ATL: LEE - Remnants - Discussion

[HurricaneBrain]

well if you follow the CLIPER then the GFS is right on....

personally you see the EURO in the short term 2 runs in a row depicting the same trek really hard to go against it....especially with all the GFS issues we have seen.....

what exactly is the euro showing as far as landfall and strength?

Looks to be a stalling tropical storm below the SETX/LA border

[ConvergenceZone]

Yea, southerngale, I don't think the wind will be an issue with this, just the potential of some good rains HOPEFULLY in Texas

[tolakram]

live loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=15

latest saved image

[underthwx]

Rock...or anyone...what is the cliper?..a type of model?

[Stormcenter]

It still has a ways to go. IMO

live loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=15

latest saved image

http://img690.imageshack.us/img690/6986/69761670.jpg

edited by tolakram, changed image to link

[HurricaneBrain]

Rock...or anyone...what is the cliper?..a type of model?

Climatology and persistence model basically.

[tolakram]

That's the climatology model I tried to remember earlier today. It predicts the most common path of the storm given climatology. It's historical and not really a 'model'.

http://www.srh.noaa.gov/ssd/nwpmodel/ht ... htm#CLIPER

[Tireman4]

I love XTRP myself.

[HurricaneBrain]

IVCN and SHIPS models forecast a weak hurricane.

[RL3AO]

Rock...or anyone...what is the cliper?..a type of model?

Its forecasts is entirely based on climatology. The more accurate CLIPER is the "easier" the storm or season was to forecast. Its the baseline on which the NHCs verification is based off.

[jasons2k]

From Jeff Lindner:

Tropical cyclone formation likely over the NW Gulf of Mexico Friday/Saturday.

Residents along the TX/LA coast should review hurricane preparation plans and be prepared to enact these plans this weekend.

Confidence remains low, but starting to get better model agreement

Models have come into slightly better agreement today on the formation of a tropical system currently located over the SE Gulf of Mexico between SW FL and the Yucatan. Satellite images suggest thunderstorm activity is increasing in this area and NHC has raised the chance of tropical cyclone formation in the next 48 hours to 30%. While there is good agreement on the actual formation of the system, there is poor agreement on where it forms and how it tracks. GFS continues to be the outlier solution showing a low developing off the LA coast and drifting E then NE across FL, this model shows the system getting caught in the trough passing across the northern plains. The GFS looks too deep with the trough and hence the E motion appears unlikely at this time. The ECMWF shows development S of The TX/LA border and then greatly deepens the system all the way down to a strong 968mb hurricane while drifting it W then WSW toward the middle TX coast. The CMC is similar to the ECMWF, but not as strong and more northward toward the upper TX coast. The NAM showing a steady NW motion then a slowing and drift toward the WNW/NW off the SW LA/SE TX coast. Heavy coordination with NHC/HPC and local WFO’s this afternoon are in agreement to lean toward the ECMWF, CMC, NAM, and numerous ensemble members suggesting a low forms over the central or NW Gulf on Friday and then drifts NW this weekend possibly making landfall somewhere on the TX coast, but also just as possible to remain offshore into the middle of next week.

Hard to really hang a forecast without an actual low center yet, where that center develops will be important as to where the system may track.

Intensity:
One thing is for sure, models have really jumped upward on the intensity today with several now showing a full blown hurricane in the NW Gulf this weekend. Up to this point, the models have been keeping the system fairly broad and moderate, but now they really want to deepen it. Looking at the factors involved over the NW Gulf: Sea surface temperatures are very warm in the (86-90 degree range), upper level winds are forecast to be somewhat favorable (likely more toward the favorable side than not), however there is a large mass of dry air over TX and LA that could get entrained into the system hindering development. With all that said, you never want to leave a tropical system sitting over the hot Gulf this time of year for any period of time. Not very confident on how strong 93L may become as the models have just recently started showing this stronger trend. Overall things looks fairly favorable for development and development could be fairly quick.

