SIO: IDAI - Post-Tropical

[TorSkk]

98S INVEST 190302 0600 16.7S 42.2E SHEM 15 1009

[TorSkk]

BULLETIN FOR CYCLONIC ACTIVITY AND SIGNIFICANT TROPICAL WEATHER IN
THE SOUTHWEST INDIAN OCEAN

In the Mozambique Channel :

The residual elongated circulation in the mid-troposphere is moving WSW in association with
severe convection locally. Last ASCAT-C show no sign of a surface circulation. In the following
days, some guidance suggest a temporary deepening after the landfall on the Mozambican coast.
For now this scenario is not the chosen one.

Over the next 5 days, there is no risk of development of a moderate tropical storm over the
Northern half of the Mozambique Channel.

[TorSkk]

In the Mozambique Channel :

A strong deep convection is present on the center of the channel.
ASCAT-A show a weak circulation near the coast, but presure remains high on this area..
In the following days, some guidance suggest a temporary deepening after the landfall on the
Mozambican coast. For now this scenario is not the chosen one.

Over the next 5 days, the risk of development of an other moderate tropical storm over the
Northern half of the Mozambique Channel become weak until Tuesday.

[TorSkk]

In the Mozambique Channel :

An ill-defined clockwise circulation is centered near 18.1S/33.3E associated to a strong deep
convective activity. The LLCC is forecasted to move in land over Mozambique next night without
significantly deepening but with a strong thundery activity.

Over the next 5 days, there is no risk of development of another moderate tropical storm over
the basin.

[TorSkk]

RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 1/11/20182019
1.A TROPICAL DEPRESSION 11
2.A POSITION 2019/03/04 AT 0600 UTC:
WITHIN 20 NM RADIUS OF POINT 18.1 S / 37.6 E
(EIGHTEEN DECIMAL ONE DEGREES SOUTH AND
THIRTY SEVEN DECIMAL SIX DEGREES EAST)
MOVEMENT: WEST 4 KT
3.A DVORAK ANALYSIS: 2.5/2.5/S 0.0/0 H
4.A CENTRAL PRESSURE: 1003 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): 28 KM
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 80 SE: 70 SW: 90 NW: 80
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 300 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM
1.B FORECASTS:
12H: 2019/03/04 18 UTC: 17.8 S / 36.9 E, VENT MAX= 030 KT, OVERLAND DEPRESSION
24H: 2019/03/05 06 UTC: 17.1 S / 36.0 E, VENT MAX= 025 KT, OVERLAND DEPRESSION
2.B LONGER-RANGE OUTLOOK:
NIL
2.C ADDITIONAL INFORMATION:
T=CI=2.5
RESULTING FROM AN ILL-DEFINED CLOCKWISE CIRCULATION UNTIL 24 HOURS AGO
BUT FOLLOWED IN THE AWIO20 WARNING BULLETIN, THE CLOUD PATTERN OF
TROPICAL DEPRESSION 11 HAS EVOLVED WELL OVER THE LAST 24 HOURS.
RECENTLY, CONVECTION NEAR THE CENTER HAS INTENSIFIED. THE 0621UTC ASCAT
SWATH ALLOWS TO ESTIMATE WINDS OF 30KT, LOCALLY REACHING 35KT WHILE
THE 0330UTC MICROWAVE DATA STILL DEFINE A TIMID CLOCKWISE CIRCULATION.
TROPICAL DEPRESSION 11 IS EXPECTED TO LAND QUICKLY ON THE MOZAMBICAN
COAST DURING THE DAY ON MONDAY. THE RELATIVELY LATE IMPLEMENTATION OF
THE CLOCKWISE CIRCULATION WILL NOT ALLOW THE SYSTEM TO INTENSIFY
SIGNIFICANTLY, DESPITE THE SIGNIFICANT ENERGY POTENTIAL OF THE OCEAN.
WINDS IN THE ORDER OF 35KT MAY LOCALLY AFFECT THE SOUTHEAST QUADRANT
BEFORE THE SYSTEM LANDS. THE CONVECTION ASSOCIATED WITH THIS SYSTEM
WILL REMAIN QUITE STRONG, BRINGING REMARKABLE PRECIPITATION ON THE
LANDING ZONE ON THE MOZAMBICAN COAST.

