Bad weather has traditionally been the cause of many disappointments of backcountry trips, sleepless nights in inadequate sleeping bags, and even injury and death directly or indirectly. Becoming your own weather forecaster when exploring the great outdoors is a skill required for long-term survival.
Nature never sneaks up on the alert survivalist. In most cases, there are hours of warning given through weather signs. The trick is, being able to recognize these signs and use them to advantage.
With the advent of new synthetic insulators and other similar materials, and ultra-light backpacks and camping gear, even winter is rapidly becoming “another season” to enjoy in the backcountry.
The best source of weather information is, of course, the local television or radio station, and most weather reporters will give five-day forecasts.
If, however, one finds himself in a survival crisis situation when the radio and TV stations are off the air, then becoming alert to weather conditions and being more sensitive to nature’s warning signs of changing weather patterns could be literally a matter of life and death.
A good weather forecaster has to understand how the atmosphere works.
Our atmosphere is made up of many gases, predominately oxygen, and nitrogen. The atmosphere is a thick, 1,000-mile layer of air which surrounds the earth. However, more than 90 percent of the atmosphere is contained in the first 25,000 feet above the earth’s surface.
The atmosphere consists of five outer levels from the earth’s surface:
- The troposphere is about seven miles thick and is wider at the equator than at the poles.
- The tropopause is the boundary between the troposphere and the stratosphere.
- The stratosphere extends to about 30 miles above the earth’s crust
- The mesosphere extends to approximately 50 miles above the earth.
- The thermosphere rises to a level of about 500 miles above the earth’s surface.
The troposphere is that area which people most commonly refer to as the “atmosphere.” It is this layer of air which regulates the temperature of the earth and in turn, creates the air movement of the winds.
The earth itself is heated by the sun and is cooled by the air that surrounds it. The air itself is not heated from solar energy, in fact, solar heat is absorbed by the earth’s surface and in turn heats the air, or atmosphere on the earth’s surface by radiation.
This heating and cooling of the earth’s surface cause the air to rise when heated or drop when cooled and creates breezes or winds in the process. It is a fact that water absorbs a greater amount of the sun’s energy than does the land surface; hence, there is a greater probability of breezes or winds around large bodies of water.
The atmosphere is subjected to many variables and forces which create erratic weather patterns.
When planning an outdoor experience such as hiking, climbing, boating, or cycling, the frost chill, wind chili, or high temperatures need to be considered in planning the trip.
One more rule to keep in mind is: temperatures below 1 degree C. (Celsius) or 34 degrees F. (Fahrenheit), and above 25 degrees C. or 75 degrees F. must be considered within your plans. Not to plan around these highs and lows could invite injury or even death.
Humidity is water vapor held in the atmosphere. The bubble of air of atmosphere that surrounds the earth always contains a percentage of water vapor, and with temperature changes, water vapor condenses. The point at which water vapor condenses is called the dew point.
When the air has more water vapor than it can hold, the surplus condenses into various types of weather — dew, fog, rain, snow, or clouds.
The atmosphere can only absorb so much water vapor, and when it can hold no more, the air is said to be saturated. Warm air can absorb much more water vapor than cold air.
When hiking, cycling, or working out in warm, saturated air, one is subject to heatstroke because the air is too full of water vapor to absorb any more moisture and perspiration cannot evaporate from the skin which results in reducing the body’s cooling capability. We’ve talked about the risk of heatstroke and other heat disorders in this article.
The relative humidity is expressed in percentages. When the temperature is high, and the humidity is above 75 percent, the atmosphere is muggy and sticky. When the atmosphere has a high humidity (air holds a high percentage of water vapor), and the temperature drops, the air is cooled until there is condensation. As air cools or warms, it tends to move. Cold air sinks and warm air rises. This brings us to the next weather force… the wind.
What a weather forecaster should know about moving air
The wind is simply the movement of air and is measured in speed and direction. As air is heated by the earth’s surface, (radiation), it rises and moves. A low pressure is created when warm air rises and cold air rushes in to fill the void.
The morning sun warms the land faster than it warms the waters. Consequently, the air above the water is cooler than the air above the landmass. The warmer land air rises, creating a void and the cooler sea air rushes in to fill the space. The result is cool sea or lake breezes during the morning hours.
The pressure is defined as the weight of the air (atmosphere) on the earth at sea level, and that is about 14 pounds per square inch.
There are two basic rules regarding pressure:
- Falling pressure indicates coming bad weather.
- Rising pressure indicates good weather.
The pressure is measured in BARS, and the instrument which measures pressure is a barometer. Each bar is divided into millibars (mb) and the normal air pressure at sea level is 1,013 mb.
