"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".

Tuesday, August 2, 2011

Late Afternoon Thunderstorms With a Big Punch Possible

A Thunderstorm on August 1 working South down the Indian River as viewed over the Banana River west of Port Canaveral on SR 528 (The Beach Line)

TODAY: Some big storms with frequent to excessive lightning are possible again today, with the most lightning prolific storms with possible stronger wind gusts in heavy rainfall (wet microbursts due to moisture over-loading) after 3:30pm through 7:30pm today. Storms COULD occur over many locations today, but it appears that the largest concentration will be toward the east side of the state from near Ormond Beach South to Vero Beach by the time 9pm has rolled around (not all at the same time). There could also be some stronger storms over and near the Everglades with almost no storm motion other than via propagation along where the Lake Breeze meets outflow boundaries and other wind boundaries such as the sea breeze.  Like yesterday, a few locations could receive rainfall measuring over 2 inches, whereas other locations will be completely dry

Keep in mind. Storms over Florida in the summer almost always form along a 'boundary'. That boundary is normally a wind/thermal boundary created by Lake and Sea breezes. When those two boundaries meet, the storms become stronger or turn from rainshowers to thundershowers, or even thunderstorms (both have dangerous lightning either way though) A 700mb trough aloft will be an additional mid-level boundary for North Central Florida today.

SET UP: A 700mb (mid-level) trough of low pressure (generally at about 10,000 ft overhead) sinking south into North Florida...a bit further south from where it was located yesterday. This is coupled with a weak mid-level 700mb ridge across far South Florida.  At the surface, the ridge axis is located almost in the Florida straits surrounded by very light winds. So light of winds that 3 waterspouts were observed off the coast of Miami Beach early in the morning.  Beyond the 700mb trough along the SE U.S. Coast (toward the west), a weak high pressure area extending from the Southern Plains States (with drier air) is trying to build south toward I-10. Another trough is in the wings though a few days away.  Between those two areas, across most of the state, is a light west to east steering flow. It is a bit more from the WNW at the lower levels.  Expecting sea breezes to form earliest from Ft. Pierce and South, and Ormond Beach to JAX, with the latest onset of the sea breeze's true reflection the latest over Dead Central Florida, namely Brevard County, Southern Volusia, and maybe Indian River County.

In South Florida, slower steering (to almost none), high PWAT air (lots of moisture), and sea/lake breezes will allow showers and storms to form along those boundaries...initially just showers but evolving into thunderstorms where the two boundaries meet.  Boundary interactions could set up a stronger storm or two just about anywhere, so the graphic for today's post shows one possible location, but this could happen almost anywhere in Collier, Dade, Broward, or Palm Beach Counties.

In Central Florida, the least moist (but hardly by much, and thus most stable), is the east side of the state south of Volusia County to Vero Beach). This area should thus be the latest to receive rain because 1) it is a tad less moist 2) this is part of where the latest sea breeze will form, and thus, no boundary. 

Any sea breeze along the east coast today should remain along or east of I-95 due to general west to east winds just above the ground at 2000ft (those winds are not expected to change today).

ONE MORE NOTE FOR TODAY: Latest glance at the jet stream level winds for today  shows the strongest jet stream level winds I've seen over the state in about 2 months, at least. There are no storms at this time downstream of these winds, so those high altitude winds shouldn't be advecting high level cloudiness across the state (as can be observed at noon today that is the case so far).  The winds at one point in the plot are nearly 60kts, but mostly 30-40kt winds could be passing overhead today at the jet stream level. This would effectively spread anvil level storm tops toward the SW late today and tonight, but keep storms that are progressing from west to east headed into 'clean air' (not into an area covered by cloudiness).  It would also help prevent storms to a smaller degree from collapsing on themselves a little less readily.  The temperatures aloft today are about the same as they ended up yesterday, but any little unforeseen 'cool' pocket in the mid-levels would provide the incentive for a robust storm  to raise some eye-brows and result in a few special weather statements being issued, if not a warning toward the east coast (such as the area in black above).

Outflows from storms inland generated by the lakes should send more outflows mostly east and southward... generating more storms in stair step fashion toward the east coast. In essence, the storms will progress from west to east, with a hint at some points of moving in from the WNW to even NW.  If storms reach Volusia or Flagler County earlier than expected (around 2:30 -3:30pm), outflows from those storms could force other storms to form into North Brevard County that would work lengthwise along the intracoastal waterways and against the sea breeze.  Those storms in theory would be enhanced and made stronger (said with a bit conjecture). If so, the US1 to A1A corridor from Port Canaveral to Vero Beach might be in for a 'surprise storm' generated by very localized, misoscale boundaries.

THESE ARE THE JET STREAM LEVEL WINDS AT NOON. Nearly twice as strong (if not more) than they have been for quite some time. Winds over even 60kts (three times stronger not seen  recently, not since early June) are shown off the Georgia Coast.

TROPICS: If you've watched any TV today, you're probably aware about Tropical Storm Emily. There are so many variables at hand as of noon that a post concerning Emily's future track and strength would require a complete separate one of its own. To sum it up: 
1) Emily has slowed down in forward motion significantly since sunrise. This could mean it is gathering together its low and mid level components..that is, becoming slowly organized
2) Emily otherwise is not encountering any shearing winds and is in warm enough water for strengthening.
3) The latest flight into Emily did not show an increase in winds.
4) FORECAST TRACK NOTE: It appears the 'official' forecast track of Emily is essentially a weighted mean (statistical) of all the various tracks generated by at least 20 different track producing models. The 'mean' discounts the off the wall tracks that the 'average' would include. Do note that the track has been shifting toward the west just a bit. The GFS run of 06z was SIGNIFICANTLY different from those of yesterday..and fell back in line with earlier runs in citing that model as just one example.
5) IN GENERAL: Expect each and every model run to change to a least a small degree in regard to a future track and storm strength (and that means every SIX hours), varying from intensification to complete decay into an open wave ...especially if it starts to curve into the islands of the Great Antilles (such as The Dominican Republic).

Therefore, it's best to simply monitor the situation at one's convenience (if in Florida for instance)...AND..begin to consider what you'd need to have at hand in the case of a power outage longer than 12 hours -72 hours). 

If for any reason  this Storm (for example) were to track toward the NW as forecasts are zoning in on, then we'll have to see how strong the storm becomes after crossing any land (such as the Dominican Republic which has huge mountain tops). 

Bear in mind, the most significant strengthening of now dubbed Emily has almost always been AFTER having crossed land. Thus, what we are seeing happen in the next 48 hours might bear little to NO resemblance of what will come heading toward Friday. That is another reason why one should at least be mentally prepared to take some action.

 In that light, based on that strength and the expected track..greater preparatory measures might be required by coastal residents of the Florida East Coast, the Keys,  or in the Bahamas. So far, there has been no indication EVER that Florida Coastal Residents would need to prepare for anything beyond a power outage. Additionally, if the storm were to curve and become a hurricane of Cat 1 strength, coastal flooding would be at a minimum due to the direction of approach (and NO concern if it remains well off to the east)...for Florida.

In short, stay tuned and keep these ideas in mind. Another BLOG POST is in the works: 'Are You Sure You're Ready...?"  This will include a basic check list prepared by the Hurricane Center (with some personal ideas based on experience as well)...and a little geography lesson addressing the Caribbean Islands which are often referred to (if not always) when coverage begins on TV. I'm not so sure all of those weather men even KNOW where the Windward and Leeward Islands begin and well as where the U.S. Virgin Islands fit into the mix. But we can know, can't we..and we will in that upcoming post.

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