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Pattern Anaphylactic August

Mike Maze at WRAL posted this on Facebook.

Well sometimes a forecast is spot on and other times it's a bust and tonight is definitely one of the latter. We had storms in the forecast but did not expect them to carry on as far south and east as they have.
 
It's going to be funny if folks that saw storms tonight don't get anything Friday and Saturday when the chances are at 70%.
 
So, to summarize, only a 30% chance of storms here today, a line of storms comes through the Triad and Triangle, supposedly headed my way, and then ends up missing me to the south.

Great forecasting today.
 
Brick Tamland said:
It's going to be funny if folks that saw storms tonight don't get anything Friday and Saturday when the chances are at 70%.
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Friday afternoon through Saturday could be one of the best widespread rain events we have had. Don't you put that bad juju on it

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SD said:
Friday afternoon through Saturday could be one of the best widespread rain events we have had. Don't you put that bad juju on it

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Nah, it'll probably happen since I am going to a concert Friday night at Walnut Creek, and my daughter is supposed to have her first soccer game of the season Saturday.

Or it could just be very isolated like 90% of the storms we get around here the last 5 years or so.
 
WRAL has 50% chance of storms for tomorrow evening. Highest RAH has for tomorrow is 40%. Either way it's higher than they both had foe today.
 
Statesville is a mess. Lots of road closures and no signals working.
 
Image from my neighborhood. Guessing VEI 4? Evacuate or ride it out?

20190821_223737.jpg
 
Power estimate for my friend is Thursday night in Statesville. Requesting outside power companies to help with heavy damage.
 
Level 1 risk of severe storms for most of NC today. I might actually get a storm if they don't raise it and issue a watch.

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RAH has a 60% chance of storms tonight, 60% chance Friday afternoon, 80% chance Friday night, and 70% chance of showers Saturday. If most folks around here don't get a storm the next couple of days this will be a huge bust.

I am actually thinking of keeping a spreadsheet to keep track of storm chances, SPC levels, when a watch and/or warning is issued, and what I actually get to have a record of things.
 
Brick Tamland said:
RAH has a 60% chance of storms tonight, 60% chance Friday afternoon, 80% chance Friday night, and 70% chance of showers Saturday. If most folks around here don't get a storm the next couple of days this will be a huge bust.

I am actually thinking of keeping a spreadsheet to keep track of storm chances, SPC levels, when a watch and/or warning is issued, and what I actually get to have a record of things.
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You can't really use a single point to verify things with that much aerial coverage, it's being unfair to the science and the forecaster.

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Brick Tamland said:
RAH has a 60% chance of storms tonight, 60% chance Friday afternoon, 80% chance Friday night, and 70% chance of showers Saturday. If most folks around here don't get a storm the next couple of days this will be a huge bust.

I am actually thinking of keeping a spreadsheet to keep track of storm chances, SPC levels, when a watch and/or warning is issued, and what I actually get to have a record of things.
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I say go for it and actually not a bad idea.... however, I think to consider it accurate it would need to show results for the entire forecast area not just Wake Co. I mean I get what you are getting at, but let's say it rains everywhere but Wake county over the coming days, then that forecast isn't a bust it's actually spot on.
 
SD said:
You can't really use a single point to verify things with that much aerial coverage, it's being unfair to the science and the forecaster.

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You basically said what I said but more precise and concise..... I tend to be too wordy. Lol
 
metwannabe said:
You basically said what I said but more precise and concise..... I tend to be too wordy. Lol
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Ha I generally think I am. It's not a bad project to undertake but it has to be fair and include the entire forecast area for whatever outlet is chosen. There is really a lot of grey area if you think about it, even down to the warnings, if rah issues a tstorm warning for harnett county and a rural farm sees a 70mph gust but there's no record of it did the warning verify?

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So this discussion touches on a forecasting issue I have yet to decipher. How is a precipitation forecast considered to be either spot on or a bust? Is it by the actual areal coverage for the forecast area? Or is the metric just on the weighing the atmospheric factors together to come up with the chance rain will happen?

My main issue with the area coverage of precipitation is that sometimes a forecasting area will have different terrain factors, such as coastlines and hills that can skew this.

In my own area, for example, a local met has Louisiana parishes and Mississippi counties for which he issues a flat precip chance. But weather systems affecting the coast may leave areas away from it dry. Then he recounts the veracity of the previous day's precip forecast using rainfall maps from ANYWHERE in the TV viewing area. Maybe this is just the compromise a TV met has to make to speak to the viewers in an understandable way? I feel like a segmented forecast, addressing micro climate would be best for trying to address a weather outlook for a meteorologically diverse area. I would be curious to know what others think about this.

