Severe storms 2015 general chatter

[yoda]

..SRN PA/MD/VA/CAROLINAS/GA  

 
TWO ROUNDS OF SEVERE STORMS WILL BE POSSIBLE ACROSS THE CAROLINAS  
WHILE CONFIDENCE IS LOWER WITH NWD EXTENT FOR TWO ROUNDS OF STORMS  
INTO MD/VA/SRN PA REGION.  
 
MODERATE INSTABILITY DEVELOPING AHEAD OF THE MORNING MCS IN ERN  
TN/SRN APPALACHIANS SUGGEST THESE STORMS MAY PROCEED SEWD THROUGH  
THE CAROLINAS WITH AN ATTENDANT THREAT FOR DAMAGING WINDS. MODERATE  
INSTABILITY EXTENDING NWD MAY SUPPORT A FEW STRONG TO SEVERE STORMS  
ACROSS THE NRN EXTENT OF THE SLIGHT RISK AREA INTO THE AFTERNOON.  
ADDITIONAL STORMS /STRONG-SEVERE/ WILL BE POSSIBLE THIS EVENING  
ALONG AND EAST OF THE LEE TROUGH AS GREATER HEIGHT FALLS SPREAD  
ACROSS THE FULL EXTENT OF THE SLIGHT IN THE EASTERN STATES THROUGH  

TONIGHT.

 

[yoda]

Both of the locally run models by LWX show us having a pretty decent day storm-wise later today

[yoda]

06z NMMN4 is pretty stormy this evening into overnight... looks like there are a couple of rounds that come through... 06z ARW4N likes the 5-9pm time period for storms in the DC region

 

Both models listed above are local model runs from LWX

[mappy]

HRRRRRRRRRRRRR has a line of storms/heavy showers around 8pm 

[PhineasC]

Did yoda's parameters predict that I'd have a line of heavy thunderstorms training over my house for an hour at 3AM dumping tons of rain?

[AmericanWxFreak]

And the slight risk gets yanked for north and east of DC.

[yoda]

Decent IMO

 

[yoda]

12z NAM slams a complex through... looks like 9-10pm or so.... we get smoked   4km NAM radar looks pretty nice as well IMO

 

[Eskimo Joe]

Too much in the way of debris clouds and the SLIGHT keeps getting trimmed back...wouldn't be surprised if it's completely south of DC Metro with the afternoon update.

[yoda]

Too much in the way of debris clouds and the SLIGHT keeps getting trimmed back...wouldn't be surprised if it's completely south of DC Metro with the afternoon update.

 

Doubt it... got blue skies and sun here... I expect the SLGT risk to stay where it is, maybe even go back north some in the later OTLKs with how the NAM and HI-RES NAM look for this evening... along with the local LWX models

[high risk]

   The problem, though, is that you're looking at these simulated reflectivity plots, seeing these great simulated storms with high values, and inferring that we're going to get "smoked" or "slammed."     Those plots by themselves don't tell us much about the actual severe weather threat unless they show nice supercells or a bow echo.    You're right that some of the guidance shows really heavy lines of storms moving through here in the evening hours, and it would seem that the chances of this occurring are good.   But I would expect to see high reflectivities in this very moist environment (PWs progged near 2") - these storms will be soakers.

 

     But the bottom line is that while the environment promotes storms with a ton of water and high reflectivities, the progged 20 kt or or so of deep layer shear does not support widespread severe weather, especially with modest cape.    Also, the moist environment makes it tough to generate cold pools which limits the wind threat.    Now maybe the models are undoing the shear, and a modest increase in shear would allow for some severe, but it's hard to get excited about the severe threat as progged.    But if we're looking for gusts to 35 kt and flash flood warnings, we may be in business.

Doubt it... got blue skies and sun here... I expect the SLGT risk to stay where it is, maybe even go back north some in the later OTLKs with how the NAM and HI-RES NAM look for this evening... along with the local LWX models

[mappy]

^^ nice explanation -- when i look at the sim reflectivity, i dont really see "storms", just heavy rain, which makes sense with what you just explained.

