Rainfall For Tonight Remains "Up in the Air"

The Great Model Debate - How Far South will the Polar Jet Coming Down from Canada Dig as well as how far  west will it bottom out in the next 18 hours. Areas to consider for substantial rainfall Monday are between the lavender lines and south of the green line (South Florida) for rains on Monday OR both areas under the Green Line (north Florida).

SHORT POST AT NOON: Keeping this post fairly short today after looking at overnight model runs, including the SREF, two version of the FIM, the overnight GFS, the latest NAM, the ECMWF, and the GGEM....taking all of these and comparing to actuals and latest trends at the ground.


One big problem seems to be the record snowfall (of over 30" in the mountains of New England yesterday and overnight. High pressure is strengthening behind the low pressure system that is well out of the picture by now near Nova Scotia, and the snow covered ground left behind is likely creating persist colder temperatures at the ground over a boarder than expected expanse and thus strengthening surface high pressure all the down the eastern seaboard. During the past couple of hours pressures have been rising over the state with brisky ENE-NNE winds continuing. Diurnally, this would occur, but the are occurring more than what would be expected under the circumstances portrayed by yesterday's model runs.


The effect of the strengthening high pressure is that the surface front over the Florida straits is making no northward expansion if not pressing further south. Any rainfall that was to occur by now per some models over South Florida is not happening, or rather is occurring offshore with steering in the mid-levels in this area from the WSW (away from shore). Only low topped showers emanating down wind of the Bahamas will be able to make it to shore in this area and those are not able to materialize due to extensive cloud cover.

LATEST VISIBLE SATELLITE and LDIS REAL TIME SHOWS an inverted mid level trough extending from the Yucatan into the South Central Gulf. This COULD be a big player for the North Half of the state on Monday. Snow can be seen in this image over Pennsylvania, SE NY, and New England likely helping to strengthen the surface high due to cold air at the surface. Yellow arrows show the southern branch jet and new approaching polar jet behind low pressure near Wisconsin seen in the clouds there but not drawn in.

One school of thought is that the inverted trough of low pressure will continue to enhance. Strengthening high pressure over the mid Atlantic into the Southeast States will create a temporary 'block' and allow the jet stream from the poles to drop toward the North Central Gulf and pick this area up and swoop this area across All of North Central from JAX to Port Canaveral, creating rainfall due to isentropic lift. But will the jet phase with the southern branch and allow this to happen, or will they phase and stay further north and never pick up whatever is developing in the central gulf...OR, will they never phase at all?!


The other school of thought is that what is in the GULF has no effect, but rather general lifting of the lower pressure from the old frontal boundary and southward into the Caribbean brings that boundary  further north toward Lake Okeechobee.  This in turn takes all the rainfall to the southern 1/3 of the state, quite the opposite result. 


And finally, another school of thought shows neither to occur, possibly because the surface high pressure building south which would be indicative of the rising surface pressures and a low temperature in Crestview, Florida this morning of 32F, colder than that of where it snowed in White Plains , NY and NYC...would preclude the surface front over the Florida Straits from lifting north significantly as well as from allowing the digging upper level trough coming out of Canada to have a substantial affect with the already very stable low level layer in place across Florida (and dry to boot).


In either case, there is a chance of rain showers almost anywhere tonight through sunset Monday but where any low level boundaries will be in place and how much moisture at the NECESSARY levels of the atmosphere for rain to occur coincident with any vort maxes coming either out of the NW Caribbean (South Florida) or the Gulf (North Florida) remains   big questions.


For these reasons, I'm not actually forecasting any bulls eye's for big rains as of noon on this Sunday, October 30th. Another post will follow toward evening as more morning model runs become available. To state 'a case'.


Especially since by  now big changes in the atmosphere over Florida are not forecast to begin until after 8PM no matter which model is used. In short, the Record Snow Event for the far Northeast States might have had bigger impacts than models figured it would, namely because so much snow fell. This would not be accounted for in even the morning model runs, and might not be fully accounted for until runs become available until the 8pm soundings are made and correlated with the latest trends at the surface during daylight.  ..with the models containing that information not being available until well past midnight. By that time, whatever is going to happen (or not happen) will already have become evident on radar and satellite imagery. 


The only trend verifying so far as of noon is that some better moisture is working north in the lower levels, but in order for any substantially workable moisture to get north of South Florida it has to figuratively 'go around the block, in the back door, then re-enter through the front door' to get further north...a very long a drawn out process..will this process be able to take place before the upper level trough by passes the state altogether?