Sth Pacific & Coral Sea 2015/16 TC Season

[Nev]

NIWA released their '2015/2016 Southwest Pacific Tropical Cyclone Outlook' yesterday.

Due to the expected strength of this El Nino, they expect an above average and more stronger than normal amount of TC's in the SW Pacific this season. El Nino generally means TC formation is more likely around or east the international dateline. However, increased sinuosity (irregular or looping motions rather than a curvilinear trajectory) is also associated strong El Ninos, which means northern NZ may also have a slightly higher risk than normal of being affected by an ex-TC this season.

[Nev]

RSMC Nadi and JTWC have been keeping an eye on a TD currently about 400 km NW of Fiji, which has been showing erratic intervals of convection over the last few days. Strong convection returned last night and this morning JTWC have issued a 'TC Formation Alert'…

WTPS21 PGTW 141930
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
A 200 NM RADIUS OF 12.3S 175.5E 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 151800Z INDICATES THAT A
CIRCULATION CENTER IS LOCATED NEAR 12.3S 175.7E. THE SYSTEM IS
MOVING SOUTHWARD AT 07 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 11.6S
175.6E, IS NOW LOCATED NEAR 12.3S 175.7E, APPROXIMATELY 341 NM NORTH-
NORTHWEST OF NADI. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS DEEPENING SYMMETRIC CONVECTION ASSOCIATED WITH A WELL DEFINED
LOW LEVEL CIRCULATION CENTER AS SEEN IN A 141021Z ASCAT BULLSEYE. A
141617Z MICROWAVE IMAGE REVEALS WELL DEFINED SPIRAL BANDING WITH THE
BULK OF CONVECTION ALONG THE SOUTHWESTERN PERIPHERY. UPPER-LEVEL
ANALYSIS INDICATES THE DISTURBANCE IS LOCATED IN A MARGINAL
ENVIRONMENT WITH 20 TO 25 KNOT VERTICAL WIND SHEAR BEING OFFSET BY
AN ENHANCED POLEWARD OUTFLOW CHANNEL. GLOBAL MODELS SHOW WEAK
DEVELOPMENT OF THIS SYSTEM AS IT REMAINS QUASI-STATIONARY. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. DUE TO PERSISTENT
CONVECTION AND IMPROVED ORGANIZATION, 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
151930Z.

[NZ Thunderstorm Soc]

I think that this is a load of rubbush.
I thought that more TC are more likely to form in a La Niña episode rather than El Niño, but I could be wrong?
..but put this in another way...
What is the difference between a La Nina TC period compared with a El Niño period?
More TC seems to forms from my experience from La Nina than El Niño

[Nev]

What is the difference between a La Nina TC period compared with a El Niño period?

TC's are less likely to form in the Coral Sea area during El Nino because SST's in the western tropical Pacific are cooler than normal, so eastern Australia is far less likely to be affected by TC's, while during La Nina the opposite is true. However, El Nino also means that SST's in the central tropical Pacific are warmer than normal, so we're more likely to see more TC's form near or east of the international dateline than normal. A really strong El Nino increases the chances of activity in central tropical Pacific even more, so the chances of one or two ex-TC's curving back towards NZ also increases.

P.S. The 1997–98 season was one of the most active and longest on record…

'1997-98 South Pacific cyclone season' - Wikipedia
'March 1998 Southern NZ Ex-tropical Cyclone Yali' - NIWA

[Nev]

The TD's LLCC NW of Fiji became fully exposed during the day yesterday, but convection soon returned after dark. RSMC Nadi even included a possible track-map in a press-release late yesterday. It'll be interesting to see if anything develops today…

