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July 2013 Pattern and Discussion


griteater

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I know we're all focused on the current setup across the Southeast...but for entertainment value this afternoon's GFS brings (at the very least) a tropical wave through the Bahamas, Florida and into the Southeast in about a week...

http://mag.ncep.noaa.gov/list_files_area.php?model=gfs&cycle=12&area=wnatl&param=500_vort_ht

That and look at what the GFS has at 48 hours on the Gulf Coast. Maybe a quick spin up of a weak subtropical or tropical storm/depression ?
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wow, overnight superensemble for the 6-14 day forecast re-establishes a bit of a negative anomaly trough centered near Memphis (trough axis along the Miss River)...favoring below normal temps and above normal precip in the SE.

Saw that too. Lol it looks like the Euro weeklies may be onto something. They are calling for below normal temps and above normal rainfall.

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Today's CPC forecast analogs for the period July 13-19 show a pattern reload with a mean trough along the Mississippi river favoring below normal temps and above normal precipitation in the southeast...

 

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Awesome! Nothing I would like more than a little more rain. :P 

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I think attention needs to be turned to next weekend, 12z GFS now on board for another strong cutoff for the Southeast...Euro has hinted at is as well in recent days.

 

 

Day 5...

gfs_namer_120_500_vort_ht.gif

 

 

 

 

Day 6...

gfs_namer_144_500_vort_ht.gif

 

 

 

 

Day 7...

gfs_namer_168_500_vort_ht.gif

 

 

 

 

 

 

One caveat that we need to keep in the back of our minds...by Day 7 we could have our current INVEST 95L making an approach anywhere from Cuba to the Bahamas...the retrograding look at 500mb on day 7 is an open invitation IMO to a Gulf Coast/Florida or Southeast US landfall depending on its position by that time.

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So does virtually an entire summer with a ridge out west and a trough in the east portend anything in particular for the winter?  Didn't know if there was any correlation of a summertime pattern to a wintertime pattern or not.

The correlation is that we live in the Triangle, so the winter will be ****ty.

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I think attention needs to be turned to next weekend, 12z GFS now on board for another strong cutoff for the Southeast...Euro has hinted at is as well in recent days.

 

 

Day 5...

 

 

 

 

 

Day 6...

 

 

 

 

 

Day 7...

 

 

 

 

 

 

 

One caveat that we need to keep in the back of our minds...by Day 7 we could have our current INVEST 95L making an approach anywhere from Cuba to the Bahamas...the retrograding look at 500mb on day 7 is an open invitation IMO to a Gulf Coast/Florida or Southeast US landfall depending on its position by that time.

 

 

Yes, this could make this past week's weather looks like a walk in the park.. especially if a tropical system gets involved.  Everyone, keep a close watch on this one.

 

Robert has a good write-up on this threat at Wxsouth. If you don't have a subscription, I suggest you get it now!

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Yes, this could make this past week's weather looks like a walk in the park.. especially if a tropical system gets involved.  Everyone, keep a close watch on this one.

 

Robert has a good write-up on this threat at Wxsouth. If you don't have a subscription, I suggest you get it now!

Ya seems like we cannot catch a break here in the SE with all the rain. Next week looks very intersting and boy if a tropical system gets involved that would be a huge amount of rainfall on top of what we just got and have gotten this spring/summer.

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If a tropical storm is able to move into the weakness from an upper level trough in the southeast United States, that would just be destructive. Many areas are running well above average with rainfall this year. Some areas have already eclipsed there total rainfall for the year. Just absolutely amazing.

I will be watching how the ridges develop this week. This will be the key to the evolution of the trough forecasted to develop over the southeast. The 00z GFS and 00z EURO looked kind of wonky, so that will need to be monitored. If the ridges develop and are as strong as last time, a similar scenario may redevelop, which would bring more catastrophic flooding to places. Not good what-so-ever.

