The expected fall cold front arrived with a temperature drop and some rain…although most would likely wish they had more. The temperature regime change though will certainly catch your attention for the next couple of days…and there are more cold fronts coming down the road.

The blog today though is going to be about several weather features, including a powerful hurricane in the western Atlantic, congealing and potentially influencing our weather…in both good ways (cool to mild days) and bad ways (another potentially long stretch of dry weather).

It’s a fascinating interplay really…and it will be interesting to see how it all comes together. To some extent as well, another tropical system, that the models have grabbed onto suggesting a SE USA landfall potential may also be affected by this interesting interplay.

++++++++++++++++++++++++++++++++++++++++++

Forecast:

Today: Any showers ending this morning then variable clouds. Temperatures will be MUCH cooler with highs in the mid 60s. There is some potential for warmer temperatures…upper 60s if we get more afternoon sunshine

Tonight: Increasing clouds again. Cool with lows in the low to mid 50s

Tomorrow: Probably our best chance of more widespread rain. Cool with highs only in the low to mid 60s…maybe only 50s for some areas on the MO side.

The weekend: Warmer Saturday…low to mid 80s and seasonable Sunday with mid 70s. Lots of sunshine both days

++++++++++++++++++++++++++++++++++++++++++

Discussion:

It’s the 1st day of fall! Arrives at 8:03 PM tonight actually.

So let’s start with Fiona…

Fiona will pass west of Bermuda…and then head towards the Canadian Maritimes. This may end up being a Superstorm type transition for Fiona because it’s going to be steered by and eventually become absorbed by a decently strong upper level system moving into Eastern Canada.

So I want to show you this by taking you up to about 18,000 feet or so to show you the 500 mb height map. This is considered to be the middle part of the atmosphere on the assumption that 1000 mbs is near the ground and 0 mbs is over 30 miles up. By the way…mbs stands for millibars (a unit of pressure). There is a lot more to this chart…but let’s keep this simple.

For the purpose of this blog…we like to find dips in the jet stream…the more of a “dip” there is the stormier it can be.

I’ve labeled Fiona with an “F”. Note #1…that is a dip in the jet stream that will absorb Fiona…note as well #2…that is a dip that will then become absorbed and strengthen the combination of Fiona and #1. So we’re going to get a big merger.

Let’s put the maps into motion…and you can see the pirouette of weather systems that will be coming together.

This starts later today and continues into Tuesday evening

Can you see how they all interact. Now notice what it does to the Plains…1) it creates NW to SE flow as the newly “merged” dip develops in the Great Lakes into the eastern US. This NW flow means some additional cold fronts and it also means the fronts won’t have much or any moisture to work with…and that means a prolonged period of dry weather again heading towards the region I think, through next week. That’s the bad news through all of this.

Finally note the smallish “something” towards the end of the animation…that is a potential tropical system…of unknown strength at this point.

The system in question is the “1” on the map…not to be confused with my example earlier.

Model data varies but numerous pieces of data show this to be a “thing” somewhere towards the Gulf region. Something weaker and perhaps it stays into Central America. Something stronger though…

May allow that big dip that is in the animation to “capture” whatever named storm this may turn into…and start tugging it northwards. Then the issue is how far northwards and where.

All items that are too soon to tell since whatever the not even formed system does…it won’t really be a US factor for at least another 5 days or so…and the reason why the models will continue to struggle with this more is because the models are trying to resolve all these other pieces from the above animation. IF one or two of those pieces is “different’ the end result of the landing point of whatever tropical system this turns into perhaps, is different as well.

For US interests…at this point…it’s worth watching and preparing and that’s about it for now.

The feature photo comes from Mary Jo Seever from last Friday night.

Joe