SIO: 98S - Post-Tropical

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SIO: 98S - Post-Tropical

#1 Postby Subtrop » Thu Mar 25, 2021 5:00 am

98S INVEST 210325 0600 7.8S 63.8E SHEM 15 0
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Re: SIO: INVEST 98S

#2 Postby JW-_- » Fri Mar 26, 2021 2:56 am

Image

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98S INVEST 210326 0600 8.7S 64.5E SHEM 25 1003
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Re: SIO: INVEST 98S

#3 Postby JW-_- » Fri Mar 26, 2021 8:04 pm

Image

Invest 98S
Last Modified: 00:00 March 27, 2021 UTC

Invest 98S98S
Invest 98S has a medium chance of developing into a significant tropical cyclone over the next 24 hours.

The area of convection (Invest 98S) previously located near 9.48S 64.55E is now located near 9.9S 64.9E, 878 km (474 nautical miles) west-southwest of Diego Garcia.

Animated infrared imagery and a microwave image show formative banding and persistent convection flaring near a LLCC. Images shows 45-55 km/h winds (25-30 knots) in the northern side of a slightly elongated LLCC.

98S is currently in a favorable environment with good poleward outflow, moderate (15 to 20 knots) wind shear and warm (29 to 30°C) sea surface temperatures.

Forecast models are in overall disagreement of both track and potential tropical development over the next 1 to 2 days. Surface winds are around 45-55 km/h (25-30 knots). Minimum sea-level pressure is near 1002 mb.

Information provided by the Joint Typhoon Warning Center (JTWC).




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https://zoom.earth/storms/98s-2021/#lay ... d,nolabels
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Re: SIO: INVEST 98S

#4 Postby JW-_- » Fri Mar 26, 2021 10:59 pm

Tend too think there was likely mid-level shear impacting this system when this micro was taken. looks a weak ts atm.

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Re: SIO: INVEST 98S

#5 Postby JW-_- » Sat Mar 27, 2021 3:25 am

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Re: SIO: 98S - Tropical Depression

#6 Postby JW-_- » Sun Mar 28, 2021 12:08 am

WTIO30 FMEE 271236
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 2/15/20202021
1.A TROPICAL DEPRESSION 15

2.A POSITION 2021/03/27 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 10.4 S / 66.1 E
(TEN DECIMAL FOUR DEGREES SOUTH AND
SIXTY SIX DECIMAL ONE DEGREES EAST)
MOVEMENT: EAST-SOUTH-EAST 6 KT

3.A DVORAK ANALYSIS: 2.0/2.0/D 1.0/24 H

4.A CENTRAL PRESSURE: 998 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 95 SE: 0 SW: 0 NW: 165

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 700 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/03/28 00 UTC: 10.7 S / 67.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 85 SE: 0 SW: 75 NW: 100
34 KT NE: 45 SE: 0 SW: 0 NW: 95

24H: 2021/03/28 12 UTC: 10.9 S / 68.3 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 75 SE: 0 SW: 165 NW: 150
34 KT NE: 45 SE: 0 SW: 0 NW: 65

36H: 2021/03/29 00 UTC: 10.1 S / 69.4 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 100 SE: 0 SW: 75 NW: 75

48H: 2021/03/29 12 UTC: 9.4 S / 70.4 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 100 SE: 0 SW: 75 NW: 75

60H: 2021/03/30 00 UTC: 8.9 S / 70.6 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 0 SW: 75 NW: 95

72H: 2021/03/30 12 UTC: 8.6 S / 70.6 E, VENT MAX= 025 KT, REMNANT LOW

2.B LONGER-RANGE OUTLOOK:
96H: 2021/03/31 12 UTC: 8.2 S / 69.5 E, VENT MAX= 025 KT, REMNANT LOW


2.C ADDITIONAL INFORMATION:
FT=2.0 CI=2.0+

DUE TO THE DIURNAL CYCLE AND SHEAR, CONVECTIVE ACTIVITY NEAR THE
CENTER HAS BECOME MORE FLUCTUATING AND HAS MOVED AWAY FROM THE
LOW-LEVEL CENTER. THE AMSR2 IMAGERY FROM 0902Z SHOWS HOWEVER THAT THE
DEFINITION OF THE LOW LEVEL CIRCULATION CONTINUES TO IMPROVE. THE
INTENSITY REMAINS ESTIMATED AT 30 KT, ABOVE THE LAST AVAILABLE DVORAK
ESTIMATES OF 2.0 BUT IN THE CONTINUITY OF THE WINDS ESTIMATED BY THE
ASCAT PASSES THIS MORNING.

