“It’s just good to be here, Sir!” …

What an amazing day this past Friday for those of us who live here in Southern California. The daytime high here in our neighborhood was 86’F with winds from the North at 14mph, gust 17. Relative humidity is 13%. It is now 6:40PM and the outside temperature is 82.4 degrees. There was not a cloud to be found in the skies all day. Contrast that with Grand Forks North Dakota it was 37’F and there was a threat of rain. Most of the upper Midwest had cool to cold temperatures and there was plenty of rain to be found around the mid section of the country. It is the transitional time of year with the Sea Surface Temperatures in the western Atlantic and Caribbean along with the Gulf of Mexico downright hot and the fronts from the polar regions diving south…the interaction between the two is often volatile and sometimes deadly.

This is also the time of year when sections of the country (USA) that are typically dominated by light to moderate winds in the Summer get downright windy. If you live in the mid section of the US this can be one of the best times of year to take to the water provided you are appropriately dressed and prepared for the worst.

Water temperatures in lakes in the Northern Hemisphere (particularly far northern latitudes) are dropping fast and you may have gone for a nice swim three weeks ago in your favorite swimming hole but a dip this week may prove to be a chilling experience. The same is true for coastal waters above Cape Hatteras North Carolina and for the entire west coast of the US. The warm summer winds are going away and being replaced by cold, dense air that can have a profoundly different affect on your sailboat! For all of these reasons it is critical that you check the weather charts before taking to the water and know the water temperature for the body of water you will be sailing in and then make the appropriate clothing selections. For coastal regions you can consult the National Buoy Data Center and select your region from the map. The mid Atlantic region map below features hyper links to buoys with a vast amount of data.

Southeast Regional Map

From the NBDC you are able to get the latest marine forecast, current conditions and an archive or recent data by clicking on a buoy link for the area you will be sailing in. It is important to read the synopsis that accompanies the district marine forecast. Understanding the synopsis and forecast discussion will assist you in predicting potential severe weather in your area.

If you are sailing a centerboard boat or non positive righting boat like a multihull or some high performance keelboats it is critical that you be prepared to spend some time in the water in the event of a capsize. Understanding the hypothermic survival charts will help you make better decisions in the event you find you or your crew in cold water. For those of you sailing in water under 70’F knowing the facts about hypothermia is not just a good idea, it may be a life saver. Mustang Survival has a great article and if you’ll take just three minutes and read the article you’ll be much better prepared should you have the unfortunate experience of cold water immersion.

In the last article (Part 2) we discussed frontal passage prediction and how it affects the wind speed and direction. Understand this concept on a micro level will give you a great advantage over your competition if they don’t understand it. For those of you who remember 5th grade math, time was spent on figuring out how long it would take a car traveling at 30 miles per hour to go 75 miles. Figuring this out for most of you is about as simple as math gets. But what if the car is invisible to the naked eye and what if the car is slowing down by a percentage of forward speed each hour as it approaches? How will you find the “car” or in our example the front and how can you determine when the frontal boundary will pass?

The Internet is an amazing resource! Using satellite data, Doppler radar in real time and forecast analysis will help you make these decisions. First you will need to understand what resources are available and which tools will allow you to identify the front.

Visible Satellite loop: When there is pronounced convection along a frontal boundary a 1km or 2km visible satellite loop is a great tool during daylight hours. (Not much there today for SO CAL, but find the loop for your area the next time weather approaches) When trying to identify the frontal passage with a 2km visible satellite loop look for the distinct trailing edge on a frontal boundary. It should be fairly apparent for a sharp front and may be followed by puffy cumulous clouds which indicate cold (also called cotton balls). Gauge the distance between you and the front and the speed at which the front is moving toward your sailing area. If the forecast maps indicate that the front passes through your area and in a period of 12 hours continues on at a static speed then it is a straight time distance equation and you should be able to leverage yourself on the correct side of the shift depending where you are on the course at that time.

In the image below a pacific front approaches the Pacific Northwest.

But what if there is no clearly defined front on the satellite loop or a satellite isn’t available to you or it is night time? Doppler radar can be especially useful for finding a frontal boundary. Two years ago at Key West Race Week on the last day of competition a frontal boundary defined by thunderstorms raced southward during the day. Those who did their homework that day made out big time and were prepared for the necessary sail changes as the front came through. You can learn more about how Doppler works by clicking here.

Dry fronts- On February 3rd , 1986 I got caught single handing off of Malibu California by a strong windstorm. In a span of just thirty minutes I found myself caught in 45 knots winds (up from 10-12 knots) with gusts to 63 at Los Angeles International Airport.

The skies were crystal clear. It was a warm (even by Los Angeles standards) and there was no predicted Santa Ana condition (More on Santa Anas in future Wx editions). The winds started out from the normal direction (200) but as I watched this nasty looking navy blue line of water (wind line) approach the air chilled rapidly and shifted to 300 degrees.

As I learned later a very strong dry front (no clouds) had come through the area and changed my life forever. There were many times during the next two hours that I feared I would not survive the experience. (More on that story in later editions of weather and the modern mariner.) The National Weather Service marine forecast was for 12-18 knots from the west. Seas flat to two feet and a ground swell of eight feet from the west. I took from this experience that I owed a lot more respect to the elements in California than I was giving them having just moved here from Hawaii where air and sea conditions are challenging on a daily basis.

What I learned: I should have done MY OWN HOMEWORK* and checked the satellite water vapor loop and the up stream coastal observations before I set sail.

The water vapor satellite clearly showed a crisp front coming down the coast that could not be seen on the visible or the infrared satellite views. Buoys well up stream (West and Northwest) were reporting strong winds with the passage of this front in the San Francisco and Morro Bay areas six hours previous. The skies were crystal clear and the forecast was manageable. I never go to sea now without doing my homework. My only excuse is that I was 23 and trusted the national weather service forecast. Young, and stupid.

I’ll talk more about predicting severe weather and particularly thunderstorms on the next edition of weather and the modern mariner. As a reminder…don’t trust the public forecast, know what is coming by doing your own homework, file a float plan and always wear your life jacket.
- Mark Michaelsen.

10/24/06