"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".

Thursday, September 8, 2011

Nate's Fate (or Lack Thereof) Grows Uncertain By The Hour - And Maria?

Analysis From www.spc.noaa . gov   , The Storm Prediction Center. This nformation is extrapolated from trends, observations, and the RUC Model (without going into the finer details). This Image shows a 'disturbance' or vorticity maximum (max) crossing Central Florida. After which, things will be quite calm for a majority of the day, East Central. Another disturbance is shown to cross Central Florida During the afternoon (lower left). South Florida will remain the most unstable throughout the day, while north of the Purple area some recovery from passage of the first disturbance will take all of the afternoon to accomplish. In short, rain chances end up occurring in the same places and at the same time as yesterday for the day with some minor differences.
TODAY/FLORIDA: A disturbance is crossing Central Florida now but you'd never know it from looking outside. In its wake will be some minor drying in one atmospheric level and NVA (negative vorticity) and subsidence over Central Florida. South Florida will not contend with this settling of the atmosphere and will grow increasingly unstable during the afternoon, although the level of instability attained yesterday so far does not look to be as great as yesterday to start with.

Meanwhile, further north the passage of the boundary shown in orange above continues to impact North Florida. In fact, Tallahassee last hour was 56F degrees and Crestview was 59F. Many other readings hovered close to 60F this morning with much drier air. This influx of lower dewpoints (drier air) reaches to Flagler County  toward Brooksville if not closer toward North Tampa Bay. Temperatures this morning actually got into the low 70Fs in many locations, and last I looked Okeechobee was at 68F with light fog. It has been a LONG time since temperatures have gone this low..since late Spring.

Thus, it will take a while for the atmosphere to be in working order for storm generation today (Central)since the sun rises a bit later and is at a lower angle in the sky. Regardless, with enough destabilization at work   under sunny skies (clouds not a problem like earlier yesterday) and another disturbance approaching..thunderstorms are again a good bet across South Florida and portions of South Central Florida mainly along the east side from Vero Beach south to Ft. Lauderdale or just north of Miami beginning just away from the coast sometime after 2:30pm -3:oopm time frame. Not sure a sea breeze will come into play today, but I suspect a light one can sneak in there.Some of these storms could be rather strong with gusty winds and inherent lightning strikes.

There is a chance that if activity gets started earlier(South) than expected that outflow from these storms will work back away from the coast and generate another round well west of I-95. That same outflow could press north to St. Lucie/Indian River/and Southern Brevard Counties for activity after 4-5pm.

Further north the thunder chance looks a little less certain, but a storm might be able to get going near the Surface boundary in Northern Brevard due to outflow moving north from earlier storms to the SW and South and ramming into the prevalent synoptic scale frontal boundary.  Once again, rains could linger until around 8pm in light fashion along to just off the coast of Central Brevard south to St. Lucie Counties.

Even further north, do not believe that much beyond the Volusia county line the atmosphere will recover enough with ample moisture in depth coincident with the vort max passage to generate anything other than rain showers...but changes are in the works and this could change during the course of the late morning to early afternoon. So far though, not seeing through any guidance for storms to transpire beyond what has already been written above.

FRIDAY: Models again are showing a series of disturbances to cross the central peninsula..even more pronounced than today. Almost makes one wonder if they aren't 24 hours slow. Regardless, tomorrow looks again similar to today..however, as noted yesterday, moisture and the boundary will lift further north as Katia moves away and further North as well. That factor combined with the agreement that high pressure will press in from the east across South Florida in the wake of Maria. Dynamics should then also cross further north but not be as strong, so the fate of Friday is a bit uncertain, especially over South Florida where there will be near zero dynamics other than daytime heating, (which should be sufficient for thunder west of Miami Metro in the Glades).

