ATL: HELENE - Post-Tropical

[Kingarabian]

Some GFS consistency to say the least... Need to wait for the Euro to come on board.

[somethingfunny]

A variant on Bones:

[Stormcenter]

Latest from the NWS out N.O.,LA. as of 8/15/12

AS WE HEAD INTO NEXT WEEK ABV NORMAL RAIN CHANCES WILL CONTINUE AS
THE FRONT WILL BE RIGHT OVER THE REGION OR JUST TO THE SOUTH IN THE
GULF. EVEN THOUGH WE ARE LEANING TWRDS THE ECMWF WE WILL NEED TO
KEEP ONE EYE ON THAT WAVE. IF A TROPICAL SYSTEM DEVELOPS OVER THE
WRN BAY OF CAMPECHE EVEN THOUGH WE WILL NOT BE DIRECTLY IMPACTED BY
IT...IT WILL LEAD TO SIGNIFICANT MARINE IMPACTS AND COULD PROVIDE AN
INFLUX OF MOISTURE INTO THE REGION WITH LOCALLY HEAVY RAIN FOR THE
FIRST HALF OF NEXT WEEK. IF THE FRONT CAN MOVE TO THE GULF THEN LOOK
FOR SLIGHTLY COOLER CONDITIONS. /CAB/

[Houstonia]

Jeff Lindner (Harris County Flood Control District):

Changes from hot and dry to wet and cooler on the way.

High pressure over the SW US will gradually shift further west and combine with building high pressure over the NW US to carve out a deep downstream eastern US trough. This pattern will unlock so fairly cool air by August standards and send it southward over the northern plains and then SE toward the Ohio Valley and east coast this weekend. Across TX the cold front will arrive into the state Thursday and slowly sag southward over the weekend. Main brunt of the cold air advection will be to our NE, but the front or its associated outflow boundaries from thunderstorms will likely sag into central TX and our northern counties by late Saturday.

The combination of the frontal boundary, increasing moisture from both the Pacific and the Gulf, and short wave riding down the backside of the trough and across the frontal boundary will support much better rain chances starting Friday and continuing into the weekend. Should see some decent organization of the storms both along the frontal boundary and the inland moving seabreeze front, so most locations should see some rainfall. Pattern does favor heavy rainfall and will need to keep an eye on this aspect as the boundary will linger into early next week providing several days of wet weather.

Big wild card is whether or not some sort of tropical system will try and spin up over the western Gulf of Mexico late this weekend into early next week. GFS has been consistent on moving the remains of TD #7 across central America and the Yucatan then into the Bay of Campeche where it slows the wave and closes it off into a weak surface low. The EURO and CMC continue the wave axis westward and into mainland Mexico with no development. The GFS has performed very well this year in the tropics with both Debby and Ernesto and TD #7, so it could be on the right track. With that said, shear looks to be increasing over the western Gulf in response to the tail end of the trough over the eastern US and I think the GFS is too strong with any surface low that may develop. That pattern fits a classic western Gulf of Mexico surface trough that may close off into a weak low, but is highly sheared and all the weather is N and NE of its surface center. If the EURO is correct the frontal boundary would stall across the northern Gulf and this would also help increase the surface gradient with lowering pressures to the south.

For now will keep the frontal boundary stalled near/over our area inland of the coast and any tropical development weak. Combination of these features will keep rain chances high into early next week and if low pressure does form in the western Gulf, rain chances would likely increase into the middle of next week.

[cycloneye]

NHC_ATCF
invest_DEACTIVATE_al072012.ren
FSTDA
R
U
040
010
0000
201208150600
NONE
NOTIFY=ATRP
END

[wxwatcher1999]

NHC_ATCF
invest_DEACTIVATE_al072012.ren
FSTDA
R
U
040
010
0000
201208150600
NONE
NOTIFY=ATRP
END

Can you explain what this means please?

[cycloneye]

NHC_ATCF
invest_DEACTIVATE_al072012.ren
FSTDA
R
U
040
010
0000
201208150600
NONE
NOTIFY=ATRP
END

Can you explain what this means please?

Is no longer being tracked by ATCF that does the best track positions and intensity.

ftp://ftp.nhc.noaa.gov/atcf/tcweb/

[cycloneye]

Well,they reactivate it again.

18z Best Track.

AL, 07, 2012081518, , BEST, 0, 161N, 898W, 25, 1011, LO

ftp://ftp.nhc.noaa.gov/atcf/tcweb/inves ... 012.invest

[Houstonia]

Well,they reactivate it again.

18z Best Track.

Er... um... isn't that a little odd?

[Portastorm]

Yes it is ... but clearly many professional/government mets have interest or concerns about what may develop in the Western Gulf this weekend. NWSFOs in Texas are all mentioning it in their forecast discussions. HPC has mentioned it in the national discussion. For days now the GFS has been honking on this scenario. The Euro has not. One will clearly be right and other ... not so right.

Bones ... back off!

[Rgv20]

HPC afternoon discussion.

FINAL...

WITH THE EXCEPTION OF ADDING A SPOT LOW APPROACHING
BROWNSVILLE...TEXAS...DAYS 6 AND 7...AS PER COORDINATION WITH THE
NATIONAL HURRICANE CENTER...MADE ONLY COSMETIC CHANGES TO THE
UPDATE PACKAGE FOR THE FINAL ISSUANCE. THE LOW ALONG THE GULF
COAST OF MEXICO IS INTENDED TO REFLECT THE POSSIBILITY OF TROPICAL
DEVELOPMENT...BUT IN THE MOST PRACTICAL SENSE...ADDS SUPPORT FOR
INCREASING THE PROBABILITY OF PRECIPITATION OVER THE REGION IN THE
MOIST FLOW NEAR THE SOUTHERN EDGE OF THE WESTERLIES.

