Flight Training - June 2015 - 45

miles and last a few minutes, but sometimes the
atmosphere is primed for
this process to intensify in
a repetitive fashion. In that
case, the winds generate new
thunderstorm updrafts as
they push forward, and in
turn, this creates more rainfueled downdrafts. If there's
a brisk jet stream adding
momentum to the successive downdrafts,
then a derecho can race forward at interstate speeds along a track that's almost
bullet-straight, often traversing several
states in a single day or night."
Henson also said, "When the SPC issued
its first Day 1 Outlook at 2 a.m., the chances
of high winds in Maryland and Virginia
were less than 5 percent. As the day went
on, however, new observations and predictions from computer models based on
these were indicating that a derecho was
brewing. By 2:30 p.m. the derecho was
going strong in the Midwest with 91-mph
gusts in Indiana. The SPC raised the risk
of high winds in the Washington, D.C.,
area; local NWS offices and news media
forecasters begin issuing alerts."

A COMPOSITE IMAGE created by
the National Weather Service Storm
Prediction Center shows NWS radar
images each two hours from 2 p.m.
Eastern June 29, until 12 a.m. June 30,
2012, as a powerful derecho advanced
from Illinois to the Mid-Atlantic. The
colors show rain intensity, with red
being the most intense and green the
least intense. Rain intensity is a good
stand-in for thunderstorm power. Each
black * indicates a report of 80- to 100mph wind gusts, including many where
rain is not falling.

to help evaluate your plans. And since the
exact locations of thunderstorms can't be
forecast in detail until the storms begin
forming, you should check to see whether
they are possible across or near where
you plan to fly. A 15-percent probability
for severe thunderstorms means you
have a 15-percent chance of such a storm
occurring within 25 miles of your location. In general, your chances of getting
hit by severe weather are small. Let's say
you have a 1 percent statistical history of
severe thunderstorms within 25 miles on
this day. A 15-percent probability means
15 times the normal odds of a severe
thunderstorm occurring nearby. Fifteen
times the normal odds mean a one in 6.66
chance of a severe thunderstorm.

Some of the strongest and longestlasing derechos, including the June 2012
event, occur on the fringes of major heat
waves "It turns out that the meteorological conditions favorable for large-scale
heat waves often also are conducive to
derechos. In the United States, this is
especially true from the upper Mississippi Valley and upper Great Lakes into
the Ohio Valley and Northeast," the Storm
Prediction Center said.
HOW DERECHOS OCCUR. Bob Henson, in
the University Center for Atmospheric
Research (UCAR) newsletter, described
how a derecho differs from a hurricane or
tornado: "While the high winds of a
tornado or hurricane spin around powerful, circular updrafts, a derecho's wind
consists of rain-cooled air that descends
and plows into very warm, unstable air.
Most such downbursts only span a few

Jack Williams is an instrument-rated private
SECURE YOUR AIRPLANE. A storm
pilot, and author of The AMS Weather Book: The
that occurred on June 29 and 30, 2012,
Ultimate Guide to America's Weather.
brought the term derecho to the attention
of people along its 240-mile path. The
derecho blasted from the Midwest to the
Mid-Atlantic coast, killing 27 people and
leaving millions without power; thousands
had to cope with damage from fallen trees.
The NWS defines a derecho as a squall
line that produces 57 mph or stronger
winds along a path at least 240 miles long
over a period of hours.
Almost all derechos hit east of the Rocky
Mountains, with a focus around the area
where Kansas, Oklahoma, Missouri, and
Arkansas meet. This area averages four
derechos every three years. The main
derecho season is from May through
August, but they can occur just about
any time of the year. During the summer,
derechos are most likely in the Midwest.
During the rest of the year, they most
A MAP PRODUCED by the National Weather Service Storm Prediction Center shows the average number
of derechos affecting different parts of the United States.
often target the lower Mississippi Valley.

