After a quiet start to hurricane season, the Atlantic has awakened and is packed with storms and systems to watch — and at least one could pose a serious danger to the United States.
Next week, it could enter the Gulf of Mexico, although its exact track is still uncertain. Assuming it grows into at least a tropical storm, it will be named Hermine. The National Hurricane Center gives it a 90 percent chance to do so.
For now, anyone residing along the Gulf Coast and Florida ought to pay close attention to this as the forecast evolves in the coming days.
At present, it’s poorly organized. The reason it isn’t doing much yet is because of disruptive shear, or a change of wind speed and/or direction with height, that it’s combating. Too much shear can knock a fledgling storm off-kilter, as if subjected to a game of atmospheric tug-of-war. That shear is stemming from the high-altitude outflow, or exhaust, of Fiona far to the northeast.
Invest 98L will meander west over the coming days, remaining hindered by shear through Sunday. Things will escalate very quickly Sunday evening into Monday.
That’s when shear will relax at the same time 98L moves over some of the warmest waters in the Atlantic. The northwest Caribbean is replete with ocean heat content, or thermal energy contained in bathlike sea waters, which will support expedited consolidation and strengthening of the nascent storm.
Simultaneously, 98L — by then probably a named storm — will move beneath an upper-level high pressure system. That will work in favor of 98L in two ways:
- Divergence. High pressure means air spreading apart. That divergence in the upper atmosphere will have a vacuum-like effect, creating a void and making it easier for surface air to rise. This enhancement of thunderstorm updrafts will hasten how quickly warm, moist “inflow” can rush into the storm.
- Outflow. Highs spin clockwise. That’s the direction of tropical cyclone outflow in the northern hemisphere. That high pressure will work with 98L to evacuate “spent” air at high altitudes away from the storm, allowing it to ingest more juiced-up air from below. Imagine placing a suction fan at the top of a chimney. Air would be pulled up and out, which means more air would rush in from the bottom and the fire at the base would grow. This storm will do the same.
The potential exists for a very strong storm to be located somewhere in the northwestern Caribbean come Monday. It may be rapidly intensifying at that point.
However, it could track toward anywhere from Mexico’s Yucatán Peninsula to central Cuba. But the storm could also slip in between those regions, entering the Gulf of Mexico sometime late Monday or Tuesday.
There are only two escape routes that might allow the storm to avoid the gulf. There is an outside chance that, if it remains weak, it could continue westward in the Caribbean toward Central America. If it strengthens quickly, it could turn north over central Cuba and curl out toward the Atlantic. But just a minority of model simulations present these outlier scenarios.
Most model simulations project that the system will end up in the gulf — while subtleties in atmospheric steering currents will determine where the storm eventually comes ashore.
A small piece of good news is that, if the storm does make a landfall in the northern or western Gulf of Mexico, dry air from the north may weaken it slightly. That’s not much comfort, however, when virtually the entire gulf region is running warmer than average at the most active time of year for hurricanes.
If the storm tracks further east, it could evade such dry air. That would be a concern if any potential track takes it closer to Florida.