Absolute Vorticity

Good Morning and some much needed rain on Tuesday. More on the way Friday-Sunday but how much is still up in the air. Going to be some heavy rains in the Ohio Valley as tropical moisture works its way north and northwest. This is not an easy rain forecast because somewhere a cutoff of the heavier rains will occur. Then once the tropical system hooks up with the upper low to the west this will be moving northeast Saturday and Sunday. At the moment I would go with a general 1-3 inches with higher totals south. These totals could change as Helene gets closer. Winds with the tropical system could be rather steady on Friday and my guess is a general 20-30 mph with some gusts probably over 40.

Like Les mentioned this should gets us through September and what will October bring us. Hard to believe but by the end of the month we will be above normal in terms of rainfall and once again Mother Nature trying to equal things out but this time her job was much tougher with the ongoing drought but hopefully we will continue to add more rain over the fall and winter and with a weak La Nina possible this should keep the jet stream close to us over the next several months so we may go from a drought to we want the rain to stop.

6Z GFS shows a windy and rainy solution. The low is still pretty strong so 50-60 mph gusts would be possible along with a couple inches of rain. It'll be interesting to see how this pans out in the coming days. It's very rare to see the Fujiwhara effect in action in our part of the world. What we mean by that is the low from Helene pinwheels around the upper low, they kind of chase each other in a sense and one gets absorbed into the other.

tron777 wrote: ↑Wed Sep 25, 2024 6:10 am 6Z GFS shows a windy and rainy solution. The low is still pretty strong so 50-60 mph gusts would be possible along with a couple inches of rain. It'll be interesting to see how this pans out in the coming days. It's very rate to see the Fujiwhara effect in action in our part of the world.

I agree Les an interesting set up that is rare so again you would expect models and forecasters having a hard time. I am happy for the rainfall and also the boring weather we have had for many many weeks. Hopefully this helps in the colors this fall as well. No doubt the tropical season has been much lighter in numbers than predicted but the impact on the mainland USA has been rather busy. Sometimes its not the number of storms that make a decent tropical season but the impact on where folks live.

Even though we have a tropical section I believe since this will be the main story for us I will post here instead of that section. What have models shown over the past 24 hours is a tad more west with the system and also remaining stronger once it gets to our area. Still the cutoff of heavier rains will probably be sharp and like most times with weather events we tend to be in that area. Will be fun to watch the models today and something I usually do once a day will not be the case over the next few days because I find this event interesting to say the least.

tpweather wrote: ↑Wed Sep 25, 2024 6:20 am Even though we have a tropical section I believe since this will be the main story for us I will post here instead of that section. What have models shown over the past 24 hours is a tad more west with the system and also remaining stronger once it gets to our area. Still the cutoff of heavier rains will probably be sharp and like most times with weather events we tend to be in that area. Will be fun to watch the models today and something I usually do once a day will not be the case over the next few days because I find this event interesting to say the least.

It is definitely the main weather story for us (besides the drought) at this time. I like your range of 1-3" Tim. I think that is a good starting point for this system. Heaviest amounts will be over the southern parts of the forecast area and lighter as one goes north. That much I think is pretty much set in stone as far as the rainfall gradient goes. The GEFS Mean is in good agreement with the OP GFS with regards to stalling the low for a bit over Southern Ky. This would put us in a good spot on the northern side for the best rains. (Like in the winter with the deformation zone, etc). The EPS does the stalling over Western TN so not quite as favorable for the best rains. That seems to be the difference that I am seeing. When the Fujiwhara effect occurs, where is the key to the forecast IMO.

I posted yesterday that CVG broke a daily rainfall record. DAY joined the party also!

Les this system is such a fast mover and at the moment east of the Yucatan and by Friday will be in our area. We always talk in the winter about if storms or gaining strength or losing strength once it approaches. This storm as it heads towards Florida is gaining strength quickly so the impacts of wind damage and storm surge is a hit hard hit quick kind of storm and since its moving fast rainfall totals are much less than they could be with a slow moving strong storm. The app mountains could get hit with some heavy rain with the uplifting and the problem is a huge amount of rain in a short period is going to lead to some flash flooding with this system. I believe we are okay but again it could rain hard enough at times to cause some roads to have some high water at times but we should have no problem in handling the current forecast amount of rains

tpweather wrote: ↑Wed Sep 25, 2024 7:02 am Les this system is such a fast mover and at the moment east of the Yucatan and by Friday will be in our area. We always talk in the winter about if storms or gaining strength or losing strength once it approaches. This storm as it heads towards Florida is gaining strength quickly so the impacts of wind damage and storm surge is a hit hard hit quick kind of storm and since its moving fast rainfall totals are much less than they could be with a slow moving strong storm. The app mountains could get hit with some heavy rain with the uplifting and the problem is a huge amount of rain in a short period is going to lead to some flash flooding with this system. I believe we are okay but again it could rain hard enough at times to cause some roads to have some high water at times but we should have no problem in handling the current forecast amount of rains

