Tropical Cyclone Zena

[Nev]

RSMC Nadi expect to name the TD currently crossing northern Vanuatu by tomorrow morning…

TROPICAL DISTURBANCE ADVISORY NUMBER A4 ISSUED FROM RSMC NADI
Apr 050808 UTC.

TROPICAL DEPRESSION TD16F CENTRE 999HPA WAS ANALYSED NEAR 14.8S
166.4E AT 050600UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY
AND PERIPHERAL SURFACE REPORTS. DEPRESSION MOVING EAST-SOUTHEAST AT
ABOUT 12 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE
ESTIMATED AT ABOUT 30 KNOTS.

DEEP CONVECTION HAS INCREASED WITH BANDS TRYING TO WRAP AROUND LLCC.
ORGANIZATION HAS IMPROVED IN THE LAST 24 HOURS. CYCLONIC CIRCULATION
EXTENDS TO 500 HPA. SST AROUND 31 DEGREE CELCIUS. SYSTEM LIES JUST
SOUTH OF AN UPPER RIDGE IN A LOW TO MODERATE SHEARED ENVIRONMENT.
OUTFLOW GOOD TO THE EAST. SYSTEM IS BEING STEERED TO THE
EAST-SOUTHEAST BY THE NEAR EQUATORIAL RIDGE TO THE NORTHEAST. DVORAK
ANALYSIS BASED ON 0.45 WRAP YIELDS A DT=2.5, MET AND PT AGREE. FT
BASED ON DT THUS, YEILDING T2.5/2.5/D1.0/24HRS.

GLOBAL SYSTEMS HAVE PICKED UP ON THE SYSTEM AND MAINTAIN A
EAST-SOUTHEAST MOVEMENT WITH FURTHER INTENSIFICATION.

POTENTIAL FOR TD16F TO DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 9
TO 12 HOURS IS HIGH.

FORECASTS :
AT 12 HRS VALID AT 051800 UTC 16.6S 170.3E MOV ESE AT 20KT WITH 35 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 060600 UTC 19.9S 174.5E MOV ESE AT 20KT WITH 45 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 061800 UTC 18.7S 178.5E MOV ESE AT 20KT WITH 45 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 070600 UTC 19.1S 178.0W MOV E AT 18KT WITH 35 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON TD16F WILL BE ISSUED AROUND
051400 UTC.

[Nev]

JTWC tonight referring to the Vanuatu low as a TC (based on 1-minute wind-speeds)…

WTPS31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (EIGHTEEN) WARNING NR 001//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/042121ZAPR2016//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. TROPICAL CYCLONE 18P (EIGHTEEN) WARNING NR 001
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
050600Z --- NEAR 14.8S 166.4E
MOVEMENT PAST SIX HOURS - 110 DEGREES AT 18 KTS
POSITION ACCURATE TO WITHIN 045 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
…
REMARKS:
050900Z POSITION NEAR 15.3S 167.3E.
TROPICAL CYCLONE (TC) 18P (EIGHTEEN), LOCATED APPROXIMATELY 718 NM
WEST-NORTHWEST OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT
18 KNOTS OVER THE PAST SIX HOURS. CURRENTLY THE SYSTEM IS TRACKING
OVER THE NORTHERN SECTION OF THE ISLAND OF ESPIRITU SANTO. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL
CIRCULATION CENTER WITH IMPROVED DEEP CONVECTIVE BANDING. A 050700Z
SSMIS 91GHZ IMAGE SHOWS A COMPACT CONVECTIVE CORE WITH DEEP
CONVECTIVE BANDING WRAPPING TIGHTLY AROUND A WELL-DEFINED CENTER.
SURFACE OBSERVATIONS FROM NVSS (91554) INDICATE EASTERLY SUSTAINED
WINDS OF 21 KNOTS WITH SLP NEAR 998MB (HOWEVER, THIS SITE IS LOCATED
ON THE SOUTHEAST CORNER OF ESPIRITU SANTO THUS LIKELY SHIELDED BY
THE 5000 TO 6000 FOOT NORTH-SOUTH ORIENTED MOUNTAIN RANGE ALONG THE
WEST COAST). THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON
DVORAK ESTIMATES OF 35 KNOTS FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS
INDICATES A FAVORABLE ENVIRONMENT WITH LOW-MODERATE (10 TO 20 KNOTS)
VERTICAL WIND SHEAR (VWS) AND RADIAL OUTFLOW. TC 18P IS FORECAST TO
TRACK EAST-SOUTHEASTWARD TO EASTWARD THROUGH THE FORECAST PERIOD AS
IT TRACKS WITHIN ENHANCED FLOW BETWEEN THE SUBTROPICAL RIDGE AND A
BROAD SHORTWAVE TROUGH. DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT,
THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. TC
18P IS FORECAST TO INTENSIFY THROUGH TAU 24 UNDER FAVORABLE
CONDITIONS. AFTER TAU 24, INCREASING VERTICAL WIND SHEAR ASSOCIATED
WITH THE SUBTROPICAL WESTERLIES WILL SERVE TO RAPIDLY WEAKEN THE
SYSTEM LEADING TO DISSIPATION BY TAU 48. AFTER TAU 48, THE REMNANTS
ARE EXPECTED TO BECOME QUASI-STATIONARY IN THE FIJI REGION AS A LOW-
LEVEL HIGH BUILDS IN. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 050600Z IS
12 FEET. NEXT WARNINGS AT 052100Z AND 060900Z.

