ATL : HARVEY - Tropical Depression - Discussion

[Gustywind]

Latest SSD position and intensity http://www.ssd.noaa.gov/PS/TROP/tdpositions.html

Atlantic Ocean Basin:
DATE/TIME LAT LON CLASSIFICATION STORM
12/0530 UTC 10.4N 28.8W T1.0/1.0 93L
11/2345 UTC 10.6N 27.5W T1.0/1.0 93L
11/1745 UTC 11.2N 21.2W T1.0/1.0 93L

[GCANE]

Yes, it is very clear on MIMIC-TPW that 92L is being robbed of energy (boundary-layer high theta-e air) by advection of 93L

IMHO, 92L could become cut-off from the ITCZ in the next day or two.

93L could be packing a lot of energy by the time it gets close to the east Carib.

[Gustywind]

Two African waves, 92L and 93L, worth watching

Posted by: JeffMasters, 14:59 GMT le 11 août 2011
http://www.wunderground.com/blog/JeffMa ... rynum=1878

93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.

Jeff Masters

[GCANE]

Pretty tight spread on GFS

[cycloneye]

8 AM TWO remains at 40%

A BROAD LOW PRESSURE SYSTEM LOCATED ABOUT 450 MILES SOUTHWEST OF THE
SOUTHERN CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND SCATTERED SHOWERS. ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO GRADUALLY BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER THE NEXT
SEVERAL DAYS AS IT MOVES WESTWARD AT 15 TO 20 MPH. THIS SYSTEM HAS
A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

[underthwx]

So far the 06z run is quite different to previous runs. It takes 93L across the Atlantic, keeping it very weak, as a wave. Seeming to track far south of the previous forecasts, which makes sense since it's keeping it a lot weaker, closing it off for a few hours before reaching the Caribbean and then again for a few hours in the Caribbean. It looks to be back and forth with the system going between wave and closed low.

It then slowly moves westward through the Caribbean for a good few days before ending up becoming a closed low again near the Yucatan, and at 270 hours, it's pretty close to where the EURO had it at 240 hours. It then moves into the gulf, in a NW direction and makes landfall as a weak storm in Texas. Texans would love it if that run came true.

We will take the no matter from where it comes. A weak storm sounds ok right about now.

[cycloneye]

12z Tropical Models.

Code: Select all

WHXX01 KWBC 121239
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1239 UTC FRI AUG 12 2011
 
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
 
ATLANTIC OBJECTIVE AIDS FOR
 
DISTURBANCE INVEST (AL932011) 20110812 1200 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        110812  1200   110813  0000   110813  1200   110814  0000
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    11.3N  30.3W   11.2N  31.8W   11.0N  33.8W   10.8N  36.1W
BAMD    11.3N  30.3W   11.4N  32.9W   11.4N  35.5W   11.5N  38.0W
BAMM    11.3N  30.3W   11.3N  32.5W   11.1N  34.8W   11.2N  37.2W
LBAR    11.3N  30.3W   11.7N  33.8W   12.0N  37.3W   12.4N  40.7W
SHIP        25KTS          27KTS          29KTS          33KTS
DSHP        25KTS          27KTS          29KTS          33KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        110814  1200   110815  1200   110816  1200   110817  1200
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    11.0N  38.7W   12.4N  44.1W   14.7N  50.8W   17.0N  58.9W
BAMD    11.6N  40.4W   12.4N  44.5W   14.1N  48.4W   16.7N  52.1W
BAMM    11.4N  39.6W   12.6N  44.3W   14.5N  49.5W   16.9N  55.0W
LBAR    12.8N  44.1W   13.1N  49.9W   12.1N  53.1W     .0N    .0W
SHIP        41KTS          55KTS          63KTS          65KTS
DSHP        41KTS          55KTS          63KTS          65KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  11.3N LONCUR =  30.3W DIRCUR = 275DEG SPDCUR =  19KT
LATM12 =  11.0N LONM12 =  26.5W DIRM12 = 276DEG SPDM12 =  19KT
LATM24 =  10.6N LONM24 =  22.8W
WNDCUR =   25KT RMAXWD =   60NM WNDM12 =   25KT
CENPRS = 1011MB OUTPRS = 1014MB OUTRAD =  180NM SDEPTH =   S
RD34NE =    0NM RD34SE =    0NM RD34SW =    0NM RD34NW =   0NM
 


[cycloneye]

Note= Folks,with four invests it may turn somewhat confusing when posting about any of them.To be sure, look first at the invest number you want to comment about before posting. I almost post the best track of 93L at the 95L one.

12z Best Track for 93L

AL, 93, 2011081212, , BEST, 0, 113N, 303W, 25, 1011, LO

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 011.invest

[TreasureIslandFLGal]

Probably kept weak as the internal structure will be a bit of a mess as the two storms struggle to become one. They will appear as 1 in the models, but internally they will be a bit fo a mess for a while. I think that will be the biggest influence to keeping the storm weaker for longer versus the SAL issue. 92L is prepping the area ahead of 93L anyway to minimize the affect of SAL on 93L. Once they combine, then SAL may be more of an issue, but that will be much farther to the west on its way to the caribbean.

Also, the models are showing the killer ridge across the atlantic basin, but no indication of the TUTT passing over the island that the PR local weather folks are mentioning in their discussion for next week. hmmm

[cycloneye]

[Blown Away]

Models look like the are seeing a HP ridge building forcing 93L back W at the end. Interesting days ahead!

[CrazyC83]

I agree this is a southern track.

[cycloneye]

Westbound is the theme here with the GFS Ensembles.

[Ivanhater]

Model rundown for 93L

06Z GFS...Texas



Uploaded with ImageShack.us

00Z EURO....Yucatan



Uploaded with ImageShack.us

Canadian....Central Gulf

[GCANE]

IMHO, this is a GOM TC.

[Ivanhater]

IMHO, this is a GOM TC.

I agree GCANE...reposting model rundown for new page

Model rundown for 93L

06Z GFS...Texas



Uploaded with ImageShack.us

00Z EURO....Yucatan



Uploaded with ImageShack.us

Canadian....Central Gulf

[TreasureIslandFLGal]

canadian seems to show a trough or something off the east coast at the end of its run, trailing south and southwest almost to the gulf with moisture. such a setup would seem to cause an erosion of the western periphery of the ridge or at least provide a developing weakness that would pull the system north and northeast once it got into the gulf, if it was a strong system and sensitive to higher level steering.
GFS doens't seem to inidcate the same setup.
Euro shows something off the east coast, which may be the same feature moving at a faster pace and already pulling out to the northeast and maybe developing on its own.

[ConvergenceZone]

Yep, I think this will get going. This board should start getting fairly active by the end of this weekend, perhaps we will be in Code Red by then.

OT: On a side note, I had to take a screen shot of the map on storm2k.org. I don't think I've ever seen 4 invests lined up like that before...I guess we can say, the tropical lid has blown off ....

[AHS2011]

Code red soon? And will this storm ride up the Eastern Seaboard?

[cycloneye]

Code red soon? And will this storm ride up the Eastern Seaboard?

Soon means in two or three days,if not longer. It is looking less likely it rides the Eastern Seaboard as I see it right now.