JUNE 2015 FLIGHT TRAINING

/ 45



Flight Training - June 2015

Table of Contents for the Digital Edition of Flight Training - June 2015

Contents
Flight Training - June 2015 - Cover1
Flight Training - June 2015 - Cover2
Flight Training - June 2015 - Contents
Flight Training - June 2015 - 2
Flight Training - June 2015 - 3
Flight Training - June 2015 - 4
Flight Training - June 2015 - 5
Flight Training - June 2015 - 6
Flight Training - June 2015 - 7
Flight Training - June 2015 - 8
Flight Training - June 2015 - 9
Flight Training - June 2015 - 10
Flight Training - June 2015 - 11
Flight Training - June 2015 - 12
Flight Training - June 2015 - 13
Flight Training - June 2015 - 14
Flight Training - June 2015 - 15
Flight Training - June 2015 - 16
Flight Training - June 2015 - 17
Flight Training - June 2015 - 18
Flight Training - June 2015 - 19
Flight Training - June 2015 - 20
Flight Training - June 2015 - 21
Flight Training - June 2015 - 22
Flight Training - June 2015 - 23
Flight Training - June 2015 - 24
Flight Training - June 2015 - 25
Flight Training - June 2015 - 26
Flight Training - June 2015 - 27
Flight Training - June 2015 - 28
Flight Training - June 2015 - 29
Flight Training - June 2015 - 30
Flight Training - June 2015 - 31
Flight Training - June 2015 - 32
Flight Training - June 2015 - 33
Flight Training - June 2015 - 34
Flight Training - June 2015 - 35
Flight Training - June 2015 - 36
Flight Training - June 2015 - 37
Flight Training - June 2015 - 38
Flight Training - June 2015 - 39
Flight Training - June 2015 - 40
Flight Training - June 2015 - 41
Flight Training - June 2015 - 42
Flight Training - June 2015 - 43
Flight Training - June 2015 - 44
Flight Training - June 2015 - 45
Flight Training - June 2015 - 46
Flight Training - June 2015 - 47
Flight Training - June 2015 - 48
Flight Training - June 2015 - 49
Flight Training - June 2015 - 50
Flight Training - June 2015 - 51
Flight Training - June 2015 - 52
Flight Training - June 2015 - 53
Flight Training - June 2015 - 54
Flight Training - June 2015 - 55
Flight Training - June 2015 - 56
Flight Training - June 2015 - Cover3
Flight Training - June 2015 - Cover4
https://www.nxtbook.com/nxtbooks/aopa/ft_202107
https://www.nxtbook.com/nxtbooks/aopa/ft_202106
https://www.nxtbook.com/nxtbooks/aopa/ft_202104
https://www.nxtbook.com/nxtbooks/aopa/ft_202105
https://www.nxtbook.com/nxtbooks/aopa/ft_202103
https://www.nxtbook.com/nxtbooks/aopa/ft_202101
https://www.nxtbook.com/nxtbooks/aopa/ft_202011
https://www.nxtbook.com/nxtbooks/aopa/ft_202009
https://www.nxtbook.com/nxtbooks/aopa/ft_202008
https://www.nxtbook.com/nxtbooks/aopa/ft_202007
https://www.nxtbook.com/nxtbooks/aopa/ft_202006
https://www.nxtbook.com/nxtbooks/aopa/ft_202005
https://www.nxtbook.com/nxtbooks/aopa/ft_202004
https://www.nxtbook.com/nxtbooks/aopa/ft_202003
https://www.nxtbook.com/nxtbooks/aopa/ft_202001
https://www.nxtbook.com/nxtbooks/aopa/ft_201912
https://www.nxtbook.com/nxtbooks/aopa/ft_201911
https://www.nxtbook.com/nxtbooks/aopa/ft_201910
https://www.nxtbook.com/nxtbooks/aopa/ft_201909
https://www.nxtbook.com/nxtbooks/aopa/ft_201908
https://www.nxtbook.com/nxtbooks/aopa/ft_201907
https://www.nxtbook.com/nxtbooks/aopa/ft_201906
https://www.nxtbook.com/nxtbooks/aopa/ft_201905
https://www.nxtbook.com/nxtbooks/aopa/ft_201904
https://www.nxtbook.com/nxtbooks/aopa/ft_201903
https://www.nxtbook.com/nxtbooks/aopa/ft_201902
https://www.nxtbook.com/nxtbooks/aopa/ft_201901
https://www.nxtbook.com/nxtbooks/aopa/ft_201812
https://www.nxtbook.com/nxtbooks/aopa/ft_201811
https://www.nxtbook.com/nxtbooks/aopa/ft_201810
https://www.nxtbook.com/nxtbooks/aopa/ft_201809
https://www.nxtbook.com/nxtbooks/aopa/ft_201808
https://www.nxtbook.com/nxtbooks/aopa/ft_201807
https://www.nxtbook.com/nxtbooks/aopa/ft_201806
https://www.nxtbook.com/nxtbooks/aopa/ft_201805
https://www.nxtbook.com/nxtbooks/aopa/ft_201804
https://www.nxtbook.com/nxtbooks/aopa/ft_201803
https://www.nxtbook.com/nxtbooks/aopa/ft_201802
