“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.

Weather and the Modern Mariner-THUNDERSTORMS

by Mark Michaelsen

Photo courtesy of www.FredMiranda.com

This edition will focus on the severe weather phenomenon known as thunderstorms. I grew up much of my life in the Piedmont of North Carolina which believe it or not is one of the HOT SPOTS for thunderstorms in the US. My incredibly understanding parents recognized early on that I had a passion for sever weather and allowed me to go out into our front yard and get down in the three foot deep ditch and watch as the storms approached like clockwork from the West each late spring and summer day. As the rumble grew louder and the sky rapidly blackened the once absolutely still pine trees began to move with the approaching wind. First up top with just a wiggle in the branches and within minutes a screaming wail and the occasional loud "POP" as a branch or two succumbed the torrent of wind and rain my heart felt like it was going to leap from my chest. As the bolts of lightning selected their random targets my survival intuition quickly began to count the seconds between lightning strokes and the sometimes wrenching "CRACK and then THUD" as the air rapidly expanded around the bolt and created what we perceive as thunder...You knew you probably shouldn't be outside but the smell of the air as it becomes supercharged with static is intoxicating. That fresh odor of rain just before the torrent hits still makes my hair stand on end with anticipation every time I am back east and get to enjoy one of natures most spectacular  displays...The THUNDERSTORM

     Why is there “weather” in the first place? The root of all “weather” is the sun and its interaction with our planet’s atmosphere and surface layers. The heating of the sun is uneven  throughout our planet as there are distinct differences in the sun’s angle of attack to areas of the planet, differences in surface topography and physical make up, and the simply fact that ½ of the planet is in daylight while the ½ half is receiving little or no energy at night. The differences in heating leads to differences in pressure and this leads to what we perceive as wind. From this point forward I want you to think of air the same way you think of water from a fluid dynamics standpoint. Air will always seek to equalize itself and “pool” with the air flowing down from high points and settling in low points. High pressure in the atmosphere simply represents a mountain of air and the Low pressure systems represent valleys. This seems simple enough but now we will introduce the effect known a “coriolis” and it is important to the mariner because it is what allows what would otherwise be a grouping of intense but generally benign thunderstorms to become an organized spinning area of low pressure known as a tropical cyclone or “Hurricane” or “typhoon”.