"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".

Monday, October 17, 2011

Mixed Bag of Rain, Wind, and Potentially Severe Weather to End Wednesday

As of 1:30pm, it looks like there might be tropical depression off the North tip of the Yucatan, although even though satellite animations show a definite very tiny 'swirl', it is moving around a broader scale cyclonic circulation toward the SSE.  Otherwise, jet stream level winds are spreading the denser cirrus and cirrostratus clouds across much of the peninsula, with heavier rainstorms (some rotating) over the lower 3/4th of the Keys where Miami Doppler Estimated rainfall totals so far show rainfall totals ranging from 3-14 ", but most is in the 4-7" range. Already, the Keys is experiencing a rain event, and more 'events' of subtopical origin could occur elsewhere in the state through early Wednesday.

NOW: What appears to be a diffusing warm front over far South Florida is working slowly northward piece meal as high pressure stretches from the western Atlantic across the north half of the state in the mid-levels. High pressure should retreat slowly as an approaching trough works eastward from the north and central Plains, further developing east of the Rockies across Kansas, Oklahoma, and Texas by sunset.
Image below is for midnight. 

The low pressure area near the Yucatan should remain in the same general location through tonight and begin to lift north prior to daybreak, Tuesday. The series of diffuse warm fronts lift north with it as does the rain chance.
It appears the best chance of rain outside of South Florida later today will be near the east coast toward East Central along an axis of instability as the warm front works north. Some showers have already formed and dissipated toward South and Central Brevard and inland, but have since diffused under the canopy of thicker high clouds.

 After 48 hours of model runs and a lot of changes with them, the general outlook posted here on Saturday sums up to be pretty much the same thing as posted then. 

Two Tiered system with several imbedded impulses and vortmaxes to impact the state mostly from sunrise Tuesday through Wednesday in various shapes and forms, with differing results depending on where one is located.

Rain showers most likely to approach the east coast to inland by late afternoon Central toward sunset, with the chance working northward by Tuesday morning. This will not be a continuous rain by any means, but some thunder could be thrown in for good measure, most likely elevated.

TUESDAY: Chance of a tropical storm developing. However, any bone fide tropical storm to form does not appear will actually make land fall as one. The NAM is showing a warm core low to form up through 20,000 ft, but the system is quickly torn as the approaching cold front from the WNW moves in. In doing so, the surface low is displaced from the upper level core which progresses east while the surface low lifts toward the Florida Big Bend. Actually, the NAM shows the warm 500mb core to cross Central Florida along with a developing warm front from the west as the low moves to the NE. This is shown further down in the post.

Using the CIMMS tropical cyclone site as a reference, the Ocean Heat content near the Loop Current could play a critical role in development of this storm system. It is important to note that whether or not this system is named, the results of the impacts could come out to be quite similar either way. In this image the red on the top of the image is dry air, while the colors in the Eastern Gulf are the warmest ocean temperatures west of Tampa. Models have been showing actual storm tracks varying from Dead Central to the Big Bend in direction, but what might happen in reality is that there will be two storm systems with different characteristics tracking along with them both.
INVEST of interest north of Yucatan is circled in dark red. To the NE of that "I" is the warmest Gulf water/Heat Energy. North of this location is dry air at the moment. This will move out later tonight. A storm could form 'of name' in this area, or at least all the parameter formidable for storm formation will explode with energy either way. 

Below are some model tracks for a potential surface low, if one truly forms. My take, or opinion, is that if a truly tropical low is to form it would only remain tropical or subtropical by taking a track across Central to South Central Florida. Otherwise, models indicate it will become rapidly absorbed into the much larger scale trough by Tuesday late afternoon if it continues to be guided more northerly to NNE as the GFS/NAM indicate. 

This is why it is interesting why the NAM is showing the warm core aloft  to move across Central while the surface low takes off more toward the NE and the Big Bend region or more toward the south north of Tampa Bay. See image below, and the orange warm core across Central , west of Orlando, on Wednesday morning at 2AM. I did not draw that it, it is model derived.

I'm thinking the biggest concern with the system in the rotating storm (tornado) department will come with that core / trough couplet and the associated wind fields as they appear will cross the state from SW Florida near Cape Coral area and across the state , exiting the east coast from Central Volusia south toward Indian River county from near sunrise Tuesday toward just after dark. 

Meanwhile, the parent and more substantial low will track toward Cedar Key through the Big Bend and interact with the approaching cold front bringing larger rainfall totals from Gainesville and North to Jax and along I-10  toward Tallahassee in a short amount of time.