[Nev]

TC Zena was named by RSMC Nadi earlier this morning…

TROPICAL DISTURBANCE ADVISORY NUMBER A5 ISSUED FROM RSMC NADI
Apr 051359 UTC.

TROPICAL CYCLONE ZENA CENTRE 992HPA CATEGORY 1 WAS LOCATED NEAR 15.4S
167.9E AT 051200UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 16
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 40 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT WITH PRIMARY BAND WRAPPING TIGHTLY
AROUND LLCC. ORGANIZATION HAS IMPROVED IN THE LAST 24 HOURS. CYCLONIC
CIRCULATION EXTENDS TO 500 HPA. SST AROUND 31 DEGREE CELCIUS. SYSTEM
LIES JUST SOUTH OF AN UPPER RIDGE AND IN A LOW TO MODERATE SHEARED
ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH AND EAST. SYSTEM IS BEING
STEERED TO THE EAST-SOUTHEAST BY THE DEEP LAYER MEAN WEST-NORTHWEST
WIND FLOW. DVORAK ANALYSIS BASED ON 0.6 WRAP YIELDS A DT=3.0, MET AND
PT AGREE. FT BASED ON DT THUS, YEILDING T3.0/3.0/D1.5/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH FURTHER
INTENSIFICATION THEN GRADUAL WEAKENING AFTER 30 HOURS.

FORECASTS :
AT 12 HRS VALID AT 060000 UTC 16.9S 171.5E MOV ESE AT 19KT WITH 50 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 061200 UTC 18.3S 175.7E MOV ESE AT 20KT WITH 50 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 070000 UTC 19.2S 179.9E MOV ESE AT 20KT WITH 40 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 071200 UTC 19.5S 176.2W MOV E AT 19KT WITH 35 KT
CLOSE TO CENTRE

[Manukau heads obs]

at least once it moves through it will mop up all the rain associated with the slow moving ITCZ that has been bringing flooding rain to Fiji for days now

[Nev]

Could be more flooding along with high winds before Zena passes Fiji.

RSMC Nadi upgraded Zena to Cat 2 this morning and expect her to get close to Cat 3 later today…

TROPICAL DISTURBANCE ADVISORY NUMBER A6 ISSUED FROM RSMC NADI
Apr 052029 UTC.

TROPICAL CYCLONE ZENA CENTRE 988HPA CATEGORY 2 WAS LOCATED NEAR 16.5S
170.6E AT 051800UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 19
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 50 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT WITH PRIMARY BAND WRAPPING TIGHTLY
AROUND LLCC. ORGANIZATION HAS IMPROVED IN THE LAST 24 HOURS. CYCLONIC
CIRCULATION EXTENDS TO 300 HPA. SST AROUND 31 DEGREE CELCIUS. SYSTEM
LIES JUST SOUTH OF AN UPPER RIDGE AND IN A LOW TO MODERATE SHEARED
ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH AND EAST. SYSTEM IS BEING
STEERED TO THE EAST-SOUTHEAST BY THE DEEP LAYER MEAN WEST-NORTHWEST
WIND FLOW. DVORAK ANALYSIS BASED ON 0.85 WRAP YIELDS A DT=3.5, MET
AND PT AGREE. FT BASED ON DT THUS, YEILDING T3.5/3.5/D1.5/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH FURTHER
INTENSIFICATION.

