"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, September 5, 2010

UPDATE: Florida Weather Today

NOW: Surface features remain status quo with frontal boundary generally along the Florida/Georgia border and surface ridge along the southern tip of Florida. Huge explosion of convection in the Eastern Gulf west of Tampa as can been seen on Tampa's latest radar. Surface trough or boundary appears to be emanating from this complex toward Port Charlotte which is moving little. Elsewhere, appears that a very weak area of surface low pressure is forming near Southern Polk/Osceola County which the RUC has picked up on nicely.
Convection from early this morning off Daytona - Cape continues moving NE and weakening. The outflow from this convection is easily visible on animated visible satellite imagery. It managed to push through  Brevard/Volusia into Seminole and Orange but is quickly becoming indiscernible as diurnal cumulus are filling the bridge it created. As a result, an early NE wind developed along the coast, but was very light. In other words, not the sea breeze. It lingers just west of I-95 in Orange/Seminole/Osceola Counties and may become a focal point for convection this afternoon.  Lowest dew point temperatures are generally found down the interior of the peninsula though. 15z KSC sounding came in and shows warming to the standard 10C temperature at 700mb we've been encountering the past month, whereas the 500mb temp has remained constant at somewhere between -7C to -8C. It was mentioned earlier that thickness values may increase since the earlier post, and this indeed has occurred per the increased 700mb temperature. An enhanced west coast sea breeze due to early convection off Naples is sending a weak outflow toward Polk County from the SW.
It currently appears that any chance of small hail would be restricted to interior Flagler/Volusia Counties where cooler air aloft likely resides, but still need to watch to see if those thickness values alluded to in the previous post shift south again later this afternoon. If they do the tiny hail threat could be extended into Seminole, Orange, and Northern Osceola Counties.  Fly in the ointment is the convection off Tampa. Cirrus clouds are already starting to encroach parts of Central Florida due to the storm tops reaching the jet stream level right as the best heating of the day begins. At this point in time, the longer one can indulge in hot afternoon temperatures...the more likely they are to get wet much later today into tonight. Storms along the east coast could be on-going or redevelop tonight...particularly over east Brevard County where they would be the last to see rain (if it occurs at all).
Elsewhere, assuming that other storms get going which still seems pretty will be a mix of where the high clouds are most prohibitive for storm formation with where they are more likely due to a late afternoon west meets east collision with lake breeze boundaries and additional outlfows.
Storms might have a hard time reaching the immediate East Coast north of Vero Beach initially...and be more likely to do so north of the Cape by no later than early evening (before sunset)...especially in Volusia and Flagler.
MONDAY (Labor Day): No change in previous thinking other than this. It clearly ain't summer out there anymore with the lower dew points. Point is, pre-noon time convection might have a harder time to get going near the Cape, especially IF there is late evening convection near the coast and residual clouds linger. We'll just have to see what happens this evening.

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Storms Possible Today - Some May Be Strong (Later Post Likely)