WEDNESDAY: The front should be clear of Central Florida by mid-late afternoon. Whether there will be much rainfall with it is still up for debate. As of yesterday there appeared there would be a period of heavier rain across Central as the front temporarily locked up, but now it appears it will go through with nothing more than cloudiness and light rain. There is clearly much more to be learned and followed as the events unfold, and so far this one particular aspect of the system seems to be of minor concern (based on the morning GFS at least).

THURSDAY-FRIDAY: Very cool ... coldest mornings since early spring, with lows in the mid40s through the 50s as far South as Far South Florida. Overall, Thursday will be the coldest from sunrise to sunset, with Friday being the day that the most of the state   being simultaneously cooled from north to south.

SATURDAY: Winds should start to swing slightly onshore by morning along the east coast making for a noticeable warm up. The models (GFS) has been consistent with hanging the trough at the mid levels behind over Central or South Central Florida in all cases, thus rapid air mass modification with the onshore return flow and eventually low topped showers reaching the coast by Sunday or Monday. The GFS in the last run is holding off on the showers until Monday now, but impacting the coast to 20 miles inland for 2 days. Previous runs indicated showers could move in as soon as early afternoon Saturday, so this too will have to be re-evaluated late week.

BEYOND: It appears that perhaps two backdoor cold fronts could move through next week toward next weekend with little change in winds other than some wind surges from the NE to ENE, and a break in showers between them. Timing is difficult and changes with every run when these will occur. The latest morning run shows a very showery day for all of coastal NE-East Central Florida on Halloween. Lows and highs likely remaining the 70Fs round the clock.

TROPICS could could continue from north of Central America north through much of the Caribbean....through the end of the month.

RAIN: Largest rainfall totals outside of the Keys (ongoing) will be along the cold front/Gulf low merger over North and parts of North Central Florida. Although totals will not be as high as what was experienced with the last event, the rain will fall in a much shorter amount of time. Areas further south toward Central and South Central will not receive as much rain most assured as before, but already filled retention areas and high ground water could easily result in a resurrected flood threat despite the lower rainfall totals over a large area. Areas across Central will likely not experience the bigger totals due to fast shower/storm motion, but training could amount to much higher localized rainfall. Parts of SE Florida might also deal with some flooding threats in the more fabled, flood prone areas.

WIND: Strong winds of 35-55moh (at least) could occur near the Big Bend toward Brooksville and swath across North and North Central Florida from JAX to northern Volusia County, but possibly as far south as Central Brevard. The strongest winds forecast are actually just above ground at 2000 - 10,000 feet, but in heavy down pours these winds could translate to the surface .   Trees will be able to fall in these stronger winds more easily now with loosened/weakened soils in place, and additional rainfall will further aggravate the situation. The other way of looking at it though, is that the last system likely cleared up many of the already loosened or rotten fronds and branches.

STORMS: This entire event looks more to be a function of wind shear and kinematics rather the thermodynamics. Only the South 1/2 or 5/9th of the state are ever indicated to be have appreciable unstable conditions. Regardless, there appears to be a tornado threat at different times from SW Florida near Naples and along a swath extending ENE ward along and ahead of what could be the remains of any tropical type features that might be directed across the state as   a north/south running warm front or trough toward all of Brevard and portions of Volusia and Indian River Counties. This would include Sarasota, Lakeland, near Naples, Cape Coral, Polk, Osceola, Orange/Seminole Counties, parts of Lake and Volusia Counties. But this is just for starters. 

Even if instability is lacking, this system appears could act more like a tropical system with warm air aloft, and as such it will all be about the wind directions aloft and bulk shear between various levels of the atmosphere. Thus, if it comes to the point that warnings are deemed necessary, a tornado would be possible even without vast amounts of lightning. Another way of thinking of it is, any storm with more than an occasional rumble might be a big trouble maker . 

The reality in my mind is that things will unfold probably nothing like what I'm imaging or how the model rain fields are shown, nor in the way they are expected to form. The truth, or some semblance of it will evolve as things happen. Thus, early Tuesday through midnight Tuesday night so far seems to be the time for extra precautions to be at the first and forefront.

This systemh as the potential to go down in the annuls of Florida's meteorological history , if for nothing more than a case study....the Keys are likely already on their way for breaking a rainfall total record, and other records could be on the way to be broke almost anywhere. 

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