A storm forming within the Caribbean may change into Hermione and enter the Gulf of Mexico

After a quiet start to hurricane season, the Atlantic has awakened and is filled with storms and systems to watch — and at least one could pose a serious threat to the United States.

There is grave concern over a cluster of downpours north of Venezuela, dubbed ‘Invest 98L’, which has swept through the Leeward Islands with gusty winds and squalls. This one will stay tame until the weekend when it’s ready to move into a powder keg atmosphere.

It could enter the Gulf of Mexico next week, although its exact track is still uncertain. Assuming he grows into at least a tropical storm, his name will be Hermione. The National Hurricane Center gives it a 90 percent chance of doing so.

For now, everyone living in the Gulf Coast and Florida should be paying close attention as the forecast develops over the coming days.

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

It’s badly organized at the moment. The reason it’s not doing much yet is because of the disruptive shear, or a change in wind speed and/or direction with altitude it’s fighting. Too much shear can unbalance a young storm like it’s undergoing an atmospheric tug of war. This shear originates from the high-level outflow or exhaust from Fiona far to the NE.

Hurricane Fiona hit Puerto Rico on September 18, leaving residents without electricity, 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 snake west over the coming days and remain shear-impeded through Sunday. Things will escalate very quickly from Sunday night to Monday.

Then the shear relaxes as 98L moves across some of the warmest waters in the Atlantic. The northwestern Caribbean is replete with oceanic heat content, or thermal energy contained in bathing-like seawater, which will support accelerated consolidation and strengthening of the emerging storm.

At the same time, 98L — likely a named storm by then — will be moving under an upper-level high-pressure system. This works in two ways in favor of 98L:

  • deviations. High pressure means air is spreading. This divergence in the upper atmosphere will have a vacuum-like effect, creating a cavity and facilitating the rise of surface air. This amplification of thunderstorm thermals will accelerate how quickly warm, wet “tributaries” can pour into the storm.
  • drain. Treble rotates clockwise. This is the direction of tropical cyclone outflow in the northern hemisphere. This high pressure will work with 98L to evacuate “stale” air away from the storm at high altitudes, allowing more juiced air to be picked up from below. Imagine placing an extractor fan on top of a chimney. Air would be pulled up and out, meaning more air would come in from below and the fire at the base would grow. This storm will do the same.

There is a possibility that a very strong storm could hit somewhere in the northwestern Caribbean next Monday. It can quickly intensify at this point.

However, it could track anywhere from Mexico’s Yucatán Peninsula to central Cuba. But the storm could also slip between those regions and enter the Gulf of Mexico sometime late Monday or Tuesday.

There are only two escape routes that could allow the storm to bypass the Gulf. There is an outside chance that if it remains weak it could advance westward in the Caribbean toward Central America. If it strengthens rapidly, it could turn north over central Cuba and roll out toward the Atlantic. But few model simulations show these outlier scenarios.

View footage of Hurricane Fiona breaking waves on a 50-foot wave

Most model simulations assume the system will end up in the Gulf — while subtleties in atmospheric steering currents will determine where the storm eventually makes landfall.

A little bit of good news is that if the storm makes landfall in the northern or western Gulf of Mexico, dry air from the north could weaken it slightly. That’s not much of a consolation, however, when during the most hurricane-active time of the year it’s getting warmer than average across most of the Gulf region.

If the storm moves further east, it could avoid such dry air. That would be a problem if a potential stretch brings Florida closer.

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