"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".

Monday, June 27, 2011

Storm Feast or Single Serving? Big Question, Huge Differences For Today

Image portrays the jet stream level winds for early through mid-late afternoon. These winds of 40-45Kts are forecast to shift a bit south during the course of late afternoon into the evening hours.

IN GENERAL: Big debate of the day for South Central and Central Florida today is this: Will it be downpours with 2-3 inches of rain possible and frequent lightning, or will there just be a few storms with most of them on the west side of the state by later today mostly over Interior North Central Florida toward the Panhandle? The debate is up in full gear. For today's post, I'll elaborate on the worst case scenario (the most rain)...but do note, as of this writing it appears there is a 1 in 4 chance of this potential.

SITUATION: Today's activity does not appear it will driven so much by sea breezes as much as it will be by true, gradient flow. The Surface to 2000ft ridge axis is forecast to lift toward North Central Florida today providing for easterly flow, which turns more toward the SE later today. Meanwhile, mid and upper level winds remain from the SW-W because the ridge in the mid levels remains over far South Florida. This equates to steering over portions of South Central and all of North Central to be from generally the west, but at only about 10-15mph. 

The big fly in the ointment today is the cloud cover. The convective temperature per the KSC sounding of recent has a convective temperature of 87F (down from 89F earlier this morning). That seems possible inland, despite the cloud cover. Some showers and a weak storm has materialized inland in a break in the clouds.  

Instability and moisture availability are not an issue today with precipitable water values near 2.00" just about everywhere other than South Florida.

NOW: It appears the Southerly gradient flow is enhancing the sea breeze off the Southern Tip of Florida as cumulus already appear to be forming down there and clearing the coast line, pressing north toward Lake Okeechobee.  The Lake Okeechobee breeze might also be playing a role today as that seems to be forming. It is hard to say for sure because it's happening under some cloud cover. One shower has formed over the interior of North Central and seems to be..gasp..stationary. A transition seems to be under way.

TODAY: In playing the stormy scenario as dictated by the title of the post today, the reason for the 'storms' will not be so much because of sea breeze driven boundaries as much as it would be because of a synoptic scale feature. That being, 500mb and 700mb  vorticity. If that indeed is true, convective temperatures might not be all so important today. Instability will be the driving factor behind just how 'stormy' it gets and for storms to form in the first place..or if there is too much cloud coverage remaining,  mainly storms going up quickly and turning to 'anvil rain' east of the spine of the state.

A model depiction of 500mb vorticity today later today. Some is shown of greater extent a few hours earlier further north, but it spreads southward with time. The first shower of the day in this area has materialized WNW of Daytona well inland. Note the vorticity streaming across the state further south...this is where some big storms could occur today. But this is shown by only on model. Other models have the vorticity all north of I-4.

In the image above, note the lack of vorticity over South Florida..this area is also seemingly behind their sea breeze storms south of Lake Okeechobee should be in and out of that area quickly if ever...approaching mainly off of Cuba. This vorticity stream is forecast to continue through sunset to various degrees before organizing well off to the east of the state tonight.

Now: From a different model we can pull out a plot of the Energy Helicity Index. This is a value which combines energy (Convective Available Potential Energy) which can be tapped into for convection (storms) to form with helicity which is function of, in simplest terms, corkscrewing winds aloft which also provide lift.

ENERGY HELICITY INDEX FROM 0-3KM (Kilometers) this afternoon

By looking at these two images, again, we see little over South Florida..but note that area coming off of Cuba...from the south. This could mean big storms for Cuba toward the Keys by evening.

With all given:

STRONG/MARGINALLY SEVERE STORMS: Florida Panhandle due to wind gusts of 60mph and 1" hail (very isolated).

SOME STRONGER STORMS: North Central Florida North of SR 60. Some could be magnified near the coast after 6pm from Near Vero Beach north to St. Augustine as the SE winds kick in later today under enhanced gradient / sea breeze winds. BUT..will storms make it to the coast?! 

If the bigger storms go up well to the west, with slow forward motion, their anvils will overspread the areas to their east (East of Orlando)...and kill any other activity trying to move that way. On the other-hand, if storms are driven by vorticty as shown in the first image then storms might be able to hold their own without the otherwise debilitating factor of anvil debris.

IN SUMMARY: Per the title, more questions than answers abound today. Looks like there will be a feast of storms today across portions of South Central to North Florida, but just exactly where and how they manifest is debatable. If we run with high coverage of storms, they should manifest in full between 2-3pm sometime in rapid fire fashion and continue through 8pm, gradually diminishing in coverage and strength after 7pm. Otherwise, storms will be much more isolated in nature and be  dependent upon cloud breaks, sea, and lake breezes. Most likely north of I-4. South of I-4 will have just a few storms, inland..with the areas further east covered in anvil debris or light, debris cloud rains after 5pm with few if any storms south of I-4. What a conundrum.

DAYS AHEAD: No shortage of moisture is in store. Things get more interesting in days ahead as the both ridge axis' are forecast to be south of South Central Florida, if not further south than that as an upper level trough begins to dig down the Eastern Sea Board. There is hints that one day, either Tuesday or Wednesday, will be much more quiet during the transition...on the other hand..Wednesday or Thursday could be very active once again...with even stronger storms possible than the past two days. There might even be a day where rains will not be solely confined to afternoon and evening hours.

TODAY'S HAZARDS: Mainly lightning and heavy rain (driving/flood prone areas). Some rainfall totals in the worst case scenario could be over 3". Otherwise, 1-1.75" totals could occur in the heaviest storms combined with storm debris rains hovering over those same areas. Storms will be moving pretty slowly today, but large storms will move a bit faster and cover more turf/marsh/and city.

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