Little Compass RoseCaribbean Compass   June 2015

WHAT'S ON MY MIND

Windwards During Hurricane Season?
Thoughts for Cruisers Planning to Remain

by The Scottish Captain

Cruisers who wish to stay in the Windward Islands (Martinique to Grenada) during the hurricane season will all have thought about what to do in case of a hurricane. There is a lot of advice around, and that advice can be confusing as inevitably it changes, as each passing disaster prompts new lessons learned. So, how to come up with a best strategy for you and your boat? I’m afraid there is no easy answer, and after you’ve done all your research and come up with your plan, you will still have to hope luck is on your side.
When Hurricane Ivan devastated Grenada in 2004, I had already sailed back to the UK aboard a yacht that had been docked the previous year in Secret Harbour on the island’s south coast. What would I have done if I had still been in Grenada, following the advisories on the approach of Ivan? I like to think that I would have sailed south, but would I have foreseen the continued westward progress of the storm, or have been fooled by the predictions of it heading a bit further north?

In his article “Reflections on Hugo” (available at www.street-iolaire.com), Don Street shared the old adage: “All general statements are suspect, including the statement that ‘All general statements are suspect’.” This is worth repeating when discussing hurricane plans.
In reply to the comment “Never go to sea to dodge a hurricane”, Don observed, “I feel that that is far too general a statement. In ‘Reflections on Hugo’ I made a very good case for going to sea to avoid hurricanes; but that was too broad a general statement. I still feel that statement (that there is a good case for going to sea to avoid a hurricane) is true — but only if you are absolutely certain that the hurricane is going to pass through St. Lucia or islands to the north of St. Lucia. In that case you have plenty of sea room to get underneath the hurricane. If you leave at least 48 hours before the hurricane approaches, you can get below the hurricane. You have enough sea room, so much that all you should experience is a 40- or 50-knot blow. With winds from the north right up the tail under a shortened sail, a good boat with a good crew should not have any serious problems.”
He adds, “If you are going to go to sea to dodge a hurricane, you cannot dilly dally, you must stick to your plans, and get as far south of the hurricane as fast as you can. If the wind is light, then motorsail: as the wind builds, start shortening sail, well in advance of the onset of heavy weather.”

So there are circumstances when going to sea makes sense, but only in certain locations, and when following certain rules. Do not confuse “going to sea to dodge a hurricane” with “going to sea to ride out a storm”, which is NEVER a good idea! (Unless…of course…?!)
Which brings us to a discussion of “Street’s Law of Probability” for hurricanes (you’ve already read Don Street’s “Learning from the Ghosts of Hurricanes Past” in last month’s Compass, and should look for his articles “Hurricane Strategies for Those Afloat” in the July 2006 issue, and “You Can Cruise During Hurricane Season” at www.caribbeancompass.com/online/june09compass_online.pdf, page 24). Basically he states that using NOAA advisories you can use a Cone of Probability to guide your plan of action when faced with the formation and approach of a classic Cape Verde storm. This is so because these storms virtually never change direction more than five degrees in 24 hours. By plotting the reported position of the storm on a suitable chart (such as IMRAY 100) when it is still days away, and using the direction of movement to plot a ten-degree cone extending forwards from this position, you can determine what you should be doing.

You want your location to be at least 60 miles south of the southern edge of this cone. If you are anywhere north of this position, you should head south, monitoring updates, until you comply.
I don’t know if this system is still in favour, but it does have merit under certain circumstances, and when applied in a timely and consistent manner. The major problem with it is determining when a developing system warrants evacuation, and how early to respond. It will also fail to address unusual storms (such as Hurricane Tomas, see below) that develop late and leave little time for anything but battening down the hatches.

I wanted to check its effectiveness, so looked back at Hurricane Ivan’s advisories. I was impressed that even though Ivan developed and stayed very far south, if I had been in Grenada monitoring its progress and was prepared to evacuate according to “Street’s Law of Probability”, I would have avoided the storm and would not have been in Grenada.
NOAA Advisory #12 on September 5th, 2004 at 1500GMT was the second advisory that categorized Ivan as a hurricane, with sustained winds of 75 knots. The centre at that time was located about 900 nautical miles out in the Atlantic at 9.90N and 46.00W. The reported direction of the storm was towards the west, or 280 degrees, at 18 knots. If Hurricane Ivan continued westwards with this course and speed, it was set to pass just south of Grenada in 50 hours. The ten-degree Cone of Probability extended from Bequia right down to Trinidad.
So, if you had still been located in the Grenadines or Grenada on the morning of September 5th, and were assessing your hurricane avoidance plan, it should have been apparent that to comply with the recommendation to get south of the storm, and 60 nautical miles south of the ten-degree Cone of Probability, the only safe option was to run south to one of the recommended ports in Venezuela: Golfo de Cariaco or Puerto La Cruz. From Grenada to the Golfo de Cariaco is about 200 nautical miles, and from Bequia to the Golfo de Cariaco is about 250 nautical miles, or at six knots about 34 hours and 42 hours away respectively. In all likelihood, if you had been on your game and thinking conservatively, you would have left sooner. But either way, you could have been tied up somewhere secure, and more than 60 miles south of the bottom edge of the cone, in time to ride out the fringe of the storm.
The problem comes if you had been in, say, St. Lucia or Martinique. If you left early enough, you could still have made it south to Venezuela in time — but would you really have sailed south when the storm was so far south and still heading west? If your mind had told you not to go, and you had stayed in St. Lucia, what would have been your plan later if it had started to turn progressively northwestwards, when your bridges had been burned?

