Tropical Depression east of Vietnam [former 0721 PEIPAH]

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#21 Postby CrazyC83 » Sat Nov 03, 2007 8:31 pm

Now an STS.
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#22 Postby CrazyC83 » Sat Nov 03, 2007 9:30 pm

Up to 55 kt now per JTWC.
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#23 Postby Chacor » Sun Nov 04, 2007 1:54 am

370
WTPQ20 RJTD 040600
RSMC TROPICAL CYCLONE ADVISORY
NAME STS 0721 PEIPAH (0721)
ANALYSIS
PSTN 040600UTC 16.8N 123.7E GOOD
MOVE WSW 13KT
PRES 985HPA
MXWD 055KT
GUST 080KT
50KT 40NM
30KT 120NM
FORECAST
24HF 050600UTC 16.6N 120.5E 80NM 70%
MOVE W 09KT
PRES 992HPA
MXWD 045KT
GUST 065KT
48HF 060600UTC 16.3N 118.7E 150NM 70%
MOVE W SLOWLY
PRES 985HPA
MXWD 055KT
GUST 080KT
72HF 070600UTC 15.1N 117.4E 220NM 70%
MOVE SW SLOWLY
PRES 980HPA
MXWD 060KT
GUST 085KT =
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#24 Postby P.K. » Sun Nov 04, 2007 7:54 am

WTPQ20 RJTD 041200
RSMC TROPICAL CYCLONE ADVISORY
NAME STS 0721 PEIPAH (0721)
ANALYSIS
PSTN 041200UTC 16.8N 122.5E GOOD
MOVE W 11KT
PRES 980HPA
MXWD 060KT
GUST 085KT
50KT 45NM
30KT 130NM
FORECAST
24HF 051200UTC 16.4N 119.5E 80NM 70%
MOVE W 07KT
PRES 985HPA
MXWD 055KT
GUST 080KT
48HF 061200UTC 15.8N 118.0E 150NM 70%
MOVE WSW SLOWLY
PRES 985HPA
MXWD 055KT
GUST 080KT
72HF 071200UTC 14.8N 116.7E 220NM 70%
MOVE SW SLOWLY
PRES 980HPA
MXWD 060KT
GUST 085KT =
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#25 Postby Squarethecircle » Sun Nov 04, 2007 9:55 am

