"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".

Monday, January 24, 2011

High Level Of Awareness Urged For Strong Weather Tuesday Overnight

Image: Shown in this image is the Storm Prediction Center forecast (between the green lines) for a risk of severe weather between 7AM Tuesday to 7AM Wednesday. This is officially released to the general public. I have added further elaboration, with a higher likelihood of severe between the black lines, and even higher between the red lines. Those are of my own doing based strictly on morning model information at this time overlay-ed mentally with other parameters which could evolve outside the scope of weather model guidance this morning, to address what could evolve. Fact or fairy tale? Stephen King or Mother Goose? Time will tell.

RECAP: Outside of the obvious concern (noted above) everything in the weather world is evolving right on cue in regards to South and Central Florida weather this morning. Morning low temperatures were reached at the coast along the Barrier Islands at 8pm last night, from which point they slowly rose through sunrise as the marine layer slowly modified the coastal air mass. Namely in regards to rising the dewpoint temperature and moisture level (humidity).

Otherwise, indeed an inverted trough developed from near Cocoa Beach, up along A1A, then off the Cape and out to sea. Wind convergence along that boundary, a strong inversion at 850mb, and ample low level moisture generated the cloud deck we see up and down the Florida East Coast with the highest moisture concentration close to Port Canaveral where some light rain fell. There's been some other spotty trace amounts elsewhere under the cloud deck. I noticed some high level helicity values were interpreted by local data (LDIS) just to the north of this boundary, further enhancing the cloud deck. Those values are forecast to move north through the afternoon, and as such believe so will the minimal chance of non-impact rainfall. We could see some big cloud breaks this afternoon, but the general mode will be partly cloudy and sometime cloudy skies with warming temperatures. Surface low pressue begins to form along the Texas Coast which will move east along the Northern Gulf during the next 48 hours as it strengthens along the way.

TONIGHT: Warm front to evolve South Central and lift north with even higher dew point air behind it, (mid 60F s) as well as stronger SSE -SE surface winds by mid morning through afternoon. Warm front to be just north of SR 520 at sunrise continuing north. Small rain chance very early morning hours will likely be all but gone shortly after sunrise as Central Florida and South are fully within the "warm sector' south of the warm front. Over night lows in the mid-upper 50s but may go up a few degrees from South to North with passage of this boundary. Might only get down to the low 60s from Vero Beach and south.

TUESDAY: Fully in warm sector air all day long with high dew points (low to mid 60s) (humid) and breezy winds from the SE-SSE at 15-25mph during the afternoon (magnified along the causeways during peak heating). Low pressure which had evolved off the Texas Coast will be passing south of Louisiana with the warm front extending eastward across I-10 (or further north) with a cold front extending south from the low. Another mid-level trough from the Central Plains will join forces with this system during the next 24 hours and beyond to become a single entity over Georgia/South Carolina.

FIRSTLY: Granted, it will be relatively warm, breezy and humid Tuesday afternoon, so a chance of rain showers is possible, especially shortly after lunch time and beyond. Although parameters are not yet fully in play for severe weather during this time frame (mid-late afternoon), it bears watching for at least some thunderstorms. Should any thunderstorms evolve, they could be marginally severe, so it doesn't hurt to keep this in mind. At this time, rain showers appears will be the more likely mode though. During this time, we will be seeing lightning strikes well out in the Gulf and over the Florida Panhandle.

EARLY TUESDAY NIGHT: The Gulf Low continues east and the vertical wind profile aloft becomes ever oh so interesting. Surface winds remain SSE-S and remain at 15-25mph as mid-level winds increase from the SSW from 15kts to 30-35kts by afternoon while a sliver of winds above that level could increase to nearly 60kts from the WSW. See where we're heading? Picture the veering of winds with height. We may see a lull in any rain chance whatsoever for a time during the early evening, maybe not. Meanwhile, not far to the north along the I-10 corridor they will likely be getting pounded with heavy rains/thunderstorms along the warm front.

Elsewhere, the mid-level trough approaches the Central Gulf and the West Coast overnight, and in doing so crosses the warm waters of the Loop Current where thermal instability will be greater. This will likely feed the storms to the north originally with additional moisture and further amplify an already wet situation there. This will also quickly eject considerable cloud cover across South Central and Central Florida late if there wasn't enough already due to overspreading of thunderstorm anvils caught up in jet stream level winds.