FORECASTS :
AT 12 HRS VALID AT 060600 UTC 17.9S 174.3E MOV ESE AT 19KT WITH 60 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 061800 UTC 19.0S 178.4E MOV ESE AT 20KT WITH 60 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 070600 UTC 19.4S 178.0W MOV ESE AT 19KT WITH 60 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 071800 UTC 19.2S 175.1W MOV E AT 17KT WITH 60 KT
CLOSE TO CENTRE

WTPS31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (ZENA) WARNING//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 002
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
051800Z --- NEAR 16.6S 170.3E
MOVEMENT PAST SIX HOURS - 115 DEGREES AT 23 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
…
REMARKS:
052100Z POSITION NEAR 17.0S 171.3E. TROPICAL CYCLONE (TC) 18P
(ZENA), LOCATED APPROXIMATELY 472 NM WEST OF SUVA, FIJI, HAS TRACKED
EAST-SOUTHEASTWARD AT 23 KNOTS OVER THE PAST SIX HOURS. ANIMATED
INFRARED SATELLITE IMAGERY DEPICTS A TIGHT LOW-LEVEL CIRCULATION
CENTER SURROUNDED BY DEEP CONVECTIVE BANDING. A 051701Z SSMIS 91GHZ
IMAGE SHOWS A VERY COMPACT CONVECTIVE CORE WITH A WELL-DEFINED
MICROWAVE EYE FEATURE. THE INITIAL INTENSITY IS ASSESSED AT 65 KNOTS
BASED ON DVORAK ESTIMATES OF T4.0 FROM ALL AGENCIES. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW-MODERATE (10 TO
20 KNOTS)VERTICAL WIND SHEAR (VWS) WITH GOOD POLEWARD OUTFLOW. TC
18P IS FORECAST TO TRACK EAST-SOUTHEASTWARD TO EASTWARD THROUGH THE
FORECAST PERIOD AS IT TRACKS WITHIN ENHANCED FLOW BETWEEN THE
SUBTROPICAL RIDGE AND A BROAD SHORTWAVE TROUGH. DYNAMIC GUIDANCE IS
IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK. TC 18P IS FORECAST TO INTENSIFY SLIGHTLY THROUGH TAU
12 UNDER FAVORABLE CONDITIONS. AFTER TAU 12, INCREASING VWS
ASSOCIATED WITH THE SUBTROPICAL WESTERLIES WILL SERVE TO RAPIDLY
WEAKEN THE SYSTEM LEADING TO DISSIPATION BY TAU 48. AFTER TAU 48,
THE REMNANTS OF TC 18P ARE EXPECTED TO BECOME QUASI-STATIONARY EAST
OF FIJI, AS A LOW-LEVEL RIDGE BUILDS IN. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 051800Z IS 18 FEET. NEXT WARNINGS AT 060300Z, 060900Z,
061500Z AND 062100Z.//

[Manukau heads obs]

they don't need the wind...saturated ground..could loose even more trees...
and not to mention damage to crops just getting going from TC Winston

[jamie]

Could be a fun ride on the tourist hot spot, Coral Coast.

[Nev]

TC Zena was upgraded to Cat 3 earlier this afternoon, while sporting a visible pinhole eye…

HURRICANE WARNING 014 ISSUED FROM RSMC NADI Apr 060056 UTC.

TROPICAL CYCLONE ZENA CENTRE 983HPA CATEGORY 3 WAS LOCATED NEAR 17.5 SOUTH 172.4
EAST AT 060000 UTC.POSITION FAIR.
REPEAT POSITION 17.5S 172.4E AT 060000 UTC.
CYCLONE MOVING EAST-SOUTHEAST AT 22 KNOTS.
EXPECT SUSTAINED WINDS OF 65 KNOTS CLOSE TO THE CENTRE.
...

TROPICAL DISTURBANCE ADVISORY NUMBER A7 ISSUED FROM RSMC NADI
Apr 060313 UTC.

TROPICAL CYCLONE ZENA CENTRE 983HPA CATEGORY 3 WAS LOCATED NEAR 17.5S
172.4E AT 060000UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 22
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 65 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT WITH EYE DISCERNIBLE ON VIS
IMAGERY. ORGANIZATION HAS HAS GREATLY IMPROVED IN THE LAST 24 HOURS.
CYCLONIC CIRCULATION EXTENDS TO 300 HPA. SST AROUND 31 DEGREE
CELCIUS. SYSTEM LIES JUST SOUTH OF AN UPPER RIDGE AND IN A LOW TO
MODERATE SHEARED ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH AND EAST.
SYSTEM IS BEING STEERED TO THE EAST-SOUTHEAST BY THE DEEP LAYER MEAN
WEST-NORTHWEST WIND FLOW. DVORAK ANALYSIS BASED ON B EYE IN B LARGE
SURR WITH -1.0 ADJUSTMENT DUE TO W RING YIELDS A DT=4.5, MET AND PT
AGREE. FT BASED ON DT THUS, YEILDING T4.5/4.5/D2.0/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH SOME MODELS
INDICATING FURTHER INTENSIFICATION.