The ridges also play an important role in what happens with Tropical Storm Chantal. This storm is going to be moving westward before moving north westward towards the southeast. A landfall is possible in the southeast, but there is still some uncertainty how strong the storm will get. Looking at the wind shear tendency, it appears that the wind shear over the storm's center is relatively low; however, the storm may move into an area of elevated shear, therefore causing the storm to remain weak. Also, storms that develop in this time frame over the Atlantic moving rapidly west have difficulty strengthening, most of the time.

All of these factors will play a big role in our forecast, but the main players will the western ridge and the Bermuda ridge. If they amplify like last week, the heavy rain threat may return to the eastern/southeastern United States.

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If a tropical storm is able to move into the weakness from an upper level trough in the southeast United States, that would just be destructive. Many areas are running well above average with rainfall this year. Some areas have already eclipsed there total rainfall for the year. Just absolutely amazing.

I will be watching how the ridges develop this week. This will be the key to the evolution of the trough forecasted to develop over the southeast. The 00z GFS and 00z EURO looked kind of wonky, so that will need to be monitored. If the ridges develop and are as strong as last time, a similar scenario may redevelop, which would bring more catastrophic flooding to places. Not good what-so-ever.

The ridges also play an important role in what happens with Tropical Storm Chantal. This storm is going to be moving westward before moving north westward towards the southeast. A landfall is possible in the southeast, but there is still some uncertainty how strong the storm will get. Looking at the wind shear tendency, it appears that the wind shear over the storm's center is relatively low; however, the storm may move into an area of elevated shear, therefore causing the storm to remain weak. Also, storms that develop in this time frame over the Atlantic moving rapidly west have difficulty strengthening, most of the time.

All of these factors will play a big role in our forecast, but the main players will the western ridge and the Bermuda ridge. If they amplify like last week, the heavy rain threat may return to the eastern/southeastern United States.

 

Since our main concern will be flooding, due to the already saturated grounds, the strength, or lack of strength, of the system isn't that important when it comes to precip amounts. Alberto in 1994 for example. Any tropical system moving into and over the same areas hit by the heaviest precip this past week would be bad news. 

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Since our main concern will be flooding, due to the already saturated grounds, the strength, or lack of strength, of the system isn't that important when it comes to precip amounts. Alberto in 1994 for example. Any tropical system moving into and over the same areas hit by the heaviest precip this past week would be bad news.

I agree that due to the very wet antecedent conditions you mentioned, flooding will be the primary concern, like you mentioned, with any sort of tropical system that gets entrained. But would also add that the strength will be important in that any amount of significant wind will have the potential to do a lot more damage, given how wet and soft the ground will be (I know you were specifically responding to precip amounts and not wind).

Hopefully, we can avoid a strong tropical cyclone moving into the area. If not, there will be widespread devastation. Fortunately, conditions don't really look favorable for a really strong cane, at this time.

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Since our main concern will be flooding, due to the already saturated grounds, the strength, or lack of strength, of the system isn't that important when it comes to precip amounts. Alberto in 1994 for example. Any tropical system moving into and over the same areas hit by the heaviest precip this past week would be bad news. 

 

Agreed with the statement, I should have been more clear. Flooding appears to be the major concern, but with a weaker system, it is harder to determine the track of the storm, which is the key. Also, the storm may become sheared apart and fall apart (very unlikely). We will wait and see what happens with the storm, it should definitely be interesting to watch!

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A definite trend today on the GFS away from the big cutoff low...however it takes the current Bahamas TUTT feature combined with some energy from the upcoming trough to develop a weaker version of a cutoff over the Gulf Coast Region. That feature takes Chantal and hooks back into the Southeast Coast Day 6...

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A definite trend today on the GFS away from the big cutoff low...however it takes the current Bahamas TUTT feature combined with some energy from the upcoming trough to develop a weaker version of a cutoff over the Gulf Coast Region. That feature takes Chantal and hooks back into the Southeast Coast Day 6...

The Canadian eh is really, really wet. It keeps the upper low idea and continues to bring the leftovers of Chantal into the SE coast as the NW Atlantic ridge builds back west. If it's right, then wow at the rainfall amounts. What a flood there will be!