Will continue to stress the very slow expect storm motion and potential for several days of impacts across the NW Gulf.

Impacts:

For now will temper back the model intensities, but follow closely the above mentioned track reasoning and let that help guide the expected impacts. Please understand that confidence is very low and significant changes will be likely over the next 2 days.

Rainfall:

Will start to see moisture increase on Thursday with scattered showers on the seabreeze, then bring rainbands into the coastal areas starting Friday. Will limit the western extent of the rainfall to the US 59 corridor for now. Should confidence build that the system will in fact move more W over the weekend, significant rain chances will be needed for all areas and totals will need to be raised. Widespread rainfall of 2-4 inches is possible S of US 59 Friday-Sunday and this could really be on the conservative side. HPC progs nail the offshore area with 8-12 inches over the weekend!

Tides:

Position of the surface center leads to a prolonged E fetch aimed at the upper TX coast with winds gradually increasing over the northern Gulf starting late Thursday. Large long period swells will begin to arrive on the coast by midday Friday and build into the weekend. Combined effects of large waves and fetch will result in some degree of coastal water level rise. Hard to pin down right now how much and where, but prolonged nature of this event could push a lot of water toward the coast over the weekend.

Winds:

Gradient will tighten into the weekend, how strong and how long is still up for debate, but could see at least TS force winds over the coastal waters starting late Friday and possibly lasting into much of the weekend. For now will not spread this wind inland much due to the uncertainty in the track, but as with the rainfall forecast above, if a westward track does develop, then winds will need to be increased over much of the area. Winds will likely back to the E following the seabreeze on Thursday afternoon and then back to the ENE and NE by Friday evening.

Residents along the TX and LA coasts should continue to closely monitor information on this developing tropical system.

[southerngale]

Thoughts on 93L by Houston NWS AFD:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
348 PM CDT WED AUG 31 2011

.DISCUSSION...
THE PRIMARY CONCERN IN THE FORECAST FOR THE NEXT 7 DAYS IS THE
MOVEMENT AND POTENTIAL DEVELOPMENT OF THE TROPICAL WAVE CURRENTLY
LOCATED OVER THE SE GULF OF MEXICO. THE MODELS ARE IN GOOD
AGREEMENT ON THE HANDLING OF THIS SYSTEM THROUGH FRIDAY MORNING
THEN BEGIN TO DIVERGE SIGNIFICANTLY AFTER THAT.

THE MAJORITY OF THE MODELS SHOW THE TROPICAL WAVE LOCATED OVER
THE CENTRAL AND NORTH CENTRAL GULF FRIDAY MORNING WITH A SURFACE
LOW DEVELOPING ABOUT 250 NM SOUTHEAST OF GALVESTON. ONE THING
THAT IS CERTAIN IS ANY MOVEMENT BEGINNING FRIDAY IS GOING TO BE
SLOW AS THE STEERING CURRENTS COLLAPSE. AS TO THE MODEL
DIFFERENCES: THE 12Z GFS TAKES THE SYSTEM EASTWARD TOWARD THE
CENTRAL GULF COAST...THE 12Z NAM/CANADIAN BRING THE SYSTEM ONSHORE
THE UPPER TX COAST THIS WEEKEND...WHILE THE 12Z ECMWF STALLS THE
SYSTEM OUT FOR SEVERAL DAYS. ALL OF THE MODELS SHOW FAIRLY
SIGNIFICANT DEVELOPMENT WITH THE LOW. HAVE IGNORED THE GFS
SOLUTION. WHILE THE SYSTEM COULD CERTAINLY MOVE EAST OR NORTHEAST
WITH TIME...IT SEEMS UNLIKELY TO DO THAT THROUGH SATURDAY WITH
SUCH STRONG RIDGING TO THE NORTH. AFTER COORDINATION WITH
SURROUNDING WFOS...HAVE LEANED TOWARD THE ECMWF SOLUTION SINCE IT
HAS A BETTER HANDLE ON THE RIDGING OVER THE SOUTHERN STATES AND
SHOWS THE MOST CONSISTENCY WITH PREVIOUS RUNS.

