About the climate when traveling
Well, maybe there isn't much you
can do to guarantee good weather but you can do some things to help
minimize disappointment. Be sure to do your homework. Look up reference
books on the subject and use them to help select the most favorable times
and travel locations. Remember, when interpreting climate information,
some statistics are necessary but they could sometimes be misleading.
Look for comparison. Especially compare the prospective location with an
area at home or with which you are familiar.
Sources of weather
information
Up to date weather conditions
and forecasts may be obtained from various sources. A current weather
map, which is based on information furnished by government as well as
private weather services, is the main way of getting a general picture of
weather patterns over a large area. These weather maps show conditions
around the country at ground level. Elements which are of particular
interest to travelers and may be shown on the map include temperature,
pressure changes, wind speed and direction, cloud type, current weather,
and precipitation.
Of course, the weather
information and projected forecasts must be interpreted. You may do well
to alter your itinerary and stay clear of areas that project undesirable
or threatening weather conditions. Especially keep alert for severe
weather conditions such as storms, heavy rains, etc. For example, you
should remember when traveling in mountainous regions that flash floods
can strike with little or no warning. Distant rain may be channeled into
gullies and ravines, turning a quiet stream-side campsite into a
rampaging torrent within minutes. Incidentally, there is excellent
literature available through the US Government Printing Office prepared
by the National Weather Service. The information includes advice on
staying safe during lightning, flash floods, hurricanes and tornadoes.
Basic elements on how they
could affect your travel preparations
After you have had an
opportunity to review reference materials on climate and sources for
weather forecasts, you should become acquainted with the meaning of some
basic weather elements and learn how they may affect your travel plan.
Perhaps the most crucial weather element is temperature which is a good
indicator of body comfort. The ideal air temperature is around 27°C.
Temperatures generally decrease at higher latitudes and at higher
elevations, on average by around 1.7°C for every 300 meters increase in
elevation up to 9,000 meters.
Wind, which is air in motion, is
another important weather element. Winds are caused by pressure
gradients, the difference in pressure between two locations. Air moves
from an area of high pressure toward an area of low pressure. The greater
the pressure gradient, the faster the wind. Sea breezes form when cool
high pressure air flows from the water onshore to the low pressure area
created by warm air over the land. On a clear, hot summer day, the sea
breeze will begin mid-morning and can blow inland as far as 16 km at wind
speeds of 16 to 24 kph. In the evening, the process is reversed. An
offshore land breeze blows at a more gentle speed, usually about half the
speed of the daytime onshore wind.
A somewhat similar situation
occurs in the mountains and valleys. During the daytime, the valley floor
and sides and the air above them warm up considerably. This air is less
dense than the colder air higher up so it rises along the slopes,
creating a "valley wind". In the summer, the southern slopes receive more
sun, and heat up more which results in valley winds that are stronger
than their north slope cousins. At night, the process is reversed and
down-slope, "mountain winds" result from the cold air above the mountain
tops draining down into the valley.
Winds are also affected by such
factors as synoptic (large area) pressure differences and by day-night
effects. The sun produces maximum wind speeds, while at night winds near
the ground are usually weak or absent. Wind speed is also influenced by
how rough the ground is. Over smooth water surfaces, the wind speed
increases very rapidly with increasing altitude and reaches a peak speed
at a height of about 180 meters. Over rough terrain, the wind speed
increases more gradually with increasing altitude and does not reach its
peak until about 450 meters.