Agreed Tim. The wind will be an issue over the S Apps as well with models showing 50-70 mph gusts down there. I think that if the low remains as strong as projected on some of the modeling, we will see 40-50 mph gusts around here. I like the 1-2" idea of rainfall also. Friday looks to be the big day for the most rain and wind. We will see lingering chances though over the weekend and perhaps into Monday of next week as well. The system will be slowing down as it approaches due to the interaction with the upper low. Then it lingers thru the weekend and finally moves off to the east early next week. We can thank the blocking pattern we are in for this set up.

Les blocking can be bad like we have seen in the past month or so but can be good in this case to keep us with chances of rain this weekend. Just got an a shower here and total since Saturday is 1.61. I went 0.75-1.25 as a range and that happened in many areas but over 2 inches reported as well so my forecast of rainfall this past Sat-Tues worked out well though maybe a tad to low. This Fri-Mon I believe 1-3 seems like a good range and higher totals more likely south but depending where the storm stalls will also determine where some of the higher totals will happen. That is why somebody in the southern half of the Ohio Valley could get closer to 4 inches but this would be isolated

tpweather wrote: ↑Wed Sep 25, 2024 7:09 am Les blocking can be bad like we have seen in the past month or so but can be good in this case to keep us with chances of rain this weekend. Just got an a shower here and total since Saturday is 1.61. I went 0.75-1.25 as a range and that happened in many areas but over 2 inches reported as well so my forecast of rainfall this past Sat-Tues worked out well though maybe a tad to low. This Fri-Mon I believe 1-3 seems like a good range and higher totals more likely south but depending where the storm stalls will also determine where some of the higher totals will happen. That is why somebody in the southern half of the Ohio Valley could get closer to 4 inches but this would be isolated

Great post Tim. Completely agree! I've even seen some models go as high as 5" but that maybe a little far fetched.

Just a wonderful video by Brian. We are lucky to have him nearby. Just want to make a few points and first is with Eric who posted the other day about heavy rains. I mentioned that heavy rains would be less along the gulf coast because of the faster movement but this system is somewhat rare and yes heavy rains further north into the mountains of North Georgia,Eastern Tennessee and Western North Carolina. So yes Eric you were correct and my bad for not even thinking about how this could produce more rain in that area than falls along the coast.

Rainfall totals and again I believe we probably need another 12 up to 24 hours to pinpoint these amounts and at the moment I just went a general 1-3 locally and this includes the whole weekend. Severe weather and yes this can happen and usually on the eastern side of these storms. We may be lucky enough where the rainfall is heavy enough and the clouds thick enough and this holds off severe weather in our area. Got a feeling though southeast Ky may have enough daylight hours where the atmosphere can ramp up and you can have some nasty winds but also a tornado or two.

When you get a rare situation and I believe this is one because I don't remember this happening we will need to adjust on the run. It is very possible that if you get under a band of heavy rain that lasts 3 hours you can be in that 2-3 inch in that period and rainfall totals are a bust. Another chance is dry air or a dry slot forms once the systems combine and you get a couple hours of rainfall and all of a sudden it stops for several hours. I have no ideal where this may happen and Friday is going to be busy for met's as we know but also on this forum this is and exciting storm and what a way to go from heat and a drought to quite a bit of rain and then a much cooler period next weeks.

Trends in the track continue to be more south near the Tenn/Kentucky border. That’s not a good trend for most of Ohio, with the better QPF struggling to get past the Ohio river. Lets hope that trend stops

Bgoney wrote: ↑Wed Sep 25, 2024 11:09 am Trends in the track continue to be more south near the Tenn/Kentucky border. That’s not a good trend for most of Ohio, with the better QPF struggling to get past the Ohio river. Lets hope that trend stops

Great point Bgoney and why is this happening and really the upper system southwest of here looks to get stronger after it combines with the leftovers of Helene and this really this really cuts down the coverage later Friday. Becomes a rather strong system to the southwest and yes the system will head north and east so Saturday become quite rainy and raw. Where the line is for heavy rain is going to be a fine line and of course no way of knowing this far out plus models are looking at something that has very little in the way of previous storms in the system. My guess is some folks especially northeast of CVG in Ohio may see its biggest rainfall totals on Saturday and not on Friday. Though the Hurricane is a fast mover once it gets involved the upper low takes over it does slow down which hopefully helps in terms of rainfall. I guess one area that may really get shafted is across central Indiana but again to soon to really say that is going to happen.

