April 5 Mod/High Risk bust, what happened?

[audioguy3107]

Fishel's post on the main event thread seems to be a good one:  https://www.americanwx.com/bb/topic/49916-april-5-6-severe-threat/?page=28#comment-4541945.......I figure I'd start a "moderate to high risk" bust thread and see if there is enough interest, but hard to get all the snow lovers here to get excited about severe season.  That being said, I could go on and on about the reasons that we continually bust on severe weather here (this is really meant for the north Georgia posters BTW), but it really comes down to one thing:  the damn wedge.  

The wedge here is the bane of our weather existence, it either giveth or taketh away.  It pretty much dictates what happens, when it happens, and how bad it happens.  It cannot be denied, if it is present, all other weather phenomena cease to exist.  The only season it goes into hiding is in the middle of the summer.  During the winter, 99.5% of the time it makes for a miserable wet, windy and cold day, the other 0.5% of the time it causes widespread power outages, tree damage, and has prevented Atlanta for ever hosting another Super Bowl due to the ice storm until we built a 1.6 Billion dollar stadium. Amazing that in some way, the wedge ultimately caused the building of Mercedes Benz Stadium.  

I know I'm being a bit silly, and I in no way want to simplify the complex forecasting of meteorology, but seriously, there is no and will never be any type of severe weather in north/northeast Georgia (i.e. CAD areas) with the presence of the wedge, I don't care what the SPC says, forecasts, etc.  I've tracked severe weather here for over 30 years, and in my lifetime, no severe weather of any major importance has happened in NE Georgia with the wedge present.  It's pretty much that simple.  Yes we can have some hail or a gusty dying squall line or some lightning and thunder (although the wedge is excellent at preventing that too), but if you're excited about a moderate or high risk severe outbreak, ask yourself one question:  Will there be a wedge or any type of residual cold pool/damming?  Yes.  No.  If no, get prepared (i.e. April 27, 2011, April 8, 1998, Palm Sunday 1994).  If yes, don't waste time tracking the event because it won't happen.  And I'll add that the NAM consistently showed the absence of any instability in northeast Georgia for at least a day leading up to April 5, I assume due to the early morning convection that came to pass in all it's glory.

Perfect case study:  the high risk Enterprise, AL tornado outbreak of March 2007.  I attached the day 1 outlook, now granted, NE Georgia and the upstate of SC were not in the high risk area, but Atlanta was close enough and well into the moderate risk area.  This was the PDS Tornado watch that was issued, I remember it well....I remember it because I was watching drizzle and showers at a balmy 49 degrees.  The discussion:

DISCUSSION...AIR MASS EXPECTED TO RAPIDLY DESTABILIZE ACROSS THE WATCH AREA THRU THE AFTERNOON IN ADVANCE OF THE INTENSE UPPER TROUGH AND MID/UPPER LEVEL JET. THUNDERSTORMS WILL CONTINUE DEVELOPING E/NEWD AS AIR MASS DESTABILIZES WITH TORNADIC SUPERCELLS EXPECTED. POTENTIAL FOR STRONG/VIOLENT TORNADOES DEVELOPING DURING THE AFTERNOON.

From the mesoscale discussion:  STORMS DEVELOPING OVER NRN GA CURRENTLY APPEAR ELEVATED. THE STRONG LOW LEVEL JET WILL RESULT IN NWD DESTABILIZATION WITH TIME AS FAR N AS NRN GA LATER THIS AFTERNOON...AND THIS WILL CONTRIBUTE TO AN INCREASING TORNADO THREAT AS STORMS BECOME SURFACE BASED.

No it won't.  Now I'm sure this would've come to fruition had there not been the presence of the wedge, but the wedge was easily strong enough to hold off this intense upper trough and mid/upper jet.  And this is only one example of countless examples I can think of.  The wedge is likely to hold off just about anything short of category 5 Hurricane Katrina, although it would probably put up a good fight.  I can only imagine what Georgia's tornado statistics would look like without the presence of the CAD ares in the NE, which I ultimately is a blessing although not as fun for weather enthusiasts.  Anyway, severe weather forecasting is complicated and I understand you have to err on the side of caution, but if you are expecting a severe weather event north of I-20 in Georgia or the upstate of SC, all you really need to know to get started is whether you know what will be present.

[LithiaWx]

Great post.  The wedge is king when present. I remember looking at the mesoscale analysis page late yesterday afternoon and the wedge was in full command.  You could easily see it on the maps.  The storms literally fell apart when they crossed the AL/GA border.  

 

Saying the wedge is responsible for building of Mercedes Benz stadium was awesome. 

 

 

[Snowless in Carrollton]

I don't remember all the details from April 27, 2011, but was the wedge responsible for all the storms missing Atlanta ?

[audioguy3107]

7 hours ago, Snowless in Carrollton said:

I don't remember all the details from April 27, 2011, but was the wedge responsible for all the storms missing Atlanta ?

Nope, not that time, that was just random luck for the Atlanta area, plus there were tornadic storms in the mountainous areas that never would have made it had CAD been present.

[nrgjeff]

I agree the Wedge giveth or taketh away. Anchored in, especially with rain like last Wednesday 4/5, the Wedge is holding. If it is in retreat, behaving more like a warm front, expect trouble.

Forecasters tend to treat it like a warm front, or even an outflow boundary south of the synoptic WF. However equating it that way can be a mistake. Wednesday 4/5 a backed and screaming LLJ was ripping over North Georgia; however, it was advecting stable air. So much for rapid destabilization. 

If the Wedge retreats look out. Low level winds will remain somewhat backed. Warm air advection will destabilize. Right along the retreating wedge low level helicity will be higher, but it should be retreating. Otherwise, cell crosses into stable air.

Edit: Yes 2011 North Georgia was on the wedge retreating, not good. In 2008 a clutch 3-pointer sent the SEC Basketball Championship game into overtime, likely keeping fans inside and safe compared to if the game had ended in regulation.

[EmersonGA]

Don't forget that the 2008 Atlanta tornado was on the edge of a retreating wedge.  Also, those of us in the north metro would beg to differ about 2011.  There are plenty of tornado scars still present from that one.

[burrel2]

http://www.weather.gov/cae/april_5_2017_event_review.html

 

Detailed write up of the Johnston/Ridge Spring tornado.