Two Wild and Crazy Storms
August 29, 2016
I started tracking Hurricane Hermine in late August. She was strange from her very inception. She was the first hurricane to hit Florida since 2005, the same year that Katrina had devastated New Orleans over a decade before.
After she swept across Florida Hermine regained strength in the Gulf of Mexico, whose temperatures were close to an unprecedented Ninety degrees. Then she barreled back across the Florida panhandle and proceeded offshore.
She was exactly what I had been looking for, a hurricane far enough away to not cause very much damage on Plum Island, but strong enough to send long period waves crashing down on the island while her dunegrass was still lush and green. But I also knew I only had about an hour to get photos of the waves breaking over the dunes during the single tidal cycle when all these conditions would coincide with decent daylight.
I knew this because the year before I had turned left as I arrived at North Point Beach and just happened to catch a twenty-foot high wave as it exploded over a well-vegetated dune. I figured this would happen all the way down the beach so had turned back to the right and hustled toward the high dunes at the end of the beach.
But there were no more twenty-foot waves along the entire length of the beach. It took me several days to figure out that the long period waves had been able to sweep into the mouth of the Merrimack River unnoticed because, although they were 20 feet long, long period they were only a few feet high when travelling through deep water.
It was only when they rode up on the back of a sandbar in the river that they had bunched up to become twenty-foot high breakers trailing wispy manes of iridescent spume. The high waves hitting what geologists call a wing bar stood out because the rest of the waves in the deep water of the river were still only a few feet tall.
Having learned those lessons in 2015, I was able to calculate the exact half-hour that I should be able to get similar shots during Hermine in 2016. I was rewarded with a few decent photographs but nothing like that lucky one I had caught the year before.
So I figured I had missed my chance. There probably wouldn’t be any more offshore hurricanes and the tips of the dunegrass were already turning yellow as the end of the summer approached.
But I had actually witnessed the beginning of the 2017 erosion season. The erosion season usually starts when you get an offshore hurricane late in the summer. The storm will act like a boxer throwing a few heavy blows just before the end of the first round of a match.
The blows are intended to soften up the boxer’s opponent for the remaining rounds of the ten round fight. So Hurricane Hermine had done her pugilistic duty by eroding 5 feet off the dune behind the wing bar and about two feet along the rest of the beach.
September 28, 2016
But on September 28th I switched on my computer, clicked over to the National Hurricane Center and was delighted to see a depression sitting off the Lesser Antilles with an 80% chance of developing into a tropical storm.
But my delight soon switched to consternation as I watched the incipient storm increase from a Category 0ne hurricane to a Category Five hurricane in 48 hours. Nobody had ever seen that happen before. I had just witnessed the birth of Hurricane Mathew and now it was a monster packing 150 mph winds.
But, instead of heading north like most well behaved hurricanes, Mathew dipped south to ravage the Venezuela and Columbia coasts with wind, rain and crashing waves. This was the furthest south a North Atlantic hurricane had ever gone before.
Then, after regaining strength from the superheated Caribbean waters Mathew proceeded to pummel Haiti and Jamaica killing well over 800 people, and destroying tens of thousands of shanties and barns along with the cows, pigs, chicken and crops that families needed to survive on the island that was still reeling from the devastating earthquake of 2010.
Meanwhile, meteorologists were going nuts trying to make sense of the swarm of spaghetti models spitting out of their super computers. In the morning the models would show Mathew avoiding Florida but making a direct hit on New England. But in the afternoon they would show Mathew joining up with a northern storm that would hang around for several days ravaging our coasts. But the next morning the models would predict that it was all just a big joke, Mathew was going to move offshore and leave us alone.
But by the evening of October 5th forecasters were truly amazed. The European model, which is generally considered to be the most reliable model because it includes so much data and calculating power, showed Mathew striking Florida than making a giant loop offshore and hitting Florida again!
The National Hurricane Center explained the totally unprecedented occurrence in their staid, rather bureaucratic language. But Penn State Meteorology professor Bill Ryan explained it with far greater eloquence.
“What they were really trying to say was that the euro model run had just gone batshit. It had Mathew going offshore in GA then making a big loop out to sea and back again and on up the East Coast.”
“Generally in situations like that, you would just ignore the run and stick with your previous forecast while waiting to see whether that model would return to the consensus, or if it would stay the same and the other models would trend toward it.”
That was exactly what happened. On the 11PM run the Euro track traced a perfect loop de loop just offshore. It looked like an April Fool’s joke but there it was, and forecasters had to take it seriously because millions of people’s lives and homes depended on their accuracy.
The next morning the Euro model had Mathew co-joining with nearby Hurricane Nichole to make a super storm marriage that would devastate Florida and possibly still go on to hit New England. I shut down my computer and went outside to bring in our outdoor furniture.
By now everyone knows that Mathew was one of the most destructive hurricanes to ever hit the Southeast Coast. Although it only killed 10 people, it caused billions of dollars in property damage, and only delivered slightly elevated waves to Plum Island.
A Cautionary Tale?
Of course, initially everyone thought Mathew would prove to be a cautionary tale about relying too heavily on such models. The further away from the storm you got the less accurate the models were. In fact at one point the models had Mathew approaching Cape Cod then suddenly jogging off to the East. But that jog wasn’t the real track. It just showed where the consensus line jumped from a less reliable model to more reliable one.
The European model was the main point of concern. For years it had been considered the most reliable of the 13 models used, but in recent years it seemed to have lost its edge. Some people blamed the abundance of superheated waters caused by global warming and El Nino, others suggested that the new climatological conditions had altered the underlying physics that the model was based on.
It is always important to remember that any model is just a simplification of nature. They try to separate out the most important factors that drive a system while subtracting the noise.
In the end, of course, Euro got it mostly right. Mathew didn’t end up marrying Nichole but he did perform a partial loop de loop before giving up the ghost. A human forecaster would never have come up with such a fanciful forecast for fear of being booted out of America’s Apocryphal Meteorology Club and being laughed at by his peers.
But so far, computers haven’t been programmed to be embarrassed. They just do their calculations like the brightest student in the class confident in their superior abilities. Of course I shouldn’t say that. It would be anthropomorphizing computers. And they hate that sort of thing.
William Sargent’s latest book, Plum Island; 4,000 Years on a Barrier Beach, is available in local bookstores and at http://www.ingramcontent.com.