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本帖最后由 pocketbox 于 2026-1-1 16:20 编辑
WTIO30 FMEE 010653
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 21/5/20252026
1.A SEVERE TROPICAL STORM 5 (GRANT)
2.A POSITION 2026/01/01 AT 0600 UTC:
WITHIN 20 NM RADIUS OF POINT 16.0 S / 68.8 E
(SIXTEEN DECIMAL ZERO DEGREES SOUTH AND
SIXTY EIGHT DECIMAL EIGHT DEGREES EAST)
MOVEMENT: WEST-NORTH-WEST 5 KT
3.A DVORAK ANALYSIS: 3.5/4.0/W 0.5/6 H
4.A CENTRAL PRESSURE: 989 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 55 KT
RADIUS OF MAXIMUM WINDS (RMW): 46 KM
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 75 SE: 100 SW: 150 NW: 140
34 KT NE: 0 SE: 0 SW: 95 NW: 100
48 KT NE: 0 SE: 0 SW: 0 NW: 65
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 700 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP
1.B FORECASTS (WINDS RADII IN KM):
12H: 2026/01/01 18 UTC: 15.9 S / 68.1 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 95 SE: 120 SW: 155 NW: 130
34 KT NE: 0 SE: 75 SW: 95 NW: 85
24H: 2026/01/02 06 UTC: 15.6 S / 67.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 95 SE: 150 SW: 130 NW: 120
34 KT NE: 0 SE: 75 SW: 95 NW: 75
36H: 2026/01/02 18 UTC: 15.1 S / 66.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 0 SE: 155 SW: 140 NW: 95
34 KT NE: 0 SE: 0 SW: 85 NW: 0
48H: 2026/01/03 06 UTC: 15.0 S / 65.1 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 165 SW: 150 NW: 0
60H: 2026/01/03 18 UTC: 15.1 S / 63.8 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 165 SW: 130 NW: 0
72H: 2026/01/04 06 UTC: 15.4 S / 61.9 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 185 SW: 155 NW: 110
2.B LONGER-RANGE OUTLOOK:
96H: 2026/01/05 06 UTC: 15.8 S / 58.0 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 150 SE: 220 SW: 195 NW: 140
120H: 2026/01/06 06 UTC: 16.4 S / 53.6 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 165 SE: 260 SW: 205 NW: 155
2.C ADDITIONAL INFORMATION:
T=3.5 CI=4.0
OVER THE LAST 6 HOURS, GRANT'S WEAKENING TREND HAS CONTINUED. THE
SYSTEM NOW DISPLAYS A SHEAR PATTERN WITH A CENTER ON THE EASTERN EDGE
OF AN INTENSE CDO, WITH CLOUD TOPS BELOW -85C AND SIGNIFICANT
THUNDERSTORM ACTIVITY. THE EASTERN PART OF THE LOW-LEVEL VORTEX IS
NOW EXPOSED. SUBJECTIVE DVORAK ANALYSIS YIELDS A DT OF 3.5 WITH A
CENTER LESS THAN 20 NM FROM THE CONVECTIVE MASS. MET ADJUSTED BY PT
IS ALSO AT 3.5. A 0101Z SAR RCM1 PASS MEASURED WINDS OF 60-65 KT
(10-MIN WINDS), SHOWING A MORE ASYMMETRICAL AND ELONGATED WIND
STRUCTURE. TWO SUCCESSIVE ASCAT PASSES (ASCAT-B AT 0432Z, ASCAT-C AT
0511Z) MEASURED MAXIMUM WINDS BETWEEN 45 AND 50 KT UNDER INTENSE
CONVECTION IN THE WESTERN SEMI-CIRCLE (EQUIVALENT TO AT LEAST 55 KT
TAKING INTO ACCOUNT THE ASCAT'S UNDERESTIMATION), WHILE WINDS NO
LONGER REACH 35 KT IN THE EASTERN SEMI-CIRCLE. THEY ALSO SHOW A CLEAR
BROADENING OF THE RADIUS OF MAXIMUM WINDS. THESE VARIOUS DATA ENABLE
US TO ESTIMATE THAT GRANT IS AT SEVERE TROPICAL STORM STAGE WITH
MAXIMUM WINDS OF 55 KT IN THE NORTHWEST QUADRANT. IN ADDITION, THE
SYSTEM'S MOVEMENT HAS CONTINUED TO SLOW DOWN AND HAS BEGUN A WEST TO
WEST-NORTHWEST TURN.
