ATL: Tropical Depression Fay

[Aquawind]

Dang.. It did show signs of the landfall and mountains today, but yeow the convection is gettings it's groove on. NHC seems to be doing a good job and as bad as it looked earlier.. Fay is taking advantage of her time over water.

[MiamiensisWx]

The following post is NOT an official prognosis.

Fay forecast and analysis #1

Currently, Tropical Storm Fay is situated near 19.0 N 74.5 W, as documented by recent reconnaissance data. The system remains poorly organized; although the mid level circulation and (slightly) partially exposed LLC are co-located, the best upper level divergence and ascent is located farther south, aiding additional development of thunderstorms on the southern semicircle. Earlier (and now), this factor and inflow disruption via Hispaniola to the south and east have hindered Fay from organizing and deepening more significantly. However, the upper air environment remains quite conducive, with an excellent diffluent regime and upper low to the northeast, the latter of which continues to result in an excellent outflow channel on Fay's southern semicircle. In addition, a 300 mb anticyclone remains in place over the TC; however, the anticyclone has weakened over the past ~12 hours in response to a deepening upper level shortwave over the Northeast. WV imagery indicates a weak retrograding TUTT to the west of Fay, which is inducing southerly wind shear at 300 mb over the TC's western semicircle. If Fay exhibited a well defined inner core with better structural organization, the shear would have been a less significant issue; however, in combination with the other aforementioned negative factors above, it appears to be hindering thunderstorm development and sustained convection over Fay's LLC. Therefore, I anticipate slower intensification over the next ~12 hours, followed by greater organization as the TUTT moves SW, reducing the upper level shear slightly. Overall, I digress with the higher intensity estimates progged by the NHC, but I do expect a strong (60 kt) tropical storm prior to landfall on Cuba. Since Fay will traverse the flatter and narrower portion of Cuba, when combined with the fact that I anticipate a formative inner core prior to Cuban landfall, I continue to believe Fay will regain hurricane intensity over the Gulf of Mexico. However, the prospects of a stronger TC than ~70 kt look much more scanty than the preceding day(s), based on the track and Fay's lower intensity over the Caribbean.

The intensity forecast (over the short, medium, and long term) is a conundrum, but the track is even more perplexing. Currently, reconnaissance fixes and satellite data indicate Fay is moving slightly north of due west. Since Fay will likely be less intense than forecasted within the short term, the TC will likely move farther west than originally expected. Indeed, several of the more reliable models and their variations have shifted west throughout the day. The unreliable GFDL (based on the GFS) initializes a deeper system than reality, resulting in a rapid NW turn and strike on the southeast coast of Florida. A few additional models have also periodically (and incorrectly) initialized the TC as a deeper system than reality. In summation, Fay will likely be influenced primarily by the low level (H7-H85) steering over the next ~36 hours as it passes just south of the island of Cuba. Based on all available data, a landfall on the western half of the island is indicated in the forecast. After ~36 hours, it is likely that another deepening shortwave will erode the mid/upper level ridging to the north; however, prior to this time frame, heights will rise over the Florida peninsula. It is important to note that the 12Z operational GFS indicated a weaker H5 ridge over the Florida peninsula (in the initialization) than reality. Based on this data, as Fay turns north, I expect a track slightly farther west than the official NHC tropical cyclone forecast points. After landfall in the Tampa Bay area, it is likely that the rebuilding ridge will force Fay (with decreasing forward speed) on a slow WNW track into southern Georgia.

http://img58.imageshack.us/img58/595/fayforecast2008atl1ts4.png

Based on the angle of approach, this could produce a localized storm surge event across the Tampa Bay region. This could be the first hurricane to directly strike the Tampa/Bradenton/Sarasota/Saint Petersburg area since Storm #5 of 1946 made landfall as a Category 1 hurricane near Cortez Beach (in the vicinity of Bradenton). The last major hurricane to affect the area struck Tarpon Springs, Florida in 1921 as a Category 3 hurricane. It was the Tampa Bay area's most destructive tropical cyclone since another Category 3 hurricane affected the vicinity in 1848. Interestingly, there were two major hurricanes that affected Tampa in 1848.

The TC will likely be deepening prior to landfall, so strong TS/localized Cat 1 winds (1-min) may mix more efficiently to the surface in swaths. As seen with Dolly and Wilma, these winds can be quite intense. Tampa Bay has not experienced hurricane force winds over the past several decades. You could classify Fay as another Dolly in the end. Unfortunately, this one could be quite detrimental to many poorly constructed buildings and other vegetation/infrastructure via strong winds and localized storm surge in the region. Many structures haven't been subjected to strong TS/hurricane force winds since 1946, 1950 (Easy brush), and 1968 (Gladys brush). Many residents believe another hurricane can't occur again in the region, so Fay could be a wake-up call that should be heeded. Tampa Bay is eerily similar to the Georgia coast and Big Bend area of Florida in regards to recent "dead" decades.

