"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, September 28, 2017

Large Rainfall Totals Late Friday - Monday Possible (Flood Potential Aware)

The NWS Service Offices - MLB & JAX To Be Watching The St John's River Valley Basin 
TODAY: Mainly sunny and pleasant North and Central Florida with chance of showers/thunder restricted to South Florida and parts of South Central.

FRIDAY: Guidance is coming into some 'form of agreement' to what is forthcoming in the period Friday- Monday, though surely this will change over the next 24 - 36 hours and as such all items expressed herein from this point out can be based only on what is being presented this morning, and are thus subject to change. 

Consult the National Weather Service for the latest information
 in regard to this upcoming potential situation.

In general, appears a broad area of low pressure will be forming somewhere over South Florida on Friday with a focus toward the east coast to somewhere between West Palm Beach to Cape Canaveral. It is unknown as to whether the surface  low which might form will head for the warm waters of Gulf Stream as a warm water source or remain closer to the coast. That first and foremost will greatly determine the amount of rainfall possible along the Florida east coast anywhere from Miami to the Cape initially in the upcoming 48 hours.  

The GFS model run of this morning focuses the mid level low right over the Cape  by midnight Friday night into Saturday morning (as an example)

So far, reliable guidance is agreeing regardless that the 'best chances of rainfall' in relation to this 'unfolding TBD drama' will be 'somewhere along the east coast' and 'east of the spine of the state' from JAX south toward the West Palm Beach area. For now will try not to be too specific.

In regard to 'wind', no strong wind is foreseen other than perhaps some gusty wind in the vicinity of any  thunderstorms that might occur, which is possible as well. The main concern as noted in the Subject Image (above) is rainfall due to  that the St John's River is already above Flood Stage , as could be read.   

Below is an image of where some of the heavier rainfall might occur over  a three day period coupled with the areas that are most impacted by the St John's River

Largest rainfall totals IF a low pressure area Remiains at the coast migh be largest from Volusia County and North
if a low remains on the coast. If the low stays out over the Gulf Stream instead, rainfall totals will be considerably lower

SATURDAY: Will say at this point only that if the GFS were to verify that Saturday might for the most part be 'deceptively' dry, even into Sunday for most areas other than across NE Florida.

Any low to form , even over the Gulf Stream might well be advected back to the coast across North Florida and then dampen out  westard as an 'open' wave as Stout High Pressure builds eastward behind a departing cold front across the Great Lakes region. This High Pressure region will span from much of Far Eastern Canada southward all the way to Florida and be met with conflict by a broad area of low pressure over much of the Western  Caribbean and into the the Eastern and Southern Gulf of Mexico (GOM). The net affect will be a period of prolonged, long fetch easterly winds extend up through the depths of the atmosphere.   (see below)

MONDAY-THURSDAY: Phase II of 'said' potential rain event commences as easterly flow extends from the surface up through 10,000. Brisk easterly wind generally in the 15 mph range gusting to around 25mph might be in place for several days if not all of next week. As the depth of the wind increases we could well dry out as the high PWAT (preciptable water) air is pushed off to the west of the state. But then another issue keeps developing on our paper Magic Eight Ball (The GFS model specifically in the 'Beyond' ).

Temperatures as a result will vary little with lows in the upper 70Fs to near 80F and highs in the mid 80Fs. A 'drying' out period might in fact commence heading into Wednesday but the winds will continue in 'fall like fashion'.

BEYOND: Heading toward the second week of October the GFS is once again up to it's shenanigans which really is fairly typical of the models this time of year -- have seen it before. Guidance can for over two weeks forecast a tropical storm or hurricane to form in the region of the Southern GOM or Western to Central Caribbean..and for all that time nothing actually ever forms worth mention.  This has happened in years past and could be the case this year as well.

Then again, something can form. Given the current projections, it appears that if something does form it wouldn't be to the caliber of the storms we've seen this year due to more than likely upper level wind shear. On the other hand,    'rain fall'  would still be big - bug-a-boo to be concerned about in light of the current situation.

Just to give an idea of how nuts the GFS model went in this morning's run..(and the previous one wasn't any more reasonable) we can see that it implies Three Tropical system simultaneously forming all at once. Highly unlikely.

(the first one ever...)

WRAP UP: In summary, tropical season isn't over yet for Florida in whatever form it might take be it wind or rain...but we'll be on the down swing heading toward week three and beyond.

Hurricane Season Lasts through November, though a search from a "Historical Perspective' as far as records are concerned back into the 1800s showed only two hurricanes   to hit Florida in November, Kate over the Panhandle in 1985, and an unnamed storm in 1935 that crossed South Florida only. Beyond that  there have been about 7 tropical storms (which can still produce tornadoes and/or flooding rains); granted , going back to 'as far as records go' isn't necessarily saying much when considering the big picture; but from a time-scale percentage aspect, it gives one a little perspective on the increasing 'rarity ' as we swim out of October - but first we basically the first three weeks of October to deal with.

No comments: