"But seeing they could not See; hearing they could not Hear"
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"From its chamber comes the whirlwind, and cold from the scattering winds." - Job 37:9.

"The wind blows to the south and turns to the north; round and round it goes, ever returning on its course".

Sunday, April 17, 2011

Strong Lightning Storms Possible Southeast Florida Later This Afternoon

Graphic of Severe Storm Reports Thursday -Saturday
(0.25" - 0.75" is not severe)
See third image down for much finder details
Breaking it down into Tornado Clusters/Families
An epic severe weather event started Thursday afternoon as a warm front/cold front/surface low/dry line collaborated to join forces all embedded with the periphary of a deep 500mb trough aloft. Net effect - tornadoes/hail/high winds, especially along the dryline in Oklahoma.

The parent 500mb trough continued to dig SSE-ward into the Deep South overnight and things calmed down a bit but not entirely for the state of Arkansas. Shortly after the first light of day on Friday the system rejuvenated. Closer proximity to a moisture source (the Gulf of Mexico), storms formed in SE Louisiana and all through Mississippi and moved into Alabama during the early -mid afternoon as upper level divergence in a split jet stream pattern developed, adding an 'upward vacuum' from the upper atmosphere.  Most of the reports are actually from a few long-lived/long tracking supercell thunderstorms as you can see by the 'tracks' in the next image.  A repeat performance ensued on Saturday, particularly over North Carolina where it is possible they experienced an all time record tornado event. Note the tracks of 'red tornado dots' in the image below over North Carolina. These might be all one tornado, or one that lifted with another to set down shortly thereafter from the same long-lived supercell thunderstorm. Radial velocity imagery on the Raleigh storm was clearly picking up debris within the knob of the hook echo. This 'hook' persisted for a remarkable amount of time. Warnings were issued well in advance of the storm's approach.

Here we can see the tornado reports in red. Note the storm tracks of red dots in North Carolina , Mississippi, and Alabama as well as in South Central Oklahoma. Last I heard it is possible that up to 47 deaths can be attributed to this 3 Day event, at least half of which were in North Carolina

Countless videos and photos streamed in across the Internet through all the big social media outlets such as Twitter, Facebook, and YouTube. New images and photos were coming in as fast as the next event was already occurring. This had to have been one of the most epic performances made by modern times for the United States, as equally made throughout the world during and after the earthquake/tsunami in Japan not too long ago. Perhaps some 'newly found' tornado video will eventually show up to surprise us all further in the next few days.

TODAY: A frontal system has passed through the North Half of Florida overnight. It appears the boundary will get about as far as West Palm Beach this afternoon before washing out while a thermal heat low forms over all of South Florida this afternoon. Given the synoptic scale wind pattern during the afternoon south of the washed out boundary combined with a localized east coast sea breeze strong lightning storms are possible over SE Florida beginning mid-afternoon and lasting until about sunset. There are a variety of other 'enhancing' features popping up on various models at various times...but they are never absolutely constant. 

The only factor that is to prevent the weather in South Florida from being most assuredly notable will be the weakness in the low level convergence of the sea breezes and deeper atmospheric moisture, but only as it appears now. However, it seems given that the best likelihood of said activity with those limiting factors aside will exist from somewhere to near Boynton Beach into all of  Broward County and down to near Miami Metro. It appears activity will push toward the east coast from the WNW-NW.  Temperatures aloft will be cold enough to support hail...and as is the case with any storm in Florida when hail can reach the ground rather than melt, lightning I'd think will be quite active in any storm. This has been my personal observation on numerous occasions over the years. Storms are not expected to be numerous (probably because of the limited atmospheric moisture content)..but rather the energy is expected to be 'savored' by a few select storms, wherever that may be.  There is a sharp demarcation to the northward extent as to where storms can manifest today. Latest run of one model showed a delayed onset of storms near West Palm very late in the period prior to 8pm, but not of the strength possible further south, as the old frontal boundary weakens further and the thermal low acts to break it down, pushing various parameters back northward a bit.

This image shows the 0-3KM Helicity that could be advected south and east during the afternoon

This is the RUC 1000mb (near surface) vorticity this afternoon clustered on the SE Coast. I've drawn in the expected afternoon sea breeze and noted that in another graphic a weak 500mb lobe is shown on the west side of the state

MONDAY: Prolific Lightning Storms are possible over a broader expanse of Florida to include Central Florida, when similar upper level temperatures will exist. The washed out boundary will wash out overnight and southerly winds return to Central Florida in the process.  It is impossible to say with any guarantees this morning just exactly where they will/won't occur, but at time the SW side of South Florida and the east side of South Central/North Central seem to be the favored locations.  There are areas shown this morning where I stronger storm could not occur, whereas there are other areas they seem most likely; however, given that this is a recent chain of possibilities to unfold since late last night, the evolution and/or de-evolution of tomorrow's storm chances is yet to be fully resolved, flailing figures and parameters around all over the place. For now, it's a safe bet to say there could be some isolated strong storms tomorrow over a larger expanse than that which will possibly occur today. 

FLY IN OINTMENT: There's always one doing the backstroke it seems, and tomorrow may be no different. The one clincher for tomorrow will be the amount of moisture available at around the 10,000ft level. Last night's runs first hinted at some respectable storm possibilities for Tuesday, so my eyes were focused on that day..and in even more isolated fashion. The morning 06z runs were not only sooner with the activity, but covered a more vast expanse. The 12Z runs are coming out now (one already is, I just haven't looked at it)...there is still disagreement converning the amount of moisure available aloft, as well as whether or not there will be a 'warm cap' at around 5000 ft (850mb)..which would stunt cloud growth to nothing more than cumulus clouds, no matter how unstable the surface conditions are.

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