FORECASTS :
AT 12 HRS VALID AT 061200 UTC 19.0S 176.8E MOV ESE AT 22KT WITH 65 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 070000 UTC 19.8S 178.7W MOV ESE AT 22KT WITH 65 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 071200 UTC 20.1S 174.4W MOV ESE AT 21KT WITH 65 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 080000 UTC 20.5S 170.4W MOV E AT 21KT WITH 65 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON ZENA WILL BE ISSUED AROUND
060800 UTC.

[Nev]

JTWC had Zena bordering Cat 4 this afternoon as it nears Fiji…

WTPS31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (ZENA) WARNING NR 003//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 003
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
060000Z --- NEAR 17.7S 172.8E
MOVEMENT PAST SIX HOURS - 115 DEGREES AT 26 KTS
POSITION ACCURATE TO WITHIN 015 NM
POSITION BASED ON EYE FIXED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
…
REMARKS:
060300Z POSITION NEAR 18.1S 173.9E.
TROPICAL CYCLONE (TC) 18P (ZENA), LOCATED APPROXIMATELY 321 NM WEST
OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 26 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY REVEALS A
5 NM WIDE PINHOLE EYE FEATURE WITH PERSISTENT, DEEP CONVECTION
AROUND THE SYSTEM, WHICH SUPPORTS THE CURRENT BEST TRACK POSITION
WITH HIGH CONFIDENCE. A 052214Z AMSU 89 GHZ IMAGE DEPICTS TIGHTLY
CURVED CONVECTIVE BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER. THE CURRENT INTENSITY IS ASSESSED AT 90 KNOTS
AND IS SUPPORTED BY AGENCY DVORAK VALUES OF T5.0 FROM PGTW AND KNES.
THE UPPER LEVEL ENVIRONMENT REMAINS FAVORABLE WITH DUAL CHANNEL
OUTFLOW AND MODERATE (15 TO 25 KNOTS) VERTICAL WIND SHEAR (VWS). TC
ZENA IS TRACKING WITHIN ENHANCED FLOW BETWEEN THE SUBTROPICAL RIDGE
AND A BROAD SHORTWAVE TROUGH. THIS SYSTEM IS FORECAST TO CONTINUE
TRACKING EAST-SOUTHEASTWARD AND THEN EASTWARD WITHIN THIS ENHANCED
WESTERLY FLOW THROUGHOUT THE FORECAST PERIOD. TC 18P WILL WEAKEN
RAPIDLY OVER THE NEXT 48 HOURS AS VWS BECOMES UNFAVORABLE. THE
SYSTEM IS FORECAST TO BEGIN SUBTROPICAL TRANSITION AT TAU 36 AND
COMPLETE SUBTROPICAL TRANSITION BY TAU 48, AS IT BECOMES FULLY
EMBEDDED WITHIN THE SUBTROPICAL TROUGH. DYNAMIC MODEL GUIDANCE IS IN
EXCELLENT AGREEMENT ON THE TRACK OF TC ZENA, LENDING TO HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 060000Z IS 22 FEET. NEXT WARNINGS AT 060900Z, 061500Z,
062100Z AND 070300Z.//

[Manukau heads obs]

sea surface temperatures have been above normal in the area for a while now, so it will be taping into that energy

[Nev]

Looks like Fiji's main islands may be spared the worst of this midget's fury as she brushes just to the south the them. Zena also looks to have weakened slightly and eye has become cloud filled as she encounters increasing shear and SST's lowering to around 29C…

TROPICAL DISTURBANCE ADVISORY NUMBER A8 ISSUED FROM RSMC NADI
Apr 060808 UTC.

TROPICAL CYCLONE ZENA CENTRE 975HPA CATEGORY 3 WAS LOCATED NEAR 18.7S
175.4E AT 060600UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 25
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 70 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT. EYE HAS BECOME CLOUD FILLED.
ORGANIZATION REMAINS GOOD. CYCLONIC CIRCULATION EXTENDS TO 300 HPA.
SST AROUND 29 DEGREE CELCIUS. SYSTEM LIES SOUTH OF AN UPPER RIDGE AND
IN A MODERATE TO HIGH SHEARED ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH.
SYSTEM IS BEING STEERED TO THE EAST-SOUTHEAST BY THE DEEP LAYER MEAN
WEST-NORTHWEST WIND FLOW. DVORAK ANALYSIS BASED ON EMBEDDED CENTRE
PATTERN WITH LLCC EMBEDDED IN LG YIELDS A DT=4.5, MET=4.0 AND PT=4.5.
FT BASED ON DT THUS, YEILDING T4.5/4.5/D2.0/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH GRADUALL
WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 061800 UTC 19.4S 177.9E MOV ESE AT 25KT WITH 70 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 070600 UTC 20.6S 175.2W MOV E AT 22KT WITH 60 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 071800 UTC 21.2S 170.7W MOV E AT 21KT WITH 55 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 080600 UTC 21.8S 166.7W MOV E AT 21KT WITH 35 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON ZENA WILL BE ISSUED AROUND
061400 UTC.

