WTIO30 FMEE 061311



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 1/2/20172018

1.A MODERATE TROPICAL STORM  2  (IRVING)



2.A POSITION 2018/01/06 AT 1200 UTC:

WITHIN 30 NM RADIUS OF POINT 12.8 S / 89.8 E

(TWELVE    DECIMAL EIGHT   DEGREES SOUTH AND EIGHTY NINE    DECIMAL

EIGHT   DEGREES EAST)

MOVEMENT : WEST 10 KT



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



4.A CENTRAL PRESSURE: 994 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 35 KT

RADIUS OF MAXIMUM WINDS (RMW) :37 KM



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

28 KT NE: 220 SE: 220 SW: 90 NW: 90

34 KT NE: 70 SE: 70 SW: 60 NW: 60







7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1005 HPA / 1800 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/01/07 00 UTC: 13.9 S / 86.6 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

24H: 2018/01/07 12 UTC: 15.3 S / 84.1 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

36H: 2018/01/08 00 UTC: 17.1 S / 80.9 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

48H: 2018/01/08 12 UTC: 19.5 S / 77.9 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

60H: 2018/01/09 00 UTC: 22.2 S / 75.3 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

72H: 2018/01/09 12 UTC: 25.2 S / 72.0 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2018/01/10 12 UTC: 32.9 S / 68.5 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

120H: 2018/01/11 12 UTC: 45.3 S / 70.0 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

T=CI=2.5+



THE UPPER EASTERLY SHEAR CONSTRAINT IS CLEARLY AFFECTING IRVING'S

CONVECTION AND CONCENTRATING IT MAINLY IN THE WESTERN SEMI-CIRCLE.

NEVERTHELESS, 1215Z SSMIS MICRO-WAVE IMAGES SHOW THAT THE INTERNAL

STRUCTURE OF THE STORM REMAINS WELL DEFINED AND EVEN TENDS TO

CONSOLIDATE. THE LAST SAT IMAGES CONFIRM THIS IMPRESSION AS STRONG

CONVECTIVE BURSTS REMAIN WELL AXED OVER THE CIRCULATION CENTER.



IRVING'S TRACK IS STEERED BY A STRONG RIDGE IN THE SOUTH-EAST. FROM

WEDNESDAY, THE STORM SHOULD BE ATTRACTED TOWARDS THE MID-LATITUDES BY

A TROUGH ARRIVING FROM THE SOUTH-WEST. IRVING SPEED SHOULD BE RATHER

HIGH AND THE AVAILABLE GUIDANCE DISPERSION REMAINS VERY LOW ALONG

THIS CLASSIC PARABOLIC TRACK.



THE UPPER SHEAR AFFECTING IRVING SHOULD TURN NORTHEASTERLY THEN

NORTHERLY OVER THE PERIOD BUT WITHOUT WEAKENING. THIS UPPER

CONSTRAINT IS DRIVEN BY A DEEP UPPER TROUGH AXED ALONG THE 65TH

MERIDIAN. THE QUICK SOUTH-WESTWARD MOTION OF IRVING SHOULD PARTLY

COMPENSATE THE NEGATIVE EFFECTS OF THE SHEAR. IRVING IS THUS LIKELY

TO SLOWLY DEEPEN UNTIL REACHING 25S. SOUTH OF THIS LIMIT, THE OCEANIC

HEAT CONTENT BECOMES LIMITED AND THE INFLUENCE OF THE UPPER TROUGH

STRONGER. IRVING SHOULD THEN BEGIN TO WEAKEN WHILE BEGINNING AN

EXTRATROPICAL TRANSITION.=