Some updates from yesterday evening…

ABPW10 PGTW 150600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND
/SOUTH PACIFIC OCEANS/150600Z-160600ZOCT2015//
...
(1) THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 12.3S
175.7E, IS NOW LOCATED NEAR 12.3S 177.1E, APPROXIMATELY 324 NM NORTH
OF NADI, FIJI. ANIMATED MSI SHOWS A FULLY EXPOSED LLCC THAT HAS
TRACKED EAST, NORTH OF THE DEEPEST CONVECTION. HOWEVER, A 132354Z
RSCAT IMAGE SHOWS GOOD WRAPPING 15 TO 20 KNOTS OF WIND. UPPER-LEVEL
ANALYSIS INDICATES THE DISTURBANCE IS LOCATED IN A MARGINAL
ENVIRONMENT WITH 20 TO 25 KNOT VERTICAL WIND SHEAR BEING OFFSET BY
AN ENHANCED POLEWARD OUTFLOW CHANNEL. GLOBAL MODELS SHOW WEAK
DEVELOPMENT OF THIS SYSTEM AS IT REMAINS QUASI-STATIONARY. 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. SEE REF C (WTPS21 PGTW 141930) FOR FURTHER DETAILS.

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Oct 15/1023 UTC 2015 UTC.

TROPICAL DEPRESSION 02F CENTRE [1003HPA] ANALYSED NEAR 12.3S 177.5E
AT 150900UTC. TD02F SLOW MOVING. POSITION POOR BASED ON IR/EIR MTSAT
IMAGERY AND PERIPHERAL SURFACE OBSERVATION.

CONVECTION HAS INCREASED IN THE SOUTHWEST QUADRANT OF LLCC IN LAST 06
HOURS. ORGANISATION REMAINS POOR. SYSTEM LIES UNDER AN UPPER RIDGE IN
A MODERATE TO HIGH SHEARED ENVIRONMENT. CYCLONIC CIRCULATION EXTENDS
TO 700HPA. SST IS AROUND 28 DEGREES CELSIUS.

GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND SLOWLY MOVE IT SOUTHWARDS
WITH SLIGHT INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS MODERATE TO HIGH.

[Nev]

JTWC are now referring to this low as a TC, although that's based on 1-minute sustained winds rather than 10-minute winds…

WTPS31 PGTW 152100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 02P (TWO) WARNING NR 001//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/141921 OCT 15//
AMPN/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL CYCLONE 02P (TWO) 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:
151800Z --- NEAR 12.1S 177.8E
MOVEMENT PAST SIX HOURS - 025 DEGREES AT 02 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
…
REMARKS:
152100Z POSITION NEAR 12.2S 177.5E.
TROPICAL CYCLONE 02P (TWO), LOCATED APPROXIMATELY 362 NM NORTH OF
SUVA, FIJI, HAS TRACKED NORTH-NORTHEASTWARD AT 02 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
A PERSISTENT BALL OF DEEP CONVECTION ASSOCIATED WITH A CONSOLIDATED
LLCC THAT HAS REMAINED RELATIVELY QUASI-STATIONARY (QS) OVER THE
PAST 12 HOURS. A 151604Z 91 GHZ SSMIS IMAGE FURTHER REVEALS THE
TIGHTLY WRAPPED, COMPACT NATURE OF THE SYSTEM WITH THE BULK OF DEEP
CONVECTION LOCATED IN THE WESTERN QUADRANTS. A 151309 RSCAT PASS
INDICATES 30-35 KNOT WINDS SURROUNDING THE SYSTEM CENTER WHILE
DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES REMAIN AT 2.0.
THE INITIAL POSITION IS BASED ON THE AFOREMENTIONED IMAGERY WITH
GOOD CONFIDENCE. THE INITIAL INTENSITY IS BASED ON THE RSCAT IMAGE
AS WELL AS THE SATELLITE FIXES FROM PGTW AND KNES AND HEDGED ON THE
HIGHER END. UPPER LEVEL ANALYSIS INDICATES AN ENVIRONMENT
CHARACTERIZED BY MODERATE (15-20 KTS) VWS OFFSET BY STRONG POLEWARD
OUTFLOW. TC 02P IS EXPECTED TO SLOWLY MIGRATE TO THE SOUTHWEST OVER
NEXT 48 HOURS. THE SYSTEM IS EXPECTED TO REACH A PEAK INTENSITY OF
45 KNOTS AS VWS IS FORECAST TO RELAX IN THE NEAR TERM. AFTER THAT TC
02P WILL THEN DISSIPATE OVER WATER AS IT ENCOUNTERS INCREASING VWS
ALONG TRACK. DYNAMIC MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT;
HOWEVER, DUE TO THE RECENT QS MOTION OF THE SYSTEM THERE IS
CURRENTLY LOW CONFIDENCE IN THE JTWC FORECAST. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 151800Z IS 8 FEET. NEXT WARNINGS AT 160900Z AND
162100Z. THIS WARNING SUPERSEDES AND CANCELS REF A, JOINT TYPHOON
WRNCEN 141921 OCT 15 TROPICAL CYCLONE FORMATION ALERT (WTPS21 PGTW
141930).//
NNNN