BEYOND: Saturday and 'Beyond' depends on the pressure  and moisture pattern more closely related to tropical activity, which has been changing rapidly this morning now that overnight model data has become available and will still be filtering in through 3 pm this afternoon. Speaking of the Tropics:

TROPICS: In summary and to cut to the chase, models are trending to agree to disagree this morning. Last night almost all guidance was in near complete and total agreement that Tropical Storm Nate would be doomed for shelling pesos in Mexico; however, the 2AM GFS (which has been quite good all summer)...just shifted gears into reverse. It was first to show that NATE would now lift out of the BOC (Bay of Campeche) once Katia pulls further away...and other more frequently processed data is starting to follow suit.

 Although there is very dry air over the Northern Gulf behind the boundary that is over Central noted previously, that boundary is to lift north as Katia moves further north and the ridge builds in across South Florida (Friday). This in turn lifts moisture north as well as merges it with some that has oozed south around the backside of the broad expanse of territory covered by old Lee which is now all in the mid-levels of the atmosphere. Until this can be fully ascertained to be of truth, the future forecast for Florida remains uncertain. We will know with much greater certainty though by 3pm this afternoon. But note that even the shorter term track models are trending the turn northward as opposed to only 3 hours ago prior to this writing.
Most recent 8AM EDT information. Earlier, only 2 tracks took NATE northward. I have also drawn in YELLOW the latest forecast 2AM track of the GFS Model. The official forecast track is shown in WHITE.
Note that the GFS takes NATE as a tropical Storm/Depression into a loop around North and Central Florida as the system begins  to bump heads with high pressure building across the Mid-Atlantic Region. 
NATE is shown in the little white circle , center of image. In lavender is the error of margin in the official forecast track. Two things to notice is that there is abundant heat energy to the north of the system, partially under that dry air by those reds and oranges over the Northern Gulf Coast region. There is energy under that dry air though, as well as in the Caribbean. The CARIBBEAN has not been touched this hurricane season and could easily remain a hot bed for future activity. That area has been shown to get active from time to time now...but guidance has yet to figure how, when, or why.

Elsewhere, there is Maria. This storm is just ekeing out  tropical storm strength and is moving rapidly to the west around 23 mph. I've noted in this image the forecast margin cone of error the Hurricane Center has generated (yellow arrows). Included as well are notes that the greatest shear currently is toward the north side of that cone and the best heat energy is located to the south side of the cone. Forecast tracks of consensus models are very close to the official forecast track, but several other models are taking Maria further south toward the Central Leeward and maybe even northern portions of the Windward Islands. That is what the NAM model has been showing, but then again, the NAM has not been remotely reliable in months. 

Here we see the steering in the white arrowed lines. If Maria remains weak (which looks likely at this time)..the storm could continue west and into the greatest heat energy levels in the water. This heat energy extends into the Caribbean. Thus, this storm ALSO needs to be watched, although all models at this point are taking Maria well north of the windward islands, and then to curve out to sea even further east of the U.S. than Katia has. 
Lastly, some model guidance had indicated that a tropical wave would be pushed out ahead of Maria toward the Caribbean and South Florida during the next 72 hours. Whether or not this will even come to fruition is too soon to set in concrete, but if so, would affect the weather outlook for Florida going into latter parts of the weekend.  Also to note, the GFS has been showing every other run or so for another storm, perhaps Ophelia, to form or move into the Caribbean heading toward the last week of September. The last run no longer shows this. Perhaps it was actually picking up on Maria though but has yet to resolve the information as it filters in (?).  

To further complicate matters is that fall is trying very hard to take hold of Florida. Typically, the first cold frontal passage into Central Florida occurs during the mid-last portions of the month, although last year this did not happen in full until September 31st. It was with that event that summer ended immediately overnight with a flick of a switch as a tropical system cut past far South Florida.  That event ended summer for all but SW Florida for another 7 days as easterly flow took over. The GFS of 8pm showed that to occur as soon as next week, but as of 2AM that all abruptly changed. We will need another 2 runs to confirm  Which will it be..End of Summer or Beginning of Fall? 

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