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I get what y'all are saying, but I am just curious to see how it works out for me personally. I know that if there's a severe storm warning for Wake County, but I don't get a storm, the forecast wasn't a bust, but for me personally it was a miss. That's what I am curious to see. I just wanted to keep track of things to see if I really am accurate in saying I get more storms personally when we're not under a watch and/or the SPC outlook for severe storms is low versus when I am under a watch and/or the SPC outlook is higher, say a level 3 or more. I'm just trying to compare what I actually get versus the forecast.

However, I will say the worst storm that Wake County has had this year happened May 13 when the tornadoes hit Wendell and Zebulon, and we were not under any kind of watch.
 
Will Rossman said:
So this discussion touches on a forecasting issue I have yet to decipher. How is a precipitation forecast considered to be either spot on or a bust? Is it by the actual areal coverage for the forecast area? Or is the metric just on the weighing the atmospheric factors together to come up with the chance rain will happen?

My main issue with the area coverage of precipitation is that sometimes a forecasting area will have different terrain factors, such as coastlines and hills that can skew this.

In my own area, for example, a local met has Louisiana parishes and Mississippi counties for which he issues a flat precip chance. But weather systems affecting the coast may leave areas away from it dry. Then he recounts the veracity of the previous day's precip forecast using rainfall maps from ANYWHERE in the TV viewing area. Maybe this is just the compromise a TV met has to make to speak to the viewers in an understandable way? I feel like a segmented forecast, addressing micro climate would be best for trying to address a weather outlook for a meteorologically diverse area. I would be curious to know what others think about this.

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Interesting read here from one Met Brad P that get's referenced often.... makes sense but also can see the confusion

http://wxbrad.com/why-a-50-chance-of-rain-usually-means-a-100-chance-of-confusion/
 
And from the NWS and I'll add to the bottom statement, if there is a 40% chance of precip at any one point that also means there is a 60% chance of no precip at any one point. Ok sorry we hi-jacked the August thread. Lol

Explaining "Probability of Precipitation"​


Forecasts issued by the National Weather Service routinely include a "PoP" (probability of precipitation) statement, which is often expressed as the "chance of rain" or "chance of precipitation".
EXAMPLE
ZONE FORECASTS FOR NORTH AND CENTRAL GEORGIA
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
119 PM EDT THU MAY 8 2008

GAZ021-022-032034-044046-055-057-090815-
CHEROKEE-CLAYTON-COBB-DEKALB-FORSYTH-GWINNETT-HENRY-NORTH FULTON-
ROCKDALE-SOUTH FULTON-
INCLUDING THE CITIES OF...ATLANTA...CONYERS...DECATUR...
EAST POINT...LAWRENCEVILLE...MARIETTA
119 PM EDT THU MAY x 2008

.THIS AFTERNOON...MOSTLY CLOUDY WITH A 40 PERCENT CHANCE OF
SHOWERS AND THUNDERSTORMS. WINDY. HIGHS IN THE LOWER 80S. NEAR
STEADY TEMPERATURE IN THE LOWER 80S. SOUTH WINDS 15 TO 25 MPH.
.TONIGHT...MOSTLY CLOUDY WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE EVENING...THEN A SLIGHT CHANCE OF SHOWERS
AND THUNDERSTORMS AFTER MIDNIGHT. LOWS IN THE MID 60S. SOUTHWEST
WINDS 5 TO 15 MPH. CHANCE OF RAIN 40 PERCENT.
What does this "40 percent" mean? ...will it rain 40 percent of of the time? ...will it rain over 40 percent of the area?
The "Probability of Precipitation" (PoP) describes the chance of precipitation occurring at any point you select in the area.
How do forecasters arrive at this value?
Mathematically, PoP is defined as follows:
PoP = C x A where "C" = the confidence that precipitation will occur somewhere in the forecast area, and where "A" = the percent of the area that will receive measureable precipitation, if it occurs at all.
So... in the case of the forecast above, if the forecaster knows precipitation is sure to occur ( confidence is 100% ), he/she is expressing how much of the area will receive measurable rain. ( PoP = "C" x "A" or "1" times ".4" which equals .4 or 40%.)
But, most of the time, the forecaster is expressing a combination of degree of confidence and areal coverage. If the forecaster is only 50% sure that precipitation will occur, and expects that, if it does occur, it will produce measurable rain over about 80 percent of the area, the PoP (chance of rain) is 40%. ( PoP = .5 x .8 which equals .4 or 40%. )
In either event, the correct way to interpret the forecast is: there is a 40 percent chance that rain will occur at any given point in the area.
 
mcd1832.gif


Mesoscale Discussion 1832
NWS Storm Prediction Center Norman OK
0102 PM CDT Thu Aug 22 2019

Areas affected...Parts of southwestern/south central Virginia and
northern North Carolina

Concerning...Severe potential...Watch unlikely

Valid 221802Z - 222000Z

Probability of Watch Issuance...20 percent

SUMMARY...An evolving cluster of thunderstorms may persist, and
could intensify further, while spreading eastward along the western
into central Virginia and North Carolina border area through 4-6 PM
EDT. This activity may be accompanied by a period of strong wind
gusts, which, while probably remaining mostly less than 50 kt, could
still be locally damaging.