For myself I believe this could be one of the most interesting systems in quite a while so any model that gets this correct this far out gets an a+

Wonderful posts guys! Keep 'em coming! 12Z GFS is coming in now...

Part of the issue maybe that the block is so strong to our north plus the fact that we might be seeing the interaction between Helene and the upper low to be a tad quicker which would limit the northward extent. We need the interaction to be a tad slower for better rainfall potential. The faster the interaction occurs, the sooner the system will be pulled more west then north.

Les I am looking at the models more than a winter storm. Gfs continue to get stronger and maybe a CAT 4. Great post above Les and with blocking to the north and the east and when you get a strong tropical system like this one you also get stronger highs away from the storm as well

Also of note... and the GFS keeps doing this... is that Helene is moving right along (I know you brought up this point also Tim) and that will cause the winds to be stronger as well due to a stronger low pressure system. 12Z GFS has a 977 MB low located over the S Apps by Fri morning where the 6Z run had it at 980 MB. IMO wind could certainly be an issue with this system with regards to isolated power outages Fri / Sat time frame. 12Z GFS is showing the heaviest rains S of the River as Bgoney has mentioned.

Gfs is stronger of course but moves rainfall further north on this run. This is almost as exciting as a winter storm or maybe its been so quiet for so long I am just happy to see weather happening lol

Something to look at as well is once it just becomes the upper system around where does it go. Still blocking north and east and this thing could be around the eastern USA into the middle of next week.

Cmc stronger as well and has the upper system further east than yesterday. Going to be some bouncing around imo so all we can do is report what the models are throwing out but I know myself not even close to final forecast by any means

tpweather wrote: ↑Wed Sep 25, 2024 12:21 pm Something to look at as well is once it just becomes the upper system around where does it go. Still blocking north and east and this thing could be around the eastern USA into the middle of next week.

Could be Tim, I agree. I am keeping POPS in the forecast thru Monday. Currently Friday and Sat are the highest chances for us locally IMO.

tron777 wrote: ↑Wed Sep 25, 2024 12:24 pm

tpweather wrote: ↑Wed Sep 25, 2024 12:21 pm Something to look at as well is once it just becomes the upper system around where does it go. Still blocking north and east and this thing could be around the eastern USA into the middle of next week.

Could be Tim, I agree. I am keeping POPS in the forecast thru Monday. Currently Friday and Sat are the highest chances for us locally IMO.

We are on the same page and yes we may be dry by Tuesday but along the east coast and even the mountains may still have some rainfall. Going to need a strong cold front to push move things along and that does have a shot next week and yes could we be talking a early frost and not going to say yes but upper upper 30's and low 40's seem like they may happen late next week and with the vegetation getting some moisture this will make it easier for frost to form. My guess it would be in outlying areas like usual at first so not expecting CVG or urban areas to have frost.

tpweather wrote: ↑Wed Sep 25, 2024 12:32 pm

tron777 wrote: ↑Wed Sep 25, 2024 12:24 pm

tpweather wrote: ↑Wed Sep 25, 2024 12:21 pm Something to look at as well is once it just becomes the upper system around where does it go. Still blocking north and east and this thing could be around the eastern USA into the middle of next week.

Could be Tim, I agree. I am keeping POPS in the forecast thru Monday. Currently Friday and Sat are the highest chances for us locally IMO.

We are on the same page and yes we may be dry by Tuesday but along the east coast and even the mountains may still have some rainfall. Going to need a strong cold front to push move things along and that does have a shot next week and yes could we be talking a early frost and not going to say yes but upper upper 30's and low 40's seem like they may happen late next week and with the vegetation getting some moisture this will make it easier for frost to form. My guess it would be in outlying areas like usual at first so not expecting CVG or urban areas to have frost.

Speaking of a strong cold front, it'll likely pass thru the area dry but that should be on Wed of next week. That frontal passage should give us a taste of Fall for a change as you mentioned. I do not expect it to be cold enough for frost but it'll at least get us thinking about it. I expect another strong front down the road too around the 10th or so of October give or take. Long range GFS on past runs tries to get another hurricane into the Gulf in the fantasy range too. Could we get impacted by another tropical system? Stay tuned... At least we're out of this boring weather pattern now.

Today's 12Z GFS has the fantasy cane still showing up past Day 10 in the Gulf gathering strength. Meanwhile another trough is entering the pacific NW and Rocky Mountain states. Wow...