A storm developing in the Caribbean could pose a danger to the United States

A storm developing in the Caribbean could pose a danger to the United States

After a quiet start to hurricane season, the Atlantic has woken up and is full of storms and systems to watch out for – and at least one could pose a serious danger to the United States.

Great concern exists over an accumulation of showers in northern Venezuela dubbed “Invest 98L”, which crossed the Windward Islands with gusty winds and squalls of rain. This one will remain tamed until the weekend, when it’s about to move into an atmospheric powder keg environment.

Next week it could enter the Gulf of Mexico, although its exact path is still uncertain. Assuming it turns into at least one tropical storm, it will be called Hermine. The National Hurricane Center gives it a 90% chance of doing it.

For now, anyone residing along the Gulf Coast and Florida should pay close attention as the forecast is changing in the coming days.

Fiona will hit parts of Canada as the region’s strongest storm on record

So far, it’s poorly organized. The reason it doesn’t do much yet is because of disruptive shear, or a change in wind speed and/or direction with height, which it fights. Too much shear can destabilize an incipient storm, as if subjected to an atmospheric tug-of-war. This shear originates from Fiona’s high altitude exit or escape far to the northeast.

Hurricane Fiona hit Puerto Rico on September 18, leaving residents without power, water and safe shelter. Residents of Ponce and Salinas shared their stories. (Video: Zoeann Murphy, John Farrell, Drea Cornejo/The Washington Post)

Invest 98L will meander west over the next few days, remaining hampered by shear through Sunday. Things are going to get very worse quickly from Sunday evening to Monday.

This is when the shear will relax as 98L moves over some of the warmest water in the Atlantic. The northwest Caribbean is full of oceanic heat content, or heat energy contained in bath-like sea waters, which will support accelerated consolidation and strengthening of the incipient storm.

Simultaneously, 98L – then likely a named storm – will move under an upper level high pressure system. This will work in favor of 98L in two ways:

  • Divergence. High pressure means air is spreading. This divergence in the upper atmosphere will have a vacuum effect, creating a vacuum and facilitating the rise of surface air. This enhancement of the storm’s updrafts will speed up how quickly a warm, moist “influx” can rush into the storm.
  • Exit. The treble rotates clockwise. This is the flow direction of tropical cyclones in the northern hemisphere. This high pressure will work with 98L to vent high altitude “spent” air away from the storm, allowing it to ingest more refreshed air from below. Imagine placing an exhaust fan at the top of a chimney. Air would be pulled up and out, meaning more air would rush out from below and fire at the base would grow. This storm will do the same.

It is possible that a very strong storm will be somewhere in the northwest Caribbean next Monday. It can escalate quickly at this stage.

However, it could be heading anywhere from Mexico’s Yucatán peninsula to central Cuba. But the storm could also slip between those regions, entering the Gulf of Mexico late Monday or Tuesday.

There are only two escape routes that could allow the storm to avoid the gulf. There is an outside chance that, if it remains weak, it could continue west through the Caribbean into Central America. If it strengthens quickly, it could veer north over central Cuba and curl toward the Atlantic. But only a minority of model simulations present these outlier scenarios.

Watch footage of Hurricane Fiona surfing from the top of a 50ft wave

Most model simulations predict the system will end up in the gulf – while the intricacies of atmospheric steering currents will determine where the storm will eventually land.

A bit of good news is that if the storm makes landfall in the northern or western Gulf of Mexico, dry air from the north may weaken it slightly. That’s not very comforting, however, when virtually the entire Gulf region is warmer than average at the most active time of year for hurricanes.

If the storm heads further east, it could escape this dry air. It would be a concern if a potential lead brought it closer to Florida.

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