[TorSkk]

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

0.A WARNING NUMBER: 2/11/20182019

1.A TROPICAL DEPRESSION 11

2.A POSITION 2019/03/04 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 17.9 S / 37.2 E
(SEVENTEEN DECIMAL NINE DEGREES SOUTH AND
THIRTY SEVEN DECIMAL TWO DEGREES EAST)
MOVEMENT: WEST 4 KT

3.A DVORAK ANALYSIS: 2.5/2.5/S 0.0/6 H

4.A CENTRAL PRESSURE: 1002 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): 28 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 80 SE: 70 SW: 90 NW: 80

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 300 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM

1.B FORECASTS:
12H: 2019/03/05 00 UTC: 17.5 S / 36.5 E, VENT MAX= 000 , OVERLAND DEPRESSION
24H: 2019/03/05 12 UTC: 16.8 S / 35.5 E, VENT MAX= 000 , OVERLAND DEPRESSION

2.B LONGER-RANGE OUTLOOK:
NIL

2.C ADDITIONAL INFORMATION:
T=CI=2.5

OVER THE LAST 6 HOURS, THE CONVECTION ASSOCIATED WITH TROPICAL
DEPRESSION 11 HAS MAINLY BEEN MAINTAINED IN CONVECTIVE CLUSTERS NEAR
THE CENTRE, ACCOMPANIED BY STRONG CONVECTION EXTENDING OVER THE
MOZAMBIQUE CHANNEL. THE LATEST INTENSITY ESTIMATES DO NOT ALLOW TO
VALIDATE THE 35KTS THRESHOLD, AS SATELLITE WIND MEASUREMENTS REACH
THIS THRESHOLD ONLY LOCALLY IN THE SOUTHEAST SECTOR. SO SYSTEM 11 WILL
ARRIVE ON COAST WITHOUT BEING BAPTIZED.
TROPICAL DEPRESSION 11 IS EXPECTED TO LAND IN THE COMING HOURS ON THE
MOZAMBICAN COASTS, WITH MAXIMUM WINDS OF 30KT, REACHING THE 35KT
THRESHOLD IN THE SOUTHEAST SECTOR AT SEA. THE CONVECTION ASSOCIATEDWITH THIS SYSTEM REMAINS QUITE STRONG, BRINGING REMARKABLE
PRECIPITATION ON THE LANDING ZONE NEAR THE CITY OF QUELIMANE ON THE
MOZAMBICAN COASTS.

FOLLOWING THE IMMINENT LANDING OF THE SYSTEM, THIS IS THE LAST WARNING
ISSUED ON THIS SYSTEM BY LA REUNION RSMC.

[TorSkk]

Overland Depression n°11 :

Position at 09UTC : 16.9S/37.3E
Movement : Northward 5kt
Maximum 10 min mean winds : 20 kt
Central MSLP : 1002 hPa

The available models suggest a return of the 11th system over the Mozambique Channel but with
different timings. For the American model (GFS), the return over sea is occurring from Friday while
the Euro (IFS) model is suggesting Sunday. The ensembles also suggest a significant cyclogenesis
probability associated to this system for next week-end. However, after such a long journey
overland, the structure of the circulation could suffer more than suggested by the models, which
would make an eventual reintensification more difficult.

From Saturday, the risk that a moderate tropical storm forms over the northern half of the
Mozambique Channel becomes low.

[TorSkk]

[TorSkk]

THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 17.3S 37.6E, IS NOW LOCATED NEAR 16.8S 37.2E, APPROXIMATELY 575
NM WEST-NORTHWEST OF ANTANANARIVO, MADAGASCAR. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH PERSISTENT CONVECTIVE BANDING
WRAPPING INTO THE CENTER DESPITE BEING OVER LAND. UPPER LEVEL
ANALYSIS INDICATES LOW (5-15 KNOTS) VERTICAL WIND SHEAR WITH
FAVORABLE EQUATORIAL DIFFLUENCE ALOFT. A RECENT ASCAT PASS INDICATES
A BROAD CIRCULATION WITH A SWATH OF 20-25 KNOT WINDS ON THE EASTERN
PERIPHERY OF THE SYSTEM IN THE MOZAMBIQUE CHANNEL. SEA SURFACE
TEMPERATURES (30-31 CELSIUS) REMAIN CONDUCIVE FOR DEVELOPMENT IN THE
MOZAMBIQUE CHANNEL ALTHOUGH THE SYSTEM IS CURRENTLY OVER LAND.
GLOBAL MODELS SHOW THE SYSTEM MOVING EASTWARD BACK OVER THE
MOZAMBIQUE CHANNEL WITH GRADUAL STRENGTHENING AT LATER TAUS. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR
THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS REMAINS LOW.