Latest JTWC prognostic reasoning report (NOT OFFICIAL!!!!) -

WDPN31 PGTW 041500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W WARNING NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TYPHOON (TY) 21W (PEIPAH) HAS CONTINUED TO INTENSIFY UNDER THE
COMBINED INFLUENCES OF LOW VERTICAL WIND SHEAR, FAVORABLE UPPER LEVEL
OUTFLOW
AND HIGH OCEAN HEAT CONTENT. A BANDING EYE HAS APPEARED IN
RECENT MICROWAVE SATELLITE IMAGERY, INCLUDING A 040938Z WINDSAT PASS.
INTERACTION WITH THE ISLAND OF LUZON IS DISRUPTING THE WESTERN PORTION
OF THE STORM CIRCULATION, HAMPERING DEVELOPMENT OF ASSOCIATED CONVEC-
TION IN THAT REGION OF THE STORM.
B. THE CURRENT STORM INTENSITY IS BASED ON DVORAK SATELLITE INTEN-
SITY T-NUMBERS OF 4.0/4.0 FROM BOTH PGTW AND RJTD. STORM POSITION IS
BASED ON SATELLITE POSITION ESTIMATES FROM PGTW AND RJTD AND A HOST
OF RECENT MICROWAVE SATELLITE IMAGES. RECENT ANIMATED WATER VAPOR
SATELLITE IMAGERY REVEALS THAT A WELL-DEVELOPED MESOSCALE ANTICYCLONE
ALOFT IS PROVIDING GOOD RADIAL OUTFLOW
AND THAT A STRONG POLEWARD
OUTFLOW CHANNEL DISCUSSED IN PREVIOUS PROGNOSTIC REASONING BULLETINS
PERSISTS.
3. FORECAST REASONING.
A. THE FORECAST REASONING HAS NOT CHANGED SIGNIFICANTLY SINCE THE
PREVIOUS ISSUE OF THE PROGNOSTIC REASONING BULLETIN.
B. TY 21W IS EXPECTED TO CONTINUE TRACKING WESTWARD FOR THE NEXT
24 HOURS UNDER THE STEERING INFLUENCE OF A WESTERN PACIFIC SUBTROPI-
CAL RIDGE EXTENSION TO THE NORTH. A MID-LATITUDE TROUGH MOVING EAST-
WARD THROUGH SOUTHEASTERN CHINA IS EXPECTED TO TRANSIT EASTWARD OVER
THE NEXT DAY, ALLOWING RIDGING TO BUILD IN ITS WAKE OVER THE NORTHERN
SOUTH CHINA SEA. THIS SECOND, DEVELOPING RIDGE IS EXPECTED TO INFLU-
ENCE STORM MOTION AFTER TAU 24, INDUCING BOTH A REDUCTION IN FORWARD
TRACK SPEED AND A GRADUAL TURN TOWARD THE SOUTHWEST. AS THE STEERING
INFLUENCE OF THE SECOND STEERING RIDGE BECOMES MORE PRONOUNCED AFTER
TAU 48, TRACK SPEEDS WILL INCREASE. TY 21W WILL WEAKEN OVER CENTRAL
LUZON DURING THE NEXT SEVERAL HOURS
BEFORE REEMERGING INTO THE SOUTH
CHINA SEA AROUND TAU 12. THEREAFTER, THE STORM IS EXPECTED TO REIN-
TENSIFY SLOWLY AS INCREASING VERTICAL WIND SHEAR AND MARGINAL OCEAN
HEAT CONTENT COUNTER THE EFFECT OF FAVORABLE EQUATORWARD OUTFLOW.
C. THE STORM WILL CONTINUE TRACKING GENERALLY SOUTHWESTWARD IN
THE EXTENDED TAUS WITH A SLIGHT INCREASE IN THE WESTWARD COMPONENT
OF MOTION OCCURRING AS THE STEERING RIDGE AXIS ASSUMES A MORE ZONAL
ORIENTATION TO THE NORTH. THE CURRENT FORECAST CALLS FOR LANDFALL
IN SOUTHEASTERN VIETNAM BETWEEN TAU 96 AND TAU 120. AS THE SYSTEM
TRACKS OVER LAND AFTER TAU 96, DISSIPATION WILL BEGIN.
FORECAST TEAM: ALPHA.//
NNNN

JMA most likely will not upgrade to typhoon until after the storm re-emerges into the South China Sea.
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#26 Postby CrazyC83 » Sun Nov 04, 2007 10:41 am

Could this become a major storm in the South China Sea?
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#27 Postby CrazyC83 » Sun Nov 04, 2007 10:44 am

04/1330 UTC 17.0N 122.2E OVERLAND PEIPAH -- West Pacific Ocean

Landfall made as an STS/Cat 1 (1-min).
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#28 Postby Squarethecircle » Sun Nov 04, 2007 12:02 pm

CrazyC83 wrote:Could this become a major storm in the South China Sea?

Most likely not, intensifying should occur slowly, and this season is not known particularly well for exploding storms into major status, although there have been some rapid intensifiers. Also, the heat content generally doesn't support too much intensification, and although there is a significant possibility, it's only a possibility. But Vietnam landfall is somewhat likely, which would make two typhoon landfalls for Vietnam in one season.
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#29 Postby HURAKAN » Sun Nov 04, 2007 1:23 pm

Image
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#30 Postby Squarethecircle » Sun Nov 04, 2007 4:01 pm

Interestingly enough, JTWC still reports a typhoon while most of the convection over land has died off. JMA has yet to upgrade, most likely due to the storm having lower 10 minute winds than 1 minute, which is normal for a storm.
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#31 Postby wxmann_91 » Sun Nov 04, 2007 5:20 pm

Squarethecircle wrote:
CrazyC83 wrote:Could this become a major storm in the South China Sea?

Most likely not, intensifying should occur slowly, and this season is not known particularly well for exploding storms into major status, although there have been some rapid intensifiers. Also, the heat content generally doesn't support too much intensification, and although there is a significant possibility, it's only a possibility. But Vietnam landfall is somewhat likely, which would make two typhoon landfalls for Vietnam in one season.

