WPAC: Sonamu - Severe Tropical Storm

[P.K.]

using 1 min for winds, sonamu is the third tropical storm in january since 2000...there are countless of other storms forming in this month but for earliest, i have yet to check...

Ah yes but you already know one minute winds are irrelevant in this basin. Sure Jan storms aren't exactly uncommon which is why when I mentioned the 1979 fact I listed the last couple of late Dec storms which have carried across into Jan.

[supercane4867]

JMA has upgraded Sonamu to a STS

STS 1301 (SONAMU)
Issued at 00:45 UTC, 5 January 2013
<Analyses at 05/00 UTC>
Scale -
Intensity -
Center position N8°25'(8.4°)
E112°00'(112.0°)
Direction and speed of movement W 20km/h(10kt)
Central pressure 990hPa
Maximum wind speed near the center 25m/s(50kt)
Maximum wind gust speed 35m/s(70kt)
Area of 30kt winds or more NW220km(120NM)
SE170km(90NM)

[euro6208]

Typing this from my iPhone and it's really hard lol

Sonamu with 40 knots winds but it is running into an increasingly unfavorable environment.

[euro6208]

TPPN10 PGTW 050314

A. TROPICAL STORM 01W (SONAMU)

B. 05/0232Z

C. 7.8N

D. 111.7E

E. THREE/MTSAT

F. T3.0/3.0/D0.5/24HRS STT: S0.0/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 19A/PBO XPSD LLCC/ANMTN. CONVECTION WRAPS .60 ON
LOG10 SPIRAL YIELDING DT OF 3.0. MET AND PT AGREE DBO DT.

I. ADDITIONAL POSITIONS:
04/2238Z 8.2N 112.3E SSMS
04/2317Z 8.2N 111.9E TRMM


CASPER

[Meow]

TPPN10 PGTW 050314

A. TROPICAL STORM 01W (SONAMU)

B. 05/0232Z

C. 7.8N

D. 111.7E

E. THREE/MTSAT

F. T3.0/3.0/D0.5/24HRS STT: S0.0/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 19A/PBO XPSD LLCC/ANMTN. CONVECTION WRAPS .60 ON
LOG10 SPIRAL YIELDING DT OF 3.0. MET AND PT AGREE DBO DT.

I. ADDITIONAL POSITIONS:
04/2238Z 8.2N 112.3E SSMS
04/2317Z 8.2N 111.9E TRMM


CASPER

I think the JMA also anylysed CI3.0 so they upgraded Sonamu to a STS.

[dexterlabio]

After all, this one was named and those other January tropical storms weren't... I think that makes this one different. It's actually tiring to talk about JMA vs. JTWC or 1-min vs. 10-min thing here.

And though January TC's do happen, it is still unusual to see storms spawn at this time of the year when the cold surge from the north blows and high pressure dominates the Western Pacific.

[euro6208]

some slight strengthening before weakening is forecast...look at that loop...


WTPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL STORM 01W (SONAMU) WARNING NR 009
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
051200Z --- NEAR 7.6N 110.7E
MOVEMENT PAST SIX HOURS - 255 DEGREES AT 07 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 055 NM NORTHEAST QUADRANT
000 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
REPEAT POSIT: 7.6N 110.7E
---
FORECASTS:
12 HRS, VALID AT:
060000Z --- 7.3N 109.2E
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT
025 NM SOUTHEAST QUADRANT
070 NM SOUTHWEST QUADRANT
075 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 260 DEG/ 07 KTS
---
24 HRS, VALID AT:
061200Z --- 7.1N 107.9E
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 260 DEG/ 07 KTS
---
36 HRS, VALID AT:
070000Z --- 6.9N 106.6E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT
015 NM SOUTHEAST QUADRANT
035 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 255 DEG/ 06 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
071200Z --- 6.6N 105.4E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 72 HR POSIT: 240 DEG/ 03 KTS
---
72 HRS, VALID AT:
081200Z --- 6.0N 104.4E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 96 HR POSIT: 180 DEG/ 03 KTS
---
LONG RANGE OUTLOOK:
---
96 HRS, VALID AT:
091200Z --- 5.0N 104.4E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 120 HR POSIT: 150 DEG/ 03 KTS
---
120 HRS, VALID AT:
101200Z --- 3.9N 105.1E
MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
---
REMARKS:
051500Z POSITION NEAR 7.5N 110.3E.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 300 NM SOUTHEAST
OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-SOUTHWESTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
051200Z IS 17 FEET. NEXT WARNINGS AT 052100Z, 060300Z, 060900Z AND
061500Z.
//
NNNN

[euro6208]

WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SONAMU) WARNING NR
09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 300 NM
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT DEEP CONVECTION
IS BEGINNING TO REBUILD CLOSER TO THE LOW LEVEL CIRCULATION CENTER
(LLCC), INDICATING A SLIGHT INTENSIFICATION. THE INITIAL POSITION IS
BASED ON THE PARTIALLY EXPOSED LLCC SEEN IN THE EIR WITH GOOD
CONFIDENCE. THE INTENSITY IS ASSESSED AT 45 KNOTS BASED ON DVORAK
INTENSITY ESTIMATES FROM MULTIPLE AGENCIES. UPPER-LEVEL ANALYSIS
INDICATES STRONG (20-30 KNOTS) VERTICAL WIND SHEAR (VWS) IS STILL IN
PLACE, WITH GOOD POLEWARD OUTFLOW SOMEWHAT OFF-SETTING THE EFFECTS
OF THE VWS. GUIDANCE INDICATES THE VWS WILL EASE OVER THE NEXT 24
HOURS, AND THE OBSERVED INCREASE OF CONVECTION NEAR THE LLCC MAY
INDICATE THAT CONDITIONS HAVE BEGUN TO IMPROVE. TS 01W IS
TRACKING GENERALLY WEST-SOUTHWESTWARD UNDER THE INFLUENCE OF A LOW-
TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH. SEA SURFACE
TEMPERATURES (SSTS) ARE CURRENTLY FAVORABLE FOR FURTHER DEVELOPMENT
(28 TO 29 DEGREES CELSIUS).
3. FORECAST REASONING.
A. THE FORECAST TRACK AND INTENSITY PHILOSOPHIES HAVE CHANGED TO
REFLECT AN EQUATORWARD TURN AFTER TAU 72. AS A RESULT OF THIS TURN,
THE SYSTEM IS NO LONGER EXPECTED TO MAKE LANDFALL OVER THE MALAY
PENINSULA, AND WILL MAINTAIN WARNING INTENSITY THROUGH TAU 120.
B. TS 01W WILL REMAIN ON A WEST-SOUTHWESTWARD TRACK THROUGH TAU
72 UNDER THE INFLUENCE OF THE STR STEERING INFLUENCE. GUIDANCE
IS CALLING FOR A SLIGHT RELAXATION OF THE VWS OVER THE NEXT 24
HOURS, WHICH WILL ALLOW FOR A BRIEF PERIOD OF SLIGHT
INTENSIFICATION. AFTER TAU 48, VWS WILL PICK BACK UP SLIGHTLY,
RESULTING IN A VERY GRADUAL DECREASE IN INTENSITY. THE TRACK THROUGH
TAU 72 IS FAIRLY CLOSE TO PREVIOUS JTWC FORECASTS, HOWEVER SPEEDS
HAVE BEEN SLOWED TO TAKE INTO ACCOUNT THE EQUATORWARD TURN BEGINNING
AT TAU 72 AS THE WESTERN LOBE OF STR OVER THE ANDAMAN SEA BEGINS TO
BUILD DOWN EQUATORWARD, HAMPERING FURTHER WESTWARD MOVEMENT.
C. IN THE EXTENDED TAUS, TS 01W IS FORECAST TO TURN EQUATORWARD
AND THEN CURVE BACK TO THE EAST AS THE SYSTEM ENTERS A WEAK
STEERING FLOW ENVIRONMENT ASSOCIATED WITH THE COL AREA BETWEEN TWO
LOBES OF THE STR. MODEL GUIDANCE HAS INCREASINGLY CONVERGED ON THIS
RATHER UNUSUAL EQUATORWARD TURN, ALBEIT TO WIDELY VARYING DEGREES.
THE NOGAPS SOLUTION IS STILL THE MOST WESTWARD OF THE GUIDANCE, BUT
EVEN THIS MODEL IS TRENDING TOWARDS THE TURN. ADDITIONALLY, SINGLE
MODEL ENSEMBLE PRODUCTS FROM ECMWF AND GFS STRONGLY INDICATE THE
TURN. GIVEN THE LARGE SPREAD IN THE AVAILABLE GUIDANCE, THERE IS
LOW CONFIDENCE IN THE JTWC FORECAST.//
NNNN

[euro6208]

very deep convection covering a large area with heavy rains spreading over vietnam...

[Meow]

The latest JTWC forecasting is very interesting. It estimates Sonamu will make U-turn, yet the JMA estimates that the STS will become a TD within three days.

[euro6208]

1. TROPICAL STORM 01W (SONAMU) WARNING NR 015
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
070000Z --- NEAR 6.7N 107.9E
MOVEMENT PAST SIX HOURS - 250 DEGREES AT 06 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
085 NM NORTHWEST QUADRANT
REPEAT POSIT: 6.7N 107.9E


REMARKS:
070300Z POSITION NEAR 6.6N 107.6E.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 250 NM SOUTH-
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 070000Z IS 15 FEET. NEXT WARNINGS AT
070900Z, 071500Z, 072100Z AND 080300Z.//
NNNN


WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SONAMU) WARNING NR
15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 250 NM SOUTH-
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS AN INCREASE IN DEEP
CONVECTION BUILDING ALONG THE SOUTHERN HALF OF THE BROADENING LOW
LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST SIX HOURS. THE OVERALL
STRUCTURE OF THE LLCC STILL APPEARS TO OPENING ALONG THE EASTERN
HALF. THE TOTAL PRECIPITABLE WATER LOOP CONTINUES TO INDICATE A
POCKET OF DRY AIR IS WRAPPING ALONG THE EASTERN HALF OF THE LLCC
TOWARDS THE SYSTEM CENTER. UPPER LEVEL ANALYSIS HAS BEEN CONSISTENT
OVER THE PAST 12 HOURS WITH THE LLCC REMAINING SOUTH OF A
SUBTROPICAL RIDGE (STR) AXIS IN A MODERATE TO HIGH VERTICAL WIND
SHEAR (VWS) ENVIRONMENT (20 TO 30 KNOTS). THE CURRENT INTENSITY HAS
BEEN MAINTAINED BASED ON THE WEAKENING OF THE LLCC IN MSI OFFSETTING
THE IMPROVED CONVECTION. SEA SURFACE TEMPERATURES HAVE BEEN STEADY
AT 27 TO 28 DEGREES CELSIUS, SUPPORTING THE SLOW WEAKENING TREND
OVER THE PAST 24 HOURS.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 01W WILL TRACK SLOWLY ALONG THE SOUTHERN PERIPHERY OF THE
LOW- TO MID-LEVEL STR OVER THE ANDAMAN SEA IN A GENERALLY WEST-
SOUTHWESTWARD DIRECTION THROUGH TAU 48, AFTER WHICH THE WEAKENED
LLCC IS FORECAST TO DEFLECT EQUATORWARD. VWS IS EXPECTED TO REMAIN
HIGH THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE HIGH VWS
AND DRY AIR ENTRAINMENT WILL MAKE THE ENVIRONMENT INCREASINGLY
UNFAVORABLE. MESOSCALE MODEL GUIDANCE INDICATES TS 01W WILL CONTINUE
A GRADUAL WEAKENING TREND AND DISSIPATE BELOW WARNING INTENSITY BY
TAU 72 AS A RESULT OF THESE NEGATIVE FACTORS. CONDITIONS WILL BE
CLOSELY MONITORED FOR ANY SIGNS OF IMPROVEMENT IN THE ENVIRONMENTAL
CONDITIONS OR THE ORGANIZATION OF THE LLCC, AND THE FORECAST LENGTH
MAY BE ADJUSTED IF WARRANTED. THE AVAILABLE DYNAMIC MODEL GUIDANCE
IS IN FAIR AGREEMENT WITH A WEST-SOUTHWESTWARD TRACK. THE OFFICIAL
FORECAST IS TO THE WEST OF THE CONSENSUS OF AVAILABLE MODEL GUIDANCE
TO ACCOUNT FOR THOSE MEMBERS SHOWING A MORE AGGRESSIVE TURN TO THE
SOUTHEAST (GFS AND GFDN). DUE TO THE LARGE SPREAD IN THE GUIDANCE,
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.//
NNNN

[Meow]

Time to say good bye.

TD
Issued at 00:45 UTC, 8 January 2013

<Analyses at 08/00 UTC>
Scale -
Intensity -
TD
Center position N6°00'(6.0°)
E108°00'(108.0°)
Direction and speed of movement Almost stationary
Central pressure 1006hPa

[Meow]

The JTWC upgraded Sonamu to a tropical storm again and estimated it will make landfall over Sarawak.



WTPN31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL STORM 01W (SONAMU) WARNING NR 019
UPGRADED FROM TROPICAL DEPRESSION 01W
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
080000Z --- NEAR 5.5N 108.5E
MOVEMENT PAST SIX HOURS - 165 DEGREES AT 04 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 5.5N 108.5E
---
FORECASTS:
12 HRS, VALID AT:
081200Z --- 4.8N 108.6E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 24 HR POSIT: 170 DEG/ 03 KTS
---
24 HRS, VALID AT:
090000Z --- 4.3N 108.7E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 36 HR POSIT: 155 DEG/ 04 KTS
---
36 HRS, VALID AT:
091200Z --- 3.6N 109.0E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 48 HR POSIT: 120 DEG/ 05 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
100000Z --- 3.1N 109.8E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
VECTOR TO 72 HR POSIT: 095 DEG/ 06 KTS
---
72 HRS, VALID AT:
110000Z --- 2.8N 112.3E
MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
---
REMARKS:
080300Z POSITION NEAR 5.3N 108.5E.
TROPICAL STORM (TS) 01W (SONAMU), LOCATED APPROXIMATELY 330 NM
SOUTH-SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED SOUTHWARD
AT 04 KNOT OVER THE PAST SIX HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 080000Z IS 15 FEET. NEXT WARNINGS AT 080900Z, 081500Z, 082100Z
AND 090300Z.//
NNNN

[euro6208]

storms develop away and move away from the equator but sonamu is actually going towards it! very interesting...there remains alot of unknown regarding wpac storms...

[euro6208]

Former Tropical Cyclone Sonamu

[Meow]

It is still a tropical depression.



WWJP25 RJTD 100000
WARNING AND SUMMARY 100000.
...
SUMMARY.
TROPICAL DEPRESSION 1008 HPA AT 03N 111E ALMOST STATIONARY.
...

JAPAN METEOROLOGICAL AGENCY.=

[Meow]

The JMA reported that Sonamu has dissipated at 06Z.