weather and water wisdom 255
Cloud identifi cation. Do your best to identify the cloud types you are
seeing. Note in the 3-hour trend whether clouds lower and thicken, or have
vertical development. Also, log the percentage of sky covered by the diff erent
types of clouds. (Th e international symbol for each cloud type is given in the
accompanying sidebar.)
Wind waves and swell. Winds that blow over the water for a period of time
create waves, called wind waves. Aft er many hours or days, the wind stops blowing
at that location. Th e waves continue moving in the same direction, but they are now
called swell or swell waves. Swell might travel thousands of miles before breaking
onto a beach, coral reef, or cliff.
Take a bearing in the general direction of wind-driven sea waves. Height
is much more diffi cult to estimate. Enter sea wave height in feet or meters into
your weather log. Swell do not break on their tops, but roll in a generally steady
direction beneath any sea waves.
Visibility. Estimate your visibility in nautical miles (see the table Horizon
Distance Based on Height of Eye in Appendix I).
BASIC FIVE-FACTOR FORECASTING FROM A WEATHER
PATTERN LOG
Use your weather log observations to give you an idea of the weather to come.
Concentrate on these five factors:
Barometer: Steady, falling, or rising? What is the rate of change (fast or slow)?
Temperature: Steady, falling, or rising?
Wind Direction: Divide a compass into four parts (called quadrants); N to E; E to
S; S to W; W to N. Place the wind into one of those quadrants.
Wind Shift : Is the wind steady, backing, or veering?
Clouds: Th e pattern of clouds can show the advance of a warm or cold front,
indicate fair weather, or warn of an impending thunderstorm.
Q Winds from an eastern quadrant (N to E or E to S) with a falling
barometer foretell stormy weather.
Q Winds from a western quadrant (S to W or W to N) with a rising barometer
foretell clearing weather.
Q When the barometer and temperature are both falling, expect stormy
weather; when both are rising, expect clearing or fair weather.
Q Sluggish barometer readings—inconsistent, slow rising, or slow falling—
oft en indicate wet weather just ahead.
Q A rapid fall in the barometer indicates a storm on the way accompanied by
high winds. Th e faster the rate of fall, the more intensity you can expect from
the storm.