Understanding the weather can save the day

Blog post written by PA2 Levi Read, D9 External Affairs Division, with information obtained from Dave Anderson, a Coast Guard auxiliarist.

Weather moving over Michigan waterways

As the months pass and February turns to March and then April, the weather will change. Here in the Great Lakes region, the lakes will begin to thaw and many boats will be placed back in the water in preparation for the warmer weather and more boating and other outdoor activities. For those who didn’t brave the freezing weather, Spring can bring a feeling of new life and excitement for upcoming adventures. But just because the weather doesn’t bring freezing temperatures, doesn’t mean the weather is going to give you a free pass to fun.

On a routine basis, the 9th Coast Guard District reminds outdoorsmen to practice safe boating and ice recreation. Within these reminders, there is always a reminder about staying up to date with the weather.

Weather is its own kind of animal with dynamic characteristics and ever-changing personality. Weather can change a normal, fun outdoor activity into a life-and-death situation. So, understanding what the weather is doing and what the weather will be doing is very important in keeping our recreational activities fun but with a happy ending.


David Anderson, Coast Guard Auxiliary, Duluth, Minn.

However, doing this is easier said than done because even the experts freely admit that predicting the weather is an inexact science.


David Anderson, Meteorologist Duluth, Minn.

Dave Anderson is a meteorologist in Duluth, Minn., and he is also a Coast Guard auxiliarist. He has taken a few moments to share a few tidbits about forecasting the weather to help keep you safe.

“Weather is important to people in this region, because people’s lives can depend on it,” said Anderson. “An accurate forecast can avert tragedy in dangerous weather.”

There are several forecasting methods that weather experts use to give us the best information they have. You can use the methods, too, as long as you understand the limitations to these methods and retain situational awareness. We can at the very least use these methods to plan ahead for a worst-case scenario while outdoors.

The forecasting methods are:

Extrapolation — Assume fair weather high pressure systems and foul weather low pressure systems will continue to move at same speed in the same direction. In the U.S., that is west to east at about 30 mph. This forecast style does not account for air mass interaction or modification. It can be unreliable beyond a few hours.

Historical — Forecast based on climatic averages. If it has rained on a given date 30 times in the last 100 years, you in theory have a 30% chance of rain this time. This method is fine if you have access to your region’s weather and climate history charts; not so useful if you don’t. Keep in mind this system has no relation to current weather so that limits it right away. Remember: “Climate is what we expect; weather is what we get.”

Analogy — Forecast evolution of present weather pattern based on known evolution of similar patterns in the past. For example, the last time the clouds lowered and thickened, it rained. The clouds are lowering and thickening now. Therefore, it should rain again. This system requires familiarity with past weather patterns. It becomes unreliable beyond two or three days. Handy pocket forecast books tend to use this system. If you know the cloud type and wind direction, the book will let you know what the most logical weather progression is.

Numerical — Apply physical formulas to project atmospheric properties from present values. These are the computer models many broadcast meteorologists talk about. This forecasting style requires huge numbers of observations and a super-computer. Luckily, you can access computer model data by going online and searching for “NWS MOS forecast.” MOS stands for “model output statistics.” This NOAA site includes computer model data for hundreds of cities around the U.S. and possessions. The site also includes a decoder you can use to decipher the numbers on your own. With this method, accuracy decreases as length of projection increases. – Unreliable beyond 4 – 5 days.

The two methods that would best help the “Everyday Joe” on a boat or just outside are extrapolation and analogy.


Cloud development graphic

The extrapolation method is best understood when you know the different types of clouds and the formation of those clouds along with where the wind is coming from, how fast it is moving, and if it is changing direction.

Using the analogy method is to understand where to look and when. What assets are available and how do they help? Before you go out watch the Weather Channel, local news, or check your newspaper for current and expected weather conditions. If you’re already outside enjoying the outdoors, look to the west for approaching weather and track the winds for direction and speed of advance. You can do this by carrying an anemometer or something as simple as picking up some leaves or blades of grass and tossing them into the air and watching what direction they fly and how fast it goes.

Coastal Warning Display system

Coastal Warning Display System

A few rules of thumb:

Weather — Look west for approaching weather changes.

Newspaper maps

Key to reading most printed weather maps

Wind – One of the natural elements is known as jet stream. Jet streams are fast flowing, narrow air currents found in the atmosphere of Earth . The major jet streams on Earth are westerly winds (flowing west to east). Their paths typically have a meandering shape; jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including the opposite direction of most of the jet. Watching the clouds can give you a general idea of what a jet stream is doing. With an east or west jet stream, one can expect moderate winds. A north or south movement tends to bring high winds and converging jet streams bring very high winds. Always make sure you look for the wind warning flags that are flown at your local marina or Coast Guard station.

Temperature — Surface temperatures and dew points come from the west and may be modified by the terrain. The dew point temperature is the temperature at which the air can no longer “hold” all of the water vapor, which is mixed with it, and some of the water vapor must condense into liquid water. The dew point is always lower than (or equal to) the air temperature. If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form.

Warm Front

Warm front graphic

Cold Front

Cold front graphic

If there is then further cooling of the air, say because the air parcel is rising to higher (and thus colder) levels in the atmosphere, even more water vapor must condense out as additional dew, fog or clouds, so that the dew point temperature then falls along with the air temperature. This is how precipitation forms. 

Fog — Expect fog toward the evening and close to a stationary front and when the dew point is within five degrees of the surface temperature. Understanding the dew point level becomes extremely important as the summer approaches and boaters go offshore. Offshore temperatures are usually lower, the dew point is going to be higher, which, as explained earlier, can create fog. Fog can often disorient boaters causing them to make a call for help.

Precipitation — And with the formation of clouds comes the higher probability of precipitation. The type of precipitation is formed from the equation of temperature vs. altitude. Precipitation can be expected when cloud cover is extensive and cloud tips are high.

Sea State — The best rule of thumb here is to check NOAA data buoys and then combine that information with the expected winds to determine whether the sea state will increase or moderate.


List of precautions for Hot and Cold weather

It is best to remember that these are just tips to help the outdoorsman plan ahead. It is always best to stay up to date by checking current and future weather at your local marina as well as listening to the U.S. Coast Guard broadcasts for coastal forecasts and storm warnings of interest to the mariner on VHF-FM channel 22A following an initial announcement on VHF-FM channel 16. These forecasts are produced by local National Weather Service Forecast Offices. The Coast Guard VHF network provides near-continuous coverage of coastal Great Lakes. Typical coverage is 20 nautical miles offshore, but can be significantly greater.

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