NOTICE: The information contained within this document is copyright © U.S. Coast Guard Auxiliary No attempts to add, modify or delete information contained within this document shall be made. If errors are discovered, please contact the U.S. Coast Guard Auxiliary’s National Training Department.

Department of Training AUXILIARY WEATHER SPECIALTY COURSE INTRODUCTION AND CHAPTER ONE prepared by Weather Branch Copyright  2004 U.S. Coast Guard Auxiliary Association, Inc. Photo courtesy of National Oceanographic and Atmospheric Administration

ABOUT THIS COURSE PURPOSE Practical weather assessment Coastal patrols by Auxiliary vessels Train PE instructors SCOPE Basic principles of meteorology Physics 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 H H  CENTER OF HIGH PRESSURE L L  CENTER OF LOW PRESSURE FRONTS COLD WARM OCCLUDED STATIONARY JET STREAM OV1-3

MEASURING ATMOSPHERIC PRESSURE OV1-4 THE ANEROID BAROMETER SCALE IS ALSO CALIBRATED TO READ INCHES OF MERCURY INCHES OF MERCURY BAROMETER ANEROID BAROMETER VACUUM ANEROID BAROMETER VACUUM

THERMOMETERS OV BI-METAL STRIP BOILING POINT OF WATER 212 o F 100 o C FREEZING POINT OF WATER 32 o F 0 o C MERCURY OR ALCOHOL FAHRENHEIT CELSIUS LIQUID

HYGROMETERS HAIR EXPANDS OR CONTRACTS AS HUMIDITY CHANGES SCALE CALIBRATED IN “RELATIVE” HUMIDITY OV1-6 HAIR SPRING

ANEMOMETERS ROTATING CUP TYPEPROPELLER 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 or WESTERLY NORTH or NORTHERLY SOUTH or SOUTHERLY EAST or EASTERLY OV1-8

CHANGES OF WIND DIRECTION WEATHER DETERIORATING WEATHER CLEARING COUNTER CLOCKWISE “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

DAY NIGHT WARNINGWIND SPEED (KNOTS) UP TO 33SMALL CRAFT HURRICANE64 OR MORE STORM48 TO 63 GALE33 TO 47 OV1-10B

SURFACE CLASSIFICATION OF CLOUDS OV1-11 BY HEIGHT “FAMILIES” LOW (no prefix) MIDDLE “ALTO-” HIGH “CIRRO-” BY SHAPE “FORMS” CIRRUS ALTOSTRATUS CUMULUS ALTO  CUMULUS CIRRO  CUMULUS CIRROSTRATUS STRATUS

CLOUDS WITH EXTENSIVE VERTICAL DEVELOPMENT TOWERING CUMULUS WILL LIKELY GROW TO CUMULONIMBUS CUMULONIMBUS ARE THUNDERSTORM CLOUDS OV1-12

FRONT MILES 1, CIRRUS CIRROSTRATUS ALTOSTRATUS NIMBOSTRATUS STRATUS RAINFALL LIGHT TO MODERATE STEADY 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 SHOWERS TYPICAL SPEED OF ADVANCE: 20 – 30 KNOTS MILES FRONT 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 OV o HEIGHT = 0.2 x DISTANCE USE KNOWN DISTANCE TO OBJECT UNDER CLOUD EDGE or ESTIMATED DISTANCE (25,000 FT) TO LOSS OF DETAIL

EXAMPLE USING LOSS OF DETAIL DETAIL SEEN HERE DETAIL DISAPPEARS HERE HEIGHT = 1 1 / 2 x 0.2 x 25,000 = 3,750 FEET WORKS BEST FOR LOW CLOUDS OV1-16 HORIZON ABOUT 1 1 / 2 HANDS

HEIGHT = 1,000 x (AIR TEMP. – DEW POINT TEMP.) ÷ 4.4 TEMPERATURES IN FAHRENHEIT HEIGHT IN FEET OV1-17 ESTIMATING CLOUD BASE HEIGHT FROM SURFACE TEMPERATURES EXAMPLE AIR TEMPERATURE = 81 o F DEW POINT TEMPERATURE = 70 o F 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