Tropical Cyclone 14S (Fourteen) Warning Issued at 06/2100Z
062100Z POSITION NEAR 13.1S 70.3E.
TROPICAL CYCLONE (TC) 14S (FOURTEEN), LOCATED APPROXIMATELY 377 NM
SOUTH-SOUTHWEST OF DIEGO GARCIA, HAS TRACKED WESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS CONSOLIDATED DEEP CONVECTIVE BANDING OVER THE
NORTHERN SEMI-CIRCLE SLOWLY WRAPPING INTO AN EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). A 061730Z METOP-B MICROWAVE IMAGE REVEALS
THE BULK OF THE DEEP CONVECTIVE BANDING IS LOCATED OVER THE
NORTHWEST QUADRANT OF THE LLCC AND IS WRAPPING TOWARDS THE
CENTER. THE INITIAL POSITION IS BASED ON THE MSI AND MICROWAVE IMAGE
WITH HIGH CONFIDENCE. A RECENT ASCAT PASS INDICATES A 30 KNOT
CIRCULATION WITH 35 KNOT WIND BARBS ALONG THE NORTHERN AND SOUTHERN
PERIPHERIES. THE INITIAL INTENSITY OF 30 KNOTS IS BASED ON THE
AFOREMENTIONED ASCAT PASS AND HEDGES HIGHER THAN DVORAK ESTIMATES
FROM PGTW, KNES AND FMEE. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM
IS LOCATED IN A MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE (15
TO 20 KNOT) VERTICAL WIND SHEAR OFFSET BY GOOD EQUATORWARD OUTFLOW.
TC 14S IS CURRENTLY LOCATED IN A WEAK STEERING ENVIRONMENT, LEADING
TO SLOW MOVEMENT AND IS EXPECTED TO TURN SOUTHEASTWARD IN THE NEAR
TERM AS A SUBTROPICAL RIDGE (STR) BUILDS IN FROM THE EAST. AFTER TAU
48, TC 14S IS FORECAST TO TURN SOUTH-SOUTHWESTWARD AS THE STR WILL
DOMINATE THE STEERING PATTERN THROUGHOUT THE REMAINDER OF THE
FORECAST PERIOD. MOREOVER, IMPROVING UPPER-LEVEL CONDITIONS, WARM
(GREATER THAN 28 DEGREES CELSIUS) SEA SURFACE TEMPERATURES AND HIGH
OCEAN HEAT CONTENT ARE CONDUCIVE FOR FURTHER DEVELOPMENT, ALLOWING
THE INTENSITY TO PEAK AT 60 KNOTS BY TAU 72. DUE TO A WEAK STEERING
ENVIRONMENT IN THE NEAR TERM AND A SLIGHT SPREAD AMONG AVAILABLE
MODEL TRACKERS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST
TRACK, WHICH IS POSITIONED CLOSE TO CONSENSUS. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 061800Z IS 8 FEET.
Tropical Cyclone 13S (Edilson) Warning Issued at 07/0300Z
070300Z POSITION NEAR 27.0S 55.4E.
TROPICAL CYCLONE 13S (EDILSON), LOCATED APPROXIMATELY 375 NM SOUTH-
SOUTHWEST OF PORT LOUIS, MAURITIUS, HAS TRACKED SOUTHWESTWARD AT 18
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
DEPICTS THE OVERALL STRUCTURE FOR TC 13S HAS BEEN DEGRADED AS A MAJOR
LONGWAVE TROUGH HAS TRACKED EASTWARD INTO CLOSE PROXIMITY TO THE
SYSTEM. INCREASING UPPER LEVEL SUBSIDENCE ASSOCIATED WITH THE TROUGH
IS BEGINNING TO IMPACT THE EQUATORWARD AND POLEWARD OUTFLOW CHANNELS
AND IS CREATING INCREASED LEVELS OF VERTICAL WIND SHEAR. ADDITION-
ALLY, DRY AIR ENTRAINMENT ALONG THE WESTERN AND NORTHERN PERIPHERIES
HAS STARTED IN THE MID-LEVELS. SEA SURFACE TEMPERATURES ARE MARGINAL
(26 TO 27 DEGREES CELSIUS) BUT ARE EXPECTED TO RAPIDLY DECREASE OVER
THE NEXT 12 TO 24 HOURS, FURTHER WEAKENING TC 13S. A CULMINATION OF
ENVIRONMENTAL IMPACTS WILL START THE EXTRA-TROPICAL TRANSITION OF
THE LOW LEVEL CIRCULATION CENTER BY TAU 36. INCREASING INTERACTION
WITH THE MID-LATITUDE TROUGH WILL FINISH THE TRANSITION PROCESS BY
TAU 72. THERE IS THE DISTINCT POSSIBILITY THAT THIS PROCESS OCCURS
MORE QUICKLY THAN FORECAST AS THE APPROACHING TROUGH INTERACTS WITH
THE SUBTROPICAL RIDGE STEERING TC 13S LEADING TO AN ACCELERATED
TRACK SPEED. BASED ON THE GOOD AGREEMENT OF AVAILABLE MODEL
GUIDANCE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 070000Z IS 18 FEET.
- JTWC
