Tracking the Tropics:

[srainhoutx]

The afternoon ensemble guidance suggests a brief window for stirring the cyclone N then NE Wednesday into Thursday as a trough swings through the Eastern US. The trough is quickly replaced by an expanding upper Ridge across the Central Plains Friday with ridging building back toward the Mid Atlantic. I tend to believe this afternoon that a turn NE is the most likely solution. That said this disturbance has not behaved the way most of the reliable computer guidance has suggested. Let's see what things look like tomorrow...

[unome]

I tend to believe this afternoon that a turn NE is the most likely solution. That said this disturbance has not behaved the way most of the reliable computer guidance has suggested. Let's see what things look like tomorrow...

most of the reliable computer guidance has not been reliable huge swings back and forth on the GFS & ECMWF both - forecasters pulling their hair out over this one.

[jasons2k]

Yeah been saying all week nothing significant until Fl straits....watching folks get worked up over every Dmax and Dmin all week has been...well amusing at times. This really isn't surprising using old fashioned chart anayisis instead of model hugging. Anyway... I will say I didn't expect the ridge to break down this week so quickly. I was thinking a LA/Mobile storm but it looks like Cedar Key area now.

[unome]

from the discussion: http://www.nhc.noaa.gov/text/refresh/MI ... 2055.shtml

The depression will be moving through a marginal environment for intensification during the next day or so, with vertical shear of 15 to 20 kt. As a result only slow strengthening is expected in the short term. Later on, the environment may improve a little as the shear is forecast to decrease somewhat and become southwesterly, which should allow for a little more strengthening. However, there are mixed signals in the model guidance, with the ECMWF now showing the cyclone dissipating in the Gulf, while the GFS delays development until 4-5 days. Much of the tropical cyclone guidance is more aggressive. Given this uncertainty, the NHC intensity forecast is quite conservative and shows the system peaking at 45 kt, below all the explicit intensity guidance in consideration of the negative signal from the ECMWF. Needless to say, the confidence in the intensity forecast is even lower than usual for this system.

when intensity forecast confidence is this low, it just goes without saying that track forecast is also not set in stone

[worrybug]

from the discussion: http://www.nhc.noaa.gov/text/refresh/MI ... 2055.shtml

The depression will be moving through a marginal environment for intensification during the next day or so, with vertical shear of 15 to 20 kt. As a result only slow strengthening is expected in the short term. Later on, the environment may improve a little as the shear is forecast to decrease somewhat and become southwesterly, which should allow for a little more strengthening. However, there are mixed signals in the model guidance, with the ECMWF now showing the cyclone dissipating in the Gulf, while the GFS delays development until 4-5 days. Much of the tropical cyclone guidance is more aggressive. Given this uncertainty, the NHC intensity forecast is quite conservative and shows the system peaking at 45 kt, below all the explicit intensity guidance in consideration of the negative signal from the ECMWF. Needless to say, the confidence in the intensity forecast is even lower than usual for this system.

when intensity forecast confidence is this low, it just goes without saying that track forecast is also not set in stone

Track forecasts seldom are. Any more than model runs, I assume.

[tireman4]

from the discussion: http://www.nhc.noaa.gov/text/refresh/MI ... 2055.shtml

The depression will be moving through a marginal environment for intensification during the next day or so, with vertical shear of 15 to 20 kt. As a result only slow strengthening is expected in the short term. Later on, the environment may improve a little as the shear is forecast to decrease somewhat and become southwesterly, which should allow for a little more strengthening. However, there are mixed signals in the model guidance, with the ECMWF now showing the cyclone dissipating in the Gulf, while the GFS delays development until 4-5 days. Much of the tropical cyclone guidance is more aggressive. Given this uncertainty, the NHC intensity forecast is quite conservative and shows the system peaking at 45 kt, below all the explicit intensity guidance in consideration of the negative signal from the ECMWF. Needless to say, the confidence in the intensity forecast is even lower than usual for this system.

when intensity forecast confidence is this low, it just goes without saying that track forecast is also not set in stone

That is an understatement.