Actually this season has been known for it's all or nothing capriciousness (that is, many of the storms that have formed have become rather powerful). But the key is that it's November. Yeah, it's the prime time of the season for monster Philippine Sea storms, but the dry NE monsoon kills any storm that wanders too far north in the S China Sea. Also important to note is that Peipah's inner core has been decimated by the high mountains of northern Luzon.
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#32 Postby Squarethecircle » Sun Nov 04, 2007 6:35 pm

Again, though, the winds don't seem to be damaged, although I would surmise that that would be biggest threat to the storm. With that in mind, the JMA and the JTWC don't seem to be too far off the mark, at least for now. The major threat is shear or dry air entering the already convection-deprived storm. Most of the convection seems to be over water, though, so there is still enough to wrap around if it (convection) survives. That, however, seems likely, as there isn't enough shear to rip it apart. Also, the intense anticyclone to the east may help a little as well.
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#33 Postby CrazyC83 » Sun Nov 04, 2007 10:42 pm

Back over water now, down to 55 kt but expected to strenghten to a typhoon now.
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#34 Postby Squarethecircle » Mon Nov 05, 2007 8:34 am

Darn, can't get access to the JTWC, it seems the service is down. Pressure is at 985 hPa, according to the JMA. Hook shaped now, which seems very odd. Clouds are dragging out to the north. However, the visible seems to show good circulation around the center. Convection flaring on the east side, and track forecast remains unchanged. Still forecast to make typhoon.
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Re: Severe Tropical Storm 0721 PEIPAH (21W/PAGASA: Kabayan)

#35 Postby Squarethecircle » Mon Nov 05, 2007 5:37 pm

Typhoon from JTWC again, forecasted until landfall. JMA actually has the same report, though it may have moved to the west a little. Convection is closer to the center now, although there is a weird hole (may be a forming eye, I'm not confident though), and shear is fairly low.
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#36 Postby RattleMan » Tue Nov 06, 2007 1:55 am

WTPQ20 RJTD 060600
RSMC TROPICAL CYCLONE ADVISORY
NAME TY 0721 PEIPAH (0721) UPGRADED FROM STS
ANALYSIS
PSTN 060600UTC 18.6N 118.5E GOOD
MOVE NNW SLOWLY
PRES 970HPA
MXWD 070KT
GUST 100KT
50KT 60NM
30KT 160NM NORTH 110NM SOUTH
FORECAST
24HF 070600UTC 18.3N 116.0E 80NM 70%
MOVE W 06KT
PRES 970HPA
MXWD 070KT
GUST 100KT
48HF 080600UTC 17.1N 113.4E 150NM 70%
MOVE WSW 07KT
PRES 980HPA
MXWD 060KT
GUST 085KT
72HF 090600UTC 14.8N 111.5E 220NM 70%
MOVE SW 07KT
PRES 980HPA
MXWD 060KT
GUST 085KT =

The upgrade to typhoon was at 0300z, but the JMA never removed "TY 0721 PEIPAH (0721) UPGRADED FROM STS" for their 0600z one...
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Re:

#37 Postby Chacor » Tue Nov 06, 2007 3:11 am

RattleMan wrote:The upgrade to typhoon was at 0300z, but the JMA never removed "TY 0721 PEIPAH (0721) UPGRADED FROM STS" for their 0600z one...


That's because 0300z is just a bulletin and 0600z is the actual full advisory...
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Re: Typhoon 0721 PEIPAH (21W/PAGASA: Kabayan)

#38 Postby Squarethecircle » Tue Nov 06, 2007 7:55 am

If I can see correctly, I believe there is an eye developing...
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#39 Postby Chacor » Tue Nov 06, 2007 10:26 am

Here's the latest (15z) JTWC prognostic:

