Extratropical Depression Lee

[jpeters3]

Let's say that the waters were of the same temp. all of the way to the ocean floor. ( I know this is not realistic, but that's beside the point.) Wouldn't a TC still cause cooling of the water (although I assume not as quickly) simply because it is taking energy away from the water? In other words, even if there isn't any cooler water for 93L to upwell, would it still cause sig. cooling if it lingers over an area for a long time?

It would, but only to a minute extent. If water temps were the same all the way to the ocean floor, it would take an utterly tremendous amount of energy loss to significantly cool the water column. Yes, there might be some surface cooling, but this would mix out due to agitation from the cyclone itself.

[am19psu]

Let's say that the waters were of the same temp. all of the way to the ocean floor. ( I know this is not realistic, but that's beside the point.) Wouldn't a TC still cause cooling of the water (although I assume not as quickly) simply because it is taking energy away from the water? In other words, even if there isn't any cooler water for 93L to upwell, would it still cause sig. cooling if it lingers over an area for a long time?

Yes. That's the basis for WISHE.

[Srain]

It looks as if we have a surface low forming around 26N/90W this morning. It does appear rather broad and movement looks to to be slowly N and W...

[wxmx]

The main difference between yesterdays 12z Euro and today's 0z Euro is the pattern upstream in the Pacific. The PNA ridge in the latter is quite strong, making the ridge more N/S oriented and a bit farther west, and a stronger trough in the E CONUS... and that ridge is ruled even farther upstream by the Aleutian low... a stronger low that stays over water would pump the PNA ridge further.

12z Euro ... ridge is a bit squashed south, with a more E-W orientation.

0z Euro ... classic +PNA ridge over W Canada... you can see the differences around the Great Lakes, for example.

[wxmx]

The main difference between yesterdays 12z Euro and today's 0z Euro is the pattern upstream in the Pacific. The PNA ridge in the latter is quite strong, making the ridge more N/S oriented and a bit farther west, and a stronger trough in the E CONUS... and that ridge is ruled even farther upstream by the Aleutian low... a stronger low that stays over water would pump the PNA ridge further.

12z Euro ... ridge is a bit squashed south, with a more E-W orientation.

0z Euro ... classic +PNA ridge over W Canada... you can see the differences around the Great Lakes, for example.

Their respective ensembles support the operational. The 0z GFS and it's ensembles support the 0z Euro, but the 06z GFS has a stronger +PNA ridge, but not quite as strong as the Euro... could this be a trend?

[wxmx]

The main difference between yesterdays 12z Euro and today's 0z Euro is the pattern upstream in the Pacific. The PNA ridge in the latter is quite strong, making the ridge more N/S oriented and a bit farther west, and a stronger trough in the E CONUS... and that ridge is ruled even farther upstream by the Aleutian low... a stronger low that stays over water would pump the PNA ridge further.

12z Euro ... ridge is a bit squashed south, with a more E-W orientation.

0z Euro ... classic +PNA ridge over W Canada... you can see the differences around the Great Lakes, for example.

Their respective ensembles support the operational. The 0z GFS and it's ensembles support the 0z Euro, but the 06z GFS has a stronger +PNA ridge, but not quite as strong as the Euro... could this be a trend?

Edit: The Canadian ensembles are something in between also.

[stormtracker]

I'm honestly hoping for a Texas landfall (GFDL) solution. Those folks need the water. NOLA, not so much. Would be nice to have more than the GFDL on board though.

[Big O]

And wrong?

The new Euro ensemble members are spread out NE/SW by 108 hours, but fewer members are in the SW camp than the NE camp.

But the track of the ensemble mean backs southwest thereafter. In addition, the European Ensemble Prediction System Control model (PPV) has the system as a formidable storm impacting southern Texas Thursday and Friday of next week.

Does anyone know what the difference between the ensemble mean and ensemble predication system control? Is one more reliable than the other?

[needbiggerboat]

Not sure if the 12z NAM is to be believed, but obviously a distressing scenario for NOLA

[lsukev]

Not sure if the 12z NAM is to be believed, but obviously a distressing scenario for NOLA

Yeah, not good for NOLA. The peeps on the Gulf Coast WX board are already getting anxious. I might have to prep the bachelor pad for the 'rents.

[Terpeast]

Not sure if the 12z NAM is to be believed, but obviously a distressing scenario for NOLA

Bad for TX, and bad for New Orleans. Bad for everyone.

But the NAM is still an outlier. At least for now.

[Ed Lizard]

6Z GFS a little less depressing with almost 2 inches of rain total in Houston, which would keep all the not quite dead trees going a little longer.

Initialization seems close to what early visible satellite frames are suggesting. One bad thing, GFS landfall looks awfully close to the International Border, hopefully it'll pick one side or the other if Josh wants to chase.

Not sure what the apparent GFS trend towards the Euro means. Looping the 500 mb heights 93L barely misses the trough.

[Ed Lizard]

NAM looks a little more intense, pressure wise, than I'd want to see around New Orleans, but the rain wouldn't be all bad. Not the exceptionally extreme drought of Texas, but they have been abnormally dry as well.

[Srain]

Morning HI RES imagery suggests a W to WNW motion of a broad circulation S of Louisiana. Some unconfirmed reports offshore are coming in with winds to 35 already. We'll see if the trigger is pulled and we see an upgrade a bit later.

[PSUBlizzicane2007]

Morning HI RES imagery suggests a W to WNW motion of a broad circulation S of Louisiana. Some unconfirmed reports offshore are coming in with winds to 35 already. We'll see if the trigger is pulled and we see an upgrade a bit later.

