ATL: PHILIPPE - Post - Tropical - Discussion

[wxman57]

1800z ASCAT shows a defined low-level circulation near 8.5N 20W, albeit still a tad messy, with light 20 kt winds; it's not entirely there yet.

http://manati.orbit.nesdis.noaa.gov/asc ... MBds32.png

The actual satellite pass times are at the bottom of the image in purple - 11Z not 18Z.

[bg1]

That's some pretty worrisome TCHP in the Caribbean as we go into October - what's odd is that the SSTs are near-normal, but the TCHP is ridiculously high.

Any of the pro mets around know why we keep getting these insanely vigorous, well-organized waves, despite the Atlantic being so hostile? It seems weird that they keep coming off the Sahara so healthy, then fizzle in the open Atlantic.

I'm not a pro met, but I think every year a lot of healthy waves come off Africa (continental instability?). Whether they organize or not depends on the environment they track into.

[wxman57]

That's some pretty worrisome TCHP in the Caribbean as we go into October - what's odd is that the SSTs are near-normal, but the TCHP is ridiculously high.

Any of the pro mets around know why we keep getting these insanely vigorous, well-organized waves, despite the Atlantic being so hostile? It seems weird that they keep coming off the Sahara so healthy, then fizzle in the open Atlantic.

The waves are called African Easterly Waves. They originate in the Ethiopan Highlands, regardless of the conditions in the Atlantic Basin. Each year (since 2005) we've been counting between about 50-60 waves coming off of Africa. So far this year, we're at about 38. In 2005, we were at around 35 as of this date. Just so happened that almost every wave developed in 2005.

[Gustywind]

23/1745 UTC 9.8N 22.6W T1.0/1.0 90L

[EyewallReconstructor]

That's some pretty worrisome TCHP in the Caribbean as we go into October - what's odd is that the SSTs are near-normal, but the TCHP is ridiculously high.

Any of the pro mets around know why we keep getting these insanely vigorous, well-organized waves, despite the Atlantic being so hostile? It seems weird that they keep coming off the Sahara so healthy, then fizzle in the open Atlantic.

The West African Monsoon system is fairly robust year in and year out (mainly due to strong temperature gradient between Sahara and Gulf of Guinea), so the African Easterly Jet is always propagating African Easterly Waves (AEWs) toward the west coast of North Africa. Further east, topography such as the Ethiopian Highlands and the Darfur Mountains help to initiate convection as the flow is forced up and over these features. The jet takes care of delivering these disturbances to the east Atlantic while the waves grow via baroclinic and barotropic energy conversions. There is some debate about how important the wave initiation between Darfur and Ethiopia is compared to the wave maintenance via the jet. However, you can count on a wave exiting the African coast about every 2 days. Waves that exit the African coast exhibit intraseasonal variability (i.e. - the frequency, strength, etc. varies within the summer season), which is why we get periods of strong AEWs and periods of not-so-strong AEWs. Also, these waves do not come from the Sahara. They need the moisture of the Sahel and further south in order to thrive. Hope this helps!

[AdamFirst]

Crank up that ACE...

[EyewallReconstructor]

So this system has an LLC, convection close to the center, and 25kt winds. Can anyone explain to me why this not TD17? I understand it's no threat right now, but NHC has been inconsistent this year about when they initiate advisories ...

[HurricaneWarning92]

18z models (BAM)... slight shift west,

[wxman57]

So this system has an LLC, convection close to the center, and 25kt winds. Can anyone explain to me why this not TD17? I understand it's no threat right now, but NHC has been inconsistent this year about when they initiate advisories ...

That's frequently been the case with storms near Africa. NHC likes to watch them to see if they'll hold together for a day or two before upgrading. Often, such systems appear to be TDs when they move offshore, only to dissipate a day or two later.

[cycloneye]

Up to 50%

SHOWERS AND THUNDERSTORMS HAVE BECOME MORE CONSOLIDATED NEAR THE
CENTER OF A LOW PRESSURE SYSTEM LOCATED ABOUT 325 MILES SOUTH OF
THE CAPE VERDE ISLANDS. ENVIRONMENTAL CONDITIONS ARE CURRENTLY
CONDUCIVE FOR ADDITIONAL DEVELOPMENT...AND THE LOW HAS A MEDIUM
CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH.

[cycloneye]

00z Best Track

AL, 90, 2011092400, , BEST, 0, 100N, 233W, 30, 1008, LO

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

[cycloneye]

00z Tropical Models.

