Hispaniola No Longer on Dorian's Forecasted Track to Florida
As of 8 a.m. Wednesday, Aug. 28.

As of 8 a.m. Wednesday, Aug. 28.

The premise of this analysis was that Tropical Storm Dorian might be the storm that tested a famous hurricane hole on Hispaniola. But once again, as predicted by weather forecaster Chris Parker, this was not to happen.

Hispaniola had been dead center on Dorian's forecasted track. 

The track 28 hours ago.

The track 28 hours ago.

Hispaniola is big and mountainous and contains two nations, Haiti and the Dominican Republic. The latter has a famous hurricane hole called Luperon Harbor, shown at the top of the page. The question was: If Dorian becomes a hurricane and if it stays on track, would the storm confirm or confound that reputation? The Hurricane Center graphics strongly suggest that the question is now academic, but you might learn something from the analysis anyway.

Geography has made Luperon a great hurricane hole for several reasons—some obvious and some not. A narrow entrance opens into two basins, both of which are surrounded by hills and have deep sticky muck for holding. But it has a climatological advantage as well. The best shelter in the world isn’t much good if the location itself is a hurricane magnet. The opposite is demonstrably true in the case of Luperon, which has not had a direct hit since hurricane tracking began in 1851.

The white dots in the upper of the two bays are boats waiting out hurricane season. This aerial of Luperon Harbor was taken in early July.

The white dots in the upper of the two bays are boats waiting out hurricane season. This aerial of Luperon Harbor was taken in early July.

Irma came close in September, passing 50 miles north of Luperon as a Category 5. Neither Irma nor Hurricane Maria did much harm to Luperon, which as usual provided refuge for dozens of foreign cruising vessels as well as native commercial craft from across the D.R.’s North Coast and the Turks & Caicos. The latecomers ran lines from their bows into the dense mangroves that surround the harbor and finished the job with stern anchors. Mangroves are another feature that make a hurricane hole great by providing something flexible and forgiving should a vessel be blown ashore. They are surely better than concrete bulkheads and pilings.

My main man for weather, especially throughout the Bahamas and Caribbean, is weather router Chris Parker of the Marine Weather Center. Parker likes Luperon as a hurricane hole because of two overarching factors: Hurricanes at this latitude tend to move from east to west, and Luperon Harbor has its back to a mountain range called the Cordillera Septentrional. Parker explains the science behind his thinking: 

Prudent mariners know the right-front-quadrant (relative to its forward motion) of a hurricane is typically the most dangerous part. In the right-front-quadrant, not only do winds blow toward the path of the hurricane, but strength of wind increases by the forward speed of the hurricane, and we typically find about 90 percent of tornadoes and waterspouts and most destructive microbursts in this quadrant.

Conversely, left-quadrant (relative to its forward motion) of a hurricane is its "navigable semicircle". In the left-quadrant, wind blows away from the path of the hurricane, we subtract two times its forward speed from the "max sustained wind" (usually found in the right-front-quadrant), and we typically see fewer severe weather events. Let's illustrate the difference in wind speed due simply to storm motion.

Let's examine a stationary Category 2 hurricane with 90 knot sustained winds. Now put the hurricane in motion at 10 knots of forward speed. The moving hurricane will support 100 knots (Category 3) winds in its right-front-quadrant, but only 80 knots (Category 1) winds in its left-front-quadrant. In addition, although hurricane structure varies, with most west-moving hurricanes along he latitude of the Northern Caribbean, the bulk of inbound tropical moisture feeds from the south into the right-front-quadrant while air feeding into the left-front-quadrant is pulled from the north (less-moist mid-latitudes).

No location in the western North Atlantic is completely safe from hurricanes, but if we were looking for a relatively safe spot, it would lie on the north coast of a large, mountainous landmass. Almost all hurricanes move in a general westerly direction during most of their time in the tropics. Later they turn north, then northeast or east-northeast. There are exceptions, but this is the usual pattern. If a west-moving hurricane passes along or just north of the north coast of our large mountainous landmass, then harbors along the north coast will experience the less-strong south side (left-front-quadrant) of the hurricane.

If a west-moving hurricane passes over our large mountainous landmass, dry air and tall mountains disrupt the hurricane's structure causing rapid weakening of the entire system. If a west-moving hurricane passes south of our large mountainous landmass, then it is so far from the north coast that conditions on the north coast are mild.

Where can we find a protected harbor along the north coast of a large mountainous landmass? Luperon is one excellent example: In order for a west-or northwest-moving hurricane to affect Luperon, it would pass over 100-200 miles of the mountainous Dominican Republic, including several 10,000-foot-plus peaks located south of Luperon. This would severely weaken the hurricane, minimizing damage in Luperon.

The North Coast of Cuba enjoys a similar topographical advantage, and there is a harbor very similar to Luperon called Puerto Vita, which benefits from the same overall tracking patterns and topography.

These are all the storm tracks in the Southwest North Atlantic since tracking began in 1851. Luperon is dead center of the circled area in the top image. No hurricanes have hit Luperon since tracking began. The few direct hits have all been tropical storms, which are represented by green lines.

These are all the storm tracks in the Southwest North Atlantic since tracking began in 1851. Luperon is dead center of the circled area in the top image. No hurricanes have hit Luperon since tracking began. The few direct hits have all been tropical storms, which are represented by green lines.

Boat Station San Juan personnel pull their Coast Guard 45-foot Response Boat Medium out of the water as part of storm avoidance preparations at Coast Guard Base San Juan Aug. 27 2019 in anticipation to Tropical Storm Dorian's approach to Puerto Rico.

Boat Station San Juan personnel pull their Coast Guard 45-foot Response Boat Medium out of the water as part of storm avoidance preparations at Coast Guard Base San Juan Aug. 27 2019 in anticipation to Tropical Storm Dorian's approach to Puerto Rico.

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