THE CURRENT AND FORECAST ENVIRONMENTAL CONDITIONS FOR THE NEXT FEW
DAYS ARE MIXED TO UNFAVORABLE: THE LOW LEVEL CONVERGENCE IS CURRENTLY
GOOD ON THE NORTHERN AND SOUTHERN SIDES OF THE SYSTEM. IT WILL BECOME
VERY INDIRECT FROM MONDAY, WHERE THE STRENGTHENING OF THE EQUATORIAL
WESTERLIES IS NOT EXPECTED TO FEED THE CIRCULATION DIRECTLY. THE
SYSTEM IS CURRENTLY EXPERIENCING AN EASTERLY SHEAR AT THE NORTHERN
EDGE OF THE UPPER LEVELS RIDGE. THIS CONSTRAINT SHOULD CONTINUE
DURING THE NEXT FEW DAYS AND EVEN STRENGTHEN FROM MONDAY ONWARDS
DEPENDING ON THE FORECAST TRACK (POSSIBLE NORTHEASTWARD TREND KEEPING
THE SYSTEM OUT OF PHASE WITH THE UPPER LEVELS RIDGE FURTHER SOUTH).
IN THIS SHEAR CONTEXT, THE MID-LEVELS DRY AIR OF AVERAGE COULD ALSO
THWART THE INTENSIFICATION. THE OCEANIC POTENTIAL IS SUFFICIENT OVER
WATERS AT 28-29C AT THE SURFACE WITHOUT HOWEVER A DEEP WARM WATER
RESERVE. CONSIDERING THE IMPROVEMENT OF THE LOW LEVEL CIRCULATION ON
THE LAST AMSR2 PASS, A SLIGHT INTENSIFICATION IS NOW ENVISAGED IN THE
SHORT TERM, BEFORE THE STRENGTHENING OF THE SHEAR. THE LAST GUIDANCE
SHOWS A LITTLE LESS SPREAD AROUND THIS INTENSITY FORECAST.

IN TERMS OF TRACK, THIS ONE IS DRIVEN OVER A GOOD PART OF THE PERIOD
BY THE DYNAMIC OF THE NEAR EQUATORIAL WESTERLY FLOW WHILE THE
SUBTROPICAL RIDGE, TO THE SOUTH, IS NOT VERY MARKED, NOT VERY THICK
AND TENDS TO WEAKEN IN THE SHORT TERM, BEFORE STRENGTHENING DURING
THE PERIOD. A SIGNIFICANT DISPERSION EXISTS AROUND THIS SCENARIO
AMONG THE GUIDANCE AND THE UNCERTAINTY ON THE FUTURE TRACK IS HIGHER
THAN NORMAL.

THIS SYSTEM HAS NO IMPACT ON THE INHABITED LANDS OF THE BASIN DURING
THE NEXT 5 DAYS.=


Image

JTWC
2. REMARKS: THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 9.9S 64.9E IS NOW LOCATED NEAR 10.2S 65.6E, APPROXIMATELY 439
NM WEST-SOUTHWEST OF DIEGO GARCIA. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC)
LOCATED NEAR THE NORTHEAST EDGE OF A MASS OF CONVECTION THAT HAS
EXHIBITED PULSING BURSTS DURING THE PAST 6 HOURS. SATELLITE IMAGERY
INDICATES THAT THE MID-LEVEL CIRCULATION CENTER IS DISPLACED WEST OF
THE LLCC AS A RESULT OF 10-15 KTS OF EASTERLY VERTICAL WIND SHEAR,
AND THE LLCC IS PARTIALLY EXPOSED ON THE NORTHEAST SIDE. HOWEVER, A
270533Z ASCAT-C IMAGE REVEALS A COMPACT CIRCULATION THAT HAS SEEN
ITS RADIUS OF MAXIMUM WIND CONTRACT SUBSTANTIALLY TO AROUND 20 NM
DURING THE PAST 12 HOURS, WITH A BAND OF 30 KT WINDS ENCOMPASSING
THE ENTIRE NORTHWESTERN SEMICIRCLE. HEALTHY UPPER-LEVEL OUTFLOW IS
OBSERVED IN ALL QUADRANTS EXCEPT NORTHEAST. INVEST 98S IS LOCATED IN
A MOSTLY FAVORABLE ENVIRONMENT WITH SEA SURFACE TEMPERATURES AROUND
29C AND LIGHT-MODERATE VERTICAL WIND SHEAR. WATER VAPOR SATELLITE
IMAGERY AND PRECIPITABLE WATER DATA INDICATE A BAND OF DRY AIR
LOCATED ABOUT 200 NM SOUTHWEST OF THE SYSTEM, BUT DOES NOT APPEAR TO
BE WRAPPING INTO THE CIRCULATION AT PRESENT. NUMERICAL MODELS HAVE
MIXED OPINIONS ON DEVELOPMENT, WITH MOST SHOWING ONLY SLIGHT
INTENSIFICATION OF 98S IN THE SHORT TERM. HOWEVER, MOST MODELS
DEPICT 98S WITH A BROADER AND WEAKER CIRCULATION THAN IS BEING
OBSERVED, SUGGESTING THAT DEVELOPMENT CHANCES ARE HIGHER. INVEST 98S
IS EXPECTED TO TRACK EAST-SOUTHEASTWARD AND THEN TURN EASTWARD UNDER
THE INFLUENCE OF A WESTERLY WIND BAND TO ITS NORTH. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR
THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
280900Z.//
NNNN





TPXS11 PGTW 271822

A. TROPICAL DISTURBANCE 98S (W OF DIEGO GARCIA)

B. 27/1745Z

C. 10.72S

D. 66.74E

E. FIVE/GOES-IO

F. T2.0/2.0/D1.0/21HRS STT: S0.0/03HRS

G. IR/EIR

H. REMARKS: 47A/PBO PTLY XPSD LLCC/ANMTN. CNVCTN WRAPS .30 ON
LOG10 SPIRAL YIELDING A DT OF 1.5. MET YIELDS 1.5. PT YIELDS
2.0. DBO PT.

