Risk of More Rainfall Over Swollen Tributaries Continues (Mainly North) Through Tuesday

TODAY: Latest radar animation out of Melbourne in combination with model guidance depictions  up to the mid-levels appear to support that a broad cyclonic circulation exists over Central Florida .  

This area might move a bit further north during the day as 'vorticity lobes' glide around it. The areas more likely to be in The Positive advection of that energy appears will be north of a line from Melbourne to Tampa Bay (in general).

There is a chance that some 'negative vorticity' advection will be on-going south of that line so that the risk of shower/storm coverage will be much lower in that area despite the presence of more than ample atmospheric moisture. 

At this point will only mention that all NWS Forecast Offices do see how problematic forecasting this 'messy situation' is that we have at hand today  going into Sunday.  It well could rain across the regions further south, but suspect that any rainfall there will be much more spotty in nature.

Counter-clockwise circulation 'appears' to be at play in the below radar animation from earlier this morning from Melbourne's WSR-88D radar, centered over Osceola County (up through 4AM).

For this post, will use the reasoning that an old frontal boundary that passed through the Northeast states and off the Mid-Atlantic Coast weakly extends southward from well off shore over the Atlantic and arching back south and west toward the Florida - Georgia Border. High pressure building in behind it from the north from Eastern Canada will breach well south toward this aforementioned boundary and in due time will extended its girth down the rest of the state, but that will not truly begin until around Monday and be especially 'noteworthy' in regard to the wind field as we go into Tuesday (winds increasing from the east to east-northeast).  

Hence, the period from Tuesday - Friday look much like what would typically be expected as 'fall weather' with temperatures having little more than a 10F degree diurnal variation, mainly ranging in the mid-upper 70Fs (lows) and lower-mid 80Fs (highs), depending on cloud coverage and proximity to the Atlantic Ocean. The closer to the beach one is, the less the variation in temperature will be.

The net affect is that as the high pressure builds south so to will be what remains of the 'convergence source' (ie, the frontal boundary). This would enable rain-showers to continue to advect on shore in 'random' fashion for a time, until the boundary washes out and a period of dryer air works in .
GFS guidance numerically shows rain chances all next week, but in looking at several models I question whether the depth of moisture will be sufficient for rain every day. The days least likely to see rainfall would be Wednesday and at least part of Thursday (at least on a wide-spread basis). 


The GFS then has been consistent in showing a 'Tidal Wave' of moisture approaching form the east as accompanied with deep easterly flow.

Again, heading from Today through Tuesday expecting 'most rainfall concentrations' (but not all) to be focus across the Northern Portions of the state closer to the frontal boundary.

Heading toward the Friday time frame, as the wind decreases just a bit  there is a chance that an inverted trough would develop along the western side of the Gulf Stream which would act as convergence area for heftier showers to advect on shore the east coast, mainly during the over night through early morning hours, coincident with the presence of this 'TBD approaching moisture'.

Heading to beyond the end of the week into the following weekend...a plethora of 'tropical' solutions begins again to be introduced. 

Given that this is within the 10-Day window (even an 8 Day one) the tropics will again bear watching. Though at this stage a 'strong system' is not being advertised, the GFS is showing what looks like would be a tropical storm lifting northward across the state in some fashion, whereas the latest ECMWF has a system lifting north well east of the state. Other models  imply a smorgasbord of possible 'low pressure areas' both to the west and to the east of the state heading toward next weekend and/or into the beginning of the following week.

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.

"TROPICAL STORM OUTBREAK!"  OCTOBER 9TH
(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.

Chances of Showers/Thunder South of I-4 : Potential 'Active Event' Going into October

Rain Squalls Preparing to Make Landfall Saturday Afternoon - Cape Canaveral, Florida

TODAY: Ample moisture combined with sufficient instability and  stronger jet stream level wind from the SSW-SW well aloft rounding the base of an upper level low just west of the state might combine to result in showers and thunderstorms later today from 'South to "North" as the day progresses. 

Exactly how far "North' they will be able to manifest is in question. The better bet is along a line running from South of Melbourne beach west toward interior West Florida east of Sarasota area and south. There is a random risk storms and/or showers might be able to manifest late toward dark as far north as Titusville and across the Orlando area (however). Areas north of I-4 look to have an even less chance of seeing activity today except perhaps toward southern Lake County.

Weekend and Beyond: In lieu of getting tangled up in the next few days to follow which look rather dry and continued quite warm though there might be a  rain chance toward South Florida, especially over the interior, will bring a mention of greater potential relevance/importance  - which is the time from October 1 (Sunday) - October 14. 

GFS, ECMWF, and in some regard the Canadian model are at time sharing in the development of a particular scenario involving the formation of a surface low  across South Florida (generally) either toward the West or East coast (or somewhere in between). Timing in regard to exactly when all this 'might' transpire is still in question; however, the best bet so far points to overnight Saturday night into early Sunday and all through Sunday day.  GFS and in some regard ECMWF models show   quite gusty surface wind to accompany this low  along it's north side which , and if so, would be  a particular pointing to the immediate east coast from Central Volusia County and southward especially for Brevard and Indian River Counties.

Will say that for now this is but a 'heads up' and nothing is set in regard to if any thing will actually transpire. The GFS model has been attempting to peg something down now for several days but keeps changing its tune, but as of this morning several models have jumped on board with 'some kind of scenario' developing during the time frame from Saturday lasting even potentially through to around October 12th (in various phases) as a broad area of low pressure  develops across the Western Caribbean region accompanying by strong high pressure to it's north extending from the Canadian Border southward toward Southern Georgia. 

