"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, February 13, 2011

Spring Begin For South Central/South Florida on Wednesday?

Images: 1)Surface forecast plot for this Sunday afternoon. Note the location of the sprawling surface high encompassing the Gulf of Mexico and providing a cool northerly flow down the peninsula shown with the blue arrow 2) Surface forecast plot for Wednesday evening. Note now the location of the surface high in the Atlantic and weak east coastal trough (black dashed line) forming as easterly flow runs perpendicular to the warm Gulf Stream waters. Also note the extent of warm air being pumped from the Gulf into the South Central Plains toward the Great Lakes shown with the red arrows.

TODAY: Cool and sunny pretty much sums it up for all of Florida today. Looks like a day that someone will have the A/C on just a bit too strong. The 500mb trough axis has finally cleared the state (in general). It swooped through North and Central Florida yesterday through sunset accompanied by a well depicted swoop of vorticity (as was forecast by models to occur for several days prior) which created the broad band of clouds well overhead from late afternoon through the evening, which progressed south overnight. As we can see now, the vorticity has cleared the state and skies are clear late this morning with the high clouds very long gone. The clouds and showers that plagued South Florida yesterday have moved out and what remains is over the Southern Bahamas and Central Cuba, with some stratocumulus already forming over the Gulf Stream waters off South Florida not too far from shore.

So, in essence, looks like what we see out there this morning will remain today. Not much to see is there? Temperatures will remain somewhat cool, but as written yesterday should be about 5 degrees warmer than yesterday. Mid-upper 60s South Central, and upper 60s to teetering with 70F South. The coolest locations look like will be along A1A from Cocoa Beach north where a northerly afternoon breeze will ride down the coast and pick up on some of the very cool ocean, nearshore air (and to some degree the intracoastal ones as well) where highs will be in the lower side of the 60s.

On a side note, passing of that final upper level trough accompanied by clouds just ahead of it (during the positive vorticity advection phase) as well as winds remaining a bit elevated kept overnight lows just a bit warmer than thought would be over interior South Florida, particularly around Lake Okeechobee. The low on my porch was 1 degree cooler than on Saturday morning at 44F as was expected would be the outcome.

TONIGHT: It now appears that frost will again be possible tonight with the ridge axis almost directly overhead with the near ground level attaining a bit more moisture tonight after full sun today heats upon the ground moisture under full sunshine and evaporation ensues (and in the absence of northerly, dry winds which will abate quickly as the sun sets). Expect the temperatures most areas to be about the same as this morning's, although they should be colder over western portions of South Central Florida in a 'cold pool' where frost will be likely as well as many areas of interior Central Florida in the absence of last night's clouds and winds.

MONDAY AFTERNOON: Another day similar to today, but just a few degrees warmer ...especially (if things develop as models depict)..along A1A Central. Approach of a trough riding over the ridge across the mid-Atlantic states should back the surface wind to more of a westerly component which will advect the warmer inland mid-upper 60s to the coast under full sun. Might even squeak out a low 70F most areas tomorrow. Some low stratocumulus clouds could also begin to move on shore over SE Florida.

MONDAY NIGHT-TUESDAY: Light northerly winds with slightly higher dew points should lift overnight lows a good 5F degrees by Tuesday morning. High pressure over the Gulf builds north and merges with high pressure building behind the trough passing through the Mid-Atlantic as it moves well offshore. Winds become NE Tuesday afternoon, only impacting A1A toward US1 with some cooler air again keeping daytime highs coolest there up and down the entire east coast with highs teetering in the low 70s other areas, with mid-70s over South Florida. Light onshore flow overnight into Tuesday will prevent lows from falling below 55F many areas east of I-95 as the coastal trough drawn in the second image begins to take shape. By Tuesday afternoon the trough moves onshore as somewhat of a 'back door front' in reverse. In reverse in the sense that it actually will aid to modify the air mass significantly in regards to higher dew point air and warmer overnight coastal low temperatures. By Tuesday afternoon we might even see this change over being heralded by a band of stratocumulus with perhaps some very low topped sprinkling showers, but the showers chance is very low (the "silent 10 percent" chance), but perhaps most likely overnight. Going into Wednesday high pressure off the Mid-Atlantic will begin to sink south into the SW Atlantic with a continued east to ESE flow for many days to come.

Could Wednesday, with the above scenario unfolding, be the onset of Spring for all of South Central and South Florida (other than A1A)?!! In looking at a few items of interest....

By some schools of thought, spring begins over this region when afternoon high temperatures reach and average at least 75F degrees in the afternoon (thus, on a near continuous basis). This certainly appears will be the case with highs away from the coast all of South Central and South to reach mid to eventually upper 70s by next weekend, and even some low 80s over Southwest portions of the state where the prevailing east to east southeast winds over South Florida will have to cross the heated land mass before reaching the west side of the state. The immediate A1A corridor has a bit of a harder time to warm up due to its close proximity to the ocean waters that are below 75F. In fact, much of A1A might not see continuous 75F degree high temperatures for a few more weeks.

Early spring over much of Central Florida is accompanied by some pretty big temperature variations between morning lows and afternoon highs because the air mass is still relatively dry (compared to summer), which allows heat to escape into the atmosphere after dark (making for cool evenings), but also to heat up more during the day in the absence of cold intrusions and a higher sun angle. It can also herald the beginning of a very dry season in the absence of fronts which are the rain producers during winter as well as the absence of summer rain storms. When it rains in early spring (namely March), it can often, but not always, be a big one in regards to severe weather. This is why Severe Weather Awareness Week was conducted last week in preparation for the coming season.

But some springs come and go as gentle as a lamb, while others are quite the inversely roaring lion. As it looks now, into the last week of February, the sheep are out to pasture without a care in the world. All the big bad wolfs look like they will be sheep in wolves clothing for the South Central Plains states beginning sometime Wednesday where they will be eyeing the possibilities of severe weather from time to time at the same time we in Florida transition to extreme benign-ness while under the influence of stacked high pressure systems. Only another back-door front or two is foreseen in the next 10 days for the state. But even with those, highs most locations appear will remain above 75F away from the coast (on average).

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