SIO: 05S - Tropical Cyclone

[Subtrop]

99S INVEST 241225 1800 12.1S 101.7E SHEM 15 1009

[cycloneye]

WDXS31 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (FIVE) WARNING NR
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 12.5S 96.4E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 33 NM SOUTHWEST OF THE COCOS ISLANDS
MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 09 KTS
SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) O5S IS INDUBITABLY ON A STEADY WEAKENING TREND
AS INDICATED IN THE ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY. DEEP CONVECTION HAS FRAGMENTED AND IS NOW SHEARED OVER THE
WESTERN SEMICIRCLE OF A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC). A 271204Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE
REVEALS SHALLOW BANDING OVER THE SOUTHERN SEMICIRCLE WRAPPING INTO
THE WESTERN QUADRANT OF A WEAKLY-DEFINED LLCC, WITH SPARSE,
DISORGANIZED CONVECTION. THE INITIAL POSITION IS PLACED ON THE
NORTHERN EDGE OF THE SHALLOW CURVED BAND WITH MEDIUM CONFIDENCE.
ENVIRONMENTAL CONDITIONS HAVE DEGRADED WITH HIGH (25-30 KNOTS)
EASTERLY TO EAST-NORTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET
SLIGHTLY BY MODERATE POLEWARD OUTFLOW. THE INITIAL INTENSITY IS
ASSESSED AT 35 KNOTS ON THE HIGH END OF THE SUBJECTIVE DVORAK
ESTIMATES RANGING FROM 30-35 KNOTS.

[cycloneye]

WDPS31 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06P (SIX) WARNING NR
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 17.3S 176.9E
INITIAL INTENSITY: 50 KTS
GEOGRAPHIC REFERENCE: 98 NM WEST-NORTHWEST OF SUVA, FIJI
MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 14 KTS
SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 06S (SIX) HAS TRANSFORMED AT AN INCREDIBLE
PACE FROM A 30 KNOT ILL-DEFINED CIRCULATION EMBEDDED WITH THE SPCZ,
TO A STRONG TROPICAL CYCLONE WITH A MICROWAVE AND RADAR EYE
FEATURE. POST-ANALYSIS SUGGESTS THAT THE 290000Z INTENSITY WAS
VERY LIKELY WELL ABOVE 35 KNOTS BUT A LACK OF DATA, THE VERY SMALL
NATURE OF THE SYSTEM AND THE OVERALL WEAK APPEARANCE IN VISIBLE AND
INFRARED SATELLITE IMAGERY PRECLUDED ASSESSING IT AT A HIGHER
INTENSITY AT THAT TIME. A 290158Z AMSR2 MICROWAVE PASS CHANGED ALL
THAT IN AN INSTANT, WHEN IT REVEALED A CLEAR, VERTICALLY ALIGNED
MICROWAVE EYE IN BOTH THE 89GHZ AND MOST STRIKINGLY IN THE COLOR
ENHANCED 36GHZ IMAGE. A QUICK GANDER AT THE RADAR DATA OUT OF NADI,
CONFIRMED THE SYMMETRIC AND ALIGNED NATURE OF THE VORTEX, WHICH
CONTINUED TO BECOME BETTER DEFINED. BASED ON THE RADAR DATA, THE
SYSTEM LIKELY REACHED PEAK INTENSITY AROUND 0400Z-0500Z. BY 290600Z
THE CENTER WAS PASSING VERY CLOSE TO WAYASEWA AND KUATA ISLAND,
MOVING EASTWARD AT ABOUT 14 KNOTS. THE RADAR DEPICTION HAS BECOME
INCREASINGLY RAGGED SINCE THE 0500Z PEAK. THE MSI AND ENHANCED
INFRARED (EIR) IMAGERY HAVE NEVER SHOWN A CLEAR EYE, THOUGH THERE
WAS BRIEFLY A WARM SPOT IN THE BD-ENHANCED EIR. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE RADAR EYE
FEATURE. THE INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE, AS
THE SMALL SIZE OF THE SYSTEM IS PRECLUDING ACCURATE DVORAK-BASED
INTENSITY ESTIMATES AND CIMSS OBJECTIVE ESTIMATES ARE NOT YET
AVAILABLE, MEANING THE INTENSITY ASSESSMENT IS BASED ALMOST
ENTIRELY ON THE APPEARANCE OF THE SYSTEM IN THE MICROWAVE IMAGERY.
THE ENVIRONMENT IS GENERALLY FAVORABLE, WITH WARM SSTS, LOW VWS AND
MODERATE POLEWARD OUTFLOW.