[NDG]

A little old, but I wonder what model's forecasted track did they used for the SHIPS intensity model (which turns it into a hurricane) since all the BAM models keep it tracking westward towards MX.
My guess, GFS.

Code: Select all

TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1833 UTC WED AUG 15 2012
 
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 SEVEN (AL072012) 20120815 1800 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        120815  1800   120816  0600   120816  1800   120817  0600
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    16.1N  89.8W   16.8N  92.1W   17.6N  94.2W   18.3N  96.0W
BAMD    16.1N  89.8W   17.0N  92.1W   17.8N  94.1W   18.6N  95.9W
BAMM    16.1N  89.8W   16.8N  92.1W   17.4N  94.3W   17.9N  96.2W
LBAR    16.1N  89.8W   17.1N  92.2W   18.2N  94.8W   19.4N  97.3W
SHIP        25KTS          26KTS          30KTS          35KTS
DSHP        25KTS          26KTS          27KTS          31KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        120817  1800   120818  1800   120819  1800   120820  1800
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    18.9N  97.6W   19.9N 100.2W   20.8N 101.1W   21.4N 101.3W
BAMD    19.0N  97.7W   19.5N 100.6W   19.1N 102.1W   18.5N 103.4W
BAMM    18.2N  98.0W   18.4N 100.9W   18.2N 102.3W   18.0N 103.0W
LBAR    20.8N  99.7W   23.6N 102.8W   26.2N 103.5W   28.3N 101.5W
SHIP        44KTS          56KTS          65KTS          71KTS
DSHP        40KTS          52KTS          61KTS          67KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  16.1N LONCUR =  89.8W DIRCUR = 290DEG SPDCUR =  13KT
LATM12 =  15.2N LONM12 =  87.0W DIRM12 = 288DEG SPDM12 =  17KT
LATM24 =  14.3N LONM24 =  83.6W
WNDCUR =   25KT RMAXWD =   70NM WNDM12 =   25KT
CENPRS = 1011MB OUTPRS = 1013MB OUTRAD =  150NM SDEPTH =   S
RD34NE =    0NM RD34SE =    0NM RD34SW =    0NM RD34NW =   0NM
 
$$
NNNN



[Hurricane Alexis]

The 00z Euro is going for development in the SW Gulf and a landfall in SW Louisiana.



Uploaded with ImageShack.us

[Chickenzilla]

Sorry for the offtopic, but what is that strong tropical cyclone ENE of Puerto Rico?

[tolakram]

That is being discussed in the global models thread. viewtopic.php?f=31&t=104813&hilit=&p=2250626#p2250626

It might also be the wave currently over Africa

viewtopic.php?f=31&t=113357

[Hurricaneman]

Sorry for the offtopic, but what is that strong tropical cyclone ENE of Puerto Rico?

Its the wave about to come off of Africa, theres a topic on it in talkin tropics

[cycloneye]

8 AM TWO:

A TROPICAL WAVE...THE REMNANTS OF TROPICAL DEPRESSION SEVEN...IS
LOCATED OVER SOUTHEASTERN MEXICO AND THE WESTERN YUCATAN PENINSULA.
THIS DISTURBANCE IS PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS
OVER THE BAY OF CAMPECHE...THE YUCATAN PENINSULA...SOUTHEASTERN
MEXICO...AND GUATEMALA. ALTHOUGH THERE IS CURRENTLY ONLY A SLIGHT
CHANCE OF REGENERATION WHEN THE WAVE EMERGES OVER THE BAY OF
CAMPECHE...LOCALLY HEAVY RAIN IS POSSIBLE ACROSS PORTIONS OF
CENTRAL AMERICA AND SOUTHERN MEXICO THROUGH LATE TODAY. THIS
SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT
ABOUT 15 MPH.

[Houstonia]

Jeff Lindner:

Early Next Week:

Decent agreement in the model guidance through Sunday begins to diverge early next week. Tropical wave (old TD 7 remains) currently over the southern Yucatan and central America will lift WNW into the Bay of Campeche this weekend. GFS has backed away from its tropical cyclone development and has fallen in line closer to the EURO and CMC and keeping the system a tropical wave. Two main questions focus on early next week: 1) how much moisture is pulled northward from this tropical wave along the western Gulf coast and 2) how far south does the frontal boundary move. EURO and CMC try and push the front offshore early next week allowing a drier air mass the move into the region, while the GFS keeps the boundary over the area with deep tropical moisture in place. Convective outflows could push the front southward into the Gulf, but then again it is mid August. Will take a blend of the GFS and other guidance and show the front making slow progress toward the coast early next week. With several days of a stalling boundary and deep tropical moisture in place, many rounds of heavy rainfall appear likely. As the ground saturates over time with daily rains, will start to see increased run-off and the threat for flooding may increase especially if the boundary lingers into the middle of next week.

[tailgater]

This could be a feature to watch, I don't think it's actually ex td -7 because it came on shore last nite just north of Belize
Just something to watch it has a little rotation to it.

[img]

Uploaded with ImageShack.us[/img]

[lrak]

On the latest visible I can see a small spin just off the west coast of the Yucatan. Very small spin

http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=10