|Image shows a departing disturbance east of Florida and a much larger and organized disturbance (up to this point in time at least) approaching the West Coast of Florida from the WSW-W. Nate is shown in the Bay of Campeche (BOC)|
Rather interesting and a bit complex day in store. As has been the case, a stationary frontal boundary remains across Dead Central. This boundary has oscillated a bit off and on, sometimes acting more like a warm front as it moves north a bit (Wednesday) and then south a bit as a cold front (Thursday). It looks as if today the boundary will act again as a warm front...which means better chances for thunder as opposed to predominant rain with only isolated thunder that stays more toward South Florida. Today's post, being what it is, almost completely disregards the model forecasts for today since none of them seemed to have picked up on this system. The main fall back or 'concern' is how well put together this area will remain during the course of the afternoon. Since early this morning it has not faltered, and lightning activity associated with it has increased. It is even showing up on a Tropical Web site , appearing almost more impressive than Nate to the untrained eye. (see the figure further below). The clincher today will be whether this 'complex of storms' holds together or simply fizzles before reach Florida. This post trusts it will hold together, but either way there is still a rain chance over the South half of Florida.
Timing of the actual disturbance shown in the image west of Tampa Bay puts it toward the East Side around 9-11pm tonight, but it is the lifting in the atmosphere ahead of it that might actually generate (and potentially enhance) rainfall coverage and strength of thunderstorms particularly south of the surface boundary. The air so far today, like the past three days, is most unstable over South Florida or roughly from Ft. Pierce and South. However, it is possible a good part of that instability will be lifted north later today closer to the stationary boundary into Central Florida as this disturbance presses closer to the west coast.
This Gulf Disturbance does not have any vorticity analyzed with it, but it does have Low Level Convergence and Upper Level Divergence with it..which means that perhaps the vorticity is not being picked up and/or showing on analysis, which after all is extrapolated from a model (which I've tossed for today).
TODAY:Having not seen any official forecast discussions regarding what is in the Gulf remains an allusive mystery this hour of the day. Timing clearly showing it moving toward the East or ENE and approaching Tampa Bay..per their radar. Based on this timing, it will cross central Florida from late afternoon through and past midnight...in some form or another. Thus, it could cross as merely cloud cover, under the assumption it even makes it as far as the state. Models for two days showed something coming to Florida today, but for some reason as of this morning it was no longer portrayed. This sure looks like one to me though.
The best thunder/rain should occur system or not this afternoon over South Florida working north with time. Again, guidance has been a bit all over the place with where the best or strongest thunder will occur today, but the consensus would be from near Boynton Beach north to Vero Beach. Yet further north ...North Brevard to the Volusia Line could be a contender for thunder or heavy rain (or perhaps long lasting light to moderate rain) due to outflows from the south meeting up with the surface boundary combined with increasing mid-level lift ahead of the system to the west. Although in the image below is a caption reading 6pm and beyond for the northern areas, 5pm might be a better time frame for starters just to play it safe. Some stronger storms appear to be most likely to occur, if any where, over Palm Beach, Martin, St Lucie, and Indian River Counties.
TROPICS: As of now, Nate is not expected to get beyond his little Watering Hole in the Bay, as opposed to the sudden shift in models that occurred yesterday. This bears with the initial line of thinking and forecast reasoning, as well as with what history has told us over the past 120 years..so why change now? Likewise, Maria's fate is uncertain if there is to be one. The official forecast has the storm heading right through the Lee ward Islands and toward the Bahamas which at that point uncertainty becomes quite large. In fact, the storm's short term course toward the WNW for days ahead seems a bit flaky.
If per chance the storm were to follow a path noted earlier of low level convergence it would again be steered a bit more toward the west..in which case then any projections further out in time are already out of sync/agreement with reality. Even the most southern track in the forecasts though have the system curving before reaching Florida. That seems quite realistic as of today ...namely because the Blocking Pattern Referred to the other day remains...and thus so does the surface boundary over Florida.
*** Future Forecast no matter What I'm hearing on "TV" are being disregarded by this listener. The future of the forecasts is completely contingent upon when the blocking pattern breaks down..which can be anywhere from 4 -10 days (at least)...we are on Day 3-4 now..and the pattern so far looks to hold until AFTER Maria presses north of Florida to the east. Models keep breaking it down (which is normal to have happend)..but the truth of the matter remains uncertain. It's a day by day deal. ..therefore, until the blocking pattern has clearly broke which could be as soon as Sunday or as late as Wednesday...the best forecast rule to follow is "Run With Persistence"...and keep an eye on Maria.
For pre planning purposes though, late Sunday through Monday look to have much better chances for rain.