[Nev]

Not surprisingly, RSMC Nadi still reluctant to call this a TC. LLCC has become exposed again this morn, although it is looking a lot more organised...

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Oct 15/2337 UTC 2015 UTC.

TROPICAL DEPRESSION 02F CENTRE [1006HPA] ANALYSED NEAR 12.3S 177.7E
AT 151800UTC. TD02F SLOW MOVING. POSITION POOR BASED ON VIS MTSAT
IMAGERY AND PERIPHERAL SURFACE OBSERVATION.

CONVECTION REMAINS PERSISTANT IN THE SOUTHWEST QUADRANT OF LLCC IN
LAST 06 HOURS. ORGANISATION HAS IMPROVED IN THE PAST 12 HOURS. SYSTEM
LIES UNDER AN UPPER RIDGE IN A MODERATE TO HIGH SHEARED ENVIRONMENT.
CYCLONIC CIRCULATION EXTENDS TO 500HPA. SST IS AROUND 28 DEGREES
CELSIUS.

GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND SLOWLY MOVE IT SOUTHWARDS
WITH SLIGHT INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS MODERATE TO HIGH.

[Nev]

RSMC Nadi issued their first advisory this arvo with estimated 10-minute central mean winds of 25 kts, so don't expect to name it until around midday tomorrow…

TROPICAL DISTURBANCE ADVISORY NUMBER A1 ISSUED FROM RSMC NADI
Oct 16/0316 UTC 2015 UTC.

TROPICAL DEPRESSION TD02F CENTRE [1003HPA] WAS LOCATED NEAR 12.9S
177.5E AT 160000 UTC. POSITION FAIR BASED ON HR GMS VIS IMAGERY AND
PERIPHERAL SURFACE REPORTS. SYSTEM IS MOVING SOUTH-SOUTHWEST AT 02
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 25 KNOTS.

ORGANISATION HAS IMPROVED IN THE PAST 24 HOURS. CONVECTION REMAINS
PERSISTENT BUT DETACHED TO EAST OF LLCC. THE SYSTEM LIES IN A
MODERATE SHEARED ENVIRONMENT AND THE SOUTH OF AN UPPER RIDGE. OUTFLOW
GOOD TO THE SOUTH DUR TO DIFFLUENT UPPER RIDGE. SST IS AROUND 28
DEGRESS CELSIUS. DVORAK ANALYSIS BASED ON 0.3 WRAP YIELDS DT=2.0, MET
AND PT AGREE. THUS, YIELDING T2.0/2.0/D0.5/24HRS.

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHWESTWARDS WITH
FURTHER INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE WITHIN
THE NEXT 18 TO 30 HOURS IS HIGH.
…

[Nev]

This low is looking a little less organised overnight. Quite a bit of disagreement between RSMC Nadi and JTWC on the strength of this storm. This morning JTWC have estimated 1-minute central mean-winds of 40 kts, while Nadi still maintain only 10-minute winds of 25 kts, and have decreased its chances of being named in the next 18 to 30 hrs to moderate, so it's looking increasingly likely that won't ever be named.

TROPICAL DISTURBANCE ADVISORY NUMBER A4 ISSUED FROM RSMC NADI
Oct 16/2021 UTC 2015 UTC.

