"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".

Sunday, April 3, 2011

Much Warmer Monday, Some Strong Storms Possible Tuesday

Attached is the Official Storm Related Outlook Issued by the Storm Prediction Center at 3:29AM Sunday morning, valid for Tuesday. SPC has placed the Florida peninsula in "See Text". This is reserved for when 1) some storms could be strong; or 2) it is deemed that strong activity seems fairly likely, and that the area is being monitored for an upgrade to a "Slight Risk" of severe weather. Please see the body of this post under "TUESDAY" for an explanation of the markings I've superimposed on the image.
TODAY: The second of the two cold fronts associated with Friday's storm system now long gone has cleared the Florida peninsula. Winds immediately behind the boundary are northeasterly becoming easterly today, eventually ESE to SE over far Southeast Florida by late this afternoon into the evening. For the most part, today will be much like yesterday with changes in store beginning late this afternoon first over SW Florida. Otherwise, highs today along the A1A corridor in the upper 70Fs with low 80Fs far inland and all of the west side, some mid 80F SW Everglades region. More moist air will work into South Florida later today, and a rain shower is possible west of metro Miami and eventually NW ward toward Sarasota until 9pm. Once daytime heating has been sufficiently squelched the rain showers there will end.

MONDAY: Winds becoming SE-SSE all day, breezy along the east coast/beaches particularly and up the intracoastal of Brevard into Southern Volusia, especially 2pm -6pm. Moisture will increase throughout the day with the long fetch persistent SSE flow at play bringing dewpoint temperatures into the low-mid 60F degree range, and near 70F far South Florida. Rain showers are highly unlikely anywhere.

MONDAY NIGHT: After hemming and hawing over 6 model runs of 3 different models, it appears that somewhere in Central Florida will receive a rain shower which will form after peak heating in the late afternoon. Guidance has been all over the place as to where this would occur, but the focus has been somewhere in South Central Florida, with a new one popping up in the morning GFS in NE Florida.  Based on averaging all these locations together, the most likely scenario this morning after the 12z runs came out is for a small cluster of showers, perhaps initially a weak thunderstorm to form near the Polk/Osceola County line inward toward Orlando Metro. If this does indeed develop, the activity will be swept ENE-NE ward toward the east coast and weaken. Thus, somewhere between Daytona Beach to Cocoa Beach could have a rain shower somewhere between midnight and 4am. Overall rain chances are basically zero...but I noticed that the NWS has thrown a 10 percent chance of rain into the forecast for some folks overnight which backs this theory up.

 Meanwhile, a very mean storm system will be developing this afternoon over the east central Plains states with an associated cold front. Strong jet stream level winds and deeply rich moisture laden air with cold air aloft will spread across portions of the Deep South later today, combined with veering wind profiles will set the stage for all modes of severe weather beginning late today and expanding in terrain going into tonight and tomorrow morning, Monday. There is a chance of large, damaging hail initially over East Central Kansas spreading NE ward into Missouri before dark, after which stronger wind fields will move in to the north of this area going into the evening. The hail threat will translate into a tornado threat further north toward Chicago mainly just to the SW of that location...but they are not left out of the game.  Activity will be on going tonight but weaken a bit in general until Monday mid-morning when the front confronts the warm, moist air that will have been on-going for a full 24 hours prior. Conflicting air masses will provide the ingredients for supercell thunderstorms and bowing line segments of particularly vicious nature. Tornadoes are very possible, almost likely from Louisiana northeastward into Mississippi, northern Alabama, Tennessee, and Southern Indiana where the warm moist air from the south confronts cold air aloft and stronger winds. This entire region is most favored in different areas for different reasons, so I won;'t go into the finer details.

