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Wet and Wild


weatherwiz

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Model guidance is continuing to suggest a strong storm system will affect much of the east coast over the course of the next 2-3 days. An area of low pressure developing down in the Gulf of Mexico will slowly strengthen as it works northward through the Gulf Coast. A trough moving into the central US from Canada will rapidly begin to sharpen and deepen. As this occurs some s/w energy will rotate around the base of the trough and begin to phase with the system moving northward through the Gulf coast states. One this occurs the system will rapidly begin to intensify and draw in a great deal of moisture from the Gulf of Mexico as well as the Atlantic Ocean. Forecast models are showing a 100-125 knot mid-level jet streak rounding the base of the trough on Wednesday, a sure tail sign that this system will not only be very strong but will pack a major punch.

By the time Wednesday rolls around we will have a fairly potent early fall storm system working it's way through the eastern 1/3rd of the US. As the primary area of low pressure tracks up through the Tennessee and Ohio River Valleys it will continue to deepen. As this occurs on the eastern side of the storm warm front will begin to accelerate northward. However, it appears as if some occlusion will take place as a secondary low tries to form near the coast. If this occurs this will halt the northward progression of the warm front, or at least make it so the warm front passes through the region AFTER the bulk of the storm has passed. At this time it appears as if much of the region, with the exception of the southern coastal plain will not get into the true warm sector.

With a 40-60 knots low-level jet working it's way into the region helping to pump in even more moisture (PWATS get up to 1.5''-2''!!) and a warm front stalling south of the region with a decent temp contrast there will be a great deal of overrunning. With a strong primary off to our west and a series of s/w energies moving through overhead along with strong mid-level/upper-level wind dynamics we are looking at the potential for a fairly big rain event.

The one thing that could save us from extreme rainfall totals and extreme flooding is the fact the system may be a quick moving system meaning we would see the rainfall in a 6-8 hour period rather than a 8-10 HR+ period. This would mean rainfall totals would be more in the 1-3'' with isolated 4'' amounts rather than something like 3-5'' with isolated higher amounts. While the 1-3'' may sound good this could pose some issues in spots. The ground has been very wet across the region so 1-3'' of rain in a 6 or 7 hour period could lead to some areas of flash flooding. If models begin to slow the system down a bit giving us a longer duration of heavy rainfall then the threat for flooding could escalate so this will have to be watched.

While the potential for some gusty winds is there, especially across the coastal areas the threat for widespread damaging winds appears low at this time despite the fact that we will have strong winds just above the surface. With the warm front looking to stay south of the region and no true warm sector getting in here we will likely have an inversion in place just above the surface (which we usually get anyways in these setups) which will likely inhibit much winds from mixing down to the surface.

Due to strong dynamics/forcing some elevated convection is possible, although most of the convection could remain south of the warm front and across the ocean.

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Nice write up Paul. Sounds like everythings lining up to what folks were talking about last week for this system. I've got to tell you that I am NOT looking forward to more rain.

I'd be curious to know how much above average the rainfall has been in my county since Irene came through. If someone tells me that we've been just average I may have to kill myself.

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Nice write up Paul. Sounds like everythings lining up to what folks were talking about last week for this system. I've got to tell you that I am NOT looking forward to more rain.

I'd be curious to know how much above average the rainfall has been in my county since Irene came through. If someone tells me that we've been just average I may have to kill myself.

Thanks

Well here are the departures dating back to mid-August so just before the impact of Irene.

Not sure if you can find zoomed in maps anywhere but this site you can't do past 60-days for regional but you can still see...INSANE

60dPDeptUS.png

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It's actually kind of meh on rain with this run.

This is going to be one strong system but it actually looks rather unorganized. I still think we see 1-3'' of rainfall with this but it certainly could be much more of a rain maker than what models are shaping it out to be. There really is not a great deal of organization in this system...it looks like the better forcing is well off to the west...as well as the best lifting and while there is a boat load of moisture over us it looks like most of the rain being generated could really be just from isentropic lift and probably some aided lift from weak secondary development.

Not to mention this system is drawing in a great deal of dry air.

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This is going to be one strong system but it actually looks rather unorganized. I still think we see 1-3'' of rainfall with this but it certainly could be much more of a rain maker than what models are shaping it out to be. There really is not a great deal of organization in this system...it looks like the better forcing is well off to the west...as well as the best lifting and while there is a boat load of moisture over us it looks like most of the rain being generated could really be just from isentropic lift and probably some aided lift from weak secondary development.

Not to mention this system is drawing in a great deal of dry air.

It's all mostly isentropic lift, but any dry air will come in after the system departs. This system is tropical in nature, but still some question as to where the heaviest sets up. NAM sometimes has trouble handling these things run to run.

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It's all mostly isentropic lift, but any dry air will come in after the system departs. This system is tropical in nature, but still some question as to where the heaviest sets up. NAM sometimes has trouble handling these things run to run.

Figuring out where the heaviest rain will setup will be a bit of a challenge until perhaps Wednesday AM when more of the mesoscale details are known. Gotta figure this area should be right about where the warm front stalls and the isentropic lift is maximized. I could see two max areas actually...one towards southwestern SNE up through Litchfield and western HFD cty into parts of Berkshire county and another across eastern MA...looks like there could be some sort of LLJ max that punches into eastern MA as well with the warm front pretty close by.

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