[tireman4]

For the pro mets (Andrew, Srain, Wxman 57, Brooks, Jeff)....how sure are you of the ridge (A mid-tropospheric shortwave trough developing over the southeastern United States is expected to induce a turn toward the north and northeast in 2 to 3 days,followed by acceleration toward the east-northeast late) pulling this (hooking) storm NE? With all of the problems ( although they seem to be in consensus now) with this disturbance, do they finally have it right?

[srainhoutx]

Large water vapor imagery shows the shortwave trough over the Western Greats Lakes that is expected to induce a weakness along the East Coast Wednesday. Just how deep of a trough will actually develop is the $64,000 question. It is also notable that there is significant drier air across the Western Gulf associated with an upper low. So we watch and wait and see how all these features interact and influence a weak and sheared TD #9 to make that slow turn N and the accelerate NE during the Wednesday/Thursday timeframe.

[Andrew]

It's actually quite amazing how strong of a shortwave/weakness that will persist over the northeast part of the gulf later in the weak. Rather unusual for late August/early September. One thing to note though is the further and further West to WNW progression of TD 9.

[tireman4]

It's actually quite amazing how strong of a shortwave/weakness that will persist over the northeast part of the gulf later in the weak. Rather unusual for late August/early September. One thing to note though is the further and further West to WNW progression of TD 9.

Yeah, I know. I keep seeing that. It is going to have to make a sharp turn eventually. This is one for the books. I wonder if there is a paper at a conference out of this..LOL...mets?

[Cromagnum]

To me it does not look like the trough will dig south and west enough in a short enough time to steer as strongly as the models are suggesting. Any chance that all of the models bust on this one and the storm goes much further west? Too tough to say yet?

[Andrew]

To me it does not look like the trough will dig south and west enough in a short enough time to steer as strongly as the models are suggesting. Any chance that all of the models bust on this one and the storm goes much further west? Too tough to say yet?

Well its also the combination of an upper level low off the coast of the Carolinas paired with the shortwave that will really open things up. Plus ridging is supposed to shift westward. It will be rather difficult for it not to get caught up to some degree. Now how much is still up for question in my opinion.

[Rip76]

There could be a chance, especially if development is much slower.

But.... The models are in pretty darn good agreement.

[tireman4]

Did you see this...pretty cool.....

Hurricane Hunter en-route from MacDill AFB, Tampa.....

http://flightaware.com/live/flight/NOAA43

[rselby0654]

http://weather.rap.ucar.edu/model/displ ... all&hours=


This shows the system missing the trough and heading more our way. Interesting. It's never over until it's over.

[rnmm]

Does the fact that it's now moving WNW and has slowed down to 5 mph do anything to the forecasted track?

[ticka1]

has NHC changed their track any over the last few advisories or stay with sharp turn to Florida and east coast?

[srainhoutx]

No change in the track reasoning given in the 5:00 PM EDT Full Package Discussion. A gradual turn N then NE is expected for TD 9. Texas and Louisiana appear safe from any direct impacts from this system, but we will continue monitoring.

Tropical Storm Warnings have been hoisted for the Outer Banks of North Carolina for TD 8.

Watches and Warnings may be required across portions of the Western Coast of Florida tomorrow if TD 9 strengthens to a Tropical Storm.

[Skyguy]

No change in the track reasoning given in the 5:00 PM EDT Full Package Discussion. A gradual turn N then NE is expected for TD 9. Texas and Louisiana appear safe from any direct impacts from this system, but we will continue monitoring.

Tropical Storm Warnings have been hoisted for the Outer Banks of North Carolina for TD 8.

Watches and Warnings may be required across portions of the Western Coast of Florida tomorrow if TD 9 strengthens to a Tropical Storm.

May I ask you a hypothetical question about TD9?

[Katdaddy]

TD 9 may become a TS later today with the recurve across FLA still expected. In the far E Atlantic we have Invest 92L. The NHC 5-day TWO brings this system to near the Lesser Antilles with a 40% chance of tropical development.