https://www.nxtbook.com/nxtbooks/aopa/ft_201801
https://www.nxtbook.com/nxtbooks/aopa/ft_201712
https://www.nxtbook.com/nxtbooks/aopa/ft_201711
https://www.nxtbook.com/nxtbooks/aopa/ft_201710
https://www.nxtbook.com/nxtbooks/aopa/ft_201709
https://www.nxtbook.com/nxtbooks/aopa/ft_201708
https://www.nxtbook.com/nxtbooks/aopa/ft_201707
https://www.nxtbook.com/nxtbooks/aopa/ft_201706
https://www.nxtbook.com/nxtbooks/aopa/ft_201705
https://www.nxtbook.com/nxtbooks/aopa/ft_201704
https://www.nxtbook.com/nxtbooks/aopa/ft_201703
https://www.nxtbook.com/nxtbooks/aopa/ft_201702
https://www.nxtbook.com/nxtbooks/aopa/ft_201701
https://www.nxtbook.com/nxtbooks/aopa/ft_201612
https://www.nxtbook.com/nxtbooks/aopa/ft_201611
https://www.nxtbook.com/nxtbooks/aopa/ft_201610
https://www.nxtbook.com/nxtbooks/aopa/ft_201609
https://www.nxtbook.com/nxtbooks/aopa/ft_201608
https://www.nxtbook.com/nxtbooks/aopa/ft_201607
https://www.nxtbook.com/nxtbooks/aopa/ft_201606
https://www.nxtbook.com/nxtbooks/aopa/ft_201605
https://www.nxtbook.com/nxtbooks/aopa/ft_201604
https://www.nxtbook.com/nxtbooks/aopa/ft_201603
https://www.nxtbook.com/nxtbooks/aopa/ft_201602
https://www.nxtbook.com/nxtbooks/aopa/ft_201601
https://www.nxtbook.com/nxtbooks/aopa/ft_201512
https://www.nxtbook.com/nxtbooks/aopa/ft_201511
https://www.nxtbook.com/nxtbooks/aopa/ft_201510
https://www.nxtbook.com/nxtbooks/aopa/ft_201509
https://www.nxtbook.com/nxtbooks/aopa/ft_201508
https://www.nxtbook.com/nxtbooks/aopa/ft_201507
https://www.nxtbook.com/nxtbooks/aopa/ft_201506
https://www.nxtbook.com/nxtbooks/aopa/ft_201505
https://www.nxtbook.com/nxtbooks/aopa/ft_201504
https://www.nxtbook.com/nxtbooks/aopa/ft_201503
https://www.nxtbook.com/nxtbooks/aopa/ft_201502
https://www.nxtbook.com/nxtbooks/aopa/ft_201501
https://www.nxtbook.com/nxtbooks/aopa/ft_201412
https://www.nxtbook.com/nxtbooks/aopa/ft_201411
https://www.nxtbook.com/nxtbooks/aopa/ft_201410
https://www.nxtbook.com/nxtbooks/aopa/ft_201409
https://www.nxtbook.com/nxtbooks/aopa/ft_201408
https://www.nxtbook.com/nxtbooks/aopa/ft_201407
https://www.nxtbook.com/nxtbooks/aopa/ft_201406
https://www.nxtbook.com/nxtbooks/aopa/ft_201405
https://www.nxtbook.com/nxtbooks/aopa/ft_201404
https://www.nxtbook.com/nxtbooks/aopa/ft_201403
https://www.nxtbook.com/nxtbooks/aopa/ft_201402
https://www.nxtbook.com/nxtbooks/aopa/ft_201401
https://www.nxtbook.com/nxtbooks/aopa/ft_201312
https://www.nxtbook.com/nxtbooks/aopa/ft_201311
https://www.nxtbook.com/nxtbooks/aopa/ft_201310
https://www.nxtbook.com/nxtbooks/aopa/ft_201309
https://www.nxtbook.com/nxtbooks/aopa/ft_201308
https://www.nxtbook.com/nxtbooks/aopa/ft_201307
https://www.nxtbook.com/nxtbooks/aopa/ft_201306
https://www.nxtbook.com/nxtbooks/aopa/ft_201305
https://www.nxtbook.com/nxtbooks/aopa/ft_201304
https://www.nxtbook.com/nxtbooks/aopa/ft_201303
https://www.nxtbook.com/nxtbooks/aopa/ft_201302
https://www.nxtbook.com/nxtbooks/aopa/ft_201301
https://www.nxtbook.com/nxtbooks/aopa/ft_201212
https://www.nxtbook.com/nxtbooks/aopa/ft_201211
https://www.nxtbook.com/nxtbooks/aopa/ft_201210
https://www.nxtbook.com/nxtbooks/aopa/ft_201209
https://www.nxtbook.com/nxtbooks/aopa/ft_201208
https://www.nxtbook.com/nxtbooks/aopa/ft_201207
https://www.nxtbook.com/nxtbooks/aopa/ft_201206
https://www.nxtbook.com/nxtbooks/aopa/ft_201205
https://www.nxtbook.com/nxtbooks/aopa/ft_201204
https://www.nxtbook.com/nxtbooks/aopa/ft_201203
https://www.nxtbook.com/nxtbooks/aopa/ft_201202
https://www.nxtbook.com/nxtbooks/aopa/ft_201201
https://www.nxtbook.com/nxtbooks/aopa/ft_201112
https://www.nxtbook.com/nxtbooks/aopa/ft_201111
https://www.nxtbook.com/nxtbooks/aopa/ft_201110
https://www.nxtbook.com/nxtbooks/aopa/ft_201109
https://www.nxtbook.com/nxtbooks/aopa/ft_201108
https://www.nxtbook.com/nxtbooks/aopa/ft_201107
https://www.nxtbook.com/nxtbooks/aopa/ft_201106
https://www.nxtbook.com/nxtbooks/aopa/ft_201105
https://www.nxtbook.com/nxtbooks/aopa/ft_201104
https://www.nxtbook.com/nxtbooks/aopa/ft_201103
https://www.nxtbookmedia.com