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AIM

10/12/17

7−1−57

Meteorology

Airport

Identifier

John F. Kennedy Intl Airport

KJFK

LaGuardia Airport

KLGA

Kansas City Intl Airport

KMCI

Orlando Intl Airport

KMCO

Midway Intl Airport

KMDW

Memphis Intl Airport

KMEM

Miami Intl Airport

KMIA

General Mitchell Intl Airport

KMKE

Minneapolis St. Paul Intl Airport

KMSP

Louis Armstrong New Orleans Intl Air-

port

KMSY

Will Rogers World Airport

KOKC

O’Hare Intl Airport

KORD

Palm Beach Intl Airport

KPBI

Philadelphia Intl Airport

KPHL

Pittsburgh Intl Airport

KPIT

Raleigh−Durham Intl Airport

KRDU

Louisville Intl Airport

KSDF

Salt Lake City Intl Airport

KSLC

Lambert−St. Louis Intl Airport

KSTL

Tampa Intl Airport

KTPA

Tulsa Intl Airport

KTUL

7−1−27. PIREPs Relating to Volcanic Ash

Activity

a. Volcanic eruptions which send ash into the

upper atmosphere occur somewhere around the world

several times each year. Flying into a volcanic ash

cloud can be extremely dangerous. At least two

B747s have lost all power in all four engines after

such an encounter. Regardless of the type aircraft,

some damage is almost certain to ensue after an

encounter with a volcanic ash cloud. Additionally,

studies have shown that volcanic eruptions are the

only significant source of large quantities of sulphur

dioxide (SO

2

) gas at jet-cruising altitudes. Therefore,

the detection and subsequent reporting of SO

2

 is of

significant importance. Although SO

2

 is colorless, its

presence in the atmosphere should be suspected when

a sulphur-like or rotten egg odor is present throughout

the cabin.

b. While some volcanoes in the U.S. are

monitored, many in remote areas are not. These

unmonitored volcanoes may erupt without prior

warning to the aviation community. A pilot observing

a volcanic eruption who has not had previous

notification of it may be the only witness to the

eruption. Pilots are strongly encouraged to transmit a

PIREP regarding volcanic eruptions and any

observed volcanic ash clouds or detection of sulphur

dioxide (SO

2

) gas associated with volcanic activity.

c. Pilots should submit PIREPs regarding volcanic

activity using the Volcanic Activity Reporting (VAR)

form as illustrated in Appendix 2. If a VAR form is

not immediately available, relay enough information

to identify the position and type of volcanic activity.

d. Pilots should verbally transmit the data required

in items 1 through 8 of the VAR as soon as possible.

The data required in items 9 through 16 of the VAR

should be relayed after landing if possible.

7−1−28. Thunderstorms

a. Turbulence, hail, rain, snow, lightning, sus-

tained updrafts and downdrafts, icing conditions−all

are present in thunderstorms. While there is some

evidence that maximum turbulence exists at the

middle level of a thunderstorm, recent studies show

little variation of turbulence intensity with altitude.

b. There is no useful correlation between the

external visual appearance of thunderstorms and the

severity or amount of turbulence or hail within them.

The visible thunderstorm cloud is only a portion of a

turbulent system whose updrafts and downdrafts

often extend far beyond the visible storm cloud.

Severe turbulence can be expected up to 20 miles

from severe thunderstorms. This distance decreases

to about 10 miles in less severe storms.

c. Weather radar, airborne or ground based, will

normally reflect the areas of moderate to heavy

precipitation (radar does not detect turbulence). The

frequency and severity of turbulence generally

increases with the radar reflectivity which is closely

associated with the areas of highest liquid water

content of the storm. NO FLIGHT PATH THROUGH

AN AREA OF STRONG OR VERY STRONG

RADAR ECHOES SEPARATED BY 20−30 MILES

OR LESS MAY BE CONSIDERED FREE OF

SEVERE TURBULENCE.

d. Turbulence beneath a thunderstorm should not

be minimized. This is especially true when the