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Alberto is one of my most memorable weather experiences, especially coming so near to the blizzard.  The destructive power of too much water for the terrain is mind blowing.   Flash images of things I saw include the rooster tail of water thrown up by the spill way at the reservoir that was easily 100 feet high...and crowds of people walking out on the dam to stand right next to it.  And we wonder why folks get killed or injured during weather events. 

 The scouring out of the trees and ground along side the High Falls area in the aftermath of the flooding.  Some of the Iconic images of the flooding from Alberto are of the flooding at High Falls.

Caskets washing out of the ground south of here.  A lady dying after driving over a bridge a mile from here, and being swept into the stream.  The creek is usually about two feet wide, a foot deep, and 15  feet down under the bridge.

   Feeling like you need scuba gear to be out in it, the rain was falling so hard.  Nearly 20 inches in a few days is a thing to behold, but it took a cutoff td moving back and forth over the same area to do it.  A lot has to set up correctly for such a thing to occur, but when it does, you won't forget it.  T

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GFS continues to look wet for the next several days.

 

Thursday sure looks wet and stormy across GA and the Carolinas with the noteworthy cold front digging southeast into the super moist environment

 

This is from the aftn SPC convective outlook for Thursday / Thurs night...

AS MB TROUGH AMPLIFIES SEWD...AN ASSOCIATED WEAKNESS/TROUGH IN THEMID/UP FLOW WILL DEVELOP SE AHEAD OF IT ACROSS THE TN VLY/GULF CSTSTATES. WITH SUCH AN UPR FEATURE IN PLACE...AND A PLUME OFRELATIVELY STEEP MID-LVL LAPSE RATES ALSO IN PLACE EXTENDING EWDFROM THE SRN PLNS...IT IS NOT ENTIRELY OUT OF THE QUESTION THAT ASIZABLE..ORGANIZED MCS OR TWO COULD MOVE S OR SE ACROSS PARTS OF THEMID-SOUTH AND/OVER THE VA/NC AREA. CONFIDENCE IN SUCH ASCENARIO IS TOO LOW TO WARRANT UPGRADE TO SLIGHT RISK ATTM. BUTPARTS OF THE CURRENT 5% PROBABILISTIC FCST AREA NOW DEPICTED MAYREQUIRE UPGRADE TO SLIGHT RISK IN LATER OTLKS AS STORM/MCS-SCALEDETAILS OF THE CONVECTIVE EVOLUTION BECOME MORE CLEARLY DEFINEDTNGT/EARLY THU.
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Well...looks like we got another retrograding event getting ready to set up across the Southeast US, while not projected to be as potent as the last one the potential is still there for many areas to get decent rainfall totals over a multi-day period. Normally 2-4 inches over a 4-5 day period isn't too much but the current state of things, 2-4 inches in a relative short period of time can cause significant problems...the flash flooding last night in Asheville area a prime example.

 

 

Trough axis will be setting up along the spine of the Appalachians with the feature starting to cutoff over West Virginia by 36 hours...after a very active Thursday/Thurs Night for the Southern Apps and Southeast, some drier air will briefly enter parts of the region (Tennessee, Western Carolinas, North Georgia, North Alabama) literally for the first time this month...

 

gfs_namer_036_500_vort_ht.gif

 

 

 

Like I said, the hint of drier air will be very brief...the developing upper low will begin to retrograde west across the Upper Ohio Valley Region late Friday night and then eventually into the Mid Mississippi River Valley by Sunday...all of this thanks to a piece of the Bermuda High that will be flexing its muscles again...this will quickly allow the flow to return to an east or southeast orientation across all of the southeast including the Apps...the high from the Atlantic should focus a stream of higher moisture content including some assistance from a remnant piece of the former Chantal...Let's just hope the models are not underplaying the moisture content...with the Ghost of Chantal possibly in play, I think its possible

 

gfs_namer_084_700_rh_ht.gif

 

 

 

gfs_namer_084_500_vort_ht.gif

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