[TorSkk]

Overland Depression n°11-20182019 :

Position at 09UTC : 15.1S / 36.7E
Movement : North-North-Westwards 5 kt
Maximum 10 min mean winds : 20 kt
Central MSLP : 1002 hPa
The associated low level vorticity remains well defined on visible imagery despite the landmass
interaction. The upper level environment remains favorable with good divergence and low deep
vertical windshear. The latest available guidance still bring back the low level vorticiy associated
with this system over the Mozambique channel before Sunday (still some uncertainty about this
timing that should occur between Friday night and Sunday morning). This generally
east-south-easterly track should be steered by the low to mid level monsoon surge. The system is
expected to benefit from good environmental conditions once it will get back overseas. However
there is still the possibility that the system failed to intensify if it remains close to the coasts.

From Saturday, the risk that this system becomes a tropical storm over the Mozambique
Channel becomes moderate.

[wxman57]

Circulation has remained intact over Mozambique. If it moves back offshore, then it will almost certainly redevelop this weekend.

[TorSkk]

Overland Depression n°11-20182019 :
Position at 09UTC : 15.2S / 35.0E
Movement : Westward 5 kt
Maximum 10 min mean winds : 20 kt
Central MSLP : 1004 hPa

The associated low level vorticity remains well defined on visible imagery despite the landmass
interaction. The upper level environment remains favorable with good divergence and low deep
vertical windshear. From Sunday morning, numerical guidance suggest that this low or a another
one will come back oversea or reform over the Mozambique Channel, followed by a new deepening
phase. Indeed, lower converge is forecast to be excellent as the upper divergence should be good at
south first on the north-western semi-circle. If the low move enough offshore, it will probably reach
tropical storm status. Available guidance is in a good agreement with this scenario but differ on the
track with some differences in the comeback timing.

From Saturday, the risk that this system or a another one becomes a tropical storm over the
Mozambique Channel becomes moderate.

[TyphoonNara]

(1) THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 15.3S 35.6E, IS NOW LOCATED NEAR 15.4S 34.8E, APPROXIMATELY 436
NM NORTHWEST OF EUROPA ISLAND. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS AN OBSCURED LOW LEVEL CIRCULATION (LLC) WITH A BROAD
AREA OF DEEP CONVECTION TO THE EAST. A 080336Z SSMIS F-17 91GHZ
MICROWAVE IMAGE SHOWS MID-LEVEL CONVECTION OVER THE LLC WITH DEEPER
CONVECTION TO THE SOUTHEAST ASSOCIATED WITH A SOUTHERNLY INFLOW
CHANNEL. 98S IS CURRENTLY EXPERIENCING EXCELLENET WESTWARD OUTFLOW
AND VERY LOW (5 TO 10 KNOTS) VERTICAL WIND SHEAR (VWS). SEA SURFACE
TEMPERATURES ARE WARM (28 TO 29 CELSIUS) IN THE MOZAMBIQUE CHANNEL.
GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 98S WILL TRACK OVERWATER
AND RAPIDLY INTENSIFY WHILE SHARPLY TURNING SOUTH. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS REMAINS MEDIUM.

[TorSkk]

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

0.A WARNING NUMBER: 3/11/20182019

1.A TROPICAL DEPRESSION 11

2.A POSITION 2019/03/09 AT 0600 UTC:
WITHIN 20 NM RADIUS OF POINT 17.0 S / 40.4 E
(SEVENTEEN DECIMAL ZERO DEGREES SOUTH AND
FORTY DECIMAL FOUR DEGREES EAST)
MOVEMENT: EAST 3 KT

3.A DVORAK ANALYSIS: 2.5/2.5/D 0.5/6 H

4.A CENTRAL PRESSURE: 1000 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): 56 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 150 SE: 150 SW: NW:

