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"From its chamber comes the whirlwind, and cold from the scattering winds." - Job 37:9.

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Saturday, August 7, 2010

Wet Periods Ahead Through Tuesday, Finally!

SYNOPSIS: Surface frontal boundary off the NE and Mid-Atlantic coast curves WSW-W and onshore and is strewn across Southern Georgia this Saturday morning.  This boundary will sag further south toward the Florida/Georgia border by this evening as high pressure builds in behind it.  At the same time, a high pressure ridge axis is extended south of this boundary general in east/west fashion south of the peninsula in the vicinity of the Central  Keys into the SE Gulf.  The gradient flow between these two systems from the surface up to 15,000 ft is from the WSW to W in the low to mid and becomes more from the NW at upper levels.  Abundant tropical moisture at all levels is being depicted by both the Tampa and KSC sounding data.
Also shown by satellite imagery and by looking outside is considerable high level cloudiness which is being advected across the state from the ENE-NE from convection well off shore in the Atlantic east of Jacksonville to South Carolina.  Rain showers are increasing in coverage across western portions of North/Central Florida which are moving toward the east and approaching Lake County.
TODAY: Not much change overall in the synoptic features other than that the frontal boundary in South Georgia will sink further south by late afternoon toward the Florida border. A definitive west to east steering current for showers and thunderstorms is well entrenched and will remain as such throughout the day. As such, the afternoon sea breeze will have a little bit of difficulty developing, but believe it will form south of the Cape but will remain only 10-20 miles west of the coast at most where it does develop. North of the Cape the sea breeze might not develop at all.  Early day high level clouds will keep the temperatures from reaching their highs of mid 90s at bay and into normal or just below normal levels...and also preclude anything more than isolated late morning showers from forming over the intracoastal waters.
Between early to mid-afternoon the shower/thunderstorm coverage now impinging on North-Central Florida will increase in coverage with other activity developing pretty much anywhere over the peninsula, particularly around Lake Okeechobee and maybe (but not as much so) over the Kennedy Space Center/Titusville region.  These two locations yesterday are where a funnel cloud was sighted (near KSC) and a waterspout was filmed (Lake Okeechobee).  Assuming the sea breeze does form south of the Cape (which would be around 1pm)...additional storms will form near the immediate East coast at that time over/near the Indian/Banana Rivers.  Additionally, as we work into the mid-late afternoon...the west coast sea breeze will push across the state. That, combined with outflows from earlier inland storm activity...will increase coverage to a broad expanse of rain and thunderstorm activity over the east 1/2 of the state by late afternoon.  Exact locations as to where the strongest activity will occur is almost impossible to determine at this time of the morning given the current/broad synoptic set up of uniform conditions.
Late afternoon-mid evening.  Activity will be begin to wane from West to East as activity moves off shore and much of the atmosphere has been worked over by the storms of the day light hours.  Additional isolated storm activity is possible though over extreme eastern portions and around the Big Lake through 9pm...especially further south around the Lake.
SUNDAY-TUESDAY: Leaving tomorrow open for another day's discussion. But will suffice it to say, just for now, that similar conditions appear to be likely as today.  Big changes could be in store though beginning over night Sunday through all of Monday and into Tuesday.  Models are not in any form of agreement as to the details of the upcoming scenario..but do agree in general that a mid-upper level low which is currently NE of the Bahamas will retrograde in a general westward fashion and toward the peninsula...or that another one will form very close to, if not over, the state during this time frame near the base of the mid-level trough just off shore.  Unlike over a month ago when a frontal boundary stalled over the state and precipitation forecasts were high and all we got was mostly cloudiness I do not believe this will be the case this time.  Wherever the center of low pressure develops we will also have pockets of mid and upper level vorticity (a trigger) rotating over the state, particularly south of line from Jacksonville on the east coast to Crystal River on the west coast.  It is also worth mentioning that SOMEBODY could be in for a 'rain event' of sorts somewhere along the East coast..anywhere from Daytona to Miami.  This would likely come in the form of flat out rain with some imbedded thunder thrown in....but seeing as how the parameters for such an event have yet to even develop this is worth only a broad brush possibility mention at this time.
Again, the models do not agree at all on the specifics..but do agree on generalities. They also agree that whatever does develop should be out of the picture and west of the state by Wednesday.  These mid-upper level features are very difficult to predict at this time of year when the jet stream is well north near the Canadian border...they seem to have a mind of their own.  Who knows, the region of question which is forecast to develop might move slower than forecast and linger into parts of Wednesday (but at this time that scenario does not appear likely).
FRIDAY-NEXT WEEKEND: After a brief interlude of rain activity as the synoptic features transition (Wednesday-early Friday) it currently appears that the Atlantic ridge of high pressure will re-establish somewhere across South/Central Florida to Central Florida with abundant moisture remaining in place. The exact placement of this ridge will determine shower/storm motion in the future and what areas will be most likely to receive afternoon and evening thunderstorms.

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