"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".

Tuesday, September 7, 2010

Interesting Mesoscale Labor Day

(Image: LDIS plot of averaged midlevel winds shows a counterclockwise circulation over Okeechobee County and lots of moisture (blue))
RECAP: As mentioned yesterday, it appeared there might have been some sort of low pressure circulation Okeechobee County. I've included an image depicting the averaged mid-level winds from around 6pm last night. If you follow the direction the barbs point, it does indeed draw out a counterclockwise circulation in that spot 8 hours after that observation. This was not a tropical fact, it really wasn't a low at all, at least not at the surface as was observed by looking at surface barometric pressures for the same area. Otherwise, very light winds at the surface prevailed before the showers formed, and I was on the hunt for waterspouts. It was also observed that once heating began some very strange low level clouds were racing down the barrier islands ...parallel to Merritt Island and the A1A strip from North to South. Although winds just above them were very light. Something strange was going on yesterday, and it got more complex as the day wore one. The potential for waterspouts/funnels quickly waned by 1pm and was replaced with building thunderstorms across extreme East Central Florida whereas south of Palm Beach it remained relatively dry. One of the greatest lightning generating storms passed nearly over the same location as the previous day somewhere just west or southwest of Rockledge as it appeared on data. Hard to say for sure. Eventually all of East Central to Southeast Florida filled in. Also, shortly before the time I saved the included image there was a brief period of quite gusty winds from the ESE right along the coast perhaps exceeding 25mph. They were probably associated with outflow from heavier rains to the south, but the direction from which they came from was suspicious. In any case, whatever "that" was over Okeechobee is long gone...I suspect it lost identity and drifted south, which would explain the eruption of storms over extreme SE Florida and right on Key Biscayne around 9pm last night.
SYNOPSIS: Broad area of high pressure over the SE states with the axis as far north as the Carolinas. Much drier air worked south over the North half of the state to as far as Vero, but it seems that was mostly dry air in the most upper levels. Sure enough, the KSC sounding just became available and is showing a PWAT of 2.14" (very moist). Winds are generally light from the east at all levels, although there was oddly a slight offshore component to flat out calm winds over Brevard and Indian River County at sunrise and even now at 8am. Regardless of the surface winds, showers have a definitive east to west motion and have been pushing onshore the Shuttle Launch pad area to Titusville, with the latest one working into near Oak Hill in Southern Volusia. It appears the southern extent of dry air is being eroded from the south right at Central Brevard, and animations show this trend continuing at another location well off shore. Very oddly, it almost appears that a cyclonic circulation might be imbedded in the mid-level almost right over the tip of the Cape as I write right where the winds are nearly calm and skies are blue. Showers are wrapping around the top of this 'circulation', circumventing Central and South Brevard for the time being. Elsewhere, a shower came in near Ft. Pierce, but the area from roughly St. Lucie County south is under a totally different weather regime for the moment with much less shower activity off shore and over the Bahamas than what is off shore East Central Florida. Nothing much else going on around the state at 7am.
TROPICAL STORM HERMINE: Hermine came on shore within a few miles of Brownsville. The lowest pressure I saw an hour ago reported was near Alice, Texas at 29.35". The winds was from the south at 39 gusting to 52mph, but was from the East the hour prior...I.e., a tropical storm, with the actual eye just to the west of Alice.
Although winds from Hermine will weaken today, the big deal with this storm is going to be the moisture as it works toward San Antonio and points North. I have a feeling we're going to be hearing about "The Moisture from Hermine" for many days to come with flash flooding becoming the big issue over the East half of Texas into Oklahoma. These systems have a weird way of behaving when they get in this region, and memorable flooding disasters in the past have occurred from similar scenarios. Needs watching, especially since it will be interacting with a cold front moving in from the west.  In the meantime, a tornado watch is currently in place for much of SE Texas as would be expected to the east and northeast of a land falling tropical system.
TODAY: Very tricky forecast at this time of day, so a lot of what I'm going to write is mostly 'gut feeling' oriented. Moisture will remain over the area with little in upper level winds, but generally from the east. Winds even now are still generally calm over east Brevard, which gives reason to suspect that greater, unforeseen forces might be at work. Initially, this day could start out as a 'teaser' with plentiful showers over the Gulf Stream waters approaching the coast from S. Volusia- Indian River County, but never quite making it to land once that get away from the Gulf Stream waters. But things could change pretty quickly between 10:00am - 1pm with heating of the day. This time frame might be the make or break point. If showers start to make it onshore in earnest, much of the first half of the day through late afternoon will be a series of showers and eventually some thunder after 12:30pm, with brief periods of gusty winds (around 25mph) near the heavy ones. With winds the way they are right now, showers might be able to form over the Intracoastal with very little movement, especially after 12pm.  Toward Indian River County to Miami things might hold off much longer. Actually, some of the models indicate little activity  from West Palm to Ft. Lauderdale essence, east of Lake Okeechobee...but we'll see. Moisture is plentiful down that way right now. My gut says that anything significant to occur further south will be west of I-95 (which by the way is pretty close to the coast) in South Florida. Maybe even much further west than that. The west coast will see the rains by mid-late afternoon from Naples to just south of Bradenton. Tampa will hold off even longer, but eventually get in the action.
The other option further north into extreme East Central Florida is that no showers make it on shore and it remains relatively rain free all day. But just inland it will be a different story..particularly west of I-95 through Orange/Seminole/Okeechobee/Lake Counties after 1-2pm and much more so by 4pm. Could see some good rain coverage today inland.
WEDNESDAY-THURSDAY: Again, another tricky period. Moisture will be aplenty, but mid-upper level temperatures could go up a degree or two which would make a significant difference as far as rainfall possibilities are concerned. No big weather systems or pressure areas will affect Central or South would expect a more summer like pattern, one which favors the inland counties and the west side of the state by late in the day, but as has been typical this summer, of less overall coverage than what one would normally expect to see.
Beyond Thursday: Nothing significant to occur per last night's models. Haven't seen today's runs as they are not yet available. But as mentioned yesterday, a pattern that could favor more of the east side of the state could be in the works by Friday or Saturday, but even that general pattern looks weak and remains a big question mark. There simply isn't much going on during the waning thunderstorm season when nothing tropical is waiting in the wings, but we still have generally 2 more weeks of the season which comes in spurts rather than being an everyday occurrence. Hints are there that we might be in for a 2-3 day period of NW steering flow aloft, which although this results in less storm coverage, some of the best storms I've seen on the east coast have come from that direction.
TROPICS: Other than Hermine, nothing much. Gaston is pretty much no more. Remnants will approach the Leeward Islands and Puerto Rico, and anything that remains beyond there would go into the Dominican Republic and be torn apart by that landmass's rugged terrain. The next storm would be named IGOR. Will IGOR be another Atlantic Storm? Probably, but we need to start watching the Gulf of Mexico in the next two weeks. Hermine really wasn't that big a surprise. Heck, we were seeing something going on down in the Bay of Campeche for days as was referred to in the posts, but it wasn't being hyped by the press ..or even mentioned. Thus, many folks thought this system came out of nowhere...granted, it did become a named entity quickly, or so it seems...only because it was so close to an affected U.S. region when this occurred. The same thing happens out in the Atlantic, but no one cares because there's no one out there to be directly affected other than folks with marine interests.

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