Update cycloon Amphan: Landfall binnen enkele uren

Hierbij de laatste update omtrent voormalig supercycloon Amphan. De storm (cat. 3) komt binnen enkele uren als een cat. 2  aan land ten zuiden van Calcutta. De gemiddelde windsnelheid is gelukkig afgenomen tot zo'n 160 km/u met stoten tot 180 km/u. Groot punt van zorg blijft de stormvloed die op sommige plaatsen 6 meter hoog zal zijn. De Golf van Bengalen werkt hierbij als soort van trechter en zorgt daarmee voor extra wateropzet. Tevens zal de zware neerslag, met op sommige plaatsen meer dan 300mm in 24  uur, voor problemen gaan zorgen. Na landfall zal de storm snel oplossen door interactie met de westelijke circulatie en terrein / reliëf en daarmee als "gewone' depressie verder gaan.

Tekst en illustraties van het JTWC

https://www.hurricanezone.net/#01b

WTIO31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 01B (AMPHAN) WARNING NR 016//
RMKS/
1. TROPICAL CYCLONE 01B (AMPHAN) WARNING NR 016   
   01 ACTIVE TROPICAL CYCLONE IN NORTHIO
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   200000Z --- NEAR 19.2N 87.4E
     MOVEMENT PAST SIX HOURS - 015 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 040 NM
     POSITION BASED ON CENTER LOCATED BY A COMBINATION OF
     SATELLITE AND RADAR
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 064 KT WINDS - 045 NM NORTHEAST QUADRANT
                            045 NM SOUTHEAST QUADRANT
                            035 NM SOUTHWEST QUADRANT
                            030 NM NORTHWEST QUADRANT
   RADIUS OF 050 KT WINDS - 095 NM NORTHEAST QUADRANT
                            095 NM SOUTHEAST QUADRANT
                            100 NM SOUTHWEST QUADRANT
                            095 NM NORTHWEST QUADRANT
   RADIUS OF 034 KT WINDS - 175 NM NORTHEAST QUADRANT
                            200 NM SOUTHEAST QUADRANT
                            150 NM SOUTHWEST QUADRANT
                            165 NM NORTHWEST QUADRANT
   REPEAT POSIT: 19.2N 87.4E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   201200Z --- 21.5N 88.1E
   MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT
                            020 NM SOUTHEAST QUADRANT
                            020 NM SOUTHWEST QUADRANT
                            010 NM NORTHWEST QUADRANT
   RADIUS OF 050 KT WINDS - 040 NM NORTHEAST QUADRANT
                            050 NM SOUTHEAST QUADRANT
                            040 NM SOUTHWEST QUADRANT
                            040 NM NORTHWEST QUADRANT
   RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT
                            160 NM SOUTHEAST QUADRANT
                            100 NM SOUTHWEST QUADRANT
                            090 NM NORTHWEST QUADRANT
   VECTOR TO 24 HR POSIT: 020 DEG/ 11 KTS
    ---
   24 HRS, VALID AT:
   210000Z --- 23.6N 88.9E
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   RADIUS OF 050 KT WINDS - 030 NM NORTHEAST QUADRANT
                            035 NM SOUTHEAST QUADRANT
                            035 NM SOUTHWEST QUADRANT
                            030 NM NORTHWEST QUADRANT
   RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT
                            130 NM SOUTHEAST QUADRANT
                            100 NM SOUTHWEST QUADRANT
                            065 NM NORTHWEST QUADRANT
   VECTOR TO 36 HR POSIT: 020 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   211200Z --- 24.9N 89.4E
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 48 HR POSIT: 040 DEG/ 06 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   220000Z --- 25.8N 90.2E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
200300Z POSITION NEAR 19.8N 87.6E.
20MAY20. TROPICAL CYCLONE 01B (AMPHAN), LOCATED APPROXIMATELY 212
NM SOUTH-SOUTHWEST OF KOLKATA, INDIA, HAS TRACKED NORTH-
NORTHEASTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY INDICATES THAT TC 01B HAS
MAINTAINED ITS OVERALL SYMMETRICAL CORE STRUCTURE THROUGH THE 0000Z
HOUR, THOUGH SUBSEQUENT IMAGERY SHOWS THAT THE CENTRAL DENSE
OVERCAST (CDO) IS STARTING ERODE ON THE NORTHEAST SIDE AND THE
SYSTEM IS BECOMING INCREASINLY RAGGED LOOKING. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON 192307Z DMSP SSMIS 37 GHZ
AND 89 GHZ COLORIZED IMAGES, SHOWING A WEAK MICROWAVE EYE IN THE
FORMER AND MUCH STRONGER MICROWAVE EYE FEATURE IN THE LATTER. RADAR
DATA FROM INDIA SUPPORTS THE ASSESSMENT OF THE MICROWAVE DATA AND
THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED WITH LOW
CONFIDENCE AT A GENEROUS 95 KNOTS BASED ON A PGTW CURRENT INTENSITY
ESTIMATE OF T5.5 (102 KNOTS), HEDGED SLIGHTLY LOWER IN LIGHT OF AN
ADVANCED DVORAK TECHNIQUE ESTIMATE OF T4.8 (87 KNOTS) AND A
SATELLITE CONSENSUS ESTIMATE OF 75 KNOTS. THE OVERALL ENVIRONMENT
REMAINS MARGINAL, WITH MODERATE (20 TO 25 KNOTS) VWS, STRONG
POLEWARD OUTFLOW AND WARM (30-31 CELSIUS) SSTS. THE SYSTEM CONTINUES
TO TRACK NORTH-NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF A DEEP-
LAYER NER CENTERED FAR TO THE EAST AND THIS TRACK MOTION IS EXPECTED
TO MAINTAIN THROUGH THE FORECAST PERIOD. SHEAR HAS BEGUN TO TAKE ITS
TOLL ON THE SYSTEM AS INDICATED BY THE EROSION OF THE CDO AND THIS
TREND IS EXPECTED TO CONTINUE OVER THE NEXT 12 HOURS, WITH AN
ADDITIONAL 10 KNOTS OF WEAKENING FORECAST PRIOR TO LANDFALL. AFTER
MAKING LANDFALL SOUTH OF KOLKATA NEAR 201200Z, THE SYSTEM WILL TRACK
INLAND WHILE RAPIDLY WEAKENING DUE TO INCREASED WESTERLY VWS AND
TERRAIN INTERACTION, BEFORE DISSIPATING BY TAU 48. DYNAMIC GUIDANCE
IS IN GOOD AGREEMENT THROUGHOUT THE FORECAST PERIOD, LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 200000Z IS 40 FEET. NEXT WARNINGS AT 200900Z, 201500Z,
202100Z AND 210300Z.//
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