WTPS31 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (ZENA) WARNING NR 004//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 004
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
060600Z --- NEAR 18.5S 175.1E
MOVEMENT PAST SIX HOURS - 110 DEGREES AT 23 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
…
REMARKS:
060900Z POSITION NEAR 18.8S 176.3E.
TROPICAL CYCLONE (TC) 18P (ZENA), LOCATED APPROXIMATELY 190 NM WEST
OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 23 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES A
GENERAL WEAKENING TREND WITH DECAYING CORE CONVECTION AND THE LOSS
OF THE VISIBLE EYE FEATURE, THEREFORE, DVORAK INTENSITY ESTIMATES
HAVE DECREASED TO 4.5 (77 KNOTS). CONSEQUENTLY, THE INITIAL
INTENSITY IS NOW ASSESSED AT 80 KNOTS. UPPER-LEVEL ANALYSIS
INDICATES INCREASING WESTERLY VERTICAL WIND SHEAR (VWS) AT MODERATE
TO STRONG LEVELS (20 TO 30 KNOTS), HOWEVER, OUTFLOW HAS REMAINED
ROBUST. TC 18P IS TRACKING QUICKLY EAST-SOUTHEASTWARD UNDER ENHANCED
FLOW BETWEEN THE SUBTROPICAL RIDGE AND A BROAD TROUGH, AND IS
FORECAST TO CONTINUE TRACKING EAST-SOUTHEASTWARD THROUGH THE
FORECAST PERIOD. TC 18P IS FORECAST TO WEAKEN THROUGH THE FORECAST
PERIOD AS IT ENCOUNTERS INCREASING VWS ASSOCIATED WITH SUBTROPICAL
WESTERLY FLOW. THE SYSTEM IS FORECAST TO TRANSITION TO A SUBTROPICAL
LOW BY TAU 48, HOWEVER, TC 18P MAY WEAKEN BELOW 35 KNOTS AFTER TAU
36. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT OVERALL, THEREFORE
THERE IS HIGH CONFIDENCE IN THE OFFICIAL FORECAST. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 060600Z IS 22 FEET. NEXT WARNINGS AT
061500Z, 062100Z, 070300Z AND 070900Z.//
NNNN

[Nev]

Fast moving Zena looks to have just brushed Fiji's forth largest island of Kadavu. She continued to weaken last night, due to increased wind-shear and convection is displaced to the SE of her LLCC. Zena is currently nearing Tonga.

TROPICAL DISTURBANCE ADVISORY NUMBER A9 ISSUED FROM RSMC NADI
Apr 061358 UTC.

TROPICAL CYCLONE ZENA CENTRE 980HPA CATEGORY 3 WAS LOCATED NEAR 19.7S
178.1E AT 061200UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 25
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 65 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT. CLOUD TOPS COOLING PAST 3 HOURS.
ORGANIZATION REMAINS GOOD. CYCLONIC CIRCULATION EXTENDS TO 300 HPA.
SST AROUND 29 DEGREE CELCIUS. SYSTEM LIES SOUTH OF AN UPPER RIDGE AND
IN A HIGH SHEARED ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH. SYSTEM IS
BEING STEERED TO THE EAST-SOUTHEAST BY THE DEEP LAYER MEAN
WEST-NORTHWEST WIND FLOW. DVORAK ANALYSIS BASED ON EMBEDDED CENTRE
PATTERN WITH LLCC EMBEDDED IN MG YIELDS A DT=4.0, MET AND PT AGREE.
FT BASED ON DT THUS, YEILDING T4.0/4.5/D1.0/24HRS. CI HELD AT 4.5 DUE
TO CI RULE FOR INITIAL WEAKENING.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH GRADUALL
WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 070000 UTC 21.0S 177.1W MOV ESE AT 24KT WITH 55 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 071200 UTC 21.6S 172.6W MOV E AT 22KT WITH 40 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 080000 UTC 22.5S 168.0W MOV ESE AT 21KT WITH 30 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 081200 UTC 23.7S 163.9W MOV ESE AT 21KT WITH 25 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON ZENA WILL BE ISSUED AROUND
062000 UTC.

