Straight Talk on this Hurricane Season - SailNet Community
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Straight Talk on this Hurricane Season

I've always had a vague distaste for late summer. I suspect this stems in part from a long history of being lassoed and dragged back for a new school year, or maybe it's just the fact that summer is sadly winding down. But in the main, it's because I feel the heart of the hurricane season looming ahead.

The season has been eerily quiet thus far. A barely marginal hurricane (Arlene) wandered up through the central Atlantic in mid-June, but then July slipped by without even a tropical storm or hurricane in the Atlantic basin. There was but one tropical dork, a rather dubious level-two Tropical Depression in the Gulf of Mexico, and that was it. (Probably classified as a TD because the Hurricane Center was bored.) So the bad news is that all the appropriate goodies necessary for storm development are currently in place for an active hurricane season.

Of the world's typhoons and hurricanes, our interest is the storms of the North Atlantic basin, the ones that affect the United States and the adjacent cruising waters. Oh yeah, on rare occasions a southeast Pacific storm can affect Southern California, but our main concern are those spawned in the North Atlantic, Caribbean and Gulf of Mexico.

Much have been written about hurricanes, some of which lays claim to having the straight skinny on hurricane forecasting and avoidance. I'd like to caution that, for the most part, it's all hogwash. Despite years of study and research, there has been very little significant advance in hurricane-forecast techniques and accuracy. Let's get right to the point: There is no source on earth, human or computer, that can indicate with any consistent assurance where these hurricanes will be from day to day during their lifetime--or that they will even develop, for that matter. And the National Hurricane Center would be the first to admit this.

Sure, we know a great deal more about a hurricane's structure, characteristics and presence, and that's due to greatly advanced observational tools offering increased accuracy. The satellite and the brave and dedicated personnel of the hurricane reconnaissance aircraft are the source of this vastly improved data. These two sources along with much improved communications are responsible for the warning systems that have enabled ships to avoid storms that in previous years might not have even been known to exist, and have helped to dramatically lower the loss of life attendant to hurricane landfalls.

But when it comes to longer-range forecasts of hurricane movements, climatology and persistence are as good a set of tools as any model. I have no idea how many tropical-cyclone models are currently being used, but they are numerous, and they rarely agree. A so-called official forecast will use whatever model seems to best fit the current day's prediction. And that's typically a different model for any given day. When the choice of reliable models is reduced to one or two consistent ones, rather than the model du jour, longer-range forecasting will have a foothold. Until then the only way to truly protect a boat from a hurricane is to have it moored in Nebraska. (Where, I hasten to add, it will not be safe from tornadoes. The good news is that tornado forecasts are showing significant advances.)

I have no glib forecast of hurricanes. Tropical cyclones simply do not lend themselves to accurate forecasts. A French curve and a pair of dividers may still be the best forecast tool. The problem is that a tropical cyclone is like an embarrassment to the atmosphere. It's a warm-core low pressure system that rather than being an integrated part of the overall flow pattern, is simply moving along on its own, feeling all the various subtle influences of the larger-scale dynamics around it. It's sort of like projecting the position of a cork floating down river. Basically, it's trying to follow the path of least resistance, dodging here, darting there, in response to weaknesses and soft spots in the overall flow pattern. Satellites help us to understand those weaknesses better, but overall, the data available are not precise enough to build a model to understand the problem very well.

A significant side affect of the unreliability of the forecast is that based on it, a boat can be moved from one place to another, only to have the storm jog a few miles at the last minute, to take dead aim at the new, now not so safe, location. The only good news in this is that the odds of a storm hitting one particular spot during any given year are very low, and also that the catastrophic damage swath of even a major, category 3 to 5 hurricane is relatively narrow.

If the boat is at sea, the odds of taking a direct hit are small, but certainly not zero. And the slower the boat, the more vulnerable it is. About the only thing that can be done is to take a heading that the odds indicate would place the boat in the least likely path. What is that least likely path? There's no foolproof answer but, in general, a hurricane, or tropical storm, in the tropical Atlantic basin will move toward the west to northwest, and ultimately curve more north and northeast in the middle latitudes. As a rule, forecasts are better for faster moving storms and for the larger, better-developed circulations. A small, slow moving, or stalled, center is nothing better than a coin toss.

I've always regarded any tropical cyclone to the south of a boat's position as a threat, regardless. Obviously, this is highly over-simplified as the safest route to take with a storm in the area will greatly depend on your latitude and other considerations. But, holding with that oversimplified approach, the trick is to not be in the storm's immediate right front quadrant. But while dodging, a major problem with a tropical cyclone is the generated sea state. Since the maximum wind circulation is so tight, typically less than 100 miles diameter, the generated wind waves quickly become swells, as the wind direction changes rapidly over them. This rapid direction change of swell and wave can result in huge waves coming at each other, as much as 180 degrees opposed. So, not only are the significant combined seas very large, but with chaotic directions and periods.

In any case, I wouldn't want to be more than two to four days from a bailout land location. The two-day bailout is for birth areas of the Gulf and Caribbean, and four days in the higher latitudes, say north of 30 degrees, where the development and movements of a storm are telegraphed in time to allow reaching that bailout point. However, this is, by no means foolproof either.

The 1938 New England storm went right over my young head, but I don't regard that as meaning that I've paid my dues. I'll be watching each new convective cluster with the same apprehension as everyone else should.

Bob Rice is offline  
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