MONDAY NIGHT/EARLY TUESDAY PRIOR TO SUNRISE: The storm system's main energy will be carried to the NE and into less favorable northern latitudes to sustain severe storms, but the southern more portions will continue east ward as an advancing squall line composed of strong straight line winds as the winds aloft become more unidirectional with height. Further south, a tornado threat will continue, but the likelihood of formation becomes less favorable with time due to the departing upper level support. Don't get me wrong though, there will still be plentiful factors at the storm threat continues east and south into the Florida Panhandle.  

By sunrise Monday morning the front will be advancing into NW Florida toward North Central. All models agree that the front will enter the far reaches of North Central Florida around 8am.

It is at this point we refer back to the annotated image at the top of this post:

TUESDAY: Peninsular Florida will remain warm, moist and breezy over night Monday the frontal boundary approaches stronger upper level winds will spread across all of North Florida, sinking into a portion of North Central at daybreak. There might be a brief lull in the activity over the peninsula near sunrise, but that could change after 8am as a secondary upper level broad streak of stronger winds moves in from across the Gulf


  By that time the boundary will be approaching Daytona Beach. The South HALF of Florida in the meantime will have ample time to warm and become modestly unstable, but not tremendously with almost no convective inhibition. With dewpoints near 70F far South and in the mid-60Fs South Central...storms very well could ignite by 10AM and expand in coverage well in advance of the actual frontal boundary. If storms remain more isolated they could be strong. Greater coverage, even if only showers, will cloud up the sky and cut off the 'heat' supply. If they remain more isolated, a severe storm is possible south of the red line I've drawn in with all those little red question marks inserted to emphasize this point.  

NOTE: It was not until late yesterday that this pre-frontal shower activity was hinted at by one model. The subsequent model runs not only showed that more than one model was following suite, but also that it would be more likely, especially (and quite rapidly) after 10AM Tuesday morning.  There was one run that showed near severe category level intensity type storm over the Everglades and SW Coast, as well as the Lower East Coast region, but that has not re-emerged as a viable option, yet.  But the fact that this was implied once might mean it could come to fruition in later guidance.

Outside of South Florida, it gets very complicated along the 'red line'. The front is forecast by the two mainstream models to be situated along that line around the 1-2:30pm time frame. The strongest wind profiles with this storm system throughout all of the atmospheric levels are not expected to make it much further South than Port Canaveral...however at one level they remain the whole way to South Florida.

For this reason, do not foresee a strong outflow boundary to suddenly swoop southward as a result of the main line suddenly collapsing.  The strongest activity should occur near the same location as where it occurred both last Thursday and Friday, being that area will receive both the benefit of the destabilizing air mass over South Florida and the last of the remaining stronger wind fields aloft. I've drawn in a potential area that COULD be upgraded to Slight Risk of Severe in later outlooks, although the NWS in Tampa has made no reference to such.  Probably 'wantful for excitement' thinking on my part, with no one to bounce such illogic against me.  It is possible that all of South Florida would be upgraded, but unlikely. We'll see.

Further east toward Orlando and the Space Coast, this system could come through as a "multi-tasker"...with both the unstable Southern Peninsular activity combined with the passage of the front as heating will have begun.  The fly in the ointment here is that antecedent cloud cover will likely reduce CAPE (Convective Available Potential Energy) more than what model guidance indicates.

However, if cloud coverage is not as thickly distributed across dead Central Florida...a series of  storms could ride along or near this line depending on where multi-parmaeters have set up boundaries between where they are weak vs. strong.  We will not know where to draw the line until Tuesday morning. In other words, at this point this is strictly a 'theory'.

Otherwise, at this point in time given the amount of unsurenesses already at hand...we can generalize in writing with saying that there's a chance of showers and thunderstorms, and a couple could be strong. I will watch each and every model run from here to eternity to see how subsequent runs vary within and between them through tomorrow to monitor the trends and future evolution of any unforeseen circumstances.

IN CLOSING: This system does not appear will be nearly as 'threatening' as the ones last week. So an elevated awareness at this point in time is not required.  Just be aware for now. 

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