TROPICAL DEPRESSION 02F CENTRE 1002 HPA WAS LOCATED NEAR 14.0S 176.7E
AT 161800 UTC. POSITION POOR BASED ON HR GMS IR/EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. THE SYSTEM MOVING TOWARDS SOUTHWEST AT
ABOUT 6 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE
ESTIMATED AT ABOUT 25 KNOTS.

CONVECTION REMAINS PERSISTENT BUT DETACHED TO SOUTHEAST OF LLCC.
SYSTEM LIES IN MODERATE SHEARED ENVIRONMENT AND IS MOVING TO AREA OF
INCREASING SHEAR. OUTFLOW GOOD TO SOUTH DUE TO DIFFLUENT UPPER RIDGE.
SST AROUND AROUND 28 DEGREE CELSIUS.
DVORAK ANALYSIS BASED ON 0.3 WRAP YIELDS DT2.0, MET AND PAT AGREE.
THUS YIELDING T2.0/2.0/S0.0/24HRS

GLOBAL MODELS HAVE PICKED THE SYSTEM AND AGREE ON ITS SOUTHWESTWARD
WITH SOME INTENSIFICATION. POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO
A TROPICAL CYCLONE WITHIN THE NEXT 18 TO 30 HOURS IS MODERATE.

WTPS31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 02P (TWO) WARNING NR 003//
RMKS/
1. TROPICAL CYCLONE 02P (TWO) 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:
161800Z --- NEAR 14.2S 175.3E
MOVEMENT PAST SIX HOURS - 235 DEGREES AT 13 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
…
REMARKS:
162100Z POSITION NEAR 14.7S 174.8E.
TROPICAL CYCLONE 02P (TWO), LOCATED APPROXIMATELY 294 NM
NORTHWEST OF SUVA, FIJI, HAS TRACKED SOUTHWESTWARD AT 13 KNOTS
OVER THE PAST SIX HOURS. ANIMATED IR SATELLITE IMAGERY DEPICTS
PULSING DEEP CONVECTION ASSOCIATED WITH A CONSOLIDATED AND COMPACT
LLCC. A 161757Z AMSU-B IMAGE REVEALS THE TIGHT WRAPPING OF THE LLCC
AS WELL AS THE BULK OF THE DEEP CONVECTION ALONG THE SOUTHWEST
QUADRANT OF THE SYSTEM. A 161023Z ASCAT PASS INDICATES 35-45 KT WIND
BARBS ALONG THE SOUTHERN PERIPHERY OF THE SYSTEM. DVORAK CURRENT
INTENSITY ESTIMATES ARE RANGE FROM 2.0-2.5, RESPECTIVELY. THE
INITIAL POSITIONS OF THE STORM IS BASED ON THE AFOREMENTIONED
IMAGERY WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS BASED ON THE
ASCAT PASS AND FIXES AND HEDGED ON THE HIGHER END AT 40 KTS. UPPER
LEVEL ANALYSIS INDICATES AN ENVIRONMENT CHARACTERIZED BY LOW TO
MODERATE (10-20 KTS) VWS AND STRONG POLEWARD OUTFLOW. TC 02P IS
EXPECTED TO CONTINUE ON ITS SOUTHWEST TRAJECTORY OVER THE NEXT 36
HOURS. THE CURRENT FAVORABLE UPPER LEVEL CONDITIONS MAY ALLOW FOR A
SLIGHT INTENSIFICATION OF THE NEXT 12 HOURS, HOWEVER INCREASING VWS
THEREAFTER WILL LEAD TO THE DISSIPATION OF THE SYSTEM WITHIN 36
HOURS. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT, LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 161800Z IS 15 FEET. NEXT WARNINGS AT 170900Z AND 172100Z.

