"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".

Wednesday, August 25, 2010

Potentially Interesting Forecast Days Through Saturday

(Image: Sunrise on this date one year ago near the Cocoa Beach Pier)
RECAP: Deep, moisture laden SW-WSW flow prevailed yesterday with a few rampant rumbles of thunder, but for the most part rains were light of stratiform (non-cumuliform) nature. Eastern portions of Central and SE Florida from near West Palm to Ormond Beach had their 'peak experience' between 1pm -4pm followed by a broad expanse of stratiform type rains from Indian River County toward Daytona to the north to the west coast. This activity was enhanced through the early-late evening over far eastern portions of Central Florida due to a vorticity max the moved slowly offshore extreme North Brevard. As such, there was very light rain reports continuously for 4-6 areas over this area.  This morning it was primarily Palm Beach County and areas to the WSW that were under a stratiform shield all morning..that very light rain is quickly coming to an end.
SYNOPSIS: Weak area of low pressure continues near the Georgia/Alabama border (southern most parts) at 11:30am with a quasi-stationary boundary snaking roughly WSW and ENE-E ward from it. Ridge of high pressure continues over the Florida Straits. The strongest of WSW winds at the mid-levels seems to be over E. Central Florida with winds in that elevation nearly 30 knots uniformly from the WSW. Finally have a chance to see the KSC sounding again today and things have changed. Both the 700mb/500mb level temperatures have dropped roughly 2C degrees from the past two weeks.  Convective temperature is 88 degrees which we will just barely reach, and if we do it won't be until at least 2pm due to the nuisance mid-level cloud deck overhead much of the state. Another weak surface and mid-level low is persisting in the far west-central Gulf as alluded to yesterday in the tropical portion of the post. This feature will unlikely form into a tropical entity, but it's continued presence will serve to exasperate the forecast as we work into the Friday/Saturday time frame (see more on this below).
TODAY: Given the current synoptic set up combined with the latest sounding, satellite, radar data...much of Central and South Central Florida could have moderately strong thunderstorms today (due to down draft winds in and very near heavy rainfall); the clincher is the mid-level cloud deck which will put a damper on what would otherwise be some down right decent instability due to its preventative surface heating properties.  Indeed, in the pocket least covered by clouds earlier today a thunderstorm went up without hesitation during the last hour over Volusia County just north of Oak Hill. Observed earlier today as I was outside was a low altocu deck of clouds with little white tufts on top of them (wanna be altocumulus castellanus)...indicative of some rising air in that layer and instability. Upon seeing this cloud formation I was eager to see the KSC sounding. In fact, some of these cloud patches showed up on radar as light rain (even though there was none to be felt on the ground).
Believe that some patches of thunderstorms will eventually form, although any thunder will be isolated.  But any storms that can manage to eke out could be strong, particularly between the hours of 2:00pm -7pm.  I'd be watching the sky towards the WSW today during that time frame if you're looking to avoid rain an not having an umbrella handy.  Inland folks, don't forget to look up too...showers could form directly overhead.
Storms could be much stronger today if (1) we got a light sea-breeze to work, (2) the mid level clouds were not out there. But such is not the case, so "The Summer of 2010 - A Tale of Weak Storms" (not to discount the handful that has occurred) will continue otherwise.  The mid-level clouds and thus lack of surface heating also prevents the lake breezes to function in full - - one additional defunct in the thunderstorm producing machine today.
If one isn't in or near a thunder producing storm today, it will be just 'another cloudy', muggy day that could eventually end up in 'drip drip drip' mode by dinner time....just like the last two. Interestingly, though, the NAM shows that convective precipitation could pile up along the East Central Florida Coast during the early evening whereas the RUC shows virtually NADA pretty much everywhere. I'm hedging more toward the RUC solution but not in full. At least not as of 11am...the folks in south Brevard toward West Palm might be the ones getting the 'real rains' when all is said and done. We shall see.
THURSDAY: WSW - SW flow will be in the process of pulling out during the course of the day. Mid-upper level clouds will once again be a big factor for determining the eventually meteorological outcome for the remainder of the day. More cloud cover would mean less destabilization and weaker low level convergent boundaries off the larger lakes as well as the strength of the sea-breeze. Models are insistent on keeping a narrow swath of 15-20kt winds just above the surface over East Central Brevard tomorrow...such a narrow slot that it's probably negligible. Still seems assured the sea breeze will form south Sebastian-Vero..but further north it's  touch and go. Don't think we'll see as much cloud cover in the morning tomorrow (or Friday) just might be one of our last big fling days at our chance for a good summer thunderstorm  over coastal East Central Florida for the year.
FRIDAY-SATURDAY: Mainly putting these two days together because it is this time frame that things get SO sketchy. The NAM, and to some degree the GFS, indicate that  weak surface-mid level lows could form off the Central Florida East Coast at the tail end of the stronger mid-level southwesterlies as they pull out. The other low is depicted somewhere along or near the Gulf Coast of the western Florida Panhandle.  As mentioned earlier in the synopsis, this low seems to be generated from an inverted trough extending from the low in the far western Gulf toward the Mississippi River mouth or just east of there. Thus, the longer that Gulf low persists without moving into Mexico or near Brownsville..the more we'll have to watch for this possibility. The most pronounced one at this time is the Atlantic low. The past couple of runs of the GFS were showing continued rain chances for extreme eastern portions of Central Florida with little explanation as to how this could be other than that the moisture we have had lately remains in place longer than what one would normally expect...but now there is another reason why rain chances might continue for a bit longer. This would likely not be of thunderstorm nature though regardless..particularly on Saturday. We're going to have to see what comes out of the upcoming situations before digging into this presented 'forecaster grave'. (ie., shooting myself in the foot).
MONDAY - MOST OF NEXT WEEK: By this time whatever does (or doesn't) form off either coast should be out of the picture as we shift into a different mode through much of the first week of September along the Florida East Coast. Don't like it..but the first signs of early fall and the end of the daily thunderstorm cycle mode are showing their signs of coming to a fatal demise. We have one more chance of this type of day for the 'afternoon cycle' to occur as it looks now...but that's still at least a week away beyond Friday.  Otherwise, we shift into more of an early fall mode, where our most significant rainfall events are of tropical (directly or indirectly generated) origin. After about September's more toward South Florida and the West Coast.
TROPICS: Watching Danielle, and soon to named Earl, then perhaps Fiona in the next 72 hours or so.  The GFS run over night was plain crazy. Clustering all 3 systems so closely together that none of them gains a winning hand and keeping them at Cat 1 or perhaps 2 strength or less. Additionally, it took Danielle into New York City!..interesting possibility, but remember, earlier this same model took what was yet to be Danielle into Daytona Beach.  Note: that is not a forecast, just an observation. The system in the Gulf is no threat to Florida or anyone for that matter, other than an open handed slap in the face for maybe some flooding near the Texas/Mexico border coast...but that is yet to be seen or forecasted.

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