Cumulonimus Clouds

Predicting Weather II

Well here it is April 15th, I was BBQ’ing dinner last night in the bright sun and fairly comfortable temperatures, and today there is another 6 inches of snow on the ground with more on its way.  I can’t say that I am surprised, I have seen snow as late as May in lower elevations in Colorado, and as late as July in the mountains.  Plus this storm has been talked about in the news for several days leading up to today.  But even without television, radio, and the internet, you should be able to understand the basics of predicting weather, whether you are deep in the wilderness on a multi-day trip, or if you are taking a day hike not far from home.

The first thing to do is learn the weather patterns of the areas you frequent.  Just as this snow storm in Colorado isn’t real pleasant, it is not abnormal by any means.  For me, most of my outdoor activities take place in Colorado, and while the seasons often tend to blend in with each other, some things are very predictable year after year.  For example, if I’m on a fishing trip in the mountains, I never head out for the day without a rain coat, even if the sky is clear blue in the morning.  You can almost count on an afternoon rain storm in the mountains from June through September, and I have been in some very violent thunderstorms during those months.  The same applies to the plains, although they tend to die down in late July, and you can usually see the storms coming a lot easier than you can when you are in the mountains.  When I am hunting in the mountains in the early fall I have to be prepared for frigid mornings, hot afternoons, rain, hail, or snow, and cold nights.  If I am not prepared for all these types of weather, I could end up having a miserable time.

One time on a muzzle loading elk hunt in September, my friend Rich got an elk the evening before we were going to be picked up on horseback by our outfitter.  We didn’t quite finish taking care of the elk before we were chased back to camp by an evening thunderstorm, so we figured we would finish up the next day when we went to pick up the elk with the horses.  The next morning we were sitting around in jeans and tee shirts waiting for Rick, our outfitter.  The wind began to swirl, clouds came in, and in less than two hours we were in a blizzard.  The elk was down in an area a few miles away with no clear trail to get to it, and that was one of the most miserable rides of my life going to pick it up.  We were soaked to the bone and freezing by the time we got there, and finishing up the elk was quite a challenge being as cold as we were.  I would have been a lot better off had I worn proper gear on that ride, but I had no idea it was going to be that bad.  A lesson learned for sure.


Cloud Identification

This brings me to predicting weather.  In the example above I mentioned the swirling wind; I will talk about wind in a minute.  To keep things simple, in addition to understanding the weather patterns of where you go, learning some basics about clouds and wind will give you some fundamental knowledge that will help you predict the weather.

Cumulus clouds are the large, white, puffy clouds that build up during the day, often turning into towering masses of anvil-shaped storms.  These clouds can cover miles and miles, and be several miles tall in the sky.  When mixed with nimbus clouds, these are typically the clouds that produce strong thunderstorms, hail, wind, heavy rain, and even tornadoes.  Nimbus clouds are lowing hanging dark masses of overcast without specific formations.  If these clouds are present, it is likely already raining or snowing.  Nimbus clouds mixed with cumulus clouds definitely means rain or storms. Cirrus clouds are the high, wispy, white clouds often called “Mare’s tails” because they look like the tail of a horse.  Cirrus clouds do not hold storms, but watch them closely.  If their numbers grow it can be an indication that a storm is on its way in a few hours to a day.  Stratus clouds are long, low banks of clouds that may not bring rain or snow, but may be an indicator of a storm to come.

I mentioned in another article about understanding what direction the prevailing winds in an area will blow.  If you know this for specific seasons, you will likely know from which direction a storm will come.  What happened yesterday and today is a perfect example of this where I am; although yesterday was clear and mild, you could feel the wind shift to coming almost directly from the north with cooler air following.  This morning it was snowing, and it is expected to continue for another full day.  There is a saying in Denver that if you can smell Greeley (a small town to the north with lots of cattle), it’s going to snow, and you could definitely smell Greeley yesterday.

global-wind-patternsAs a general rule in North America, a modest wind from the southwest is generally a good indicator of clear weather for at least 24 hours from the time that wind begins.  But the longer it continues, the more likely the weather will change, usually bringing rain.  Keep an eye on the clouds, and if this southwesterly wind continues for three days, rain is likely on the way.  If that southwesterly wind shifts to the west it normally means clear weather for a while, although usually cooler air.  If that wind continues to shift and comes from a northwestern direction it usually means a big snow or period of rain is on its way.  If the wind shifts to come directly from the north you can almost bet the farm that a big storm is coming, although it will likely blow through quickly and be followed by milder weather.  We had this exact thing happen one week ago tonight; it was a beautiful afternoon, the wind shifted to the north and was blowing very hard with cold air, and within a few hours it was snowing.  While the snow only lasted for a day, the cold air lingered, then by Friday it was shorts weather again.

So there are some basic tips for understanding and predicting weather based on clouds, wind, and prevailing weather patterns.  This is especially important to know if you are in a survival situation; this knowledge can help you understand when the best time is to travel, or when you need to hunker down and build shelter.  By Friday it will be 52 degrees and sunny again, hopefully this is the last storm of the season, I’m ready for spring!