老農民版夜神月

基本資料  
編號              ：90 S
擾動編號日期：2019 年 04 月 21 日 03 時

撤編日期　　：2019 年 04 月 30 日 21 時

90S INVEST 190420 1800 5.0S 79.0E SHEM 15 0

MAX MFR 80 JTWC 75

霧峰追風者

The basin is in a near-equatorial trough (NET) pattern axed near 5S, with westerly winds at the
equator. Near 65E, the NET is broken into two branches, probably because of the passage of a dry
phase of a mixed Rossby-Gravity wave. A moderate convective activity is concentrated within these
two branches of NET : to the North-East of Madagasar and East of Diego Garcia. The development
of two suspect areas within both NET branches is suggested by the available guidance.

North of Madagascar :
From tomorrow, the upper divergence becomes excellent over the western NET branch. Monday, a
weak clockwise circulation could appear and gradually develop from Tuesday. Both the Euro and
American deterministic models are suggesting the formation of a significant tropical low from
Wednesday, North of the Mozambique Channel. This cyclogenesis risk is also shown within the
ensemble members of the last probabilistic runs. However, the lack of equatorward low-level
convergence could slow down the development of the system and keep it at a moderate intensity at
first.
For the next five days, the risk of formation of a moderate tropical storm becomes low
Thursday north of the Comoros archipelago.

East of Diego Garcia :
Benefiting from conducive environmental conditions aloft and from a good low-level convergence,
a clockwise circulation should emerge within the Eastern NET branch by the end of the week-end.
From Tuesday, the strengthening upper divergence should allow the development of the system. The
available guidance is in good agreement to forecast a moderate cyclogenesis risk for the second half
of next week.
For the next five days, the risk of formation of a moderate tropical storm becomes low
Wednesday then moderate from Thursday east of Diego Garcia.
The strengthening of the cyclonic activity expected next week over the basin is probably linked to
the combined passages of a Kelvin and an Equatorial Rossby waves.

霧峰追風者

JTWC 14Z評級LOW

   (1) AN AREA OF CONVECTION (INVEST 90S) HAS PERSISTED NEAR 4.2S
79.5E, APPROXIMATELY 460 NM EAST-NORTHEAST OF DIEGO GARCIA.  
ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 211208Z SSMIS 91GHZ
COLOR COMPOSITE MICROWAVE IMAGE SHOW FLARING AND DISORGANIZED
DEEP CONVECTION ASSOCIATED WITH A BROAD, SLOWLY-EVOLVING
DISTURBANCE. UPPER-LEVEL ANALYSIS SHOWS FAVORABLE CONDITIONS WITH
LOW VERTICAL WIND SHEAR (5-10 KNOTS) AND STRONG DIFFLUENCE. SEA
SURFACE TEMPERATURES ARE FAVORABLE AT 29-30C. GLOBAL MODELS INDICATE
A SOUTHEASTWARD TO SOUTHWARD TRACK OVER THE NEXT FEW DAYS WITH THE
SYSTEM REACHING TROPICAL STORM STATUS IN 60-84 HOURS. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS LOW.

霧峰追風者

JTWC 17Z評級提升至Medium

(1) THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED
NEAR 4.2S 79.5E, IS NOW LOCATED NEAR 4.0S 80.2E, APPROXIMATELY 509
NM EAST-NORTHEAST OF DIEGO GARCIA. A 211538Z ASCAT PASS REVEALS AN
AREA OF 25-30 KNOTS WINDS TO THE NORTHEAST. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY AND A 211606Z MHS 89GHZ MICROWAVE IMAGE
DEPICT A CONSOLIDATING LOW LEVEL CIRCULATION (LLC) WITH CONVECTION
AROUND THE CENTER.  UPPER-LEVEL ENVIRONMENTAL ANALYSIS SHOWS LOW
VERTICAL WIND SHEAR (5-10 KNOTS) AND A POINT SOURCE ALOFT IS
ENHANCING OUTFLOW. SEA SURFACE TEMPERATURES (28-29 CELSIUS) WILL
HELP FURTHER DEVELOPMENT. GLOBAL MODELS INDICATE SOUTHEASTWARD
INITIAL MOTION OVER THE NEXT 36-48 HOURS WITH GRADUAL
INTENSIFICATION TO TROPICAL CYCLONE STRENGTH, WITH VARYING TIME
FRAMES AND INTENSITY. IT IS POSSIBLE 90S WILL INTERACT WITH AND
ABSORB A CIRCULATION TO THE SOUTHEAST BEFORE CONSOLIDATING. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR
THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO MEDIUM.

