Can someone help with beginner forecasting? (4/27 Event discussion)

[Jessie Schafer]

So... super noob/amature here. I'm currently stationed at an Army base in south central MO. Per the SPC there is currently a 15% probability highlighted here
I know I can go to the Target area discussion, as i often do to as i am a huge fan of the senior members here, but it doesn't seem like anyone is talking much about the 4/27 event.

I have been looking at the SREF model runs and was hoping someone could help me interpret what I am looking at and why this doesn't seem to be a big event or what makes it a possible bust.

I have no formal training aside from what I've taught myself, and this is the first time I've sat down and really tried interpreting Data from forecast tools, so please go easy on me

what I *think* I am seeing is roughly 1500-2000 j/kg SFC CAPE, and mid 60s Dew Points, so it seems like where I am located lies in the northern periphery of the better moisture. Not substantial, but good enough?

Now lift I really have a hard time wrapping my head around sometimes. What makes adequate lift and at what MB should I be looking?


AND



My area (South Central MO) seem to be lacking in good lift and shear from what I can see.

[Broken External Image]:http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_0-6KMSHR_SSB_MEDIAN_MXMN__f072.gif

If I am looking at this all wrong please feel free to give me constructive criticism. I am always willing to learn, especially if you take time out of your day to respond.

Thank you in advance for helping an amateur out.

SSG Schafer
U.S. Army

 

[Randy Jennings]

You on the right track for 2 of the 4 ingredients. 1500-2000 j/kg SFC CAPE is enough instability to get the job done, although you do need to look at CIN (cap strength) too. I quickly took a look at CIN, and the NAM makes the cap look a little strong in your area, GFS makes it look breakable. You got moisture. Mid-60s Td (dew point temp) can get it done too, even if it doesn't;t make a chaser salivate.

The other thing you need for a thunderstorm is lift. That is probably the hardest thing to get right. Lift probably makes a chase go bust more often than any other element. There is large scale lift ahead of upper level disturbances; this is not really enough to get thunderstorms. What typically get's you thunderstorms is the small scale lift ahead of boundaries. Drylines, fronts, and outflow boundaries are the sources of small scale lift, although just because you are near one doesn't mean you will get enough lift. I suggest you go to MetEd, signup for a free account, and search for lift and start taking it all in.

Wind shear is the element that makes a thunderstorm a severe thunderstorm. Wind shear separates the updraft from the downdraft and can cause a storm to rotate. There are 2 kinds of shear - speed and directional. Speed shear means the wind is blowing at different speeds with height (faster as you go up). Directional shear is when it blows in different directions at different heights. You want both. Deep layer shear (0-6km) of 35+ knots will cause mid-level rotation. Low level shear (0-1km at 20+ knots) is what can get low level rotation and seems to be one of the keys to get tornados. Soundings (aka Skew-T) can get you an idea of how pressure corresponds to altitude. Hope this helps.

 

[Jessie Schafer]

You on the right track for 2 of the 4 ingredients. 1500-2000 j/kg SFC CAPE is enough instability to get the job done, although you do need to look at CIN (cap strength) too. I quickly took a look at CIN, and the NAM makes the cap look a little strong in your area, GFS makes it look breakable. You got moisture. Mid-60s Td (dew point temp) can get it done too, even if it doesn't;t make a chaser salivate.

The other thing you need for a thunderstorm is lift. That is probably the hardest thing to get right. Lift probably makes a chase go bust more often than any other element. There is large scale lift ahead of upper level disturbances; this is not really enough to get thunderstorms. What typically get's you thunderstorms is the small scale lift ahead of boundaries. Drylines, fronts, and outflow boundaries are the sources of small scale lift, although just because you are near one doesn't mean you will get enough lift. I suggest you go to MetEd, signup for a free account, and search for lift and start taking it all in.

Wind shear is the element that makes a thunderstorm a severe thunderstorm. Wind shear separates the updraft from the downdraft and can cause a storm to rotate. There are 2 kinds of shear - speed and directional. Speed shear means the wind is blowing at different speeds with height (faster as you go up). Directional shear is when it blows in different directions at different heights. You want both. Deep layer shear (0-6km) of 35+ knots will cause mid-level rotation. Low level shear (0-1km at 20+ knots) is what can get low level rotation and seems to be one of the keys to get tornados. Soundings (aka Skew-T) can get you an idea of how pressure corresponds to altitude. Hope this helps.

Thank you for taking the time to explain some things to me, it is greatly appreciated.

and it does help. I will check out the site you gave me as well, happy chasing brother!