[Nev]

Looks like this low has missed the boat. JTWC's estimated max 1-minute winds of 35 kts last night translate to below TC thresholds and RSMC Nadi have maintained 25 kt 10-minute winds. Although organisation looked much better yesterday, persistent SE convection now looks to have dissipated and completely sheared…

WTPS31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 02P (TWO) WARNING NR 004//
RMKS/
1. TROPICAL CYCLONE 02P (TWO) 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:
170600Z --- NEAR 16.1S 173.2E
MOVEMENT PAST SIX HOURS - 225 DEGREES AT 15 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
…
REMARKS:
170900Z POSITION NEAR 16.7S 172.7E.
TROPICAL CYCLONE (TC) 02P (TWO), LOCATED APPROXIMATELY 321 NM WEST-
NORTHWEST OF SUVA, FIJI, HAS TRACKED SOUTHWESTWARD AT 15 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING
CONVECTION SHEARED TO THE SOUTHEAST. A 170316Z SSMI 85GHZ MICROWAVE
IMAGE SHOWS TIGHT SPIRAL BANDING WRAPPING INTO THE LLCC WITH LIMITED
CONVECTION. THE INITIAL POSITION IS BASED ON THE EXPOSED LLCC WITH
HIGH CONFIDENCE. THE CURRENT INTENSITY HAS BEEN DECREASED TO 35
KNOTS BASED ON AN ASSESSMENT OF DVORAK INTENSITY ESTIMATES AND
REFLECTS THE CURRENT WEAKENING OF THE CYCLONE SEEN IN THE ABOVE
IMAGERY. TC 02P IS IN A MARGINAL ENVIRONMENT WITH 10 TO 20 KNOT
VERTICAL WIND SHEAR (VWS) OFFSET BY A STRONG POLEWARD OUTFLOW. SEA
SURFACE TEMPERATURES (SSTS) ARE STILL CONDUCIVE AT 28 CELSIUS. TC
02P IS FORECAST TO CONTINUE TRACKING SOUTHWESTWARD THROUGHOUT THE
FORECAST PERIOD ALONG THE WESTERN PERIPHERY OF THE SUB-TROPICAL
RIDGE TO THE EAST. ENVIRONMENTAL CONDITIONS WILL ALLOW THE SYSTEM TO
MAINTAIN INTENSITY BEFORE MOVING INTO A REGION OF HIGH VWS AND
COOLING SSTS WHICH WILL LEAD TO ITS DISSIPATION BY THE END OF THE
FORECAST PERIOD. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 170600Z IS 15 FEET. NEXT WARNINGS AT
172100Z and 180900Z.//

TROPICAL DISTURBANCE ADVISORY NUMBER A7 ISSUED FROM RSMC NADI
Oct 17/1418 UTC 2015 UTC.

TROPICAL DEPRESSION 02F CENTRE [1001HPA] WAS LOCATED NEAR 16.7S
174.1E AT 171200 UTC. POSITION POOR BASED ON HR GMS IR IMAGERY AND
PERIPHERAL SURFACE REPORTS. THE SYSTEM MOVING TOWARDS SOUTHWEST AT
ABOUT 10 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE
ESTIMATED AT ABOUT 25 KNOTS.

CONVECTION REMAINS PERSISTENT BUT DETACHED TO SOUTH OF LLCC.
ORGANISATION HAS IMPROVED IN THE PAST 6 HOURS. SYSTEM LIES IN
MODERATE SHEARED ENVIRONMENT TO SOUTH OF AN UPPER RIDGE. OUTFLOW FAIR
TO SOUTH DUE TO DIFFLUENT UPPER RIDGE. SST AROUND AROUND 28 DEGREE
CELSIUS.

DVORAK ANALYSIS BASED ON 0.3 WRAP YIELDS DT2.0, MET AND PAT AGREE.
THUS YIELDING T2.0/2.0/S0.0/24HRS

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHWESTWARD WITH
FURTHER INTENSIFICATION. POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A
TROPICAL CYCLONE WITHIN THE NEXT 12 TO 24 HOURS IS MODERATE.
...

[Nev]

JTWC have been monitoring a developing TD just WNW of French Polynesia, which showed some good flaring earlier today. RSMC Nadi have only just picked up on it this afternoon and both now rate its chances of becoming a TC in the next 24 hours or so as medium…

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Feb 290332 UTC.