One important note for the weather forecaster: pressure falls about one mb every 30 feet of altitude gained, hence, at 3,000 feet above sea level, the pressure is 900 mb. As altitude increases from sea level, the air pressure will drop.
A barometer must be adjusted to the altitude for a given geographical area. Barometers are calibrated in inches of mercury, and 29.9 inches of mercury is equal to 1,013 mb, both indicate normal pressure.
When the barometer rises to 30 inches of mercury or falls to 28 inches of mercury, look for changes in the weather. Points of equal pressure are connected on a weather map by lines called isobars.
The winds of a low-pressure front will blow in a counter-clockwise direction in the Northern Hemisphere and in a clockwise direction in the Southern Hemisphere. Low pressures are usually accompanied by strong winds, precipitation, lower temperatures, cloudiness, and generally unsettled weather patterns.
Low-pressure systems usually move from west to north in an easterly direction at about 25 miles an hour. A cloud sequence which usually precedes a cold front or low-pressure cell is very high cirrus clouds forming 18-24 hours in advance of the approaching low pressure followed by stratus clouds which will finally drop to 8,000 feet elevation and produce the grey, dreary, typical wintry stormy day.
About this time, moisture in the form of rain, hail or snow may begin to fall. Fog may also be evident in patchy areas. A sudden drop in air pressure will create very strong incoming winds. The winds of a high-pressure front will blow in a clockwise direction in the Northern Hemisphere and in a counter-clockwise direction in the Southern Hemisphere.
High pressure usually indicates a clearing trend, little wind, clearing skies, warmer conditions, and more stable temperatures. High-pressure systems usually move from west to east, but may also come in from the south. The prevailing westerly winds move the fronts before them.
Often we experience a “ridge of high pressure” between two Iows. The ridge of high pressure will give us a few hours of clearing skies, and mild, windy weather. The ridge passes, and clouds and bad weather form again with the next low-pressure system.
The line between an area of warm air and an area of cold air is termed a front. The warm air rises, forming clouds, and the cold air moves in under the warm air.
Clouds classification for the weather forecaster
It is doubtful that any single factor affects the safety of the backcountry traveler greater than does the weather as evidenced by clouds. They are the best visible indication of pending weather conditions and changes.
Clouds, along with barometric and temperature changes, are a good index of weather. Clouds are formed from the condensation of moisture in the air. As air rises, it cools and reaches the dew point, thus forming clouds. As a weather forecaster, you should learn about cloud formation, and this article will help.
The cloud-forming process is as follows:
- The sun heats the land.
- The land heats the air.
- The warm air rises through the high cooler air.
- The air reaches the dew point.
- Clouds form.
The science of weather forecasting has gained tremendous credibility in the last 40 years, and especially during the last decade with the advent of weather satellites and space technology.
Even with advanced technology, though, weather forecasting in specific locales is not an exact science. The weather in the mountains can change so rapidly that weather prediction is not accurate enough for a specific location and even an experienced weather forecaster can be caught off-guard.
This is due, in part, to increased humidity from evaporation rising from lakes and snowy peaks. Since general forecasts from radio and television do not predict mountain weather accurately, it is advisable to obtain the most current weather forecast for the local area. It is a good idea to learn from the “locals” the general wind direction from which most big storms enter the area and the general severity and length of storms.
One of the best survival skills a mountain traveler can have is good judgment based on known weather signs. This skill can be learned through study and practice, and you can become a good weather forecaster if you keep practicing.
As a mild storm moves across a wide flat valley and into the mountains, it seems to intensify and become much more severe. Clouds are blown toward the mountains, which become obstacles to the wind. As the wind is forced over the mountain ranges, moisture is re-leased on the windward side resulting in heavier rates of precipitation and generally more cloudiness.
On the leeward side of the mountain, the atmosphere is drier and sunnier. As clouds begin to move into the mountainous regions ahead of storms and “pile up” on the mountain peaks, the clouds may resemble lens (cap) clouds or lenticular clouds.
The lens (cap) cloud is just what the name implies — a circular cloud formation sit-ting on top of a peak. The lenticular clouds will appear as “ripples” of clouds much like the ripples in a pond after a stone is dropped.
Lens and lenticular clouds are early warning signs of an impending storm for the weather forecaster. With these two cloud formations, other weather changing indicators will be prevalent.
High thin cirrus clouds steadily moving into an area begin to cover the sky. The barometric pressure begins to drop. If the cirrus clouds change to cumulus (a fluffy, low flying cloud usually drifting at about 10,000 feet elevation), the main part of the storm is probably localized.
The wind direction in the mountains is usually difficult for the weather forecaster to because. The mountain peaks and canyons will cause variations in wind directions. At times, the wind may seem to be blowing from every direction. Remember to watch the higher clouds for undeflected wind direction.