WTPS31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (ZENA) WARNING NR 005//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 005
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
061200Z --- NEAR 19.4S 177.4E
MOVEMENT PAST SIX HOURS - 115 DEGREES AT 24 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
…
REMARKS:
061500Z POSITION NEAR 19.7S 178.6E.
TROPICAL CYCLONE (TC) 18P (ZENA), LOCATED APPROXIMATELY 96 NM
SOUTHWEST OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 24 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
INDICATES A RAPIDLY WEAKENING SYSTEM WITH DECAYING DEEP CONVECTION
SHEARED EAST OF THE CENTER. DVORAK INTENSITY ESTIMATES HAVE
DECREASED TO 4.0 (65 KNOTS) AND THE INITIAL INTENSITY IS NOW
ASSESSED AT 65 KNOTS. UPPER-LEVEL ANALYSIS INDICATES INCREASING
WESTERLY VERTICAL WIND SHEAR (VWS) AT STRONG LEVELS (30 TO 40 KNOTS)
PARTIALLY OFFSET BY ROBUST POLEWARD OUTFLOW. TC 18P IS TRACKING
QUICKLY EAST-SOUTHEASTWARD UNDER ENHANCED FLOW BETWEEN THE
SUBTROPICAL RIDGE AND A BROAD TROUGH, AND IS FORECAST TO CONTINUE
TRACKING EAST-SOUTHEASTWARD THROUGH THE FORECAST PERIOD. TC 18P IS
FORECAST TO WEAKEN THROUGH THE FORECAST PERIOD AS IT ENCOUNTERS
INCREASING VWS ASSOCIATED WITH SUBTROPICAL WESTERLY FLOW. THE SYSTEM
IS FORECAST TO TRANSITION TO A SUBTROPICAL LOW BY TAU 36, HOWEVER,
TC 18P MAY WEAKEN BELOW 35 KNOTS AFTER TAU 24. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT OVERALL, THEREFORE THERE IS HIGH
CONFIDENCE IN THE OFFICIAL FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 061200Z IS 20 FEET. NEXT WARNINGS AT 062100Z, 070300Z, 070900Z
AND 071500Z.//

[Nev]

Zena was downgraded to Cat 2 by RSMC Nadi a few hours ago…

Special Weather Bulletin Number THIRTY TWO FOR HEAVY RAIN ISSUED FROM RSMC NADI AT 3.30AM on THURSDAY the 07TH of April 2016.

HEAVY RAIN WARNING CANCELLATION.

A HEAVY RAIN WARNING PREVIOUSLY IN FORCE FOR THE FIJI GROUP IS NOW CANCELLED.

SITUATION:
TROPICAL CYCLONE ZENA CATEGORY 2 WAS ANALYSED NEAR 19.9S 179.1E OR ABOUT 140KM SOUTHWEST OF KADAVU AT 3AM TODAY.
ZENA MOVING EAST-SOUTHEAST AT ABOUT 47KM/HR AWAY FROM FIJI.
RAIN BANDS ASSOCIATED WITH TROPICAL CYCLONE ZENA EXPECTED TO AFFECT PARTS OF FIJI TILL AFTERNOON.

FORECAST FOR THE FIJI GROUP:
OCCASIONAL RAIN AND SQUALLY THUNDERSTORMS OVER SOUTHERN LAU GROUP.ELSEWHERE, FINE APART FROM BRIEF SHOWERS AND ISOLATED THUNDERSTORMS.

[Nev]

Interesting that although shear is high and convection is slightly displaced to the east of Zena's LLCC, the shear is also aligned with Zena's forward motion, thereby mitigating the shear's effect to some degree and 'allowing TC Zena to maintain intensity for longer than would otherwise be expected in such an environment'.

TROPICAL DISTURBANCE ADVISORY NUMBER A10 ISSUED FROM RSMC NADI
Apr 062048 UTC.

TROPICAL CYCLONE ZENA CENTRE 985HPA CATEGORY 2 WAS LOCATED NEAR 20.1S
179.0W AT 061800UTC. POSITION FAIR BASED ON HR HIMAWARI-8 IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT ABOUT 25
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 60 KNOTS.