A SLOW MOVING AND STRENGTHENING TROPICAL CYCLONE OVER THE NW GULF
WOULD RESULT IN SEVERAL IMPACTS OVER THE AREA THROUGH THE HOLIDAY
WEEKEND. A PERSISTENT EAST TO NORTHEAST FETCH WOULD RESULT IN AN
INCREASE IN TIDE LEVELS OVER THE BAYS AND UPPER TX COAST. THIS
COULD BE EXACERBATED BY SUNDAY/MONDAY AS A SURFACE HIGH APPROACHES
FROM THE NORTH TIGHTENING THE PRESSURE GRADIENT ALONG THE COAST.
SWELLS FROM THE SYSTEM COULD RESULT IN DANGEROUS RIP CURRENTS AT
THE BEACHES AND THE POTENTIAL FOR BEACH EROSION.

AS FAR AS THE RAIN POTENTIAL...THE ECMWF SOLUTION WOULD KEEP MOST
OF THE RAIN CONFINED TO AREAS EAST OF US HIGHWAY 59 AS SE TX WOULD
REMAIN ON THE SUBSIDENT SIDE OF THE SYSTEM. TROPICAL SYSTEMS TEND
TO EXPAND DURING THE DAY AND CONTRACT AT NIGHT...SO BANDS OF
SCATTERED CONVECTION WOULD AFFECT THE SE THIRD OF THE AREA MAINLY
DURING THE DAYTIME HOURS. PLACED JUST 20 POPS IN THE FORECAST
THURSDAY SE HALF AS THE ENTIRE AREA WILL REMAIN ON THE SUBSIDENT
SIDE OF THE WAVE. THEN HAVE BLANKETED 30-40 POPS IN FORECAST FOR
SE HALF...20S NORTHWEST FRIDAY THROUGH EARLY NEXT WEEK. IRONICALLY...
THE INCREASE IN WINDS AND LACK OF RAIN OVER THE NW HALF OF THE
AREA COULD ACTUALLY WORSEN THE FIRE DANGER IN THESE AREAS THIS
WEEKEND.

AS FOR TEMPERATURES...EXPECT THURSDAY TO BE SIMILAR TO TODAY WITH
STRONG SUBSIDENCE OVER THE AREA. THE COMBINATION OF THE INCREASE
IN CLOUD COVER...LOWERING 850 MB TEMPS AND SCATTERED CONVECTION
WILL RESULT IN A MODERATION OF TEMPS THROUGH EARLY NEXT WEEK.

PERSONS ACROSS SOUTHEAST TEXAS ARE URGED TO CLOSELY MONITOR NWS
FORECASTS AND NHC FORECAST UPDATES FOR THE NEXT FEW DAYS. IF A
TROPICAL CYCLONE DEVELOPS IN THE NW GULF IT WILL HAVE IMPACTS
ALONG THE TEXAS AND LOUISIANA COASTS THIS WEEKEND. SIGNIFICANT
CHANGES TO THE FORECAST ARE LIKELY UNTIL THE MODELS GET A GOOD
HANDLE ON THIS SYSTEM.

[Jevo]

18z GFS +24 (Large area of low pressure)

[Ivanhater]

well if you follow the CLIPER then the GFS is right on....

personally you see the EURO in the short term 2 runs in a row depicting the same trek really hard to go against it....especially with all the GFS issues we have seen.....

To be fair Rock, the 12z Euro was very close to getting picked up by the trough. It even starts the process by moving east between 72 and 96 hours. The trough has more of an influence on it even more so than the 00z run. 12z Euro ensembles are split between taking it SW or NE.

