Rock You Like the Hurricane
By Mike Bennighof, Ph.D.
April 2017

Even in our era of advanced technology, a hurricane is such a powerful natural force that it can destroy a great city and turn tens of thousand of citizens from the world's most powerful nation into refugees. In the days before weather satellites, and even more so in the days before aircraft reconnaissance, hurricanes only became known when a ship encountered them and radioed the information. And of course in the days before radio, coastal inhabitants figured out that a hurricane was coming when the skies got really, really dark.

A tropical storm has winds from 39 to 74 miles per hour, strong enough to knock down some trees but nowhere near as destructive as a true hurricane. Hurricane intensity is measured on the Saffir-Simpson Scale, which rates them in increasing power from Category One through Category Five. A Category One hurricane has winds from 74 to 95 miles per hour, and can do some minor damage to flimsy structures. At Category Two, winds rise from 96 to 110 miles per hour and small craft are in danger. Category Three, at 111 to 130 miles per hour, is a "serious hurricane" that can damage small buildings and cause widespread flooding. A Category Four hurricane has winds of 131 to 155 miles per hour, and causes not only flooding but large-scale beach erosion. At Category Five, winds are 156 miles per hour or more, and buildings can be completely scoured away. The destructive power of a hurricane increases exponentially; a Category Two storm is four times as harmful as a Category One, and a Category Five strikes with 25 times the force.

	Hurricane Isabel very nearly put Avalanche Press out of business in 2003.

Usually more destructive than a hurricane's winds is the "storm surge" — estimates put the number of deaths caused by flooding, rather than wind damage, at over 90 percent of the toll. In a storm surge, the hurricane's wind force and low pressure combine to pile up water on the ocean surface (and in some cases, on lake surfaces). The surge can be massive — in 2005, Pass Christian, Mississippi, was hit by a record surge of over 27 feet from Hurricane Katrina.

During the period covered by our Great War at Sea games, several devastating hurricanes struck the area depicted on the map in U.S. Navy Plan Gold. In September 1900, the "Galveston Hurricane" struck the Texas port as a Category Four storm with a massive storm surge. Anywhere between 6,000 and 12,000 people were killed and the city destroyed; it has never regained its former commercial importance.

In September 1919, the "Atlantic Gulf Hurricane" was at Category Four when it passed over Key West and Category Three when it flooded Corpus Christi, Texas, and killed several hundred people. During its passage over the Gulf of Mexico the storm sank 10 ships and killed at least 500 people on board them.

The "Great Miami Hurricane" of 1926 devastated the city, killing at least 800 people with its Category Four winds and massive storm surges at Miami Beach and also on Lake Okeechobee, where a surge destroyed the town of Moore Haven. Many people died when they left their shelters as the hurricane's eye passed over Miami, and were caught in the open when the high winds resumed.

Two years later the lake saw another killer surge, as the "San Felipe-Okeechobee Hurricane" sent a 9-foot wall of water across lakeside communities and killed close to 2,000 people. A Category Five storm hit Key West on Labor Day 1935, the most intense hurricane ever to strike the United States. Over 400 people were killed, mostly laborers caught in the open while building a railroad along the Florida Keys.

Hurricane Katrina reached Category Five while over the Gulf of Mexico, but weakened as it reached shallower water and was "only" a Category Three storm when it destroyed most of New Orleans in 2005. Weakened levees and breathtaking governmental incompetence were far deadlier in that case than the storm's winds. Two years later, the city's population stood at 60 percent of its pre-storm total, with a significantly lower proportion of black and poor residents. But the Louisiana Superdome re-opened in September 2006, at a cost of $193 million.

Navy pilot Lt. Matt Udkow was re-assigned to oversee a pet kennel after answering a Coast Guard plea to rescue 110 New Orleans residents.

Hurricanes depend on the force of the Earth's rotation to give them their spin — they can't form within five degrees of the equator. But they do require warm water (at least 79 degrees Fahrenheit/26 degrees Celsius) and high humidity to give them their energy, so there's only a narrow band where they can form — far enough north for the coriolis force to have its spinning effect, far enough south for warm waters. Those that strike the Caribbean and Gulf of Mexico usually form in the Atlantic, often when thunderstorms drift offshore from Africa to provide the initial disturbance known as a "tropical wave." Prevailing easterly winds — there are no "weather fronts" this far south — then can move a growing storm across the Atlantic.

They are not particularly dangerous to ships at sea in the modern era. With the aid of satellite imagery and a very professional hurricane spotting and prediction system, a modern vessel can easily outrun a hurricane. Standard practice is to send ships to sea to ride out hurricanes rather than await them in port. In the pre-satellite era they were dangerous, and before radio absolutely deadly. Large warships are vulnerable to damage but unlikely to sink except in very powerful storms; small ones are at great risk and aircraft and airships of the 1920s easily swatted from the skies.

Weather is an important component of Great War at Sea games, but usually weather conditions are uniform across the entire map. In most regions, that's a valid model, particularly since players should not have knowledge of unique local conditions and the weather rules reflect this.

Hurricanes, as self-contained weather systems, don't really fit into this model. Weather conditions can be very good only a few dozen miles from the eye of a small, intense hurricane (a hurricane's physical size doesn't necessarily relate to the intensity of its winds). With these new rules, hurricanes are devastating in the areas they strike, but have no impact on weather elsewhere. Use them for all scenarios taking place on the Plan Gold or Remember the Maine maps.

