We wrote in a newsletter towards the end of August that the tropics would heat up somewhat heading into September, and that is exactly what is happening. Hurricane Fiona should continue to strengthen as it moves north and then northeast in the coming days — and while Fiona shouldn’t threaten the continental U.S., it has left a wake of damage in the Caribbean including heavy damage and flooding in Puerto Rico and the Dominican Republic.


The current tracked hurricanes/tropical storms and tropical waves (marked by Xs) in the Atlantic.

As Fiona moves north into the open ocean, the area to watch over the next week will become the southernmost yellow x on the map above. While this tropical wave likely won’t form into a storm in the next 3-5 days, it could rapidly begin to take shape in the period just beyond that. It’s far too early to tell if this storm will eventually threaten the U.S. — but the ocean remains warm ahead of this wave.

A map of the current sea-surface temperature anomalies in the Western Atlantic. Orange/Red means warmer ocean temperatures.

Ensembles want to develop this wave into a storm into next week, so we will certainly have to keep an eye on the tropics.

Fall Season?

Despite a few severe weather risks this past week in the Northern Plains and Midwest (and to a lesser extent into the Central Plains) — it seems like a more traditional deep western trough, SW flow event continues to remain out of reach on the ensembles. Check out this western ridge:

An ensemble model (collection of individual weather models) map showing the pressure heights in the mid-levels of the atmosphere.

As a reminder, a trough represents unsettled weather with large-scale lift. This is the big-picture background environment you look for to get severe weather on the Plains. If you are under a ridge, the air tends to sink which prevents storm development. In the map above, the red areas represent areas of ridging and the blue represents roughing. From a weather fanatic’s perspective, this is a pretty amplified ridge for this time of year, which is notable!

So for now at least, probably no major chances at severe weather in the Southern/Central Plains.

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