[high risk]

  thanks!    it would be great to have more products that connect the simulated reflectivity to the actual severe weather threat.   The updraft helicity is a great tool for this, but it's not as useful for events with lines of storms generating straight line winds.    Max 10-m wind is pretty nice to look at for the hi-res guidance and can convey the wind damage threat, but it's not easy to find on the web.    The NCEP MAG page shows it for the HRRR.

 

^^ nice explanation -- when i look at the sim reflectivity, i dont really see "storms", just heavy rain, which makes sense with what you just explained.

[mappy]

  thanks!    it would be great to have more products that connect the simulated reflectivity to the actual severe weather threat.   The updraft helicity is a great tool for this, but it's not as useful for events with lines of storms generating straight line winds.    Max 10-m wind is pretty nice to look at for the hi-res guidance and can convey the wind damage threat, but it's not easy to find on the web.    The NCEP MAG page shows it for the HRRR.

 

looks like weatherbell has gusts available too with HRRR

[yoda]

Off to our NW, but would bear watching to see if any of the storms that develop out there make the trek into VA/MD later in the evening

 

http://www.spc.noaa.gov/products/md/md1410.html

[mattie g]

Give me a storm that'll finally knock down the two dead 80+' oaks in my back neighbor's yard and I'll be happy.  Just don't let them pierce our roof and impale us.

 

Thanks.

[high risk]

         I couldn't find where they have this.    Is it labeled "gust" or "max 10-m wind"?    The former is just an algorithm based on how much momentum can be mixed down to the surface in a mixed environment and isn't really tied in to storms that the models generate.   The latter is the explicit modeled wind at the surface which includes the effects of intense downdrafts.

 

looks like weatherbell has gusts available too with HRRR

[mappy]

         I couldn't find where they have this.    Is it labeled "gust" or "max 10-m wind"?    The former is just an algorithm based on how much momentum can be mixed down to the surface in a mixed environment and isn't really tied in to storms that the models generate.   The latter is the explicit modeled wind at the surface which includes the effects of intense downdrafts.

 

Gust -- not sure if it was the same as what you were discussing

[MN Transplant]

  thanks!    it would be great to have more products that connect the simulated reflectivity to the actual severe weather threat.   The updraft helicity is a great tool for this, but it's not as useful for events with lines of storms generating straight line winds.    Max 10-m wind is pretty nice to look at for the hi-res guidance and can convey the wind damage threat, but it's not easy to find on the web.    The NCEP MAG page shows it for the HRRR.

 

 

looks like weatherbell has gusts available too with HRRR

 

College of Dupage has a 10m wind gust field for the HRRR

[yoda]

1630 OTLK basically holds the line with the SLGT risk when comparing it with the 1300 OTLK

[yoda]

URGENT - IMMEDIATE BROADCAST REQUESTED  

SEVERE THUNDERSTORM WATCH NUMBER 421  

NWS STORM PREDICTION CENTER NORMAN OK  

1235 PM EDT TUE JUL 14 2015  

 

THE NWS STORM PREDICTION CENTER HAS ISSUED A  

 

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF  

SOUTHEAST INDIANA  

NORTHERN KENTUCKY  

MARYLAND PANHANDLE  

OHIO  

WESTERN PENNSYLVANIA  

NORTHERN AND CENTRAL WEST VIRGINIA  

LAKE ERIE  

 

* EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 1235 PM UNTIL  

800 PM EDT.  

 

* PRIMARY THREATS INCLUDE...  

SCATTERED DAMAGING WIND GUSTS TO 70 MPH LIKELY  

ISOLATED VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE  

A TORNADO OR TWO POSSIBLE  

 

SUMMARY...SEVERE THUNDERSTORMS ARE ORGANIZING OVER NORTHWEST OHIO.  

