You have to admit that there is something special about the term ‘Flash Flood’.  Think about it. There are no ‘flash hurricanes’, no  ‘flash tornadoes’, nary one ‘flash earthquake’ that I’ve heard of.  It seems that only floods flash.

Lahar.  Sounds like a word that you’d find in the Klingon dictionary. I’ve lost my copy, but I do have handy the “Encyclopedia of Geological Terms”. 

Lahar:  A dense, fast flowing mixture of water, mud, ash, rock and debris.  Lahars typically form on the steep slopes of volcanoes that experience a sudden influx of water from rapid glacier melt or heavy rain.

“Positively Glacial.”  Does that expression ever come to your mind?  Standing in bank teller lines, it comes to mine.  Waiting for my teenage son to take out the trash, it comes to mine.

Sometimes when visiting out-of-state relatives on holiday I’m asked…

“How can you live in California with all those earthquakes?” 

Usually I smile and joke about getting ocean front property in Arizona.

Not so long ago, I attended a meeting in Maui.  At the reception the barista served a cold rum concoction called “Lava Flow”.  Truth to say I sampled several, however I’m here now to tale about that second kind of lava flow, the hot one.

Last round I blogged about Natural Hazards and the Demise of Civilization. The civilization was the Minoans of 1628 BC. Like the goings-on in the original Star Wars trilogy, that demise happened a long, long time ago in a place far, far away. So long and so far really, that both seem more fairy tale than fact. 

Most of us experience nature’s hazards in fairly benign ways. Perhaps our electricity goes out for a few days in an early snowstorm or we’re forced to detour for a while from our usual road because a bit of it sloughed into a creek during a heavy rain. Sure, on occasion, natural disasters are more serious. Fires and landslides do sweep through neighborhoods. Whole towns do vanish in tornados and hurricanes. Still, most of us witness large-scale disasters only on late night TV or by Google at coffee break.

The vast majority of North Atlantic Tropical Storms originate in North Africa and travel generally westward across the Atlantic gaining strength to do their damaging works in North America.  A sub-class of storms, like 2011’s Rina, are American born.  These start life in the warm waters of the southwest Caribbean and usually drift straightaway to the northwest to about the latitude of Cuba (See the map). From there, these storms can veer  in any direction from west to northeast.

I recently posted a large number of probabilistic wind forecasts for Hurricane Irene. Here are similar predictions for Hurricane Katia - Maximum Sustained Wind expected at 25% probability.

From the statistics of all historical storm tracks and storm strengths,  I have developed a method to forecast wind exceedence probabilities given a current storm position, velocity and maximum sustained wind. 

Here is a recent forecast for Hurricane Irene.  Red lines are potential tracks based on previous storm statistics and current storm parameters. By running many potential tracks, wind exceedence probabilities can be deduced.