"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".

Thursday, October 21, 2010

Say What? "Tropical Storm Richard!"

IMAGE: For each storm day, a series of forecasts from the current cycle from the NCEP global ensemble are plotted along side the observed storm center (based on preliminary position, NOT the best track position) for each storm that has reached depression stage

SYNOPSIS: In continuing from yesterday's post, we found the "then at the time" weakening cold front approaching Florida has rolled over the entire state on what seems like purely self-propelled momentum rather than via supporting upper level features. Either way, though, the base of the mid-level trough only made it to about the Florida/Georgia border as the front at the surface rolled on down the state and lost the last of its punch. Regardless of frontal passage (or not), high pressure moving east across the northern Gulf which apexes as far north as South/Central Canada, behind the departing trough now located off the U.S. East Coast, spans as far south as the Bay of Yucatan. That is quite some expanse! . As a result of the encroaching high pressure, clockwise circulation around it has brought the winds over South/Central Florida around to roughly the NNW. The long fetch of this light wind has harbored in a return to very dry atmospheric moisture under a capped aural atmosphere. Very noticeable once one is out in open areas by the thin, low layer of haze.

Elsewhere, cut off 500mb low moving over Arizona today with a southern branch jet stream rounding it's base and producing diffluent, strong upper level winds over Eastern New Mexico and eventually much of the 'West Half of All of Texas' by tonight. Diffluence aloft, convergence at the low levels, steep mid-level lapse rates, and ample surface heating combined with ample atmospheric moisture all unite to produce conditions favorable for rotating, severe thunderstorms this afternoon and into the night from SE New Mexico, most of the Texas Panhandle and Western half of that state as well. This low has been discussed for a couple of days now, and it seems to be acting obediently in that it is not lingering over the Desert SW region for days-on-end as can happen.

The low will progress east toward SW New Mexico tonight and slowly lift and fill toward the ENE through the weekend. The swath of potentially severe weather will shift east and a bit north into Oklahoma with time accordingly, as high pressure over the Deep South and northern Gulf continues to track over Florida into Monday.

LOCAL WEEK'S END/WEEKEND FORECAST: High pressure must moving in (and now obviously apparent by looking outside) rules the roost over the state through the end of the week and all weekend. As such, drier air will allow over night lows to fall to what we've been experiencing with lows at the beaches in the upper 60s and more toward the low 60s well inland as far south as SW Florida, Lake Okeechobee, and perhaps the Kendall area. Beaches on the east coast along A1A will be a good 5-9 degrees warmer over night. Daytime highs in the low-mid 80s under nearly cloud free sky conditions. Can't rule out a few afternoon specks of stratocumulus inland...otherwise the "All's Clear" Alert is 'on'.

MONDAY-further out: See "THE TROPICS:"

THE TROPICS: As mentioned yesterday, we suspected that the disturbance in the Caribbean would become a TD (Tropical Depression) by later in the day or over night, as such it is. I say "would become a TD" it is now a storm named "Richard". You can see the image shown in this post which depicts the forecast tracks of now Tropical Storm Richard based on the NCEP global ensemble. The storm is moving SE at 6mph and is located about 220NM SSE of Grand Cayman, with surface winds estimated/sustained at 40mph.

This included track set is just one of a multiplicity of other options from which to decipher through. Problem is though, at this point there really is not yet a code to break. Richard is moving slowly today (really not moving at all) and only slowly strengthening. Much of the slow motion and disorganized strengthening phase it is in now is because of the presence of the trough now departing the U.S. East Coast (the same one that brought the front near Central Florida over night) and resultant shear and drier mid-upper level air on the storm's NW side.

I have included this image because if you look at the tracks, and then the track 'swath of error' issued by the Hurricane Center ( and as shown on The Weather Channel), the margin of error as well as the locations of the tracks almost matches up perfectly with what I've attached.

BUT NOTE: I'm expecting the current official forecast track, and 'swath of error' path, to shift more toward the east and north by later today, or more toward the eastern half of the Yucatan Peninsula. The are other models not shown in the image come fairly close to this depiction as well but diverge more toward the East and North near the 'end time'. The two that come to mind off the top are the GFDL and HWRF. The GFDL takes the storm over the Eastern Yucatan as a Category 3 storm which is then weakened by the landmass. After that point it curves toward the NW and WNW toward Florida as a Category 1. The HWRF tracks the storm through the Yucatan Channel as a weaker storm overall then on toward Florida as well. Time of a West Florida Coast landfall is close to overnight Monday -noon Tuesday based on those models. The storm would then track across the state and exit the east coast as a strong tropical storm or minimal hurricane somewhere between Ormond Beach - Ft Lauderdale depending on the assumption it takes a track across the state in the first place. So what, where, why, and when do we make of all this information at this time?

First, we note the storm only slowly strengthens or even moves for that matter for the first 24-48 hours. This is in response to the high pressure area moving over the Gulf of Mexico and Florida. Additionally, shear from the departing trough is hampering faster development right now. But that will change tomorrow as the trough moves further away and high pressure bridges east and across Florida in its wake. Now what we have is another system (the High) preventing Richard from moving further north and as such the track toward the Yucatan. Just how quickly the high pressure area moves further east is all contingent upon the depth, strength, and eastward motion of the upper level low pressure trough now bottoming out over California. The faster it lifts east, the faster the ridge over Florida moves out and provides a steering direction toward Florida. The longer the same mentioned trough lingers to the west the further west Richard will go before making a definitive northward turn (if ever). Additionally, the further north this system gets (assuming it does) the greater a shearing influence by the jet stream the system will experience. In other words, if it gets anywhere beyond the Yucatan or near Western Cuba, this is where sheer increases. As such, the models pick up on a weakening trend, or at least a trend of no further strengthening from whatever status it holds when it first gets into the Gulf of Mexico.

When all is said and done, I'm leaning toward the GFDL track, but not of as strong as a storm. Once Richard crosses the Yucatan and re-emerges into the Gulf it might not even be a hurricane as it will be encountering greater shear after crossing the rugged terrain.

Much to learn in the next couple of days to see what finally evolves. But in the meantime, it does look as though by this time tomorrow (2:00pm) Richard could be on the verge of becoming a Hurricane with Cat 1 winds being measured in the East-NE quadrant by sometime Friday evening into early Saturday. Remembering that the ridge will be passing to the north, strengthening should be relatively slow at first. It all depends on what happens with the big, mean-level feature (trough) over the Western U.S. as noted above, and it's eventual motion toward the east or simply lifting in place to a higher latitude. The more out of the picture this feature is, the stronger and further north Richard can get. It's cat-n-mouse. And in this case, if the mouse (Richard) gets trapped in the cage it's free to go on it's own for a while within limits.

Also, if Richard does take a more northward track, the very mechanisms permitting that eventual track will impact the weather locally well in advance of the system with increased moisture, chances or rain showers or thunderstorms, etc...the whole kit-n-caboodle. Thus, I left the period from Monday and beyond open-ended in this post. Perhaps we can at least squeeze out the rain Central Florida needs by this time next week.

Typhoon Megi now has winds of 110mph and is now approaching mainland China. But in looking at the latest satellite trends, the storm seems to really be losing size, and strength will probably following.

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