My Test Forecast

[Sam Kennedy]

I've been looking at models and soundings and surface maps etc.. and thought I would have a shot at forecasting where storms and tornadoes could be.
My Guess is in 24 hours, most likely places for storms are: South Mississippi, South Alabama, the Florida Panhandle and South West Georgia.

I just want to see if anything happens from this, I will update it as the models and soundings are updated.

 

[Tim Vasquez]

Just as a reminder to everyone else, forecasts have to go in the Target Area, except for educational beginner posts such as this one.

I see you're in the UK... congrats for rising to the challenge of forecasting across the globe! As you get better with the model and analysis charts you'll be able to read more into them and see patterns emerge, and will be able to refine the forecast even better.

Tim

 

[David Wolfson]

Sam, I find it helps for learning purposes to post one's reasoning and how you arrived at the forecast. Here's an example of what might go into a FCST post.

What I just did is to take a quick look at the SPC Day 2 Outlook depiction just to see what areas they find interesting. Your area is certainly there. Next I took a look at the 500Mb 00Z Saturday WRF and GFS, What's unusual and immediately interested me is the short wave rounding the trough near the south MS gulf coast, It's a consistent upper feature and likely to induce localized convergence ahead of the gorilla cold front with what is otherwise possibly a diffuse situation until the linear forcing arrives. Also there looks to be an east-west anafront boundary across southern MS that could enhance low level helicity. So were I in those parts tomorrow afternoon I think I'd want to be somewhere like Exit 65 on I-59 west of Hattiesburg, MS.

That's just a quick example from an interested amateur, and not the state of the art, for sure.

 

[Sam Kennedy]

First I look for Surface Convergence:

Then I cross out the areas which have, or are about to be passed by a cold front.(and areas at sea, since I'm not chasing waterspouts!)

(Now lets be mature and NOT laugh at the shape! )
Then I look at the 500MB & 300MB chart, and look for divergence

Then I would check a sounding of the area

The part circled I like because the moisture is there, so no high-based storms, the part I scribbled in I like because it is nice and dry, so no HP storms.(I'm not 100% sure on this, so correct me if I'm wrong). The CAPE and CIN are alright, not brilliant though, same goes with the LI, but since there is convergence and divergence there are also other forms of lift. There is also speed an directional shear, but not too much. (You don't want your storm eating its own outflow air, just like you wouldn't eat your own... doesn't matter )

After that I would check the models for forecasted CAPE,LI and EHI values. I don't want this to be too long, so I wont post anymore images. Finally I would compare it against the SPC outlook, but I'm sure you have all checked that this morning.

That is basically what I do, please correct me because I'm sure I've got something wrong, and I've definately not included everything, so please give me some handy tips on how to make this better!

My final forecast area is North East Florida and South West Georgia.

 

[David Wolfson]

Seems like you're getting a good handle on the important factors, Sam. Two things I've observed from the good storm/chase forecasters is that they visualize and depict the conditions as they will be in the afternoon and early evening, which generally means projecting conditions forward from the morning; and that they look for little details that could help to focus an otherwise diffused storm potential.

 

[Mike Johnston]

My observations:

I'm a little unclear on where/how you were eliminating "areas which have, or are about to be passed by a cold front." The consensus forecast in the area is that the surface boundary will be lifting north as a warm front this afternoon and into the evening.

Also, once having narrowed down your forecast area, it's useful to read the Area Forecast Discussions (AFD's) of the local NWS offices. In this case, for example, the Charleston, SC, Jacksonville, FL, and Tallahassee, FL AFD's. These discussions are useful for 1) identifying local climatological factors (eg. the seabreeze boundary, in-situ wedge, etc.) which impact the forecast, and 2) identifying factors that may limit convection (eg. cloud cover impact on afternoon heating.)

 

[Sam Kennedy]

I'm a little unclear on where/how you were eliminating "areas which have, or are about to be passed by a cold front." The consensus forecast in the area is that the surface boundary will be lifting north as a warm front this afternoon and into the evening.

I thought that may have been a bad idea, I was thinking if an area was about to have a cold front pass through it, then any storm which could form would be elevated, and not feeding from the moisture lower down. Also the cold air would also cut of any inflow. I'm not sure if this is 100% correct though.