WTIO30 FMEE 181319



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 23/3/20172018

1.A SEVERE TROPICAL STORM  3  (BERGUITTA)



2.A POSITION 2018/01/18 AT 1200 UTC:

WITHIN 20 NM RADIUS OF POINT 21.6 S / 56.3 E

(TWENTY ONE    DECIMAL SIX   DEGREES SOUTH AND FIFTY SIX    DECIMAL

THREE   DEGREES EAST)

MOVEMENT : WEST-SOUTH-WEST 13 KT



3.A DVORAK ANALYSIS: 3.0/3.5/W 0.5/24 H



4.A CENTRAL PRESSURE: 982 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 50 KT

RADIUS OF MAXIMUM WINDS (RMW) :28 KM



6.A EXTENSION OF WIND BY QUADRANTS (KM):

28 KT NE: 150 SE: 560 SW: 520 NW: 190

34 KT NE: 90 SE: 130 SW: 130 NW: 90

48 KT NE:  SE: 70 SW: 70 NW:





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 1700 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/01/19 00 UTC: 22.6 S / 54.2 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

24H: 2018/01/19 12 UTC: 24.3 S / 52.2 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

36H: 2018/01/20 00 UTC: 26.7 S / 51.0 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

48H: 2018/01/20 12 UTC: 29.7 S / 50.2 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

60H: 2018/01/21 00 UTC: 32.2 S / 50.4 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

72H: 2018/01/21 12 UTC: 32.5 S / 51.3 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION



2.B LONGER-RANGE OUTLOOK :

96H: 2018/01/22 12 UTC: 34.2 S / 56.4 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

120H: 2018/01/23 12 UTC: 36.3 S / 58.6 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

T=3.0 CI=3.5



OVER THE PAST SIX HOURS, CONVECTIVE ACTIVITY INCREASED AROUND THE

CENTER WITH COLDER CLOUD TOPS. MICROWAVE DATA (1013Z AMSR2) AND LA

REUNION RADAR DATA DO NOT SHOW ANY SIGN OF THE REBUILDING OF THE

INNER CORE. EXACT POSITION IS THUS RATHER UNCLEAR. THE SHEAR STILL

ANALYSED AT 15KT BY CIMSS, IS STILL PREVENTING BERGUITTA FROM

DEEPENING DEPSITE THE GOOD UPPER DIVERGENCE. MSLP WAS ESTIMATED WITH

BUOY DATA.



THE SYSTEM IS NOW TRACKING SOUTHWESTWARD UNDER THE STEERING FLOW OF

THE MID-TROPOSPHERIC RIDGE LOCATED EAST. TODAY, BERGUITTA IS FORECAST

TO KEEP ON ITS MOVEMENT, MOVING AWAY FROM REUNION ISLAND AFTER ITS

THE CLOSEST PASSAGE. IT WILL THEN CONTINUE TRACKING SOUTHWESTWARD

BEFORE TRACKING SOUTHWARDS. LATER, HIGH PRESSURE FURTHER SOUTH SHOULD

SLOW DOWN THE MOVING OF BERGUITTA, AND NEXT THE SYSTEM BERGUITTA

SHOULD FOLLOW THE MID-LATITUDE CIRCULATION.



THE SYSTEM IS UNDERGOING A MODERATE NORTHEASTERN VERICAL WINDSHEAR

OVER THE NORTHEASTERN EDGE OF THE AFOREMENTIONED RIDGE. INTENSITY

FORECAST CONTINUE TO FAVOUR A SLOW WEAKENING AS THE MAIN SCENARIO.

, WITH GOOD UPPER DIVERGENCE AND A RATHER FAST SPEED. FROM SATURDAY,

NORTHWESTWARD VERTICAL WINDSHEAR IS FORECASTED TO INCREASE AHEAD AN

UPPER LEVEL TROUGH. OCEANIC POTENTIAL WILL BECOME MARGINAL AT THIS

RANGE. BERGUITTA IS EXPECTED THEN TO START ITS EXTRATROPICALISATION

PHASE.=