As the trough approaches the West Coast toward 8pm the upper level portion to the north becomes slightly 'negatively tilted', with the net affect of actually backing and increasing the mid-level winds over Central Florida to a small degree as stronger upper levels remain veered from the West and increase high over head.

9pm and Beyond: A lot of suppositions have already been made, so will state some further assumptions in regards to the potential for tomorrow at this point before walking any further toward the end of the plank with a blind fold on.

However, as it appears at this time, the weather over Central Florida could go rapidly down hill from west to east from around 11:30pm - 6AM (give or take 2 or 3 hours) Tuesday night into Wednesday morning. Whether storms that do evolve (assuming they do) take on a character of bowing line segments on radar imagery or as little round purple balls (rotating supercells) cannot be yet ascertained. The reasoning behind the rapid weather transition is due to a literal "Surging" on mid-upper level wind strength first to the west and rapidly over-spreading the peninsula after midnight.

Either way, with such strong veering wind profiles/winds aloft, plentiful moisture, moderate thermal instability (which is the least of my worries at this point) any storm will be capable of producing damaging wind gusts/straight line winds or a tornado (s) and hail. Regardless, even at night the Convective Available Potential Energy (CAPE) over Central Florida (namely East Central) remains up around 500-750j/kg (or from where it will be at sunset) and maybe even rises a bit. Another concern for far East Central (Orange County and East) is that surface winds could be a bit more backed due to the influence of the coast/intracoastal waterway. This would add a third beater to mix the batter and be the icing on the cake for low level spin.

Another thing to watch will be the storm activity far to the North. As was the case last Monday while we were in a Tornado Watch, this activity could generate an Outflow boundary during the wee hours that will shove South and interact with the parameters already in play over Central. Additionally, due to the early morning timing, a nocturnal low level jet could be established that will be stronger than indicated by model data in conjuction with lower, night time Lifting Condensation Levels (LCLs). Net result, thunderstorms will have very low bases toward the ground that erupt into an atmosphere that is essentially "spinning' aloft.

It is interesting to note that the past two runs of the NAM model have shown a very heavy precipitation band running from near Tampa to Port St John separate from the activity further north. Could this be caused by a storm, or group of them, generated by all the factors cited above? Maybe, maybe not.

Now, IS what is being forecast (as unlikely as that is considering that would be a mesoscale meteorlogical event which wouldn't be captured by a mid-range model but rather by hourly data)...a sign that even this model is picking up on the unfolding of 'something wicked this way comes"? If so, we could be looking at a few long tracking supercell thunderstorms that track from WSW to ENE (or maybe even W to E) across the entire state from around 10pm - 6AM. The storms would ride along the mentioned outflow boundary mentioned previously.

SUMMARY: No worries now, but be advised that a potentially severe weather situation could be in the making beginning Tuesday afternoon and especially between the hours of 9pm - 7am from West to East Tuesday night through Wednesday morning if you haven't figured that out yet already.

SOUTH FLORIDA: At this time it does not look like extreme South Florida will see Severe Weather, but some strong thunder is not out of the equation there either, as we can see by the graphic in this post supplied by the Storm Prediction Center where the green lines are drawn. The best chance for severe there appears will be late morning through the afternoon hours Wednesday ahead of the front with ample daytime heating creating thermal instability. Wind fields there for rotating storms look minimally to zero conducive for any organized severe.

WEDNESDAY: Next question, when will the rain chances end? Good one. Best bet is to expect it to be wet until at least early afternoon (Central), sunset (South) at this point. The time frame keeps extending to later in the day as the system was initially forecast to be through by sunrise Wednesday and long gone, could take all day to clear the area. Otherwise, quite windy behind the system Wednesday afternoon, with gust perhaps exceeding 35mph before the last of the mid-level winds pulls out and the system rapidly clears the state. No big cold air in the picture yet, not until at least Friday and even then nothing down to freezing.

Remember when this system was first brought up several posts ago, the statement was made that the longer it takes to get here the worse it could be? Uh oh.

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