Rick Crandall

Hiker, Adventurer, Author of The Dog Who Took Me Up a Mountain

The Language of Clouds

Hiking Longer, Climbing Higher / by

Probably the main reason for “reading” weather signs is to avoid being unprotected in a thunderstorm. The word “thunderstorm” focuses on the wrong threat; it is the lightning that is scary and can injure or kill.

A Short Course on Storm Forecasting

I am no weatherman, but to date I have avoided major weather issues in all but two of my high-mountain Colorado climbs by paying close attention to the weather. Most often in the Colorado mountains we get weather in two ways:  

  1. Traveling storms, typically from the west or northwest (these are easier to spot at a far distance either on radar or in plain sight if you are high enough), or
  2. Gathering cloud formations going vertical (convection), caused by summer monsoon wind patterns from Arizona. These often occur after 2 pm and include brief (30-60 minute) electrical discharges that are very dangerous and must be avoided above tree line.

Cumulonimbus clouds: storms developing

Note the broad, dark base in the picture.

When a moist warm air mass hits the mountains and is forced to rise, it creates friction and rapid cooling. Water vapor condenses, creating cumulus clouds of increasing height and darkness. The result is thunderclouds piled high, and the resulting friction against the mountain creates static electricity which discharges as lightening.

Cumulonimbus clouds can develop in as little as 20 minutes. The faster, taller, and darker they build up, the faster and more violent the energy release: downpours, wind, lightning, and hail.

Warning signs: Watch for mid-level, puffy clouds that gather in height and get increasingly darker.

Clouds that usually produce lightning have vertical development and dark anvil-shaped bases. Lightning usually coincides with rainfall, but not always. Strikes can come from almost clear skies—the “bolt from the blue.”

Even if clouds have yet to produce lightning, electricity may still be in the air.  The best method of detecting danger is to closely observe your or your hiking partner’s hair.  If you see that hair is beginning to rise into the air, take cover – at that point, a strike is probably imminent. The typical monsoonal thunderstorm cell is 15 miles in diameter and lasts an average of 30 minutes. But there are no rules when it comes to weather.

Typical late morning to midday cloud columns piling up over the 14ers (convection). At this point they look fine (no broad anvil base) but when they show as early as late morning, they will likely develop into storm cells in a few hours. Arrows from Castle Peak, Pyramid and Capital, left to right, all fourteeners.

Summer Monsoons

Precipitation increases in July with the advent of the Arizona summer monsoon. During this time, a large dome of high pressure sitting over eastern New Mexico and Texas drives warm, moist air from the Gulf of Mexico into the Southwest. A broad counterclockwise circular wind pattern drives the moist air north to Colorado. Rapid daytime heating combined with forced updraft to clear the tall mountains leads to rapid upwelling of the moist air and the formation of widespread thunderstorm cells. The monsoons can continue into mid-September, but more commonly ends in late August or early September.

Here is a typical sequence in the summer mountains, taken on the climb of Missouri Mountain. The left picture was taken at about 11:30am; the clouds were harmless then but too early in the day to stay that way. On the right is the anvil shape that was likely to go electrical soon. We were almost back at tree line by then.

Precautions: Monsoon thunderstorms in Colorado typically build up steam between 12:00 p.m. and 3:00 p.m. If thunderstorms are in the forecast, you should never be above tree line after 1:00 p.m. If you are above tree line when a storm rolls in, descend to shelter rapidly. 

Good Clouds

An example of clouds that do not threaten storms are the higher Cirrus clouds. They are thin and wispy. Some see horsetails, but they can be straighter or other shapes. The key is that they are high, somewhat transparent and wispy.

Knowing When to Turn Around

Turning around is not easy when you have an objective in mind. “Summit fever,” (i.e. driving hard to get to the summit of a peak) on a climb can encourage some people to take inadvisable risks. But often this leaves you with no time to turn back to a haven when the weather break. It is much better to live for another chance at Mother Nature on another day. As much as I have learned to forecast the weather in the tricky atmosphere of the Rockies, I still had to turn around on 13 summit attempts before finally mastering the 58 mountains higher than 14,000 feet in the Rocky Mountains.

My mental attitude has always been that a climb is as much about having fun, enjoying the challenge, and living to try the climb on another day as it is about summiting that particular day. One mountain took me three attempts and on the final one, reaching summit was all the sweeter.

Here as we came over the top of a false summit on Mt. Tabegauche and saw the real summit just two humps away, there was a cloud system building right over summit. The warm air bumps into the mountain and rises: the moisture in the air condenses and forms a cloud, and the rising effect rubbing against the mountainside creates static electricity buildup. We turned around.

How to React in a Storm

Do not panic! Move deliberately to avoid tripping and injury. This is one time to be fatalistic. You cannot hide from lightning, but you can reduce the odds of being struck. See: Caught in a Thunderstorm.

Little Bear Turnaround

One time in early September we were attempting Little Bear Peak. We were in the middle of the very steep and slippery “Hourglass Gully” that is dangerous in any weather condition. We noticed a rapid gathering of bad clouds, so we made the spot decision to descend. Thankfully we did, since as we got to the rocky final descent, it didn’t just rain, it snowed! More precisely it “graupeled” which refers to precipitation which is halfway between snow and hail.

On this final descent from the failed attempt at Little Bear Peak, I am using a single pole to prop against slipping on graupel-covered wet rock. You can see from the streaks down my face that it is still graupeling.

National Weather Service Technical Weather Forecasting

The problem I have with forecasts you get in most weather apps or TV forecasts is that they typically focus on an area, often a city. When the terrain is more complicated, as with hills and mountains, additional factors get involved like wind direction, convection and temperature change at various altitudes.

When planning a hike in a hilly or mountainous region, I have found it most useful to go right to where many weather forecasts get their information: the National Weather Service. There you can find detailed descriptions of what is happening with the weather and the data they are using for their forecasts.

If you plan on using their website, go to National Weather Service National Headquarters Site

Then you can access a local forecast on the NWS website by typing the city and state or zip code of the area you would like to learn about in the search bar on the top left of the page. The page will show you current conditions, an extended forecast, and a more detailed forecast for that area. For more in-depth information, scroll down to “Additional Forecasts and Information” and click on “Forecast Discussion” to really get into the thick of the forecast. The text will have weather terminology as links to their definitions which is helpful, and some may become part of your vocabulary.