TROPICAL DISTURBANCE TD12F [1000HPA] ANALYSED NEAR 15.9S 152.2W AT
290000UTC. TD12F SLOW MOVING. POSITION POOR BASED IN VIS/IR IMAGERGY
WITH ANIMATION AND PERIPHERAL SURFCACE OBSERVATIONS. SST AROUND 30
DEGREES CELCIUS.

CONVECTION REMAINS PERSISTANT. ORGANISATION HAS IMPROVED PAST 24
HOURS. CYCLONIC CIRCULATION EXTENDS UPTO 700HPA. SYSTEM LIES SOUTH OF
AN UPPER LEVEL RIDGE IN A LOW SHEARED ENVIRONMENT.

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHEASTWARDS WITH
GRADUAL INTENSIFICATION.

THE POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN
THE NEXT 24 TO 48 HOURS IS MODERATE.

ABPW10 PGTW 290600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND
/SOUTH PACIFIC OCEANS/290600ZFEB2016-010600ZMAR2016//
RMKS/
…
2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
1) THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 15.5S
152.5W IS NOW LOCATED NEAR 15.8S 152.5W, APPROXIMATELY 55 NM
NORTHWEST OF BORA BORA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A CONSOLIDATING, PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH DEEP CONVECTION PERSISTING OVER THE SOUTHEAST
QUADRANT. A 290050Z NOAA-19 89GHZ IMAGE SHOWS FORMATIVE BANDING
WRAPPING INTO AN ELONGATED BUT DEFINED LLCC. A RECENT ASCAT IMAGE
SHOWS A SYMMETRIC CIRCULATION WITH 25 TO 30 KNOT WINDS OVER THE
NORTHEAST QUADRANT AND 15 TO 25 KNOT WINDS ELSEWHERE. UPPER-LEVEL
ANALYSIS SHOWS A FAVORABLE ENVIRONMENT WITH LOW (10 TO 15 KNOTS)
VERTICAL WIND SHEAR AND IMPROVING OUTFLOW. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

[Nev]

The South Pacific has been very active lately, with 3 lows potentially becoming TC's. This morning JTWC issued TC Alerts for one west of Vanuatu and one just SW off Fiji. And this afternoon RSMC Nadi began issing Advisories for the one west of Vanuatu. The third low is east of Vanuatu.

WTPS21 PGTW 042000
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 20.2S 179.4E TO 22.5S 171.8W
WITHIN THE NEXT 06 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 28 TO 33 KNOTS. METSAT
IMAGERY AT 041800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 20.4S 179.9W. THE SYSTEM IS MOVING EAST-SOUTHEASTWARD AT 11
KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 19.3S
177.5E IS NOW LOCATED NEAR 20.4S 179.9W, APPROXIMATELY 266 NM WEST
OF TONGA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 041825Z
SSMIS 91 GHZ IMAGE REVEAL AN EXPOSED LOW-LEVEL CIRCULATION CENTER
WITH TIGHTLY CURVED SHALLOW BANDING WRAPPING INTO THE CENTER, AND
DEEP CONVECTION SHEARED EAST OF THE SYSTEM. EARLIER OBSERVATIONS
FROM NFFN INDICATED SUSTAINED WINDS BETWEEN 27 TO 32 KNOTS AS THE
SYSTEM PASSED TO THE SOUTH. UPPER-LEVEL ANALYSIS DEPICTS A
MARGINALLY-FAVORABLE ENVIRONMENT WITH GOOD EQUATORWARD OUTFLOW
OFFSET BY MODERATE-STRONG (20 TO 30 KNOTS) VERTICAL WIND SHEAR.
DYNAMIC MODEL GUIDANCE IS IN SOLID AGREEMENT ON THE TRACK OF 96P AS
IT MOVES SOUTHEASTWARD, STEERED BY A SUBTROPICAL RIDGE TO THE NORTH.
THIS SYSTEM HAS A SHORT WINDOW FOR INTENSIFICATION OVER THE NEXT 24
TO 36 HOURS AS 96P BEGINS TO ENCOUNTER UNFAVORABLE VWS WITHIN A
TROUGH TO THE SOUTH. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED
AT 28 TO 33 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
052000Z.//
NNNN

