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g AUXILIARY WEATHER SPECIALTY COURSE

INTRODUCTION AND CHAPTER ONE

prepared byWeather Branch

Copyright 2004 U.S. Coast Guard Auxiliary Association, Inc.

Photo courtesy of National Oceanographic and Atmospheric Administration

ABOUT THIS COURSE

PURPOSEPractical weather assessmentCoastal patrols by Auxiliary vesselsTrain PE instructors

SCOPEBasic principles of meteorologyPhysics without mathematics

EACH LESSON COVERS ONE CHAPTER

OV1-1

Copyright 2004 U.S. Coast Guard Auxiliary Association, Inc.

SYLLABUS

Getting started (Lesson 1)

Atmosphere properties and behavior (Lessons 2 – 4)

Weather systems (Lesson 5)

Internet weather products (Lesson 6)

Forecasting methods and tips (Lesson 7)

Coping with adverse weather (Lesson 8)

OV1-2

NEWSPAPER WEATHER MAPS

HH CENTER OF HIGH PRESSURE

LL CENTER OF LOW PRESSURE

FRONTS

COLD WARM

OCCLUDEDSTATIONARY

JET STREAMOV1-3

MEASURING ATMOSPHERIC PRESSURE

OV1-4

THE ANEROID BAROMETER SCALEIS ALSO CALIBRATED TO READ

INCHES OF MERCURY

INCHES OFMERCURY

MERCURYBAROMETER

ANEROIDBAROMETER

VACUUM

ANEROIDBAROMETER

VACUUM

THERMOMETERS

OV1-5

50

40

30

60

50

40

30

60

BI-METALSTRIP

BOILING POINTOF WATER

212 oF100 oC

FREEZING POINTOF WATER

32 oF0 oC

MERCURY OR ALCOHOL

304050

60

70

8090

100110

120130

140

150

160

170180190

200

FA

HR

EN

HE

IT

0

10

20

30

40

50

60

70

80

90

100

CE

LS

IUS

LIQUID

HYGROMETERS

HAIR EXPANDS OR CONTRACTS AS HUMIDITY CHANGES 

SCALE CALIBRATED IN “RELATIVE” HUMIDITY

OV1-6

HAIR

SPRING

ANEMOMETERS

ROTATING CUP TYPE PROPELLER TYPE

OV1-7

MEASURES WIND SPEED AND DIRECTION 

SHOULD BE MOUNTED 30 FEET HIGH IN A CLEAR AREA

WIND DIRECTION 

WIND BLOWS FROM A COMPASS DIRECTION

WEST orWESTERLY

NORTH orNORTHERLY

SOUTH orSOUTHERLY

EAST orEASTERLY

OV1-8

CHANGES OF WIND DIRECTION

WEATHERDETERIORATING

WEATHERCLEARING

COUNTERCLOCKWISE“BACKING”

CLOCKWISE“VEERING”

OV1-9

VISUAL OBSERVATION OF WIND

OV1-10A

DIRECTION AFFECTED BY BUILDINGS AND TREES 

SPEED OFFSHORE PROBABLY GREATER

COASTAL WARNING DISPLAY SYSTEM

COASTAL WARNING DISPLAY SYSTEM

DAY NIGHT WARNING WIND SPEED (KNOTS)

UP TO 33SMALL CRAFT

HURRICANE 64 OR MORE

STORM 48 TO 63

GALE 33 TO 47

OV1-10B

SURFACE

6500

20000

CLASSIFICATION OF CLOUDS

OV1-11

BY

HE

IGH

T“F

AM

ILIE

S”

LOW

(no prefix)

MIDDLE “ALTO-”

HIGH “CIRRO-”

BY SHAPE“FORMS”

CIRRUS

ALTOSTRATUS

CUMULUS

ALTO CUMULUS

CIRRO CUMULUSCIRROSTRATUS

STRATUS

CLOUDS WITH EXTENSIVE VERTICAL DEVELOPMENT

TOWERING CUMULUS WILL LIKELY GROW TO CUMULONIMBUS 

CUMULONIMBUS ARE THUNDERSTORM CLOUDS

OV1-12

FRONTMILES1,0005000

CIRRUS

CIRROSTRATUS

ALTOSTRATUS

NIMBOSTRATUSSTRATUS

RAINFALLLIGHT TO MODERATESTEADY OR INTERMITTENT

TYPICAL SPEED OF ADVANCE: 12 – 15 KNOTS

OV1-13

TYPICAL CLOUD SEQUENCE AHEAD OF WARM FRONT

TYPICAL CLOUD SEQUENCE AHEAD OF COLD FRONT

CIRRUS

CIRROCUMULUS

ALTOCUMULUS

TOWERING CUMULUS

CUMULUS

CUMULONIMBUS

MODERATE TO HEAVY SHOWERSTYPICAL SPEED OF ADVANCE: 20 – 30 KNOTS

MILES200150100500FRONT

OV1-14

SQUALL LINE CAN BE 50 TO 100 MILES AHEAD OF FRONT

VISUAL ESTIMATION OF CLOUD BASE HEIGHTS

WITH ARM STRETCHED – FOUR FINGERS = 10 DEGREES

OV1-15

10o

HEIGHT = 0.2 x DISTANCE 

USE KNOWN DISTANCE TO OBJECT UNDER CLOUD EDGEor

ESTIMATED DISTANCE (25,000 FT) TO LOSS OF DETAIL

EXAMPLE USING LOSS OF DETAIL

DETAIL SEEN HEREDETAIL

DISAPPEARSHERE

HEIGHT = 11/2 x 0.2 x 25,000 = 3,750 FEET

WORKS BEST FOR LOW CLOUDS

OV1-16

HORIZON

ABOUT 11/2 HANDS

 HEIGHT = 1,000 x (AIR TEMP. – DEW POINT TEMP.) ÷ 4.4

 TEMPERATURES IN FAHRENHEIT

 HEIGHT IN FEET

OV1-17

ESTIMATING CLOUD BASE HEIGHTFROM SURFACE TEMPERATURES

 EXAMPLE 

AIR TEMPERATURE = 81 oFDEW POINT TEMPERATURE = 70 oF

 HEIGHT = 1,000 x (81 – 70) ÷ 4.4 = 11,000 ÷ 4.4 = 2,500 FEET

WORKS FOR CULUMUS AND ALTOCUMULUS CLOUDS

DOES NOT WORK FOR STRATIFORM CLOUDS