#MEwx "Inverted Trough" explained

The local weather forecaster on TV has used the term “inverted trough” a few times and I didn’t know what that is. So, I looked it up. The explanation is below, and I found it on a real good web site with loads of different kinds of information that you might want to read through. I’ve copied the text below, but the pictures, as you may expect, are much better than a thousand words. The web site is:

https://www.theweatherprediction.com/habyhints/126/

“WHAT IS AN INVERTED TROUGH?”

METEOROLOGIST JEFF HABY

In the mid-latitudes of the Northern Hemisphere a

Trough is usually seen as a southerly bulge in the

height contours

. The lowest heights are generally located to the north of the trough. In an inverted trough situation, the height contours bulge to the north. This is

more common in the tropical regions where regions of low pressure ride south of a mid-latitude high pressure but can happen in the mid-latitudes when low

pressure is south of high pressure. An inverted trough bulges to the north. At first it may look like a ridge, but on further inspection it is a trough.

Both a trough and an inverted trough have a cyclonic (counterclockwise) flow pattern. A trough will tend to have more westerly winds associated with it

while an inverted trough will tend to have more easterly winds associated with it. If an inverted trough is actually a ridge then the winds will be flowing

with the height contours in the opposite direction (anti-cyclonic direction). The direction of windflow through the feature is how a ridge is discerned

from an inverted trough.

Tropical waves will show up as inverted troughs because they are generally south of mid-latitude high pressure and have an easterly wind associated with them.

Also, you may have heard the term “GFS” during the local weather forecast lately. GFS stands for “Global Forecasting System.”