(Image: Derived from the RUC, Theta-E at 7pm tonight. Note the low values north of the Florida Peninsula and the gradient indicating the surface frontal boundary)
RECAP: Rains were in small supply yesterday other than for a few select areas. The region most impacted yesterday was St. Lucie County near Ft. Pierce as well as Martin County. Like the day before, another storm went up and passed directly over Miami's Radar Beam. As expected, deeper moisture return to Central Florida came a 'day late and dollar short', but not before a small shower or two popped well after dark which fed on what heat generated remaining instability remained. This shower was located in extreme NE Osceola County which crossed into Western Brevard around 10pm. Some lightning was observed. Otherwise, the heat was own. My porch thermometer got up to 97F with a very localized delayed sea breeze. At Patrick AFB it was 89 degrees at the same time with an east wind. Within 10 minutes after this observation which was around 2pm...the sea breeze came up here as well and the temperature dropped 8 degrees within 20 minutes to 89F. Melbourne got up to 95F officially; one degree shy of their record high temperature for the date.
NOW (8:30am): Just saw the KSC 10Z (6AM) sounding. What a surprise! Precipitable Water (PWAT) is up to 1.91" from Friday's 1.71". More significantly though, 700mb temperature has dropped from +10C to +8C and 500mb temperature has dropped to between -7 to -8C...this is the coolest temperature aloft since early - mid June that I've seen (it has been at -5C). That means all summer essentially. Early morning thunderstorms went up just off the East Central Coast with mucho lightning visible before sunrise east and northeast of the Cape which from an observational perspective was very pretty to watch under locally a clear sky with the moon beaming. This activity is continuing to move away from land, and just within the past 30 minutes an outflow boundary emanating from initial collapse of these storms was visible on MLB's WSR-88D approaching the coast from just south of Daytona to the northern tip of the Cape. In the last frames that boundary appears to be washing out and making little if any additional progress into Canaveral. Some storms did back build along this boundary further north toward Daytona which couldn't quite meet the landmass. Shortly before sending this post storms really flared along this boundary which are now moving offshore Flagler County toward offshore St. Augustine. Elsewhere, no shower activity of note over or near the peninsula other than some weak showers reaching the west coast of the state well north of Tampa near Crystal River. Also of note in the sounding, there is a weak inversion and dry layer between 500-5000 ft. which will put a damper on late morning showers near the coast it seems now.
SYNOPSIS: The surface front to the north is now elongated from extreme SE Georgia to near Jacksonville westward across I-10 to between Tallahassee and Apalachicola and continues west along the extreme northern Gulf. Surface temperatures over the western Florida panhandle this morning were in the mid-60s further west and well behind the boundary. Dew points behind the boundary are in the upper 50s...whereas ahead of the boundary they are in the low 70s.  See the attached image of Theta-E values for early this evening. This indicates little motion of the boundary today. as this is how these values currently look as well. This boundary lies west and pretty much meets up with the inverted trough (at the mid-levels) emanating from a complex low pressure system which has been residing in the Southern Bay of Campeche for at least two days . This front continues NNE-NE well off the U.S. East Coast off of Maine. So essentially, all of peninsular Florida remains south of the boundary. Meanwhile, the ridge of high pressure that was somewhere between the Florida Straits and Cuba yesterday is lifting north and now is located over the Southern Tip of the state.
FIRST STAB AT TODAY: In observation of forecast 1000-500mb thickness values, there is a drop in thickness of this atmospheric layer over Central Florida this morning roughly from South Brevard to Tampa which probably accounts for the lower 700/ 500mb temperatures as noted above on KSC's sounding from 6am. This line is forecast to shift north during the first half of the day...but then return to it's current location by later this afternoon. This will be key player today, as it indicates what the upper level temperatures will be doing over our heads. Surface dew points have gone up a few more degrees across Central and South Florida, but still are not up to par for a full on summer like afternoon storm set up north of a Sarasota/West Palm line.  Mid level winds continue from the WSW but are not very strong, 15kts or less. Thus, sea breeze should start up along the entire coast within 1 hour either side of noon. Just ahead of this boundary is when a Cumulus cloud field should form and become more pronounced inland between US-1 and I-95, most likely west of I-95. We'll need to watch for showers going up along the sea breeze, particularly further south of Ft. Pierce on the east coast where greater moisture resides and winds aloft are quite light. They might be watching for waterspouts before noon from near Boynton Beach south to Miami as the mid-level ridge axis begins to move overhead there and winds aloft become very light. Otherwise, the region near or just south of Miami along the east coast MIGHT get temporarily dry slotted during the afternoon as the ridge axis passes north of their locale, which could off set the likelihood of late storms south of Miami or perhaps Ft. Lauderdale. But further north along the east shores of Lake Okeechobee over Palm Beach and Martin County chances of storms remains elevated. 
Toward Central Florida, due to initially slightly lower dew points (drier air) not believe we will see nearly as much activity as the sea breeze pushes in. Believe that later in the day as a mid-level trough passes to the north and thickness values fall once again in response,  it will be a mid-late afternoon show, initially well inland then spreading toward the east coast after 4pm almost anywhere from Flagler County, through Volusia, Brevard, Indian River Counties and further south.  Activity could linger and/or rejuvenate after dark along the coast. If in deed the cooler air aloft remains or returns as forecast, some storms could produce strong wind gusts...with the ultimate strongest producing pea hail inland where convergence boundaries first meet, particularly over East Central portions of Florida. Most assuredly though, another post will need to be made once a later KSC sounding becomes available and I can see model data that isn't 12 hours old.
MONDAY: Interesting day to say the least for Central and portions of South Central Florida. Ridge axis by noon time will be almost directly overhead the center of the state with moisture aplenty and cooler temperatures aloft. At this time, it looks like the coastal waterways and near shore Atlantic Waters could have a waterspout possibility between 10:00am -12:30pm, much like further south this morning. Steering currents for the majority of the day will be close to nil...with a continued slight westerly component well aloft and above the true steering current level.
For the majority of the afternoon and evening this will continue to be the case, but the sea breeze will have a 'propagation toward the west' influence. Thus, tomorrow could be more like a summer day than any we will see for Central Florida for the rest of the summer of 2010. Most activity and storm motion will be dictated by outflow boundaries and Lake/Sea Breeze interactions and resultant storm propagation rather than actual motion. Most of this activity will occur away from the immediate coast once the sea breeze sets in , but Orange/Osceola/Okeechobee/Lake/inland Volusia Counties are all candidates for thunderstorm activity by early afternoon.
TUESDAY-WEEKEND: First off and foremost. I'm leaning toward the GFS model in this discussion. The NAM model for 3 runs now continues to advertise a very good period of rain for East Central Florida on Tuesday (as it did yesterday) well as turns the low now in the Bay of Campeche into something resembling what would be a hurricane. In other words and as mentioned yesterday, it's being very "hyper active" with features. This has been the case for nearly a week now. The GFS is much more subtle and preferred as the tool of use, at least from a point of reference aspect.
With that preface, for this period very light, drier easterly flow ensues initially. Don't believe the coast will see showers north of Ft. Pierce as outlined yesterday...but the areas further south will continue to see showers for perhaps another day or two. Might see a brief drying out of the atmosphere on Tuesday with a period of northerly winds aloft as high pressure builds in across the Deep South, but by Wednesday mid-level flow will become lighter from the east and moisture will increase ever so slightly. Light winds aloft will not prevent the West Coast sea breeze from all sorts of chaos, primarily in the late afternoon to early evening hours will be a good bet from Tampa Bay-Naples.
TROPICS: Only thing worth noting is the low in the Bay of Campeche. The NAM model is quite aggressive with this system and practically has it a hurricane in two days, moving into SE Texas...I'm not biting on that one. The GFS shows nothing remotely close to this. Elsewhere, nothing worth getting one's dander up over for quite some time.  It looks to me like "Formerly Gaston" has two options. Either stay a no name and continue moving west, go south of Puerto Rico and the Dominican Republic (DR) and into the Yucatan...or strengthen to a depression or storm then cross Puerto Rico and the DR and die. If it gets even stronger it would curve north due to another trough that will be riding over the Deep South ridge that will be in place over Florida, Georgia, and South Carolina all week. This trough would ride over the ridge bringing another cold front to the Pilgrim/Amish States then trough on the backside of the ridge and pick up the system. Worth checking out though.

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