What I can tell you is this one will be a Gulf system

[Stormcenter]

What amazes me sometimes is how dramatically different one NWS's discussion is from to another's concerning the exact same system. You would think they were talking about totally different systems sometimes. Oh well.

[Lowpressure]

Refreshing to not be discussing recurve or not.

[Ivanhater]

NWS Mobile/Pensacola discussion

LONG TERM (FRIDAY THROUGH NEXT WEDNESDAY)...BIG QUESTION IS WHAT IS
GOING TO HAPPEN WITH THE STRONG EASTERLY WAVE MOVING OUT OF THE
WESTERN CARIBBEAN INTO THE GULF. THE VARIOUS MODELS HAVE MAINTAINED
A RATHER LARGE SPREAD IN THEIR SOLUTIONS WITH THIS SYSTEM...BUT THE
ONE THING THEY ALL GENERALLY AGREE ON IS THAT AN ORGANIZED LOW
CENTER WILL DEVELOP WITH THIS FEATURE. THEY DON`T AGREE ON WHERE
THE LOW WILL GO OR HOW STRONG IT WILL BECOME. THE LATEST 12Z GFS
BRINGS THE LOW UP INTO SOUTHEAST LOUISIANA BY SUNDAY THEN MOVES IT
VERY SLOWLY NORTHEAST ACROSS OUR AREA BY EARLY NEXT WEEK...CLOSE TO
THE PREVIOUS 00Z RUN. THE NEW 12Z ECMWF HAS MAINTAINED ITS MORE
WESTWARD SOLUTION BUT TRENDED FARTHER EAST FROM ITS PREVIOUS RUN...A
BIT STRONGER INITIALLY...THEN RETROGRADES THE LOW BACK TO TEXAS BY
THE MIDDLE OF NEXT WEEK AS IT BUILDS THE SOUTHERN PLAINS RIDGE
(SOMETHING THE GFS DOES NOT DO). RUN TO RUN CONSISTENCY AND FAITH
IN ANY ONE MODEL SOLUTION IS LOW...SO THERE IS A FAIR AMOUNT OF
UNCERTAINTY AS TO EXACTLY WHAT IS GOING TO HAPPEN WITH THE LOW THIS
WEEKEND INTO EARLY NEXT WEEK. GIVEN THE SLOW MOVEMENT FORECAST WITH
THE LOW...THE HEAVY RAIN POTENTIAL ON THE EASTERN AND NORTHERN SIDE
OF THIS SYSTEM IS SOMETHING WE MUST CONSIDER. RIGHT NOW WE ARE NOT
OUTLOOKING FLOOD IMPACTS OVER OUR AREA...BUT THAT COULD CHANGE IF
THE MODELS CONTINUE TO TREND EASTWARD WITH THE LOW. GIVEN THE
LATEST MODEL TRENDS...WE RAISED THE POPS FOR THE WEEKEND INTO EARLY
NEXT WEEK ACROSS THE AREA TO BE MORE INLINE WITH THE CONSENSUS. AS
FOR THE POTENTIAL STRENGTH OF THIS SYSTEM...A GREAT DEAL OF
UNCERTAINTY STILL EXISTS. SOME OF THE MODELS SUGGEST THIS SYSTEM
WOULD MORE THAN LIKELY BE A HYBRID SUBTROPICAL STORM SYSTEM WITH
BAROCLINIC CHARACTERISTICS EARLY NEXT WEEK. AT ANY RATE...WE WILL
NEED TO KEEP A CLOSE WATCH ON THE GULF SYSTEM THROUGH THE WEEKEND.
05/JG

[gatorcane]

18Z GFS still look to got to LA with this..., not Texas

[Jevo]

18z GFS +48

[Dave]

If you don't understand what the hdob data sets mean and would like to learn here is a help guide created by the National Hurricane Center which that explains HDOBS in more detail.

This will open in a new window:

http://www.nhc.noaa.gov/abouthdobs_2007.shtml