Similarly, how should you respond to a tropical wave, depression or storm that is not forecast to develop, but might possibly defy the forecasters and do so? Do you always run south, or do you use your judgment; do you wait and see, and then go, or do you…?  I can’t imagine that constantly taking early and lengthy evasive action, when it subsequently proves unnecessary, will endear a believer to blind adherence to this law.
On the afternoon of October 28th, 2010 the National Hurricane Center in Miami issued the following observation:
SYNOPSIS FOR CARIBBEAN SEA AND TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W 
530 PM EDT THU OCT 28 2010
SYNOPSIS...TROPICAL WAVE WILL REACH THE TROPICAL N ATLC FRI AND
WILL MOVE ACROSS THE EASTERN CARIBBEAN SAT AND SUN AND INTO THE
CENTRAL CARIBBEAN MON AND TUE ACCOMPANIED BY FRESH E TO SE WINDS.
Just 24 hours later, the NHC’s release read as follows:
SYNOPSIS FOR CARIBBEAN SEA AND TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W 
530 PM EDT FRI OCT 29 2010
SYNOPSIS...TROPICAL STORM 11.1N 57.5W AT 2100 UTC PRES 998 MB
MOVING W 15 KT WILL MOVE TO 12.9N 61.8W SAT AND TO 13.5N 64.0W
SAT NIGHT TO 14.1N 66.2W SUN AND STRENGTHEN TO A HURRICANE AND
NEAR 14.8N 70.4W MON AND INTO THE CENTRAL CARIBBEAN TUE AND WED.

So, the forecast winds went from Force 5 to Force 12 in the course of one day! This amazing development was the sudden birth of what became Hurricane Tomas, which caught St. Lucia and St. Vincent by surprise. The first public advisory from NOAA was issued that same afternoon, which meant that it was basically too late to start contemplating any evasive action. In fact, there was an interesting account in the Compass of the experience of a catamaran owner who did put to sea from Bequia to ride out the storm for insurance reasons, and quickly found himself riding out a hurricane (Caribbean Compass, January 2011, “Riding out Hurricane Tomas” by Bernard Logan, at www.caribbeancompass.com/online/january11compass_online.pdf, page 22). It is difficult to envisage any formula that could effectively cope with such rapid, unforeseen development such as we witnessed with Tomas.

On the other hand, another case in point that supports the use of the Cone of Probability was Hurricane Dean of 2007. Let’s look at the 03:00GMT NOAA Advisory #11 of August 16th, 2007 for what was then Tropical Storm Dean. It was located about 630 nautical miles east of St. Vincent with sustained winds of 60 knots, gusting to 75 knots. It was moving westwards, or 280 degrees, at 20 knots. The Cone of Probability stretched from Martinique to Bequia. So if you had been on the alert and ready to leave Rodney Bay Marina, you would have had about 30 hours to get down to Grenada and be safely tied up before Dean made landfall (and if you had been checking updates regularly you could have shortened your passage south and stopped in, say, Carriacou or Union).

Hurricane Dean passed through the channel between St. Lucia and Martinique on the morning of August 17th, as a Category 1 storm. The northern eyewall, accompanied by sustained winds of about 85 knots, passed directly over Martinique. Winds in St. Lucia peaked at about 70 knots. And then an astonishing and largely unpredicted transformation occurred:
“With upper-level outflow increasing in all quadrants, Dean then began to strengthen rapidly in the eastern Caribbean Sea, its winds increasing from 80 to 145 knots (Category 1 to Category 5 on the Saffir-Simpson Hurricane Scale) in the 24 hour ending at 0600 UTC 18 August. At 1200 UTC that day, Dean’s minimum central pressure was 923 mb.”
So even though, as it happened, Rodney Bay Marina was secure enough, and if you hadn’t gone south you should have been fine there, if the extreme intensification had occurred earlier, and a Category 5 hurricane had developed before the system’s passage through the channel, the story would have been very different, and the dash south would have been very much worth the effort.
Perhaps a general statement worth hazarding here is to first make one version of your preparation plan based solely on the actual conditions reported in the NOAA advisories, rather than based on any forecast or forecast track. So you assume the continued forward movement of the storm will be on its current track (plus or minus 5 degrees). You also assume that the storm will develop progressively (the farther away, the more potential for development), disregarding any forecaster’s predictions that conditions are not favourable for intensification.

With this plan composed, you can then start assessing forecasts and track models, and weigh up your options accordingly.
It is by studying as many past accounts and experiences as you can that you can really build up a realistic preparation plan. You could do worse than to read D. Randy West’s offering, The Hurricane Book, a Sailing Captain’s Memoirs, which recounts his experiences living through 18 (!) storms on land and sea. Also read At the Mercy of the Sea, the True Story of three sailors in a Caribbean Hurricane, by John Kretschmer, which will remind you that if you encounter a rare event like “wrong-way Lenny” or Hurricane Klaus, which approached the islands from the west, all your calculations about navigable and dangerous semi-circles in a tropical revolving storm, and where you should be heading, have to be reoriented.

But unfortunately, by being in a region prone to hurricanes, there will always be an element of risk that no amount of preparation and knowledge can eliminate completely. It is a personal matter how best to minimize the risk and how much just to trust to luck. The number of local boats operating in the islands year-round is testimony to the fact that most owners have been fortunate enough to have missed that big one. You can watch footage on YouTube of hurricane-strength winds in Marigot Bay, St. Lucia causing little damage during Tomas, as it passed south of the island, and cite the passage of Dean north of the island without wrecking the fleet in Rodney Bay, as evidence that you can weather a storm in a “hurricane hole”. And so you can. But there are storms and storms. So remember that other old adage, particularly in this year when the forecasters are predicting a below-average year for major storms: “It only takes one.”


     

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