"But seeing they could not See; hearing they could not Hear"
“The views expressed herein are those of the author and do not necessarily represent those of the National Weather Service or affiliate/related organizations. Please consult .gov sites for official information”

"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, October 25, 2011

Whether Which Witches Weather Wrist Watch is W-right?

IMAGE (11AM/TUESDAY): Old frontal boundary that provided the big cool down over Florida finally moving out into the Atlantic on its north end while the southern end lags well behind into the Caribbean. Storm system taking shape over the Rockies to move east today in the Plains with return, low level easterly upslope flow under cold, SW Flow aloft creating snow in portions of Colorado. High pressure building rapidly east northeast from Texas and into the mid-Atlantic at all levels today with return clockwise flow in the mid-levels eventually out of the east over Florida  but emanating (per streamline analysis) off Virginia by this evening, whereas longer fetch low level  flow across Florida will become more easterly across the state toward sunset and beyond. This shallow moisture return will  make for mostly sunny skies today with onshore moving stratocumulus clouds.  Hurricane Rina in the SW Caribbean moving little if at all last hour in a favorable area for strengthening, as long as it stays there. An eye was clearly visible last hour but then was obscured by the CDO (central dense overcast).  Ocean Heat Energy (the depth of warm water) is totally ample for the storm to sustain itself in this area of near zero wind shear, low level convergence, and upper level divergence.

TODAY: NE-ENE winds of 12-22mph this afternoon with a high  of 80-84F. Winds later today become more easterly and decrease a bit. Outflow cirrus clouds in the upper levels from Rina are being caught up in the Subtropical jet which has been in place 'for ages' across South Florida are  being advected to that area as a result. This should continue over this area through the day, but could come to an end tonight as a portion of the jet pulls away briefly from the state as the next trough/system approaches the Southern Plains. Overnight lows at the beaches tonight in the low 70Fs, and a good 5-10 degrees cooler further inland.

WEDNESDAY: Deeper on shore flow uniformly easterly could set up a coastal inverted trough, with moisture convergence along the coast for possible showers as soon as pre-dawn and through the day once moisture wraps from behind that frontal boundary well out in the Atlantic and manages to be advected westward around/ahead of the clockwise circulation of High Pressure building eastward into the Carolinas/Virginia and eventually centered offshore tomorrow.  Split flow over the Gulf from the departing Southern Branch tropics and the approaching Polar System (jet) in the Plains over the Gulf could induce formation of a mid-level trough into Thursday from the Central Gulf and across the Peninsula by nightfall. Once this happens, if it does, that would cut off the moisture feed by disrupting the deep easterly flow and end the chance of rain, but could  ALSO act as an elevated warm front from the tropics going into Friday (whole new story for a later time).

BEYOND: No point in going further at this point. There's as many model variations as there is hours in the 24 hour day going into Thursday through early next week. But a general observation of strictly personal note is that models are having an importunate time deciphering whatever the inevitable will be because we have 'officially' entered fall.  The general rule of thumb is that it takes one month from the time the sun is at whatever position it is at for the atmosphere to respond in the mid-latitudes through a DEEP layer of the atmosphere. The sun crossed the equator on Sept 22nd (astronomical fall). It is now just over one month later and now we have snow in the Rockies and a hurricane in the Caribbean. The mid-latitudes through a deep column are responding in earnest (granted, it has snowed already in the Rockes), while the lower latitudes are in the 80Fs with a hurricane.

The  problem the models are having is which pattern will be more dominant: 1) A polar jet stream and progressive pattern over all of the U.S.; or a 2) more progressive northerly jet stream pattern combined with a retrograding pattern in the low latitudes? Actually, both seem to be happening this morning ..and as a result the final outcome per each model varies vastly depending on which each side of the coin each one favors. To site a few examples relevant only to overnight and some early morning model runs. Or better put, these scenarios will change by later today:

GFS/FIM favored for Rina to work toward the Yucatan, getting sheared in the process, and passing toward the lower and middle Keys as a Tropical Storm going Depression. The GFS then weakens the storm further and drops it back south, whereas the FIM takes the storm toward Miami and up the east coast (after confronting high pressure in the SW Atlantic) toward Ft. Pierce then rapidly out to sea as the frontal boundary by that time is across Central Florida. Such a scenario could spell out the strongest winds across the Keys and then East Central due to pressure gradient winds in that area.

The other option is for the storm to never make it out of the Caribbean since that is where the most favorable environment for it will remain, with more shearing winds  on the approach in 48 hours to its north beyond the strong shear already in place. In fact, the latest NAM is now changing the focus of attention from Rina to Central Florida with another weak low to form along the inverted trough from the central Gulf to Central noted above. It takes this weak circulation to Central on Friday with very high PWAT air and a chance of thunder, whereas Rina is left almost in the some location it currently is placed, but closer to the Yucatan and being weakened due to its proximity to land.  

In all cases, the other thing to consider as far as detectable weather impacts is, "How far South will the front now passing through the Rockies and Plains actually proceed across Florida?". Model consensus seems to be leaning toward the actual front never clearing Central and South Florida, but rather merging with the area of low pressure Rina is within, while the actual front proceeds off to the east across the NE States. This is what is occurring now with the front out in the Atlantic and seems feasible.
Do note these forecast tracks:

IMAGE shows that the single level statistical models take Rina to Central Florida whereas the dynamical models and consensus/Ensembles leave it much further south or getting just so far north and shearing out/dying as impacts far South Florida.

It may be that those more northern tracks toward Central are actually from these models sensing development of a completely different low as advertised by the latest NAM run at 12z (8AM EDT), and to some degree the overnight ECMWF.

The  pink/red tracks across the Keys closely resemble the FIM/GFS tracks.  We also have Invest 97L not shown in the above graphic, well off toward the East Southeast of Rina. This system looks like its moving at the speed of light toward the West compared to Rina, and eventually will start to interact with the storm. Will it force Rina toward the east coast of the Yucatan or push it more toward the north? Will 97L even hold together? 

CONSEQUENTLY: A plethora of scenarios is coming into play varying from a tropical storm or depression to cross the Keys toward SE Florida to a possible severe thunderstorm threat across Central in the Friday/Saturday time frame depending on one's model preference as of early today. Too many factors are at play in the interim before late week to even supposition a confident gander. 

So far, the only thing coming to light appears to be that no cold air is on the way for Florida. The other flailing to consider is the old pre-conceived notion from the GFS of a 5-7 duration of onshore flow and coastal showers for the East Coast that has come and gone and then re-appeared since last week in its extended. In short, the forecast for late Thursday on Through Halloween weekend and into the beginning of next week is all as well as  perplexing, befuddling, and of course....frighteningly bewitching. 

No comments: