With Florence dominating the weather talk around the nation here's a little something to keep an eye on long range. It's a significant change in the SOI (southern oscillation index) that's likely to bring the coldest air since spring to the Midwest. It should also produce a wetter look but none of this happens until the 8-10 day period.
If you look at the red boxes below you will see that the SOI index September 7th was strongly negative at -32.27. It's been negative since the heavy rains ended September 5th. During that period we've been dry and mild. The change to a positive index should act as a prod to bring a shot of rain and colder temperatures by the end of next week.
The EURO EPS sees the developing changes at 500mb September 23rd. A healthy trough with a plunge of very fresh air.
These are the temperature departures two days later. Chilly willy, frost for some?
Preceding the colder weather is the return of rain after a 2 week absence. Here's what the EURO has the next 6 days. Nothing much.
But 4 days later look how the totals have gone way up.
On the subject of Florence, a dramatic weakening of the storm (not forecast by any of the hurricane models) took place Thursday. At the time of this post the storm was down to 110 mph winds which makes it a category 2. Just 48 hours earlier the storm was a cat 4 and forecast to stay that way until landfall. This is a huge change and certainly would reduce wind and storm surge damage if the hurricane does not regain any strength (which is still possible. We'll know by mid-day where that issue stands.
Despite less wind, the storm promises to be a huge rainmaker and flooding will be a major issue for much of the southeast. Here's a classic look at the eye when the storm was still a major. What a view.
Back to the Midwest. It's steady as she goes for several days. More sun and mild temperatures right on through the weekend. Here's to September's finest. Roll weather...TS