WTPS22 PGTW 042130
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 13.6S 162.7E TO 17.2S 171.2E
WITHIN THE NEXT 06 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 041800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 13.8S 163.1E. THE SYSTEM IS MOVING EAST-SOUTHEASTWARD AT 08
KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 12.9S
161.6E IS NOW LOCATED NEAR 13.8S 163.1E, APPROXIMATELY 385 NM
NORTHWEST OF PORT VILA, VANUATU. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS FORMATIVE, DEEP CONVECTIVE BANDING WRAPPING INTO THE
SYSTEM. A 041714Z SSMIS 91 GHZ IMAGE REVEALS TIGHTLY CURVED
CONVECTIVE BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH LOW-MODERATE (10 TO 20 KNOTS) VERTICAL WIND SHEAR
(VWS) AND RADIAL OUTFLOW. DYNAMIC MODEL GUIDANCE IS IN FAIR
AGREEMENT ON 97P TRACKING SOUTHEASTWARD, AND STEERED BY A NEAR
EQUATORIAL RIDGE TO THE NORTH. THIS SYSTEM HAS A SHORT WINDOW FOR
INTENSIFICATION OVER THE NEXT 36 TO 48 HOURS UNDER A FAVORABLE UPPER-
LEVEL ENVIRONMENT. AFTER TAU 48, 97P WILL BEGIN TO WEAKEN AS IT
ENCOUNTERS UNFAVORABLE VWS ASSOCIATED WITH AN APPROACHING TROUGH.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED TO BE NEAR 25 TO 30
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1003 MB.
THE POTENTIAL FOR 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
052130Z.//
NNNN

TROPICAL DISTURBANCE ADVISORY NUMBER A3 ISSUED FROM RSMC NADI
Apr 050422 UTC.

TROPICAL DEPRESSION TD16F CENTRE 1002HPA WAS ANALYSED NEAR 14.4S
165.2E AT 050300UTC. POSITION FAIR BASED ON HR GOES EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. DEPRESSION MOVING EAST-SOUTHEAST AT
ABOUT 10 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 TO THE
EAST OF AN UPPER TROUGH AND IS BEING SOUTHEASTWARD BY A NORTHWESTERLY
DEEP LAYER MEAN FLOW IN AN AREA OF LOW ENVIRONEMNTAL SHEAR. DVORAK
ANALYSIS BASED ON 0.40 WRAP YIELDS A DT=2.0, MET AND PT AGREE. FT
BASED ON DT THUS, YEILDING T2.0/2.0/D1.0/24HRS.

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

POTENTIAL FOR TD16F TO DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 12
TO 24 HOURS IS HIGH.

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Apr 050101 UTC.

TROPICAL DISTURBANCE TD14F CENTRE [1004HPA] WAS ANALYSED NEAR 16.1S
171.2E AT 042100 UTC. TD14F MOVING ESE AT 06 KNOTS. POSITION POOR
BASED ON HIMAWARI-8 VIS IMAGERY WITH ANIMATION AND PERIPHERAL SURFACE
OBSERVATIONS. SST AROUND 29 DEGREES CELSIUS.

CONVECTION PERSISTANT PAST 24 HOURS. ORGANISATION POOR. CYCLONIC
CIRCULATION CIRCULATION EXTENDS UPTO TO 700HPA. SYSTEM LIES JUST
SOUTH OF AN UPPER LEVEL RIDGE IN A MODERATE SHEARED ENVIRONMENT.

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHEASTWARDS WITH
GRADUAL INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS LOW.

*********************************************************************
***************

TROPICAL DISTURBANCE TD15F CENTRE [1003HPA] WAS ANALYSED NEAR 20.4S
179.9W AT 042100 UTC. TD15F MOVING ESE 08 KNOTS. POSITION GOOD BASED
ON HIMAWARI-8 VIS IMAGERY WITH ANIMATION AND PERIPHERAL SURFACE
OBSERVATIONS. SST AROUND 29 DEGREES CELSIUS.