DEEP CONVECTION REMAINS PERSISTENT BUT IS SLIGHTLY DISPLACED TO THE
EAST OF SUPPOSED LLCC. ORGANIZATION REMAINS GOOD. CYCLONIC
CIRCULATION EXTENDS TO 300 HPA. SST AROUND 29 DEGREE CELCIUS. SYSTEM
LIES SOUTH OF AN UPPER RIDGE AND IN A HIGH SHEARED ENVIRONMENT.
OUTFLOW GOOD TO THE SOUTH. SYSTEM IS BEING STEERED TO THE
EAST-SOUTHEAST BY A WEST-NORTHWEST DEEP LAYER MEAN FLOW. DVORAK
ANALYSIS BASED ON EMBEDDED CENTRE PATTERN WITH LLCC EMBEDDED IN 0W
YIELDS A DT=3.5, MET AND PT AGREE. CI HELD HIGHER FOR WEAKENING
TREND. FT BASED ON MET THUS, YIELDING T3.5/4.0/S0.0/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH FURTHER
WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 070600 UTC 21.0S 174.3W MOV E AT 22KT WITH 50 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 071800 UTC 21.4S 169.9W MOV E AT 21KT WITH 40 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 080600 UTC 21.9S 165.9W MOV E AT 21KT WITH 35 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 081800 UTC 22.6S 162.6W MOV E AT 19KT WITH 30 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON ZENA WILL BE ISSUED AROUND
070200 UTC.

WTPS31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (ZENA) WARNING NR 006//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 006
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
061800Z --- NEAR 20.5S 178.7W
MOVEMENT PAST SIX HOURS - 105 DEGREES AT 31 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
…
REMARKS:
062100Z POSITION NEAR 20.8S 177.2W.
TROPICAL CYCLONE 18P (ZENA), LOCATED APPROXIMATELY 218 NM
SOUTHEAST OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 31
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
INDICATES THAT TC ZENA (18P) CONTINUES TO RAPIDLY WEAKEN. A 1759Z
91GHZ MICROWAVE IMAGE SHOWS THAT THE DEEP CONVECTION IS SHEARED EAST
OF A WEAK LOW LEVEL CIRCULATION CENTER (LLCC) WITH NO CONVECTIVE
BANDING EVIDENT. INITIAL INTENSITY IS ASSESSED AT 55 KNOTS BASED ON
DVORAK DT ESTIMATES OF 3.5 FROM BOTH PGTW AND KNES. UPPER-LEVEL
ANALYSIS INDICATES TC ZENA IS CURRENTLY IN AN AREA OF HIGH (40-50
KNOTS) NORTHWESTERLY ENVIRONMENTAL VERTICAL WIND SHEAR (VWS).
HOWEVER, AS THE STORM MOTION VECTOR IS ALIGNED WITH THE SHEAR
VECTOR, THE EFFECTIVE SHEAR VALUE IS LOWER AT AROUND 20-25 KNOTS.
THE LOWER EFFECTIVE VWS VALUE IS ALLOWING TC ZENA TO MAINTAIN
INTENSITY FOR LONGER THAN WOULD OTHERWISE BE EXPECTED IN SUCH AN
ENVIRONMENT. TC ZENA IS TRACKING RAPIDLY EAST-SOUTHEASTWARD UNDER
THE ENHANCED FLOW BETWEEN THE SUBTROPICAL RIDGE (STR) TO THE NORTH
AND A BROAD TROUGH TO THE SOUTHWEST AND IS FORECAST TO CONTINUE THIS
TRACK MOTION THROUGH THE FORECAST PERIOD. THE SYSTEM WILL CONTINUE
TO WEAKEN AS IT ENCOUNTERS STEADILY INCREASING VWS ASSOCIATED WITH
MID-LATITUDE WESTERLY FLOW AND WILL DISSIPATE OVER WATER BY TAU 24.
WHILE DISSIPATING, TC ZENA WILL SIMULTANEOUSLY UNDERGO TRANSITION TO
A SUBTROPICAL LOW BUT WILL COMPLETE DISSIPATION FIRST, BEFORE
COMPLETING SUBTROPICAL TRANSITION. DYNAMIC MODEL GUIDANCE IS IN GOOD
AGREEMENT OVERALL, THEREFORE THERE IS HIGH CONFIDENCE IN THE
OFFICIAL FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 061800Z IS 18
FEET. NEXT WARNINGS AT 070300Z, 070900Z AND 071500Z.//

[Nev]

TC Zena was downgraded to Cat 1 this evening after passing just to the south of Tonga's main island around midday as a Cat 2…