WDPN31 PGTW 061500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. THE SYSTEM HAS CONTINUED TO CONSOLIDATE AND HAS INTENSIFIED
SLIGHTLY OVER THE PAST 12 HOURS. ANIMATED INFRARED SATELLITE IMAGERY,
A 061014Z SSMI IMAGE, AND A 061122Z SSMIS IMAGE CONTINUE TO DEPICT
A TIGHTLY-CURVED BANDING EYE. THE BANDING EYE FEATURE IS CLEARLY
EVIDENT IN THE MICROWAVE IMAGERY. TY 21W HAS BEGUN TRACKING MORE
WESTWARD OVER THE PAST 06 HOURS, BUT THE FORWARD SPEED REMAINS SLOW.
THE STORM REMAINS IN A RELATIVELY WEAK STEERING ENVIRONMENT AND IS
CURRENTLY MOVING WEST-NORTHWESTWARD AT 03 KNOTS.
B. THE CURRENT STORM INTENSITY IS BASED ON THE AVAILABLE DVORAK
SATELLITE INTENSITY ESTIMATES THAT RANGE FROM 65 TO 77 KNOTS. CURRENT
UPPER LEVEL ANALYSIS DEPICTS AN ANTICYCLONE OVER THE CENTER AND
POLEWARD OUTFLOW REMAINS FAVORABLE, ALTHOUGH OUTFLOW HAS SLIGHTLY
DECREASED OVER THE PAST 12 HOURS. UPPER-LEVEL CONVERGENCE SOUTH OF
THE SYSTEM CONTINUES TO HINDER THE EQUATORWARD OUTFLOW.
3. FORECAST REASONING.
A. THE FORECAST PHILOSOPHY REMAINS THE SAME AS THE PREVIOUS
PROGNOSTIC REASONING, BUT THE FORECAST TRACK SPEED HAS BEEN DE-
CREASED IN THE INTERMEDIATE TAUS.
B. TY 21W IS BEGINNING TO TRACK ALONG THE SOUTHEASTERN PERIPHERY
OF A DEVELOPING MID-LEVEL SUBTROPICAL RIDGE TO THE NORTH. THE TROUGH
THAT HAD BEEN CREATING A WEAKNESS IN THE SUBTROPICAL RIDGE HAS
CONTINUED TO TRACK TO THE NORTHEAST, ALLOWING THE SUBTROPICAL RIDGE
TO BUILD EASTWARD. THIS MID-LEVEL RIDGE WILL CONTINUE TO BUILD NORTH
OF THE SYSTEM, WHICH WILL PROVIDE A STRONGER STEERING INFLUENCE
AFTER TAU 12. TY 21W IS FORECAST TO MAINTAIN A SLOW TRACK SPEED FOR
THE NEXT 12 HOURS WHILE UNDER THE INFLUENCE OF THE WEAKER STEERING
ENVIRONMENT. AFTER THIS TIME, THE RIDGE TO THE NORTH WILL BECOME THE
DOMINANT STEERING INFLUENCE AND WILL CAUSE THE STORM TO TRACK
GENERALLY SOUTHWESTWARD AT AN INCREASED RATE OF FORWARD SPEED. POLE-
WARD OUTFLOW WILL CONTINUE TO DECREASE AS THE RIDGE BUILDS. THIS
DECREASE IN POLEWARD OUTFLOW, AS WELL AS WATER WITH MARGINAL OCEAN
HEAT CONTENT, WILL LEAD TO A SLOW WEAKENING OF THE STORM AFTER
TAU 12.
C. TY 21W WILL CONTINUE TRACKING ALONG THE SOUTHERN PERIPHERY OF
THE STEERING RIDGE DURING THE EXTENDED TAUS. THE STORM IS EXPECTED
TO TRACK MORE WESTWARD AND THE SPEED OF FORWARD MOVEMENT IS EXPECTED
TO INCREASE AS THE STEERING RIDGE REORIENTS TO THE NORTH OF THE
STORM. LANDFALL OVER SOUTHEASTERN VIETNAM IS FORECAST NEAR TAU 96
AND DISSIPATION OVER LAND IS EXPECTED TO BE COMPLETE BY TAU 120.
FORECAST TEAM: DELTA//
NNNN
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Re: Typhoon 0721 PEIPAH (21W/PAGASA: Kabayan)

#40 Postby Squarethecircle » Tue Nov 06, 2007 11:15 am

Score! I was right! The feature, however, is somewhat less apparent now. Unfortunately, there are no visible satellite pictures to confirm a well-developed banding eye. The convective pictures seem enough, though, to determine that this has some sort of eye-thing. It's interesting to note that the waters are actually somewhat warmer (than they are now under the storm) closer to Vietnam, but the ridge-based reasoning seems adequate.
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