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1008 HPA / 700 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP
1.B FORECASTS:
12H: 2019/03/09 18 UTC: 16.9 S / 40.9 E, VENT MAX= 035 KT, MODERATE TROPICAL
STORM
24H: 2019/03/10 06 UTC: 17.1 S / 41.6 E, VENT MAX= 045 KT, MODERATE TROPICAL
STORM
36H: 2019/03/10 18 UTC: 17.4 S / 41.5 E, VENT MAX= 055 KT, SEVERE TROPICAL STORM
48H: 2019/03/11 06 UTC: 17.5 S / 41.2 E, VENT MAX= 065 KT, TROPICAL CYCLONE
60H: 2019/03/11 18 UTC: 17.8 S / 40.6 E, VENT MAX= 075 KT, TROPICAL CYCLONE
72H: 2019/03/12 06 UTC: 18.2 S / 39.5 E, VENT MAX= 085 KT, TROPICAL CYCLONE

2.B LONGER-RANGE OUTLOOK:
96H: 2019/03/13 06 UTC: 18.8 S / 36.5 E, VENT MAX= 085 KT, TROPICAL CYCLONE
120H: 2019/03/14 06 UTC: 19.5 S / 34.0 E, VENT MAX= 040 KT, OVERLAND DEPRESSION

2.C ADDITIONAL INFORMATION:
T=CI=2.5-

DURING THE NIGHT, THE SYSTEM HAS GOT OUT IN SEA NEAR THE MOZAMBIQUE
COASTLINES. ACTIVE CONVECTIVE BANDS WRAP UP AROUND THE CENTER WITH
INCREASING CURVATURE.

THE SYSTEM IS FORECASTED TO MOVE SLOWLY EASTWARD UNTIL MONDAY
STEERING BY A LOW/MID NEAR-EQUATORIAL RIDGE LOCATED NORTH OF THE
SYSTEM. FROM TUESDAY, THE NEAR-EQUATORIAL RIDGE IS EXPECTED TO WEAKEN
WHILE THE SUBTROPICAL RIDGE IS FORECASTED TO STRENGTHEN SOUTH OF THE
MOZAMBIQUE CHANNEL. THE SYSTEM SHOULD CURVE SOUTHWESTWARD THEN
ACCELERATE WESTWARD STEERING BY THE SUBTROPICAL RIDGE. THE SYSTEM IS
EXPECTED TO LAND AGAIN WEDNESDAY OVER MOZAMBIQUE. MODELS ARE IN
GOOD AGREEMENT WITH THIS TRACK PHILOSOPHY BUT THE LONGITUDE OF THE
TURN WESTWARD REMAINS UNCERTAIN.

ON THIS TRACK, ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR
INTENSIFICATION. THE SYSTEM, SHOULD EVOLVE BENEATH THE UPPER LEVEL
RIDGE WITH A WEAK VERTICAL WINDSHEAR AND A GOOD POLERWARD
DIVERGENCE. OCEAN HEAT CONTENT IS VERY GOOD. IN THESE CONDITIONS, THE
LIKELIHOOD THAT A MATURE SYSTEM WITH A SIGNIFICANT INTENSITY MAKES A
LANDING OVER THE MOZAMBIQUE IS VERY HIGH

A dangerous situation for Mozambique

[TorSkk]

[WAcyclone]

JTWC has just released its first forecast. Interestingly, the last forecast point shows an intensity of 100 kt more than 100 km inland over Mozambique!

[wxman57]

Officially (La Reunion), it's still Tropical Depression 11. It doesn't make any difference if JTWC is saying it's a TS, they're not the official agency of any basin (even though I agree winds are 40-45 kts now). La Reunion is very slow to upgrade.

[TorSkk]

A. TROPICAL CYCLONE 18S (W OF MADAGASCAR)

B. 09/1745Z

C. 16.66S

D. 41.93E

E. FIVE/MET8

F. T2.0/2.5/S0.0/30HRS STT: S0.0/03HRS

G. IR/EIR

H. REMARKS: 38A/PBO SBC/ANMTN. .35 WRAP ON LOG10 SPIRAL YIELDS
A 2.0 DT. MET AND PT YIELD A 2.0. DBO DT.

I. ADDITIONAL POSITIONS:
09/1219Z 17.08S 41.22E SSMI

[TorSkk]

RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 5/11/20182019

1.A TROPICAL DEPRESSION 11

2.A POSITION 2019/03/09 AT 1800 UTC:
WITHIN 20 NM RADIUS OF POINT 17.1 S / 41.9 E
(SEVENTEEN DECIMAL ONE DEGREES SOUTH AND
FORTY ONE DECIMAL NINE DEGREES EAST)
MOVEMENT: EAST 8 KT

3.A DVORAK ANALYSIS: 2.5/2.5/D 0.5/12 H

4.A CENTRAL PRESSURE: 996 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): 56 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 170 SE: 130 SW: 90 NW: 130

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 600 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP
1.B FORECASTS:
12H: 2019/03/10 06 UTC: 17.5 S / 42.5 E, VENT MAX= 040 KT, MODERATE TROPICAL
STORM
24H: 2019/03/10 18 UTC: 17.7 S / 42.5 E, VENT MAX= 050 KT, SEVERE TROPICAL STORM
36H: 2019/03/11 06 UTC: 17.8 S / 42.3 E, VENT MAX= 060 KT, SEVERE TROPICAL STORM
48H: 2019/03/11 18 UTC: 18.3 S / 41.6 E, VENT MAX= 070 KT, TROPICAL CYCLONE
60H: 2019/03/12 06 UTC: 18.7 S / 40.8 E, VENT MAX= 080 KT, TROPICAL CYCLONE
72H: 2019/03/12 18 UTC: 19.1 S / 39.5 E, VENT MAX= 085 KT, TROPICAL CYCLONE

2.B LONGER-RANGE OUTLOOK:
96H: 2019/03/13 18 UTC: 19.3 S / 37.3 E, VENT MAX= 085 KT, TROPICAL CYCLONE
120H: 2019/03/14 18 UTC: 18.8 S / 34.5 E, VENT MAX= 000 , OVERLAND DEPRESSION

2.C ADDITIONAL INFORMATION:
T=CI=2.5

DURING THE LAST 6 HOURS, AFETR HAVING GOING UNDER THE DIURNAL CYCLE,
DEEP CONVECTION SEEMS TO ORGANISED NEAR THE CENTER ON THE VERY LAST
IMAGERY. THIS IS CONFIRMED BY THE LAST SSMIS DATA OF 1557Z WITH AN EYE
QUITE CLOSED ON 37GHZ.

THE SYSTEM IS FORECASTED TO MOVE EASTWARD STEERING BY A LOW/MID
TROPOSHERIC NEAR-EQUATORIAL RIDGE LOCATED NORTH OF THE SYSTEM. FROM
TOMOROW, THE NEAR-EQUATORIAL RIDGE IS EXPECTED TO WEAKEN WHILE THE
SUBTROPICAL RIDGE IS FORECASTED TO STRENGTHEN SOUTH OF THE
MOZAMBIQUE CHANNEL. THE SYSTEM SHOULD SLOW DOWN AND CURVE
SOUTHWARD AND THEN SOUTHWESTWARD. FROM MONDAY, THE SYSTEM SHOULD
ACCELERATE WESTSOUTHWESTWARD STEERING BY THE SUBTROPICAL RIDGE. THE
SYSTEM IS EXPECTED TO LAND OVER MOZAMBIQUE COASTLINES THURSDAY
MORNING. MODELS ARE IN GOOD AGREEMENT WITH THIS TRACK PHILOSOPHY BUT
THE LONGITUDE OF THE TURN WESTSOUTHWESTWARD REMAINS UNCERTAIN.

ON THIS TRACK, ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR
INTENSIFICATION. THE SYSTEM, SHOULD EVOLVE BENEATH THE UPPER LEVEL
RIDGE WITH A WEAK VERTICAL WINDSHEAR AND A GOOD POLERWARD
DIVERGENCE. OCEAN HEAT CONTENT IS VERY GOOD. IN THESE CONDITIONS, THE
LIKELIHOOD THAT A MATURE SYSTEM WITH A HIGH INTENSITY LANDS OVER
MOZAMBIQUE IS VERY HIGH.

[TorSkk]

Officially (La Reunion), it's still Tropical Depression 11. It doesn't make any difference if JTWC is saying it's a TS, they're not the official agency of any basin (even though I agree winds are 40-45 kts now). La Reunion is very slow to upgrade.

La Reunion tends to upgrade when CI reaches 3.0. This chart is taken from their operational plan