When Tropical Storm Philippe first showed up, it looked like it would be a well-behaved system and politely arc north, away from the Caribbean, without much fuss. The weather gods had other things in mind, however.
Philippe juked, serpentined, stalled, threatened to do-si-doed with Tropical Storm Rina, aimed itself at Puerto Rico, and drove forecasters crazy. Any responsible bartender would have cut Philippe off.
The storm finally hung a hard right as if it was off to Iceland. Then it changed course again and started bee-lining to Maine. “It’s been a mess,” said meteorologist and hurricane preparedness expert Craig Setzer of Philippe’s mercurial wanderings.
The forces that allowed the storm to be so erratic include a “flat” atmosphere with no boundaries, a rival storm, as well as the weakening of a steering force that was “chewed up” by all the storms we’ve already seen this season.
Not like the others
The first sign the storm being downright unpredictable came after Philippe arced north, just as it was supposed to do, on Wednesday, Sept. 27. The next day at noon, things went haywire.
Philippe turned hard east, in the direction of Puerto Rico and nearly stopped, moving at just 2 mph, as if it couldn’t decide where to go.
That’s basically because it had nothing telling it where to go. Normally a high pressure system over the Atlantic, known as the Bermuda or Azores High, acts as a boundary and pushes storms west, but it dissipated and equalized with a low to the south.
Setzer explains it this way: “If you think of a mountainside, that slope is the force that steers the storm, and if you knock out the mountain, it’s just flat. So the atmosphere became flat across much of that part of the Atlantic. There was nothing to push it along.”
In that flat environment, without boundaries, Philippe staggered about.
Meandering about
Another factor was Tropical Storm Rina, which followed closely in Philippe’s wake across the Atlantic. At one point it looked as though the two storms might rotate around each other in a do-si-do called the Fujiwhara Effect. “But it didn’t happen – both were too weak,” Setzer said. “To have two storms rotate around each other is very rare. They have to be pretty strong.”
Philippe then pulled a fast one, or rather, a slow one, meandering at a snail’s pace to the southeast, toward St. Lucia, an island so far south in the Caribbean that it rarely gets hurricanes.
But St. Lucia was never in the forecast cone. The National Hurricane Center always thought Philippe would make a very hard turn north and not make landfall.
Instead, Philippe just kind of slid west, as if losing its balance, toward the Leeward Islands of the Caribbean. The storm actually made a surprise landfall on Babura about 6 p.m. Monday, Oct. 2.
That’s because the winds moving the storm west were stronger at low altitudes, near the ocean, than higher up, causing the center to move more quickly to the west while top was lagging behind.
When Philippe started turning north, the top of the storm still lagged behind over the islands. This disorganized lagging inhibits strengthening, “but it spreads out all this sloppy weather,” Setzer said. That’s why there was so much rain in the Caribbean and even when the storm headed north toward Bermuda.
It turns out we’ve had such an active storm season that previous storms took out Philippe guard rails.
“We’ve just had so many storms out in the Atlantic that that normal simple east-to-west steering flow has really been chewed up,” Setzer said. “Think of swiss cheese with holes in it. The blocking ridge has been swiss cheese this year because of all the hurricanes and storms that have been chewing away at it.”
Story by Bill Kearney, South Florida Sun-Sentinel, Distributed by Tribune Content Agency