DISCUSSION...Weak inhibition associated with a relatively cool
pocket of air aloft (in the 700-500 mb layer) has allowed for
initiation of scattered thunderstorm activity along the Blue Ridge.
Perhaps more prominently, a cluster of thunderstorms appears to be
emerging from the upper Tennessee Valley, in the presence of light
west-southwesterly deep layer mean flow on the order of 10-20 kt.

Mid/upper support for the evolving storm cluster appears weak to
negligible, or is at least unclear, but activity may have already
supported the development of a substantive surface cold pool, with
2-3 mb 2 hourly surface pressure rises noted in the 17Z surface
observation from Bristol/Tri-City TN. The leading/eastern edge of
this cold pool appears to be advancing eastward at 25-30 kt, and is
providing the focus for renewed vigorous thunderstorm activity.
This appears likely to continue, with further intensification
possible, as it advances east of the higher terrain into a warm,
seasonably moist boundary layer characterized by CAPE up to 2000+
J/kg.

As convection is maintained, the cold pool may continue to
strengthen and pose increasing risk for potentially damaging winds
along its gust front, roughly either side of the western/central
Virginia/North Carolina border area through 21-22Z.

..Kerr/Guyer.. 08/22/2019
 
Very windy with the storm here north of Mt. Airy.
 
And here we go.

Severe Thunderstorm Warning
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Raleigh NC
307 PM EDT Thu Aug 22 2019

The National Weather Service in Raleigh has issued a

* Severe Thunderstorm Warning for...
Southeastern Granville County in central North Carolina...
Northeastern Wake County in central North Carolina...
Western Franklin County in central North Carolina...

* Until 345 PM EDT

* At 307 PM EDT, a severe thunderstorm was located near Wake Forest,
or 9 miles south of Creedmoor, moving east at 15 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
Raleigh, Creedmoor, Wake Forest, Franklinton, Rolesville,
Youngsville, Falls Lake, Falls Lake State Rec Area, Falls Lake Boat
Ramp and Purnell.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Straight line winds can blow down trees, power lines, and damage
mobile homes and other buildings. Seek shelter in a sturdy structure
until the storm has passed. Stay away from windows as flying debris
generated by damaging winds can be deadly.

&&
 
IF OUTDOORS





Avoid water. Avoid high ground. Avoid open spaces. Avoid all metal objects including electric wires, fences, machinery, etc... Where possible, find shelter in a substantial building or in a fully enclosed metal vehicle with the windows completely shut.Unsafe places include underneath canopies, small picnic or rain shelters, convertibles or near trees. If lightning is near when you are outside, you should crouch down, put feet together, and place hands over ears to minimize hearing damage from thunder. Also, avoid proximity to other people.





IF INDOORS





Avoid water. Stay away from doors and windows. Do not use a hard line telephone. Take off headphones. Turn off, unplug, and stay away from appliances, computers, power tools, and TV sets. Lightning may strike exterior electric and phone lines, inducing shocks to inside equipment
 
BirdManDoomW said:
IF OUTDOORS





Avoid water. Avoid high ground. Avoid open spaces. Avoid all metal objects including electric wires, fences, machinery, etc... Where possible, find shelter in a substantial building or in a fully enclosed metal vehicle with the windows completely shut.Unsafe places include underneath canopies, small picnic or rain shelters, convertibles or near trees. If lightning is near when you are outside, you should crouch down, put feet together, and place hands over ears to minimize hearing damage from thunder. Also, avoid proximity to other people.





IF INDOORS





Avoid water. Stay away from doors and windows. Do not use a hard line telephone. Take off headphones. Turn off, unplug, and stay away from appliances, computers, power tools, and TV sets. Lightning may strike exterior electric and phone lines, inducing shocks to inside equipment
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You are a life saver. Thanks.
 
Got a nice storm with the warned storm earlier. Heavy rain, lots of loud thunder, and some lightning. Looks and sounds like I am about to get another one, too.

So far the forecast today and the warnings have been on point for me. And I continue to get more storms when not under a watch versus when I am.
 
SD said:
Incoming!
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Severe warned. The NWS obviously forgot about the sink air anom and also the fact that I just got back home. Sorry man. ?
 
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