Changes to the forecast track of forecast-to-be Hurricane Henri are nerve-wracking for the eastern end of Long Island, New York, and especially southeast New England. Computer model forecasts have increasingly shown Henri coming over or close to land, and the National Hurricane Center has followed suit by edging their forecast closer to the Northeast coast.
A dance between two high pressure systems and soon-to-be Hurricane Henri are in play. Storms normally track around the western (left-hand) nose of the big high-pressure system that sits over the Atlantic every summer. When the nose is out in the ocean, the storms travel north and then arc over the North Atlantic. When the nose is over the eastern U.S., the storms go over Florida or through the Caribbean and then turn north around the end of the Atlantic high.
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In the case of Henri, the forecast position of the nose has been edging closer to the East Coast. Henri is currently drifting west, but will soon start to turn north.
Secondly, there is another high-pressure system over eastern Canada. Many computer model forecasts have been building a nose on the east end of that high which partially blocks Henri from rounding the turn and heading out to sea. In the computer simulations, the hurricane comes near or over southeastern New England and drifts around, until the block goes away. The impact on New England is extended because the storm is blocked from making progress.
If something like that plays out, Henri would likely be weakening at that time. The ocean water is too cool to sustain a hurricane. But the details of how it would play out are fuzzy.
The rule applies that forecasts of disorganized or just-developing storms have larger-than-normal errors and are subject to change until the storm consolidates. This means that all reasonable scenarios have to be acknowledged.
NOAA and the National Weather Service will deploy all their resources today to carefully measure the atmosphere around and to the north of Henri. They want to be sure the computer forecast models start with as accurate a representation of the weather systems that could affect the storm’s track as possible. We’ll see if the additional information changes the details of the forecast.
It’s an unusual setup to say the least, but not unheard of. Recall that a big block – much stronger than this one – deflected Hurricane Sandy back toward the coast of New Jersey and New York.
Sandy was a giant storm – 1,000 miles across. This is nothing like that, so the storms don’t compare. But the possible blocking scenario is a bit reminiscent. The point is, it’s not impossible.
At this point, residents and visitors on the eastern half of Long Island, along Long Island Sound, and up the New England coast need to stay informed about the latest forecasts and what local officials are ordering. Action might have to be taken as early as tomorrow if it appears dangerous conditions will impact vulnerable coastal sections over the weekend.
This is a particularly complex and difficult scenario because so many people plan their vacation in August at the beaches in the Northeast, which is often a long way from home. Getting everyone to safety would be a daunting challenge. Let’s hope the worst-case scenario of a direct hurricane hit doesn’t happen. We just can’t be sure yet.
The remnants of Fred are still spreading rain across interior sections of the Northeast and New England. Henri might bring rain to some of the same areas of Northern New England.
In the Caribbean, Hurricane Grace made landfall overnight at Tulum, just south of Cozumel, Mexico. Winds were estimated at 80 mph at landfall. The storm is moving over the Yucatán Peninsula and will likely be weaker when it emerges back over the southwestern Gulf of Mexico.
A Hurricane Watch has been issued north of Veracruz on the Mexican coast. Grace is forecast to re-intensify over the Gulf. A Category 1 storm is predicted. There is limited time for it to strengthen too much, and the environment for now is not very moist.
Out in the Atlantic, a large disturbance is moving off Africa, but it’s not forecast to develop very much with all the dust around it. Computer forecast models dissipate it or turn it north into the middle of the Atlantic.
Nothing else seems to be in the pipeline right away.