THIS ACTIVITY SHOULD EXPAND IN AREAL COVERAGE AND INTENSITY AS IT  

PROPAGATES SOUTHEAST. DAMAGING WINDS ARE THE PRIMARY SEVERE THREAT  

AS STORMS SPREAD TOWARD THE OH RIVER.  

 

[AmericanWxFreak]

Looks like some pretty nice clearing incoming form the west 

[mattie g]

URGENT - IMMEDIATE BROADCAST REQUESTED  SEVERE THUNDERSTORM WATCH NUMBER 421  NWS STORM PREDICTION CENTER NORMAN OK  1235 PM EDT TUE JUL 14 2015    THE NWS STORM PREDICTION CENTER HAS ISSUED A    * SEVERE THUNDERSTORM WATCH FOR PORTIONS OF     SOUTHEAST INDIANA    NORTHERN KENTUCKY    MARYLAND PANHANDLE    OHIO    WESTERN PENNSYLVANIA    NORTHERN AND CENTRAL WEST VIRGINIA    LAKE ERIE    * EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 1235 PM UNTIL    800 PM EDT.    * PRIMARY THREATS INCLUDE...    SCATTERED DAMAGING WIND GUSTS TO 70 MPH LIKELY    ISOLATED VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE    A TORNADO OR TWO POSSIBLE    SUMMARY...SEVERE THUNDERSTORMS ARE ORGANIZING OVER NORTHWEST OHIO.   THIS ACTIVITY SHOULD EXPAND IN AREAL COVERAGE AND INTENSITY AS IT  PROPAGATES SOUTHEAST.  DAMAGING WINDS ARE THE PRIMARY SEVERE THREAT  AS STORMS SPREAD TOWARD THE OH RIVER.    

 

Congrats, Rust Belt and Ohio Valley.

[yoda]

Congrats, Rust Belt and Ohio Valley.

 

It borders the LWX CWA and its most likely where our storms for this evening will be coming from

[Eskimo Joe]

Too bad we don't have a healthy EML and better shear in place.  This would've been a easy MOD Risk day.

[Eskimo Joe]

That's some serious downcraft CAPE and shear just to our west.  Maybe the NAM is on to something with a decently meh MCS.

 

EDIT:  18z special sounding from IAD is flat...w/e.

 

 

 

[AmericanWxFreak]

That's some serious downcraft CAPE and shear just to our west.  Maybe the NAM is on to something with a decently meh MCS.

 

EDIT:  18z special sounding from IAD is flat...w/e.

 

IAD (1).gif

 

Could you expand upon what it means by being "flat"?

[Eskimo Joe]

Could you expand upon what it means by being "flat"?

Sure.  Surface CAPE is below, 1,000 j/kg (meh).  No cap to keep the lower levels primed.  PWATS are below 1.5 in (meh).  lapse rates, both mid and surface are around 6 C/km which is meh.  the only thing thing we have going for us is some decent downdraft CAPE and mid level winds so perhaps someone on a hilltop along I-81 gets a gusty thunderstorm but nothing widespread or of interest.

[mappy]

Could you expand upon what it means by being "flat"?

 

meh across the board. 

 

this is a good blog for severe soundings

 

http://wx4cast.blogspot.com/2014/04/the-basics-of-severe-weather-sounding.html

[Eskimo Joe]

 

 

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 421

CONTINUES.

SUMMARY...SEVERE THREAT WILL SPREAD ACROSS THE REMAINDER OF WW421 BY

EARLY EVENING.

DISCUSSION...MCS IS GRADUALLY EXPANDING IN AREAL COVERAGE AS IT

PROPAGATES SEWD ACROSS OH AT ROUGHLY 30-35KT. GIVEN THE CURRENT

SPEED/MOVEMENT...SEVERE THREAT SHOULD APPROACH THE OH RIVER AROUND

21Z THEN SPREAD TOWARD SRN PORTIONS OF WW421 AFTER 15/00Z. DAMAGING

WINDS COULD BE COMMON ALONG LEADING EDGE OF SQUALL LINE.