The result of these two 'areas' alone would be stronger pressure gradient winds, but those plus a surface low of concentrated energy in the presence of PWAT (precipitable water values) in excess of  2,00" along with continued warm ocean waters could spell.. .  "B-I-G - r-a-i-n-f-a-l-l -t-o-t-a-l-s " over the extended time frame for some areas.  So far this does not look like the 'no name' event of October 7 -9, 2011 by any means when there was cold air aloft. This situation looks a bit more 'tropical in nature' than that event. Either way, bears watching. 


There is a risk that  during the course of the period from Sunday through Thursday (in general as a starting point of reference in this yet to develop scenario) that some areas could see as much as 2-5" of rainfall, and that might be conservative.  The GFS and ECMWF also follow up this event with yet another low forming in the eastern gulf which could add to the rainfall totals in a big way; however, the timing on when each model does so is several days apart from each other. 

On top of the rainfall risk, surface winds, if said low can develop could be gusting in the 35-42 mpn range in heavier activities as it comes in off the Atlantic ocean, and this point that area of interest is Brevard/Indian River Counties in particular . So far the time frame for the wind risk looks to be early Sunday through most of Monday (which could easily change).

Regardless of many uncertainties still at this stage, given the situation being presented, it could be considered warranted to provide at least a 'Heads Up!"   from a blogger perspective) that the First Two Weeks of October could be quite active in a variety of ways. Just exactly in 'what way and where' is TBD.

Frequent To "Excessive' Lightning In Storms Possible Later Today

Leading Arcus Extension of Storm's "Self' Invades  Cape Canaveral on August 29, 2014

TODAY: Not much change from yesterday's thinking. Pattern of the days of the past week proved itself to be changing late yesterday, but more so well past midnight as storms continued to be generated and even move off the east coast north of Brevard County with a last little dog leg working down to Cape Canaveral around 3AM over the intracoastal - before the 'fumes  from the heating of the day' had been exhausted. Activity likely was abetted by slightly cooler temperatures  and  upper level divergence  per latest Mesoscale model plot late this morning.

TODAY: Cooler air 'up top' (aloft) is 'anticipated' though the morning sounding at KSC shows that is not the case; at least from which would not warrant for much beyond garden variety thunderstorms with a 700mb temperature of 10C and 500mb no cooler than a -6C. 

The 700mb temperature might not drop all that much today but the 500mb would begin to go down after noon or so to around -8.5C. Much to say today in favor of strong storms mostly due to frequent to excessive lightning and heavy rainfall in short amount of time leading to localized short term flooding in prone areas if late yesterday is to be taken as an indication; on the other hand, if things do not come together as anticipated it might just be like another summer day, especially since 700mb will remain rather on the warm side. 

All in all, for now anticipating that the peak convergence of outflows from the north and west and the weight behind them meeting up with the east coast sea breeze which as of now appears will make it about 20-25 miles inland (tops) if not much less across Central Volusia and northward (but further inland toward South Central)   would begin to the north first then work south and increase in generally over more areas after 3:30pm  - and of that,  could 'peak out/ over Central Volusia and southward toward Central / Eastern Osceola County, Orange County , Seminole County, Northern to Central Brevard County then on down to South   Brevard  and Indian River much later in the afternoon.

Further south other  activities could also form as a result of the Lake Okeechobee/Sea breezes along with the potential for outflows from the north to work south. All in all could be seeing lightning in a few locations well after dark, mainly over South Central Florida to offshore.

SATURDAY: There will be a difference on Saturday with possibly a bit less coverage and not quite as much intensity. Better coverage appears will be from Southern Volusia County southward, especially South Central Florida late in the afternoon. Always a chance that the more 'Central Region' might see more of a relatively, 'early onset day' as opposed to very late in the afternoon.

SUNDAY: GFS and to some degree NAM guidance appears to be agreeing on a remnant boundary across Central is where moisture will be the greatest. Overall state coverage goes down significantly , with the best focus apparently on Central Florida , even to the coast or just in from the coast for showers/storms after 4pm to dark. Nothing 'strong' per se is foreseen on this day .

MONDAY: Though activity could be about, it will mainly be well inland toward the west coast; there is a marked decrease on Monday for the most part.


TUESDAY/WEDNESDAY: For now will say either Tuesday or Wednesday the coverage might well increase, perhaps significantly from Monday as a frontal boundary associated with an upper level trough works into the Southeast States and flow becomes more southerly to even a tad SSW aloft. GFS was showing 'that day' to be Wednesday but recently points to Tuesday. A bit skeptical on that but it's several days away anyway with plenty of time to reassess.

It is this same 'Trough-iness' over the Eastern U.S. and down to Florida   that might have an influence on the future track of Hurricane IRMA.How long it remains in place, to what depth south it extends, and how far south Irma actually is on perhaps Wednesday could all be factors on the future track of the storm as well as how well the ridge to the north of the storm maintains its western most grip. Any relaxing of the ridge to the north to provide a northward escape which the storm can 'touch'...it will certainly take. 

On the other hand - until all things become self-evident  would expect model guidance to go back and forth in various ways as to the extended range forecast in all kinds of fashion. Point being not to hedge one's bets on anything  at this point.

Beyond IRMA there is one other system that perhaps might come into view in the next two weeks...somewhere along the same latitude as where IRMA is not located and well east of the Virgin Islands.