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Update - Tracking storms along the "thunder road"

Like so many other times this summer, we have another NW-to-SE setup where strong thunderstorms will be coming down the road near the Great Lakes toward the tri-state. Fortunately we can keep an eye on them as they move.

Updates Below (most recent 12:45pm)

Greetings, Tuesday weather blog watchers!

Looks like we'll be on storm patrol again today, as another batch of showers and storms comes down the "thunder road". We have a decent Northwest flow aloft, and any storms that develop along and south of a slowly sagging cold front will be caught up in the current and curled downward in our direction. We've got several elements working in favor of storm development (warning, a little wonky, so bear with me):

1. Decent NW flow aloft around a 500mb High, with a vorticity maximum aimed in our direction.

NAM - 500mb Chart - Tuesday PM

At other times on this blog, we've dealt with 'vorticity' before. It's a measure of twisting energy going on in the atmosphere relative to the spinning of the earth. These little guys are more potent when an area of negative vorticity (the purple) is combined with an area of positive vorticity (the red). Read like a topographical map, it can show a steep hill if-you-will. These guys are called 'short-waves' because they don't represent actual fronts, but rather ripples along a wave that can enhance anything (anything) that it comes across. You can also follow the black lines from NW to SE on the map to get a good idea of the flow.

2. Decent 'synoptic' forcing

When we talk about 'synoptic' forcing, these are the front-based things. Some external entity that comes in and provides lifting of the established weather environment overhead. Here's the surface map for this afternoon (via HPC):

HPC - Surface Map - Tuesday PM

When it gets to be the deepest part of the summer, any sort of cold front qualifies as 'decent' for lifting, as the bulk of them tend to wash out as they approach the Mason-Dixon line. Indeed, even in this case I have my doubts as to just how far south it will be able to push in such a warm, humid airmass, but according to this map it does look like it has enough gusto to get to the tri-state area.

3. Impressive 'dynamics'

Just as the above map represents the external lift that comes in to an established environment, the following maps will represent that 'established environment'... and, as you will see, it's pretty juicy (via NAM):

NAM - Available Storm Energy - Tuesday PM NAM - Lifted Index - Tuesday PM

This sort of thing is the result of the build-up of heat and humidity across the region, as well as the natural increase in instability that appears with the prime heating hours of the day. As we've said before with these maps, the higher the numbers on the left-hand map, and the lower the numbers on the right-hand map, the more fertile the ground is for strong thunderstorms.

Putting it all together, you get something like this from the Storm Prediction Center:

Storm Prediction Center - Storm Risk - Tuesday AM to Wednesday AM

So yeah, it appears we're in agreement today. The storm risk is there, so we'll be watching for it. Now, I will probably be making updates to this blog post when the updated SPC threat maps come out later this morning. The above map discusses a general 'anything' that approaches severe levels. Coming up we'll break down the likelihoods for different types of severe weather. Check back often today anyway, as the storm tracking maps below will provide a great way to stay on top of our changing weather, and whether or not it will go down-hill where you're at (or, if you'll be able to tip-toe right out around it).

Update (9:00am) - Here's the latest severe weather threat breakdown from the Storm Prediction Center:

SPC - Hail Threat SPC - Wind Threat SPC - Tornado Threat

Certainly the most attention should be paid to gusty winds. This morning we already have a line of wind damage that stretches from Darlington, WI all the way past Valparaiso, IN -- a stretch of 220 miles. It takes 250 miles of wind gusts > 58mph to qualify a storm complex as a "derecho", so this looks like it's got the guts to do it.

Our saving grace today though (and one ofthe primary differences between this event and the devastating 6/29 derecho) is that there are thunderstorms sprouting out ahead of it. This will serve to use up some of the storm energy and knock down the severe weather threat a touch. However, the prime-time heating of the day may be able to make up that lost ground, which is why the red shaded areas on the map indicate a heightened threat region.

Update (10:00am) - Here's an indication of how well the storms have been able to use up available storm energy vs. how much the heating of the day has been able to replace it for when the main line of storms comes across it:

10:00am - Available Storm Energy Change over the Past Three Hours

As the first storms stumble along, they're using up about 400 joules/Kg of air, however the rising Sun and normal diurnal dynamics are replenishing that in the interim by the same amount. Hence, the system has been able to subsist on it's way through Indiana toward Ohio. We'll be looking for-- and hoping these clouds can do better work with the help of a long distance with which to chip away at the storm energy available when the main event moves in. 

Update (11:00am) - This event, now solidly in the 'derecho' category, continues to plow through western Ohio with 50+ mph wind gusts. If you check the automatically updating tracking maps below, you'll see that there are both Severe Thunderstorm Watches and Flash Flood Watches now going up in our area. This is par for the course, and completely expected. A lot of water is coming with these storms-- an ironic consequence of needing more storms to knock down the energy ahead of the derecho itself. Anyway, it's time to check back often, or check doppler radar, etc. if you're going to have any outdoor plans, or if you live near volatile streams and creeks. 

Update (12:45pm) - Now getting into the 'busy' time. Expect the biggest impacts to be along and to the west of the Big Sandy river, but the whole region is still under the Flash Flood Watch (and most of us the Severe Thunderstorm Watch). It's a fast-moving system though, so we can expect some improving skies in time for evening plans (and fairs).

Please feel free to post storm reports and updates in the comments section. That way I can see them and forward on the information, or comment if time permits.

Regional Radar/Satellite with Warnings Tracking

Accuweather Radar

From the Storm Prediction Center (below): Click For a Larger Image

Activity Overview Storm Outlook Watches Potential Watches Storm Reports
Temperatures HD Doppler Radar Estimated Rainfall Active Warnings
Current Temperatures HD Doppler Radar Estimated Rainfall Active NWS Warnings
Click For Larger Click For Interactive Radar Click For Larger Click For Larger

Have a great day everyone!

-B

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