In scenarios taking place in June through November, use the alternative weather table below:

Die-roll ............................ Result
1 ....................................... Decrease weather condition by one level
2-5 .................................... No change
6 ....................................... Increase weather condition by one level

In scenarios taking place in June through November, the Allied player rolls two dice at the end of the Weather Phase (in addition to the above die roll to determine weather conditions). On a result of 12, one tropical depression appears. If that happens, roll a second die. On a result of 1, place the tropical depression marker in zone T 61, on a result of 12, place it in zone U 61, on a result of 3, place it in zone V 61, on a result of 4, place it in zone W 61, on a result of 5, place it in zone X 61, and on a result of 6 place it in zone Y 61.

Do not roll for hurricane appearance if a hurricane has appeared within the past 18 turns. It is possible for multiple hurricane markers to be present on the map at once.

Hurricanes come in seven increasing strengths: Tropical Depression, Tropical Storm, Category One Hurricane, Category Two Hurricane, Category Three Hurricane, Category Four Hurricane and Category Five Hurricane. They always start as a Tropical Depression, and the markers for all strengths of hurricanes are referred to hereafter as “hurricane markers” (including Tropical Depression and Tropical Storm markers).

At the end of the Weather Phase, the Allied player rolls one die for each hurricane marker to see if it moves. Roll for each hurricane marker separately. On a result of 1, the hurricane marker moves one zone to the southwest. On a result of 2 or 3, it moves one zone directly west. On a result of 4 or 5, it moves one zone to the northwest. On a result of 6, roll the die again. On a second result of 1 through 4 it does not move, and on a second result of 5 or 6 it moves one zone to the northeast.

After determining whether each hurricane marker moves, the Allied player rolls another die to see if it strengthens. Roll for each hurricane marker separately. On a result of 6, replace the hurricane marker with another showing the next greatest strength. On a result of 1, replace the hurricane marker with that showing the next lower strength. On a result of 1 for a Tropical Depression marker, it breaks up and is removed from play. On a result of 6 for a Category Five hurricane marker, there is no effect. Add one to the result if the hurricane marker is at least three zones from any land (not counting islands that only exist in a single zone). Subtract one from the result if the hurricane is in or adjacent to a North or South American coastal zone. Subtract two from the result if the hurricane is in a zone in or south of Row AG.

Hurricane Zone: Each hurricane marker’s effects apply to the sea zone it occupies and all sea zones within three zones of it, except as noted below. This area within three sea zones of a hurricane marker is called a “hurricane zone.” Sea zones containing both land and sea which are within a hurricane zone are affected the same as all-sea zones, except as noted below.

Tropical Depression: All sea zones within a Tropical Depression marker’s hurricane zone are affected by Storm weather conditions (11.73), regardless of the weather condition on the rest of the map. The exception is if the weather condition on the rest of the map is Gale. In that case, the Gale conditions apply within the Tropical Depression marker’s hurricane zone normally.

Tropical Storm: All sea zones within a Tropical Storm marker’s hurricane zone are affected by Gale weather conditions (11.73), regardless of the weather condition on the rest of the map.

Category One: All sea zones within a Category One marker’s hurricane zone are affected by Gale weather conditions (11.73), regardless of the weather condition on the rest of the map. All airships and other aircraft within the hurricane zone are immediately eliminated — whether in the air or at a base. Contact die-rolls (5.4) are not allowed. Double the time required to refuel (12.3) ships and airships at minor ports that have been anywhere within a Category One hurricane zone at any time during the game. Also, at the end of each Move Fleets Phase, roll one die for each ship that was in the same sea zone with a Category One hurricane marker (the marker itself, not its hurricane zone) at any time during the phase. Subtract three from the result if the fleet was at sea during all or part of the phase; subtract four from the result if the fleet was in port during the entire phase. The ship immediately suffers a number of Hull hits equal to the modified die-roll result (treat a modified result of zero or less as 1 Hull hit). Any ships that take hull damage in this way but do not sink have their speed reduced by one level for the rest of the game (8.51). This speed loss can be repaired normally (11.27).

Category Two: All Category One effects apply, except that doubling of refueling time applies to both major and minor ports, and the die-roll modifier for hull damage to ships is -2 (-3 if the ship was in port for the entire Move Fleets phase). Also add two to the foundering die-roll (8.52) for any ship that was in a Category Two hurricane zone at any time during the turn. In addition, if a Category Two hurricane marker enters any sea zone containing or adjacent to any minor port, that port may not be used by any ships, airships or aircraft for the rest of the game.

Category Three: All Category Two effects apply, except that the die-roll modifier for hull damage to ships is -1 (-2 if the ship was in port for the entire Move Fleets phase), and the foundering die-roll modifier is +3. In addition, if a Category Three hurricane marker enters any sea zone containing or adjacent to any major or minor port, that port may not be used by any ships, airships or aircraft for the rest of the game.

Category Four: All Category Three effects apply, except that there is no die-roll modifier on the roll for hull damage to ships at sea (modify the die-roll by -1 if the ship was in port for the entire Move Fleets Phase). The foundering die-roll modifier is +4.

Category Five: All Category Four effects apply, except that the die-roll modifier for hull damage to ships at sea is +2 (do not add any die-roll modifier if the ship was in port for the entire Move Fleets Phase). The foundering die-roll modifier is +5.

Conduct weather die rolls and apply weather effects to the rest of the map as usual — a hurricane's presence has no effect on weather elsewhere.

You can download the hurricane markers here.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.