I. ADDITIONAL POSITIONS: NONE


HEINS





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Re: SIO: 98S - Tropical Depression

#7 Postby JW-_- » Sun Mar 28, 2021 4:51 pm

Tropical Depression 15-20202021:

Position at 09UTC: 11.5oS / 68.5oE
Max 10mn winds: 30 kt
Motion: ENE, 6 kt
Estimated minimum pressure: 1000 hPa

Until mid-week, Tropical Depression 15 will encounter unfavourable conditions which will lead to its gradual weakening and eventually make it vanish within the NET.
For more informations, please refer to bulletins WTIO20 and WTIO30 issued at 06UTC and following.

On the extreme East of the basin, the low pressure area which was recently in the Australian AoR is now located by 10.3S / 88.1E as of 09UTC, with 15 to 20 kt max winds and an elongated circulation. In the coming days, moderate wind shear and a dry mid-troposphere combined with a lack of equatorward low-level convergence should seriously limit chances of development.

By the end of the week, poleward surface convergence due to strengthening trade winds should help increase vorticity within the NET. Some models suggest that this could initiate a possible cyclogenesis from Friday or Saturday close to 70E, potentially from one of the pre-existing vorticity areas mentionned above. This potential system could benefit from good upper divergence on the edge of a rebuilding mid-tropospheric ridge. Thus chances of a new cyclogenesis increase at the end of the forecast range.

The risk of development of a Moderate Tropical Storm to the South-West of the Chagos archipelago becomes very low from Friday.





JTWC
98S INVEST 210328 1800 10.5S 69.2E SHEM 25 1006
TPXS11 PGTW 281831

A. TROPICAL DISTURBANCE 98S (W OF DIEGO GARCIA)

B. 28/1745Z

C. 10.40S

D. 69.20E

E. THREE/GOES-IO

F. T1.5/2.0/W0.5/24HRS STT: S0.0/03HRS

G. IR/EIR

H. REMARKS: 17A/PBO XPSD LLCC/ANMTN. THIS SYSTEM IS TOO SHEARED
TO CLASSIFY A DT. MET AND PT YIELDS 1.5. DBO PT.

I. ADDITIONAL POSITIONS:
28/1358Z 10.68S 68.75E SSMS


BT
98S INVEST 210328 1800 10.5S 69.2E SHEM 25 1006
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Re: SIO: 98S - Tropical Depression

#8 Postby JW-_- » Sun Mar 28, 2021 10:36 pm

ABIO10 PGTW 290200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR/HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE INDIAN OCEAN
REISSUED/290200Z-291800ZMAR2021//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/290121ZMAR21//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT CANCELLATION//
RMKS/
1. NORTH INDIAN OCEAN AREA (MALAY PENINSULA WEST TO COAST OF AFRICA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY: NONE.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
2. SOUTH INDIAN OCEAN AREA (135E WEST TO COAST OF AFRICA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 11.7S 68.3E IS NOW LOCATED NEAR 10.3S 69.5E, APPROXIMATELY 247
NM SOUTHWEST OF DIEGO GARCIA. ANIMATED ENHANCED INFRARED (EIR)
SATTELITE IMAGERY AND A 281357Z SSMIS 91GHZ MICROWAVE IMAGE SHOW
DISORGANIZED CONVECTION TO THE SOUTHWEST OF AN EXPOSED LOW-LEVEL
CIRCULATION (LLC). ENVIRONMENTAL ANALYSIS SHOWS INVEST 98S HAS POOR
CONDITIONS FOR DEVELOPMENT, WITH WEAK OUTFLOW ALOFT AND HIGH (20-
30KTS) NORTHEASTERLY VERTICAL WIND SHEAR (VWS), ALTHOUGH OVER WARM
(29-30C) SEA SURFACE TEMPERATURES. NUMERICAL MODELS GENERALLY AGREE
THAT 98S WILL WEAKEN WHILE TRACKING EAST-NORTHEAST OVER THE NEXT 24-
48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1003 MB.
THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS DOWNGRADED TO LOW. SEE REF A (WTXS21
PGTW 290130) FOR FURTHER DETAILS.
(2) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
3. JUSTIFICATION FOR REISSUE: DOWNGRADED AREA IN PARA 2.B.(1) TO
LOW//
NNNN



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Re: SIO: 98S - Post-Tropical

#9 Postby JW-_- » Mon Mar 29, 2021 5:04 pm

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Re: SIO: 98S - Post-Tropical

#10 Postby Iceresistance » Mon Mar 29, 2021 7:53 pm

This system had a High chance & a TCFA from the JTWC, & then, it's a goner 24 hours later . . .
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Re: SIO: 98S - Post-Tropical

#11 Postby JW-_- » Tue Mar 30, 2021 6:26 pm

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