RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 3/5/20182019
1.A TROPICAL DISTURBANCE 5
2.A POSITION 2018/12/18 AT 1800 UTC:
WITHIN 21 NM RADIUS OF POINT 10.4 S / 61.0 E
(TEN DECIMAL FOUR DEGREES SOUTH AND SIXTY ONE DECIMAL ZERO DEGREES
EAST)
MOVEMENT : SOUTH 2 KT
3.A DVORAK ANALYSIS: 2.0/2.0/S 0.0/6 H
4.A CENTRAL PRESSURE: 1003 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 25 KT
RADIUS OF MAXIMUM WINDS (RMW) :NIL
6.A EXTENSION OF WIND BY QUADRANTS (KM):
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 500 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : MEDIUM
1.B FORECASTS:
12H: 2018/12/19 06 UTC: 11.3 S / 60.5 E, MAX WIND=035 KT, MODERATE TROPICAL
STORM
24H: 2018/12/19 18 UTC: 12.1 S / 59.9 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
36H: 2018/12/20 06 UTC: 12.7 S / 59.3 E, MAX WIND=065 KT, TROPICAL CYCLONE
48H: 2018/12/20 18 UTC: 13.5 S / 58.5 E, MAX WIND=075 KT, TROPICAL CYCLONE
60H: 2018/12/21 06 UTC: 14.3 S / 57.9 E, MAX WIND=085 KT, TROPICAL CYCLONE
72H: 2018/12/21 18 UTC: 15.1 S / 57.8 E, MAX WIND=090 KT, INTENSE TROPICAL
CYCLONE
2.B LONGER-RANGE OUTLOOK :
96H: 2018/12/22 18 UTC: 17.3 S / 58.6 E, MAX WIND=095 KT, INTENSE TROPICAL
CYCLONE
120H: 2018/12/23 18 UTC: 21.9 S / 61.4 E, MAX WIND=080 KT, TROPICAL CYCLONE
2.C ADDITIONAL INFORMATION:
FT=CI=2.0+
DURING THE LAST SIX HEURES, THE CONVECTION IS REINFORCED CLOSE TO THE
DISTURBANCE CENTER AND PRESENTS A NET IMPROVEMENT OF THE CLOCKWISE
CIRCULATION. THE 1717UTC ASCAT SWATH DOES NOT ALLOW A GOOD WIND
ESTIMATE TO BE MADE. THE DVORAK ANALYSIS PROVIDES AN ESTIMATE IN THE
ORDER OF 25KT.
THE TRAJECTORY FORECAST EVOLVED LITTLE WHILE THE INTENSITY FORECAST
WAS SEEN TO INCREASE, WITH A RAPID INTENSIFICATION OVER THE NEXT 24
HOURS.
THE SYSTEM APPEARS TO BE MOVING SLOWLY SOUTHWARD IN THE LAST FEW
HOURS. OVER THE NORTHWESTERN EDGE OF A BUILDING MID LEVEL SUBTROPICAL
RIDGE, THE SYSTEM IS EXPECTED TO RESUME A GENERAL SOUTHWESTWARDS
TRACK OVER THE NEXT THREE DAYS. LATER IN THE WEEK A DEEP UPPER TO
MIDLEVEL RIDGE IS EXPECTED TO MOVE SOUTH OF THE MASCAREIGNES ISLANDS,
RESULTING IN A SIGNIFICANT AND PERSISTENT BREAK IN THE SUBTROPICAL
RIDGE. THEREFORE, THE TRACK IS EXPECTED TO SLOW DOWN AT DAY 3 BEFORE
GRADUALLY ACCELERATING SOUTH-SOUTH-EASTWARDS AT DAY 4 AND DAY 5. THE
PHILOSOPHY OF THE TRACK FORECAST IS IN GOOD AGREEMENT BETWEEN THE
DIFFERENT MODELS HOWEVER THERE IS UNCERTAINTY ABOUT THE VELOCITY OF
DISPLACEMENT DURING ACCELERATION TOWARDS THE SOUTH-SOUTHEAST.
CURRENTLY THE SYSTEM IS STILL UNDER A MODERATE EASTERLY CONSTRAINT,
BUT AS THE SYSTEM WILL GAIN LATITUDES, IT IS EXPECTED TO MOVE UNDER THE
UPPER LEVEL RIDGE WITHIN FAVORABLE TO VERY FAVORABLE ENVIRONMENT UP
TO DAY 3 TO DAY 4. IN THE SHORT TERM, A RAPID INTENSIFICATION IS ENVISAGED
LEADING THE SYSTEM TO QUICKLY REACH THE THRESHOLD OF STRONG TROPICAL
STORM TOMORROW DURING THE DAY AND INTENSE TROPICAL CYCLONE STAGE AT
3 DAYS. DURING DAY 4, INCREASING WEST-NORTH-WESTERLY SHEAR ALONG WITH
A DRYER MID LEVEL ENVIRONMENT (MAINLY WITHIN THE WESTERN SEMI-CIRCLE)
SHOULD START TO WEAKEN THE SYSTEM.
THIS TROPICAL SYSTEM HAS THE POTENTIAL TO BECOME A DANGEROUS TROPICAL
CYCLONE AND MAY POSE A POTENTIAL THREAT TO THE MASCAREIGNES ISLANDS
LATER THIS WEEK. INHABITANTS OF THOSE ISLANDS SHOULD MONITOR THE
PROGRESS OF THIS SYSTEM.