WTPS12 NFFN 191200
TROPICAL DISTURBANCE ADVISORY NUMBER B26 ISSUED FROM RSMC NADI
Dec 191303 UTC.

TROPICAL CYCLONE YASA CENTRE 994HPA WAS LOCATED NEAR 22.7S 179.4W AT
191200 UTC. POSITION POOR BASED ON HR HIMAWARI EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING SOUTHWEST AT ABOUT 16
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 35 KNOTS DECREASING TO 30 KNOTS BY 200000UTC.

ABOVE 33 KNOTS WITHIN 130 NAUTICAL MILES IN NE QUADRANT
AND WITHIN 190 NAUTICAL MILES IN SE QUADRANT
AND WITHIN 130 NAUTICAL MILES IN SW QUADRANT
AND WITHIN 070 NAUTICAL MILES IN NW QUADRANT.

ORGANISATION SLIGHTLY IMPROVED WITH CONVECTION FLARING UP LAST 6
HOURS. LLCC PARTLY EXPOSED AND SHEARED FROM CONVECTIVE CLOUD. TC YASA
LIES JUST TO THE EAST OF AN APPROACHING UPPER TROUGH IN A MODERATE
SHEARED ENVIRONMENT. THE UPPER TROUGH WILL BRING HIGH SHEAR OVER THE
SYSTEM WHICH WILL CAUSE WEAKENING. YASA IS BEING STEERED
SOUTH-SOUTHWEST ALONG THE NORTHWEST PERIPHERY OF A SUB-TROPICAL RIDGE
TO THE SOUTH. CYCLONIC CIRCULATION EXTENDS UPTO 500HPA. SST IS AROUND
27 DEGREES CELSIUS. GLOBAL MODELS MOVE YASA IN A SOUTHWESTWARD
MOVEMENT WITH FURTHER WEAKENING. DVORAK ANALYSIS BASED ON SHEAR
PATTERN WITH DT OF 2.5. MET 2.5 AND PT 3.0. FT BASED ON PT. THUS,
YIELDING T2.5/3.0/W1.5/24HRS.


FORECASTS :
AT 12 HRS VALID AT 200000 UTC 23.7S 179.8W MOV SSW AT 06 KT WITH 30
KT CLOSE TO CENTRE
AT 24 HRS VALID AT 201200 UTC 24.6S 179.5E MOV SSW AT 05 KT WITH 30
KT CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 210000 UTC 25.6S 178.9E MOV SSW AT 06 KT WITH 25
KT CLOSE TO CENTRE
AT 48 HRS VALID AT 211200 UTC 26.5S 178.5E MOV SSW AT 05 KT WITH 25
KT CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON YASA WILL BE ISSUED AROUND
190830 UTC.
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