Code: Select all

WHXX01 KWBC 240036
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
0036 UTC SAT SEP 24 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 (AL902011) 20110924 0000 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        110924  0000   110924  1200   110925  0000   110925  1200
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    10.0N  23.3W   10.4N  26.0W   10.4N  28.7W   10.7N  31.2W
BAMD    10.0N  23.3W   10.3N  25.8W   10.7N  28.2W   11.2N  30.2W
BAMM    10.0N  23.3W   10.3N  26.0W   10.6N  28.5W   10.9N  30.8W
LBAR    10.0N  23.3W   10.4N  25.9W   10.8N  28.7W   11.4N  31.3W
SHIP        30KTS          39KTS          49KTS          59KTS
DSHP        30KTS          39KTS          49KTS          59KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        110926  0000   110927  0000   110928  0000   110929  0000
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    11.2N  33.4W   13.3N  36.5W   15.3N  39.3W   17.4N  42.5W
BAMD    12.1N  31.9W   14.8N  33.9W   18.4N  34.4W   21.5N  34.0W
BAMM    11.4N  32.7W   13.3N  35.8W   15.5N  38.3W   18.0N  40.8W
LBAR    12.3N  33.6W   15.6N  36.9W   20.3N  37.7W   25.7N  34.9W
SHIP        68KTS          74KTS          70KTS          63KTS
DSHP        68KTS          74KTS          70KTS          63KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  10.0N LONCUR =  23.3W DIRCUR = 275DEG SPDCUR =  15KT
LATM12 =   9.5N LONM12 =  20.5W DIRM12 = 272DEG SPDM12 =  15KT
LATM24 =   9.5N LONM24 =  17.5W
WNDCUR =   30KT RMAXWD =   45NM WNDM12 =   20KT
CENPRS = 1008MB OUTPRS = 1012MB OUTRAD =  180NM SDEPTH =   M
RD34NE =    0NM RD34SE =    0NM RD34SW =    0NM RD34NW =   0NM


[CrazyC83]

Still wants to create Hurricane Philippe. But I don't see how it could form out there with these conditions unless it stayed REALLY low.

[Gustywind]

23/2345 UTC 10.3N 23.4W T1.0/1.0 90L -- Atlantic

[tobol.7uno]

Wow, what is the record for number of fish storms in a single season?

[tobol.7uno]

And it has the possibility of becoming a hurricane!

[WeatherEmperor]

SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE LOCATED IN
THE EASTERN TROPICAL ATLANTIC OCEAN ABOUT 325 MILES SOUTH OF THE
CAPE VERDE ISLANDS CONTINUES TO BECOME BETTER ORGANIZED.
ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR A TROPICAL DEPRESSION TO
FORM LATER TODAY...AND THIS SYSTEM HAS A HIGH CHANCE...80
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH.

[bexar]

whoa 80% now? we might have Philippe sooner than expected.

hoping for a fishie that will deliver a good chunk of ACE.

[bexar]

latest:



looks like a small system

[bexar]

NOW TD17


THE SMALL AREA OF LOW PRESSURE SEVERAL HUNDRED MILES SOUTH OF THE
CAPE VERDE ISLANDS HAS DEVELOPED ENOUGH ORGANIZED CONVECTION TO BE
CONSIDERED A TROPICAL CYCLONE. MICROWAVE DATA FROM TRMM AND AMSR-E
OVER THE PAST FEW HOURS SHOWED DISTINCT CURVED BANDS...AND EARLY
MORNING VISIBLE IMAGES SUGGEST THAT THE CENTER IS WELL EMBEDDED
WITHIN THE CLOUD CANOPY. AN EARLIER ASCAT PASS INDICATED THAT THE
SYSTEM WAS CLOSED...AND HAD WINDS OF ABOUT 30 KT...SO THAT WILL BE
THE INITIAL INTENSITY. ENVIRONMENTAL CONDITIONS APPEAR TO BE
FAVORABLE FOR STRENGTHENING FOR THE NEXT COUPLE OF DAYS WHILE THE
DEPRESSION IS OVER WARM WATERS WITH LIGHT SHEAR. AFTER THAT TIME...
THE CYCLONE COULD WEAKEN SOMEWHAT DUE TO INCREASING SOUTHWESTERLY
SHEAR FROM A LARGE UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC
OCEAN AND DECREASING SSTS. THE NHC INTENSITY FORECAST IS ON THE
CONSERVATIVE SIDE OF THE GUIDANCE ENVELOPE...BUT FOLLOWS THE TREND
OF THE LGEM MODEL.

BEST ESTIMATE OF THE INITIAL MOTION IS 280/12. A MID-LEVEL RIDGE TO
THE NORTH OF THE DEPRESSION IS FORECAST TO WEAKEN...WHICH SHOULD
CAUSE THE CYCLONE TO GRADUALLY TURN TOWARD THE WEST-NORTHWEST AND
NORTHWEST OVER THE NEXT FEW DAYS. SOME OF THE GUIDANCE TURNS THE
SYSTEM MORE TOWARD THE NORTH BY THE END OF THE FORECAST PERIOD DUE
TO A STRONG MID-LATITUDE TROUGH. FOR NOW...MOST OF THE RELIABLE
GLOBAL MODELS SHOW THE TROUGH STAYING FAR ENOUGH AWAY FROM THE
DEPRESSION TO AVOID RECURVATURE...AND THE NHC FORECAST IS ON THE
LEFT SIDE OF THE GUIDANCE ENVELOPE AND NOT TOO FAR FROM THE ECMWF
MODEL.


FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 10.7N 25.2W 30 KT 35 MPH
12H 24/1800Z 11.1N 27.2W 35 KT 40 MPH
24H 25/0600Z 11.8N 29.3W 40 KT 45 MPH
36H 25/1800Z 12.7N 31.4W 50 KT 60 MPH
48H 26/0600Z 13.7N 33.1W 60 KT 70 MPH
72H 27/0600Z 16.0N 35.5W 60 KT 70 MPH
96H 28/0600Z 18.0N 37.5W 55 KT 65 MPH
120H 29/0600Z 20.0N 39.5W 50 KT 60 MPH

$$
FORECASTER BLAKE