Cumulus clouds and cumulonimbus clouds are tall clouds which build and tower in vertical development. These clouds are formed in very unstable moist air and may develop into cumulonimbus thunderheads which may appear anvil-shaped.
Generally, storms resulting from cumulonimbus formations are quite severe in the mountains and lay down heavy snow, hail, or rain. Usually, these storms are associated with a cold front.
Strato clouds are low, flat-based clouds rising in heaps, usually seen in the winter and generally indicating bad weather. Heaped white clouds may give off a little rain or snow while frontal stratocumulus indicates a storm.
For the weather forecaster, nimbus clouds indicate min and snow and appear as large, layered grey clouds. They are menacing in appearance and always mean bad weather. They may or may not have the anvil-shaped appearance.
Lens or cap cloud formations get their name from positioning them-selves on a mountain peak. This cloud formation indicates moisture and high winds aloft.
Lenticular clouds are developed by high winds aloft and resemble the rings in a pond when a stone is thrown in. They proceed from the peaks down-wind, sometimes for miles. They also indicate high winds at higher altitudes and mountain peaks.
Stratus clouds are low lying clouds found in elevation from ground level to about 8,000 feet. When on the ground they produce ground fog, which usually burns off when the sun rises. They present the typical “winter day” look.
Nimbostratus clouds appear as a solid grey mass of low, overcast skies. They usually produce long-term, steady rains.
Alto clouds occupy the altitude levels between 8,000 and 20,000 feet. The approach of altostratus usually indicates approaching bad weather. When they begin to pack, the outlook is for the moisture of one type or another within eight to 10 hours.
Cirrus clouds are very high, delicate clouds thinly spread at an altitude between 20,000 to 38,000 feet. They are composed of ice crystals and appear as mares tails or solid bands of cirrus and indicate a front approaching with lower-level stratus and precipitation.
In northern colder climates, cirrus clouds indicate an approaching storm with unsettled weather. The altitude and direction that the clouds are moving are good indicators of weather conditions.
In the winter, many severe and freezing storms come from the arctic air mass in the north. In the summer, a storm from the north may serve to cool down high temperatures to more comfortable levels.
In the summer, high altitude cloud cover coming from the south means a deteriorating weather system with large amounts of rain, supplied from warm, moist tropical fronts.
For the weather forecaster, low clouds mean worsening weather, high clouds mean changeable weather. The higher the clouds, the better the weather outlook — unless the cloud mass is building.
Other weather indicators for the weather forecaster
Indians, trappers, and the old-timers who have lived in the woods and mountains for years look to other sources, often, to foretell the weather. Some of these are: Birds and insects fly lower to the earth’s surface in the moisture-laden air. Insect activity increases prior to a storm.
Sky color may also help the weather forecaster. “Red sky in the morning, sailor take warning. Red sky at night, sailor’s delight.”
Actually, red sky at either time of the day may indicate rain and wind within 24 hours. A light pink sky may mean pleasant weather. Lavender or pale purple sky at sunrise or sunset with blue sky in between means little moisture expected. A bright yellow sunrise usually means rain within the next several hours.
Ring around the moon usually means rain or clouds. The ring is due to ice crystals suspended in the atmosphere.
Haze over the moon usually indicates rain or clouds. When the wind is blowing from the north, northwest, or southwest, weather ‘could be changing since storms usually enter from those directions at about 25 mph.
When there is no breeze evidenced by campfire smoke rising straight into the air, one can generally predict very little or no weather change for about four to six hours.
When the rain begins soon after a cloud build-up, the storm will usually be of short duration. However, when it begins to rain after an extensive period of cloud build-up, the rain may last for hours. Wind is predicted when rippled, or mackerel clouds are visible, the ripple effect is caused by winds aloft.
When mackerel clouds are darkening towards the horizon from which they came, then worsening weather is on the way. When bright sunsets with a build-up of altocumulus clouds (thunder-heads), expect rain within 12 hours.
Cirrus clouds indicate good weather. Patchy, white cumulus clouds, cotton balls, also generally predict good weather.
Rainbows seen in the morning hours, as well as rainbows seen upwind during the day, usually mean rain. The rainbow is reflecting atmospheric moisture.
Heavy dew on the early morning grass could mean a clear day ahead while no dew may mean that rain is coming.
When cloud types and the altitudes at which they float are rapidly changing, expect a change in a relatively short period of time.
So, the outdoors person, hiker, or survivalist armed with just a rudimentary knowledge of the signs of the weather, will be able to become a fairly accurate weather forecaster. And just a little of this specialized knowledge could save your life.