Since I expect an intensifying TC prior to landfall, this could be very interesting. Hopefully, residents are attuned to the threat, despite numerous years of brushes and the "Tampa Bay shield" myth.

In conclusion, here are some interesting documents on the 1921 and 1946 Tampa Bay hurricanes, respectively.

http://www.aoml.noaa.gov/hrd/hurdat/mwr_pdf/1921.pdf

http://www.aoml.noaa.gov/hrd/hurdat/mwr_pdf/1946.pdf

Note that the 1921 hurricane produced very high tides and storm surge (greater than +9 feet) in the Tampa Bay region. The 1946 Category 1 hurricane (which featured TS winds in most locations) produced tides of +3 and +6 at Tampa and Punta Gorda, respectively.

I cannot underestimate the threat to this region even from a Category 1 hurricane. The possible angle of Fay's approach could be bad surge wise as well.

[Aric Dunn]

wow thats a novel!!!!!!

[Frank P]

Also looks like convection firing back up near the LLC on the latest Vis Sat loops... best guess on motion still appears to be WNW or north of due west, or some points inbetween...

[cycloneye]

Pressure falls to 1005 mbs in this latest VDM.Slowly getting better organized.

URNT12 KNHC 162218
VORTEX DATA MESSAGE AL062008
A. 16/21:58:50Z
B. 19 deg 17 min N
075 deg 22 min W
C. 850 mb 1461 m
D. 57 kt
E. 145 deg 66 nm
F. 146 deg 041 kt
G. 141 deg 056 nm
H. 1005 mb
I. 17 C/ 1524 m
J. 18 C/ 1524 m
K. 18 C/ NA
L. NA
M. NA
N. 1345/8
O. 0.02 / 6 nm
P. AF304 0906A FAY OB 16
MAX FL WIND 57 KT NE QUAD 20:02:00 Z

[Just Joshing You]

Where is the center? I think I see something at 20/73.5

[Aquawind]

Pretty good write up MiamiensisWx..

[KWT]

Totally agree with what Miami says in that amazing post, I still think this will come in probably as a cat-2 into Florida close to the Tampa region, as its clearly a little more to the west then some of the tracks 12hrs ago projected.

However as has been said if this is a hurricane, even a cat-1 can cause trouble...also importantly Florida will be on the dirty side so to speak, this one will be very difference to most landfalling systems as the winds will be higher on that eastern side.

Edit---last 3hrs motion almost due west...looks like the models are going to have to shift back west IMO if this keeps up...

[cheezyWXguy]

Where is the center? I think I see something at 20/73.5

19, 75.something

[Aquawind]

Pressure falls to 1005 mbs in this latest VDM.Slowly getting better organized.

57kts at fl as well...dang

[cheezyWXguy]

Pressure falls to 1005 mbs in this latest VDM.Slowly getting better organized.

57kts at fl as well...dang

wouldnt that support about 50kt?

[Steve H.]

As I said earlier today, she has plenty of energy as has been steadily improving all afternoon. I think the NHC is quite conservative with intensity, as she should stay over water south of Cuba for 24 hours.

[Aquawind]

Pressure falls to 1005 mbs in this latest VDM.Slowly getting better organized.

57kts at fl as well...dang

wouldnt that support about 50kt?

Close..certainly will be a bump up in winds 50mph at least and more time over water.. we may easily see 60mph by 5am looking a visible if that wind is real.

[NDG]

Where is the center? I think I see something at 20/73.5

19, 75.something

That's 19.3N 75.4W

[deltadog03]

I think most the wind data is being flagged though...If I am not mistaken...

[deltadog03]

Where is the center? I think I see something at 20/73.5

19, 75.something

That's 19.3N 75.4W

Looks good!! At least for today, it def. has not gained much LAT.

[Aric Dunn]

I think most the wind data is being flagged though...If I am not mistaken...

right but that 57kt was on the VDM .. so it was confirmed

[CrazyC83]

Pressure falls to 1005 mbs in this latest VDM.Slowly getting better organized.

57kts at fl as well...dang

wouldnt that support about 50kt?

That was almost 2 hours ago, and it would support 45 kt at the surface as it was at 850mb (80% reduction). It might be stronger now though.

[hial2]

I think most the wind data is being flagged though...If I am not mistaken...

What do you mean by flagged? Thanks

[KWT]

Yep I think 45kts is a pretty good estimate, its certainly stronger then it was earlier though IMO the presentation still isn't very impressive, which always tends to suggest IMo that if it does grow a big CDO it undergoes RI IMO...

Also if current motion holds for longer then NHC will have to start to slightly shift the track back westward again.