老農民版夜神月

21/12Z,JTWC升格TD

SH, 90, 2019042100, , BEST, 0, 38S, 786E, 15, 1010, DB, 0, , 0, 0, 0, 0, 0, 0, 0, 0, 0, , 0, , 0, 0, INVEST, ,
SH, 90, 2019042106, , BEST, 0, 40S, 791E, 20, 1006, DB, 0, , 0, 0, 0, 0, 0, 0, 0, 0, 0, , 0, , 0, 0, INVEST, ,
SH, 90, 2019042112, , BEST, 0, 42S, 795E, 25, 1004, TD, 0, , 0, 0, 0, 0, 0, 0, 0, 0, 0, , 0, , 0, 0, INVEST, ,
SH, 90, 2019042118, , BEST, 0, 40S, 799E, 25, 1004, TD, 0, , 0, 0, 0, 0, 1007, 275, 80, 0, 0, S, 0, , 0, 0, INVEST, S,
SH, 90, 2019042200, , BEST, 0, 39S, 802E, 25, 1002, TD, 34, NEQ, 0, 0, 0, 0, 1005, 150, 80, 0, 0, S, 0, , 0, 0, INVEST, S,

老農民版夜神月

East of Diego Garcia :
The Ascat partial ascat data of this morning show a low level clockwise circulation (LLCC) centred
near 5S/80E with maximal winds near 25 kt within the equatorward feeding. Deep convection is
strong but very fluctuating. The last micro-wave imagery doesn't show any sign of organisation but
data from buoy nr 5601534 show a decrease MSLP. Minimal pressure is estimated at 1004 hPa.
Environmental conditions are favourable for cyclogenesis. Kelvin wave and equatorial Rossby
wave should increase low level convergence. In upper level, the LLCC should take benefit from a
weak vertical windshear while a subtropical jetstreak ondulation should improve polerward upper
level divergence. Model guidance are in good agreement to forecast a significantly deepening from
Wednesday.
For the next five days, the risk of formation of a moderate tropical storm becomes strong
Wednesday east of Diego Garcia.

老農民版夜神月

目前從定位上看過去一日系統略微東進,定強維持,數值預測此系統未來將有一定程度的發展

90S INVEST 190422 1200 5.1S 80.5E SHEM 25 1003

霧峰追風者

JTWC 23Z發佈TCFA。

WTXS22 PGTW 222300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90S)//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/221421Z APR 19//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTXS21 PGTW 221430)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
160 NM EITHER SIDE OF A LINE FROM 5.0S 80.7E TO 9.3S 84.5E WITHIN
THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE
OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE
AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IMAGERY AT
221800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 5.5S
81.1E. THE SYSTEM IS MOVING SOUTHEASTWARD AT 07 KNOTS.
2. REMARKS:
THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED NEAR 4.2S
79.5E, IS NOW LOCATED NEAR 5.5S 81.1E, APPROXIMATELY 525 NM EAST-
NORTHEAST OF DIEGO GARCIA. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER WITH
STRONG CONVECTION SHEARED TO THE SOUTH, AND TWO FRAGMENTED
FORMATIVE BANDS WRAPPING IN FROM THE SOUTH AND NORTH. THE
ENVIRONMENT IS OVERALL FAVORABLE FOR DEVELOPMENT, WITH WARM (27-29C)
SSTS AND STRONG UPPER LEVEL DIVERGENCE SLIGHTLY OFFSET BY MODERATE
TO HIGH VERTICAL WIND SHEAR (20-30 KTS) THAT DECREASES TO THE SOUTH.
GLOBAL MODELS GENERALLY AGREE ON A SOUTHEASTWARD TRACK OVER THE NEXT
FEW DAYS, WITH SOME SPREAD DUE TO VARYING DEGREES OF INTERACTION
WITH A SMALLER CIRCULATION TO THE EAST. GLOBAL MODEL TIMING FOR
DEVELOPMENT OF 35KT WINDS RANGES FROM APPROXIMATELY 12 TO 36 HOURS.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO
30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000
MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
232300Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 9.7S 51.3E (WTXS21 PGTW 221430).//
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