IN TERMS OF TRACK FORECAST, THE SYSTEM'S SLOWDOWN WILL CONTINUE
THROUGH FRIDAY WITH A TEMPORARY WEST-NORTHWESTWARD TURN DRIVEN BY THE
BUILDING OF A RIDGE LOCATED TO THE WEST THAT WILL GRADUALLY SLIDE
SOUTH OF THE SYSTEM. FROM SATURDAY, AS THE RIDGE RETRACTS TO THE
SOUTH-SOUTHEAST, THE TRACK IS EXPECTED TO SHIFT WEST TO
WEST-SOUTHWESTWARDS. THERE REMAINS SIGNIFICANT UNCERTAINTY BOTH IN
TERMS OF FORWARD SPEED AND NORTH-SOUTH SPREAD.
IN TERMS OF INTENSITY, ENVIRONMENTAL CONDITIONS ARE BECOMING
UNFAVORABLE WITH STRONGER AND MORE IMPACTFUL SHEAR IN CONNECTION WITH
THE SYSTEM'S SLOWDOWN. THIS WILL LEAD TO DRY AIR DISRUPTION AND RAPID
WEAKENING UNTIL SATURDAY, WITH GRANT EXPECTED TO WEAKEN TO TROPICAL
DEPRESSION STAGE. THERE REMAINS HIGH UNCERTAINTY ABOUT THE INTENSITY
FORECAST, CLOSELY LINKED TO THE MOTION'S SPEED, WHICH MAKE THE SYSTEM
MORE OR LESS ESCAPE THE EFFECTS OF SHEAR AND DRY AIR INTRUSIONS. FROM
SUNDAY OR MONDAY, CONDITIONS COULD IMPROVE SLIGHTLY, AS THE
ENVIRONMENT BECOMES MOISTER AND WITH VERY WARM UNDERLYING SST. BUT
THE PERSISTENCE OF A SOUTH TO SOUTHEASTERLY SHEAR AND THE LACK OF
SURFACE CONVERGENCE COULD LIMIT CHANCES OF REINTENSIFICATION. THERE
IS A LOT OF SPREAD BETWEEN MODELS, WITH SOME (INCLUDING GFS)
FORECASTING REINTENSIFICATION AND OTHERS (SUCH AS IFS) FAVORING A
FILLING OF THE SYSTEM. IN THIS CONTEXT, THE RSMC PERSISTS FORECASTING
NO SIGNIFICANT REINTENSIFICATION, LEAVING THE SYSTEM AT A RELATIVELY
WEAK STAGE UNTIL TUESDAY, ALTHOUGH THIS WILL NEED TO BE CONFIRMED.
NO SIGNIFICANT IMPACT IS EXPECTED ON THE MAIN ISLANDS OF THE
MASCAREIGNES OVER THE NEXT 72 HOURS.
IN SAINT BRANDON, AS THE SYSTEM IS FORECAST TO PASS CLOSE BETWEEN
SUNDAY AND MONDAY, AT TROPICAL DEPRESSION STAGE ACCORDING TO THE
CURRENT FORECAST, HEAVY THUNDERY SHOWERS ARE EXPECTED. THE
PROBABILITY OF GALE-FORCE WINDS IS ESTIMATED TO BE LOW ACCORDING TO
THE CURRENT FORECAST, BUT GIVEN THE FORECAST UNCERTAINTY, THIS WILL
NEED TO BE CONFIRMED. |
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楼主: Ck.
发表于 2025-12-31 10:25