WTPS31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL CYCLONE 18P (ZENA) WARNING NR 007
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
070000Z --- NEAR 21.5S 176.0W
MOVEMENT PAST SIX HOURS - 110 DEGREES AT 27 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
…
REMARKS:
070300Z POSITION NEAR 21.7S 174.7W.
TROPICAL CYCLONE (TC) 18P (ZENA), LOCATED APPROXIMATELY 56 NM WEST-
SOUTHWEST OF TONGA, HAS TRACKED EAST-SOUTHEASTWARD AT 27 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A DETERIORATING CONVECTIVE STRUCTURE PARTIALLY OBSCURING A
POORLY DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WHICH LEADS TO
LOW CONFIDENCE IN THE CURRENT POSITION. THE INITIAL INTENSITY HAS
BEEN LOWERED TO 50 KNOTS BASED ON DECREASING DVORAK INTENSITY
ESTIMATES FROM ALL AGENCIES AND SUPPORTS THE CURRENT STATE OF THE
CYCLONE. THE SYSTEM IS TRACKING IN A POOR ENVIRONMENT WITH 40 TO 50
KNOT NORTHWESTERLY VERTICAL WIND SHEAR (VWS) EASILY OFFSETTING THE
STRONG POLEWARD OUTFLOW INTO THE MID-LATITUDE WESTERLIES. HOWEVER,
THE SYSTEM IS MOVING IN-PHASE WITH THE VWS KEEPING THE LLCC
PARTIALLY UNDER THE CONVECTION. TC ZENA IS TRACKING RAPIDLY
SOUTHEASTWARD UNDER THE INFLUENCE OF THE COMBINED EFFECTS OF A SUB-
TROPICAL RIDGE TO THE NORTHEAST AND A MID-LATITUDE TROUGH TO THE
WEST. TC 18P WILL CONTINUE ON THIS COURSE AND FULLY DISSIPATE OVER
THE NEXT 24 HOURS DUE TO THE EFFECTS OF THE HIGH VWS. DYNAMIC MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THE
JTWC TRACK FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 070000Z IS
15 FEET. NEXT WARNINGS AT 070900Z, 071500Z AND 072100Z.//
NNNN

GALE WARNING 019 ISSUED FROM RSMC NADI Apr 070709 UTC.

TROPICAL CYCLONE ZENA CENTRE 995HPA CATEGORY 1 WAS LOCATED NEAR 22.0
SOUTH 173.7 WEST AT 070600 UTC.
POSITION FAIR.
REPEAT POSITION 22.0S 173.7W at 070600 UTC.
CYCLONE MOVING EAST-SOUTHEAST AT 24 KNOTS. CYCLONE WEAKENING.
EXPECT SUSTAINED WINDS OF 35 KNOTS CLOSE TO THE CENTRE DECREASING TO
30 KNOTS BY 071200 UTC.
...

TROPICAL DISTURBANCE ADVISORY NUMBER A12 ISSUED FROM RSMC NADI
Apr 070733 UTC.

TROPICAL CYCLONE ZENA CENTRE 995HPA CATEGORY 1 WAS LOCATED NEAR
22.0S 173.7W AT 070000UTC. POSITION FAIR BASED ON GOES HR IMAGERY
AND PERIPHERAL SURFACE REPORTS. CYCLONE MOVING EAST-SOUTHEAST AT
ABOUT 24 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE
ESTIMATED AT ABOUT 35 KNOTS.EXPECT WINDS 33 KNOTS WITHIN 50 NAUTICAL
MILES OF CENTRE.

LLCC WEAK AND PARTIALLY EXPOSED. DEEP CONVECTION AND ORGANISATION HAS
DECREASED SIGNIFICANTLY IN THE PAST 24 HOURS.CONVECTION DISPLACED TO
THE EAST OF LLCC.SST AROUND 26 TO 27 DEGREE CELCIUS. SYSTEM LIES
SOUTH OF AN UPPER RIDGE IN A HIGH SHEARED ENVIRONMENT. SYSTEM IS
BEING STEERED TO THE EAST-SOUTHEAST BY A WEST-NORTHWEST DEEP LAYER
MEAN FLOW. DVORAK ANALYSIS DT NOT POSSIBLE AS LLCC DISPLACED GREATER
THAN 1 1/4 DEGREE FROM STRONG TEMP GRADIENT, MET=3.0 AND PT=2.0. FT
HELD AT 2.5 DUE TO FT CONSTRAINT. THUS, YIELDING T2.5/3.0/W2.0/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEAST MOVEMENT WITH FURTHER
WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 071800 UTC 22.5S 168.6W MOV E AT 24KT WITH 30 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 080600 UTC 23.6S 163.4W MOV E AT 24KT WITH 25 KT
CLOSE TO CENTRE.

OUTLOOK :
AT 36 HRS VALID AT 081800 UTC 24.7S 158.2W MOV ESE AT 24KT WITH 20 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON ZENA WILL BE ISSUED AROUND
071400 UTC.

[jamie]

This storm has been flying by the tropics. Moving fast.


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