I don't really think it is organized enough yet to be classified... however, I think by 24 hours it most certainly will.

[wxmx]

On a climo note: during exceptionally dry years, we usually see more of a Sward component to the motion for TCs in the GoM... extreme cases might be 1933, 1934 and 1936

[Terpeast]

I don't really think it is organized enough yet to be classified... however, I think by 24 hours it most certainly will.

We would probably know better than we do now if the buoy the area of low pressure is over right now was working.

[Terpeast]

On a climo note: during exceptionally dry years, we usually see more of a Sward component to the motion for TCs in the GoM... extreme cases might be 1933, 1934 and 1936

Very interesting. Thanks for bringing that up. Makes sense being the ridge that contributes to the drought could also shunt the TCs SW.

[Mallow]

94L will probably become Lee, so here's my preliminary Mariacast.

It's going to be battling with shear pretty much its entire life. Better upper level divergence and lower shear look to set up a bit further south, so I think the actual center development will occur further south than some of the models are showing. This further south spin-up would have two impacts--it would prevent a shallow, sheared Maria from racing off to the northeast under the influence of the Great Lakes trough, and it would likely mean she never fully reaches the Louisiana coast.

I don't buy the southwesterly or even south-southwesterly motion many of the models are showing under the influence of the western ridge, but I do think a steady west-southwesterly motion is reasonable... so I have it coming onshore in southern Texas as a TS (I'd guess 50-55kts).

[wxmx]

TCs west of 90W during 1933, 1934 and 1936... note that there is almost no Eward component to the motion in these cyclones.

[DaculaWeather]

Some of the buoys are showing about 20-25 mph in the Gulf.

http://www.daculawea...om/buoy_new.php

and west Gulf http://www.daculawea...oy_west_new.php

[Ed Lizard]

Better resolution visible floater than the SSD page.

[Terpeast]

Better resolution visible floater than the SSD page.

Bit too much wind shear across the northern Gulf. Less shear in the central gulf, where new clusters of thunderstorms are forming up... me thinks that's around where the circulation will start (if it does).

[VAwxman]

Bit too much wind shear across the northern Gulf. Less shear in the central gulf, where new clusters of thunderstorms are forming up... me thinks that's around where the circulation will start (if it does).

Good deal of shear over the entire Gulf right now other than the SW, which isn't where this is headed for now. Forecast to subside, but then again, the GFS (maybe other models too) has been woefully underdone on shear so far.

[Terpeast]

Good deal of shear over the entire Gulf right now other than the SW, which isn't where this is headed for now. Forecast to subside, but then again, the GFS (maybe other models too) has been woefully underdone on shear so far.

Yeah, and I think because of that they're overdoing the strength/intensity of this thing... but if the shear subsides, all bets are off especially with that bath water. I'm hoping for a weak-moderate TS making landfall across TX of course, but we shall see.

[needbiggerboat]

12z GFS through 90 gives no love to TX, and has similar placement as NAM with low off LA, and robust precip totals.

[wxmx]

Yep, it looks like the 12z GFS has a slightly deeper trough that barely hooks the TC... this will be a nightmare forecast challenge for some.

[Terpeast]

12z GFS through 90 gives no love to TX, and has similar placement as NAM with low off LA, and robust precip totals.

This model is assuming it gets picked up by the trough. Which is debatable, of course.

[Srain]

Just a bit if interest from the NHC concerning 93L...nice to see G-IV missions on tap...

NOUS42 KNHC 011650 AMD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1250 PM EDT THU 01 SEPTEMBER 2011
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
        VALID 02/1100Z TO 03/1100Z SEPTEMBER 2011
        TCPOD NUMBER.....11-093 AMENDMENT....FOR TEAL NUMBERS

I.  ATLANTIC REQUIREMENTS
   1. SUSPECT AREA (GULF 0F MEXICO)
      FLIGHT ONE - TEAL 75          FLIGHT TWO - NOAA 49
      A. 02/12Z,18Z                 A. 03/00Z
      B. AFXXX 03HHA CYCLONE        B. NOAA9 04HHA CYCLONE
      C. 02/11Z                     C. 03/1730Z
      D. 29.2N 91.5W                F. 41,000 TO 45,000 FT
      E. 02/1130Z TO 02/18Z
      F. SFC TO 15,000 FT

      FLIGHT THREE - NOAA 42        FLIGHT FOUR - TEAL 76
      A. 03/00Z                     A. 03/00Z,06Z
      B. NOAA2 05HHA CYCLONE        B. AFXXX 06HHA CYCLONE
      C. 02/20Z                     C. 02/23Z
      F. SFC TO 15,000 FT           D. 28.5N 92.0W
                                    E. 02/2320Z TO 03/06Z
                                    F. SFC TO 15,000 FT

      FLIGHT FIVE - NOAA 49         FLIGHT SIX - NOAA 43
      A. 03/12Z                     A. 03/12Z
      B. NOAA9 07HHA CYCLONE        B. NOAA3 08HHA CYCLONE
      C. 03/0530Z                   C. 03/08Z
      F. 41,000 TO 45,000 FT        F. SFC TO 15,000 FT

      FLIGHT SEVEN - TEAL 77
      A. 03/11Z-15Z - BUOY DROP
      B. AFXXX 09HHA CYCLONE
      C. 03/1030Z
      F. SFC TO 5,000 FT

   2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6 HRLY FIXES,
      G-IV AND P-3 MISSIONS EVERY 12 HRS. A SECOND BUOY
      DROP MISSION ON THE 4TH.

[Bannor]

BP is shutting in all U.S. regulated GOM platforms and evacuating all workers according to Reuters.