forecasting

Hello All,

Let me first say that I am not an expert when it comes to forecasting, but with use of the Short Fuse Composite developed by Jim Johnson (DDC NWS), I have found an EXTREMELY useful tool for forecasting where severe weather and even tornadoes will occur. To position yourself in the most favorable area for tornadic thunderstorms, you need to be just downwind of the area where the 1.5g/kg/hr moisture flux convergence isopleth (shows up on the short fuse x 10) overlaps the axis of potential temperature advection within the plateau of maximum instability with a cap of 0° to 2° C.

First example is the Almena, KS tornadic event. Below are several short fuse composites from that date, used with permission of Jim Johnson, DDC NWS, from around 1 PM CDT through 5PM CDT.

Note: These images (thumbnails on this page) have been inverted to go easier on the printer cartridge, in case anyone wants to print them. See the originals at the DDC URLs below.

	1600 UTC. The short fuse showed a huge bullseye of moisture flux convergence just southwest of the surface warm front between DDC and P28 (Medicine Lodge). Nearly coincident was an axis of potential temperature advection with a max near GCK. Also note that there is a moisture flux convergence minimum where the dryline bulge was beginning in the western OK panhandle area. The second chart shows a max LI of -13 in the OK panhandle area with virtually no capping (hence most chasers went to the OK and TX panhandle area). The warm front was moving north, so it would be reasonable to assume that with time this focus area would also move north.
	http://www.dodgecity.net/nws/jun39916z1.gif http://www.dodgecity.net/nws/jun39916z2.gif		Original plots by NWS DDC

	2000 UTC (3 PM CDT): You can see that the smfc has now moved into NW Kansas along with the potential temperature advection maximum. The second chart shows that the maximum LI has also moved northward into KS and the cap is eroding. A narrow line of cu was also forming at this time from GCK to west of HLC (I verified this).
	http://www.dodgecity.net/nws/jun39920z1.gif http://www.dodgecity.net/nws/jun39920z2.gif		Original plots by NWS DDC

	2100UTC (4 PM CDT) An hour later shows the smfc max just south of Colby, KS and the potential temp advection maximum slightly south. The moisture flux convergence max is now just downwind of the max of potential temperature advection. There is speed convergence in the surface wind streams in the area. The second chart continues to confirm destabilization with an axis of high LIs now working to the northwest of Norton. The line of cu was becoming more developed with tcu showing on satellite just west of HLC (I verified this).
	http://www.dodgecity.net/nws/jun39921z1.gif http://www.dodgecity.net/nws/jun39921z2.gif		Original plots by NWS DDC

	2300 UTC. At 5 PM, there was not much change in smfc maxima and potential temp advection maxima. The second chart shows the largest LI axis continuing to work north into the area where the first towers were developing. I could now see this cb blowing up to the west of HLC along this axis. This is the storm that would produce the long-track Almena tornado 2 hours later. Unfortunately there are no other Short Fuse charts available for that hour.
	http://www.dodgecity.net/nws/jun39922z1.gif http://www.dodgecity.net/nws/jun39922z2.gif		Original plots by NWS DDC

I have found that using these charts along with forecasting where the surface features would move, thus forecasting the movement of these maximas, has been very useful in forecasting where severe weather would occur later in the day. I used these charts in 23 out of state chases this year and in 22 chases severe weather occured, including visibly verifying 12 tornadoes. This system has worked for me and I know it can for you, too. Research on this system by the DDC NWS has shown that thunderstorms moving into the primary area as outlined at the top of this page have an 85% probability of producing a tornado within one hour and a 65% within 2 hours. Pretty incredible odds wouldn't you say????

I will post two more cases where this worked for me this year and produced visible tornadoes. They will be the 4/2 Altus, OK tornadoes, and the 4/21 Carrier, OK tornado, both of which I witnessed.

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Special THANKS! to the folks at NWSO, Dodge City, KS, for putting out these products. Check out their Storm Chaser Stuff for additional info on the Short Fuse Composite and more.