CONVECTION PERSISTANT PAST 12 HOURS AND DISPLACED TO THE EAST OF
LLCC. ORGANISATION REMAINS POOR. CYCLONIC CIRCULATION CIRCULATION
EXTENDS UPTO TO 500HPA. SYSTEM LIES SOUTH OF AN UPPER LEVEL RIDGE IN
A MODERATE TO HIGH SHEARED ENVIRONMENT.

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHEASTWARDS WITH
LITTLE INSTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS LOW.

*********************************************************************
***************

[Nev]

JTWC cancelled the TC Alert for the TD SW of Fiji this morning and downgraded its chances of becoming a TC in the 24 hrs to medium. RSMC Nadi maintain its chances, along with the TD further east of Vanuatu as 'low'. Meanwhile the TD which crossed Vanuatu last night was upgraded to TC Zena earlier this moring (see TC Zena thread).

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND
/SOUTH PACIFIC OCEANS REISSUED/051700Z-060600ZAPR2016//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/050751ZAPR2016//
REF/B/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/051651ZAPR2016//
NARR/REF A IS A TROPICAL CYCLONE WARNING. REF B IS A TROPICAL
/CYCLONE FORMATION ALERT CANCELLATION.//
RMKS/
...
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 20.4S
177.9W, IS NOW LOCATED NEAR 21.6S 175.4W, APPROXIMATELY 25 NM
SOUTHWEST OF TONGA. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS AN
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH WEAKENED CONVECTION
DISPLACED TO THE EAST OF THE LLCC. UPPER LEVEL ANALYSIS INDICATES
THAT THE SYSTEM HAS MOVED INTO AN AREA OF HIGH (20-30 KNOTS)
VERTICAL WIND SHEAR (VWS). NUMERICAL FORECAST MODELS INDICATE VWS
WILL CONTINUE TO INCREASE AS THE SYSTEM BECOMES EMBEDDED IN THE MID-
LATITUDE WESTERLY FLOW AND NO LONGER INTENSIFY THE SYSTEM. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 996 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS DOWNGRADED TO MEDIUM. SEE REF B (WTPS21 PGTW 051700) FOR
FURTHER DETAILS.
...

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Apr 050954 UTC.

TROPICAL DISTURBANCE TD14F CENTRE [1004HPA] WAS ANALYSED NEAR 18.4S
175.3E AT 050900 UTC. TD14F MOVING ESE AT 16 KNOTS. POSITION POOR
BASED ON HIMAWARI-8 IR IMAGERY WITH ANIMATION AND PERIPHERAL SURFACE
OBSERVATIONS. SST AROUND 29 DEGREES CELSIUS.

CONVECTION PERSISTANT PAST 24 HOURS. ORGANISATION POOR. CYCLONIC
CIRCULATION CIRCULATION EXTENDS UPTO TO 700HPA. SYSTEM LIES JUST
SOUTH OF AN UPPER LEVEL RIDGE IN A MODERATE SHEARED ENVIRONMENT.

GLOBAL MODELS WEAKEN TD14F AND MERGE IT WITH TD16F.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS LOW.

*********************************************************************
***************

TROPICAL DISTURBANCE TD15F CENTRE [1003HPA] WAS ANALYSED NEAR 20.9S
177.2W AT 050900 UTC. TD15F MOVING ESE 08 KNOTS. POSITION GOOD BASED
ON HIMAWARI-8 VIS IMAGERY WITH ANIMATION AND PERIPHERAL SURFACE
OBSERVATIONS. SST AROUND 29 DEGREES CELSIUS.

CONVECTION PERSISTANT PAST 12 HOURS AND DISPLACED TO THE EAST OF
LLCC. ORGANISATION REMAINS POOR. CYCLONIC CIRCULATION CIRCULATION
EXTENDS UPTO TO 500HPA. SYSTEM LIES SOUTH OF AN UPPER LEVEL RIDGE IN
A MODERATE TO HIGH SHEARED ENVIRONMENT.

GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHEASTWARDS WITH
LITTLE INSTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 TO 48 HOURS IS LOW.