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Have any of you watched Levi's update from yesterday on Tropical Tidbits? He suggests a number of factors ... both positive and negative (but mostly negative) that will either encourage or discourage further development including the shear, broad circulation, lows not vertically stacked (yet), dry air, elongated trough extending out to the NE, other upper level dynamics, jet streak presence, etc. You can't just "wish" these things away.

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18 minutes ago, larrye said:

Have any of you watched Levi's update from yesterday on Tropical Tidbits? He suggests a number of factors ... both positive and negative (but mostly negative) that will either encourage or discourage further development including the shear, broad circulation, lows not vertically stacked (yet), dry air, elongated trough extending out to the NE, other upper level dynamics, jet streak presence, etc. You can't just "wish" these things away.

Levi is the best.  Every tropical cyclone geek should be following his tweets and watching his videos.  I would not be a bit surprised if he is the NHC director someday.

Regarding 99L, it continues to be a struggle.  The shear isn't terrible and the dry air isn't terrible, but the two of them, combined with 99L's westward movement, won't allow the system to do much more than hold its own for now.  The latest visible loop still shows the surface center, or at least one sub-vort within a larger broad center, just off to the north of the deep convection and also shows outflow boundaries pushing eastward away from the system.  Perhaps it can take another step or two forward once it turns northeastward and accelerates within the shearing upper flow.

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Just now, hawkeye_wx said:

Levi is the best.  Every tropical cyclone geek should be following his tweets and watching his videos.  I would not be a bit surprised if he is the NHC director someday.

Regarding 99L, it continues to be a struggle.  The shear isn't terrible and the dry air isn't terrible, but the two of them, combined with 99L's westward movement, won't allow the system to do much more than hold its own for now.  The latest visible loop still shows the surface center just off to the north of the deep convection and also shows outflow boundaries pushing eastward away from the system.  Perhaps it can take another step or two forward once it turns northeastward and accelerates.

Yes, he is amazing. Smart, articulate, and balanced/impartial.

I'm not a Met, and I totally agree with you. From what I can tell, I wouldn't be surprised if TD9/99L doesn't strengthen much more before making landfall and if it does, perhaps becomes a minimal TS. Just isn't enough time with enough positive factors that would contribute to development. Over the Atlantic/Gulf Stream, perhaps a different story. Still, as Levi points out, lots of precip east of the center for Florida. 

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at 5:30 National weather service says  "  .SYNOPSIS...TROPICAL DEPRESSION NINE CENTERED NEAR 23.8N 86.6W  1003 MB AT 0900 UTC AUG 30 MOVING W OR 275 DEG AT 6 KT. MAXIMUM  SUSTAINED WINDS 30 KT GUSTS 40 KT. THE DEPRESSION IS EXPECTED TO  INTENSIFY TO A TROPICAL STORM LATER TODAY NEAR 24.2N 87.3W. THE  CYCLONE WILL BE LOCATED NEAR 24.9N 87.6W EARLY WED...NEAR 26.2N  86.9W WED EVENING...THEN BEGIN TO TURN N AND NE AND INTENSIFY TO  55 KT GUSTS 65 KT NEAR 27.7N 85.5W EARLY THU. NUMEROUS SQUALLS  AND SCATTERED TSTMS WILL SPREAD FROM THE SE GULF N AND NW INTO THE  E GULF THROUGH THU. THE STORM IS EXPECTED TO ACCELERATE NE AND  MOVE ACROSS NORTHERN FLORIDA THU NIGHT. "

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Posting the NAM, especially the 4km NAM, in a tropical thread adds nothing to the discussion. May have some value in short term synoptic features, for steering currents for example, but intensity wise it's crap. For track forecasts is also subpar to global models. So please post as little NAM as possible in this type of threads.

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8 minutes ago, wxmx said:

Posting the NAM, especially the 4km NAM, in a tropical thread adds nothing to the discussion. May have some value in short term synoptic features, for steering currents for example, but intensity wise it's crap. For track forecasts is also subpar to global models. So please post as little NAM as possible in this type of threads.

Actually track wise the GFS is coming in with a very similar landfall location as to the NAM. But yes I completely agree that with intensity, it is way off.

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3 minutes ago, NJwx85 said:

The 12z GFS is still a giant bucket of meh. 1004mb landfall in the big bend area in 66hrs. 

However once the system reemerges near Charleston things become more organized. It's certainly plausible that TD 9 will reach peak intensity once back in the Atlantic.

Its likely that the GFS is being too conservative strength wise. Its currently 1004mb right now.

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1 minute ago, WeatherFan202 said:

Its likely that the GFS is being too conservative strength wise. Its currently 1004mb right now.

I'm not a fan of the GFS but it's the only model that has consistently shown a weak system up to this point, so I am giving it more weight than normal.

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Don't mind much the surface pressure in the GFS, it's usually better to check the trends in the low level vorticity. The latest forecast shows a strengthening cyclone at landfall. The low level vorticity certainly supports a mid end TS, and is stronger than previous forecasts.

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4 minutes ago, wxmx said:

Don't mind much the surface pressure in the GFS, it's usually better to check the trends in the low level vorticity. The latest forecast shows a strengthening cyclone at landfall. The low level vorticity certainly supports a mid end TS, and is stronger than previous forecasts.

Wouldn't there probably be a little bit of weakening at landfall?. I been hearing that as it gets near florida shear will increase.

Quote

The best shot for rapid intensification of #TD9 is over the next 12-24 hours. More shear awaits closer to FL.

 

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3 minutes ago, WeatherFan202 said:

Wouldn't there probably be a little bit of weakening at landfall?. I been hearing that as it gets near florida shear will increase.

 

This is my interpretation of what the GFS shows. Status quo or slight strengthening the next 24-30 hours. Then it appears it gets aided by some baroclinicity processes from the approaching shortwave, and the shear is offset by this, probably due to some enhanced convection, strengthening up to landfall in 60 to 66 hours.

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4 minutes ago, WeatherFan202 said:

Wouldn't there probably be a little bit of weakening at landfall?. I been hearing that as it gets near florida shear will increase.

 

Almost all systems in the Gulf weaken before landfall because they tend to pull dry air in off the U.S. and or they reach cooler waters within the first 100 miles of shore.  That is more common along the the NRN Gulf though than Florida.

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It is interesting to see the 12Z GFS bring this very close to New England.  I am a big fan of model trends and have noticed that high pressure blocking the cyclones ne progress.  Something to watch.  The Euro has the incoming Canadian high booting the system out in front of it.  The GFS slows the system enough to wait for the high pressure to pass and forces the system more north.

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On 8/30/2016 at 10:15 AM, Thesolmachine said:

Wtf is a torcon? 

It is a tornado probability scale popularized by Dr. Forbes. Specifically it represents the probability of a tornado occurring within a 50 mile radius with each value scaled to units of 10%. So a 5 is 50%. To get the SPC equivalent for a 25 mile radius you would do SPC = 1 - ((1 - TORCON) ^ 1/4). So a TORCON of 5 would be SPC = 1 - ((1-0.5) ^ 1/4) = 1 - .84 = 0.16 or about 15% which would yield either an enhanced or moderate risk outlook depending on the significance expected which, in this case, would probably be on the lower end of the scale since EF2+ tornadoes are not prolific enough in tropical cyclones to warrant the significant designation.

 

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30 minutes ago, pcbjr said:

Not suggesting anything; just an observation.

Seems like the NHC track is south and east of most models.

storm_09.gif

Yeah, it is a bit south, but not by much when compared to the models that matter. The TVCN line is the blend between the models that most people agree matter the most.

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