a minimal standoff distance of 20
nautical miles is most often mentioned)
from building cumulus and cumulonimbus
clouds, slowing the airplane to maneuvering
speed in turbulence to minimize
structural overloads, avoiding abrupt control
deflections, and making a 180-degree
turn to exit any sketchy-looking conditions.
Next to visual avoidance, Doppler weather
radar imagery, datalinked into the cockpit
via SiriusXM Aviation weather or FIS-B,
is one of the most useful tools for avoiding
storm cells. Just be sure to give any heavy
precipitation returns or contouring cells a
wide berth; datalink is best used for strategic
avoidance and decision-making-it's
not meant for weaving your way through
a front or other convective situation with
tightly packed cells. We've all heard much
of this advice from the earliest days of our
flight training-but they bear repeating.
Conventional information leaves you
with a single impression of a cold front
and its behavior. It's boisterous, with cold
air aggressively pushing broad masses of
AOPA PILOT / June 2022
89
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ADAPTED FROM DAVID BABB, PENNSYLVANIA STATE UNIVERSITY
AOPA Pilot Magazine - June 2022

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