Tropical Cyclone Pam - SW Pacific

Nev · Unread post by **Nev** » Sun 15/03/2015 06:10

JTWC's Latest remarks expect Pam to undergo extra-tropical transition during the 24 hrs from this arvo…

WTPS31 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 17P (PAM) WARNING NR 019//
RMKS/
1. TROPICAL CYCLONE 17P (PAM) WARNING NR 019
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
141200Z --- NEAR 24.6S 171.1E
MOVEMENT PAST SIX HOURS - 160 DEGREES AT 25 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON EYE FIXED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 130 KT, GUSTS 160 KT
…
REMARKS:
141500Z POSITION NEAR 25.7S 171.9E.
TROPICAL (TC) CYCLONE 17P (PAM), LOCATED APPROXIMATELY 314 NM EAST-
SOUTHEAST OF NOUMEA, NEW CALEDONI, HAS TRACKED SOUTH-
SOUTHEASTWARD AT 25 KNOTS OVER THE PAST SIX HOURS. ENHANCED IR
SATELLITE IMAGERY DEPICTS A 20-NM EYE WITH A SLIGHT WEAKENING TREND
IN OVERALL CONVECTIVE ORGANIZATION OVER THE PAST SIX HOURS. TC 17P
CONTINUES TO HAVE INTENSE POLEWARD OUTFLOW AND LOW (10 TO 20 KNOTS)
VERTICAL WIND SHEAR. THE INITIAL INTENSITY HAS DECREASED TO 130
KNOTS AS DVORAK INTENSITY ESTIMATES HAVE DROPPED IN THE PAST SIX
HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE
EYE FIXES. TC 17P IS FORECAST TO ACCELERATE SOUTHEASTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE AND IS EXPECTED TO
BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 12 AS IT BEGINS TO
WEAKEN AND INTERACT WITH THE BAROCLINIC ZONE. TC PAM WILL COMPLETE
ETT BY TAU 36 AS IT GAINS FRONTAL CHARACTERISTICS. THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST BASED ON THE TIGHT AGREEMENT OF
DYNAMIC MODELS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 141200Z IS 45
FEET. NEXT WARNINGS AT 150300Z AND 151500Z. REFER TO TROPICAL
CYCLONE 18P (NATHAN) WARNINGS (WTPS32 PGTW)FOR TWELVE-HOURLY
UPDATES.//
NNNN

Nev · Unread post by **Nev** » Sun 15/03/2015 06:11

For archival reasons, I'll endeavour to update advisories, etc in this thread until Pam no longer has official TC status.

However, now that Pam is bearing down NZ, can I suggest that all comments about Pam's future now be directed to the Pam thread in the forum's NZ section, and that this thread be used mainly for her effects north of us etc. Hope that makes sense.

Manukau heads obs · Sun 15/03/2015 06:38

WOW
still has an eye!
and seems to be veering more S
this is bad for NZ

Nev · Unread post by **Nev** » Sun 15/03/2015 07:49

TC Pam currently at 925 hPa with central mean-winds to about 205 km/h...

MetService - Subtropic high seas forecast

Issued at 7:28am Sunday 15 Mar 2015

TROPICAL CYCLONE HURRICANE WARNING 238
This affects ocean areas: SUBTROPIC and FORTIES
Tropical Cyclone PAM [925hPa] centre was located near 26.8 South 172.7 East at 141800 UTC.
Position Fair.
Repeat position 26.8S 172.7E at 141800 UTC.
Cyclone is moving southeast 27 knots.
Expect sustained winds of 110 knots close to the centre easing to 100 knots by 150600 UTC and then easing to 80 knots by 151800 UTC with phenomenal sea.
Expect winds over 63 knots within 45 nautical miles of centre.
Expect winds over 47 knots within 150 nautical miles of centre in the sector from north through east to west and within 100 nautical miles of centre in the northwest quadrant with high to very high sea and moderate to heavy swell.
Expect winds over 33 knots within 250 nautical miles of centre in the sector from north through east to west and within 180 nautical miles of centre in the northwest quadrant with very rough sea and moderate to heavy swell.

Forecast position near 31.9S 176.6E at 150600 UTC
and near 36.0S 179.8E at 151800 UTC.
This warning cancels and replaces warning 231.

jamie · Unread post by **jamie** » Sun 15/03/2015 07:58

No maps from metservice?

Nev · Unread post by **Nev** » Sun 15/03/2015 09:48

Not that I'm aware of

, although she's moving so fast that it would soon be out of date…

Nev · Unread post by **Nev** » Sun 15/03/2015 10:36

This morn's JTWC update expect Pam to begin extra-tropical transition from sometime this evening...

WTPS31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 17P (PAM) WARNING NR 020//
RMKS/
1. TROPICAL CYCLONE 17P (PAM) WARNING NR 020
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
141800Z --- NEAR 26.9S 172.7E
MOVEMENT PAST SIX HOURS - 150 DEGREES AT 27 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON EYE FIXED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT
…
REMARKS:
142100Z POSITION NEAR 28.1S 173.6E.
TROPICAL CYCLONE (TC) 17P (PAM), LOCATED APPROXIMATELY 461 NM
SOUTHEAST OF NOUMEA, NEW CALEDONIA, HAS TRACKED SOUTH-
SOUTHEASTWARD AT 27 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED
SATELLITE IMAGERY DEPICTS WEAKENING CORE CONVECTION, HOWEVER, THE
SYSTEM HAS MAINTAINED A 18-NM ROUND EYE. OVERALL, THERE IS GOOD
CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY
IS ASSESSED AT 115 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES
OF 115 KNOTS. TC 17P IS FORECAST TO ACCELERATE SOUTHEASTWARD ALONG
THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE AND IS EXPECTED
TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 12 AS IT BEGINS TO
WEAKEN AND INTERACT WITH THE BAROCLINIC ZONE. TC 17P WILL COMPLETE
ETT BY TAU 36 AS IT GAINS FRONTAL CHARACTERISTICS. THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST BASED ON THE TIGHT AGREEMENT OF
DYNAMIC MODELS THROUGH TAU 36. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
141800Z IS 40 FEET. NEXT WARNINGS AT 150900Z AND 152100Z.

Orion · Unread post by **Orion** » Sun 15/03/2015 11:28

Link to brief video and photos from Vanuatu:
https://www.facebook.com/adra.vanuatu

Nev · Unread post by **Nev** » Sun 15/03/2015 13:48

Cat 4 TC Pam now at 935 hPa with central mean-winds to about 175 km/h...

MetService - Subtropic high seas forecast

Issued at 1:25pm Sunday 15 Mar 2015

TROPICAL CYCLONE HURRICANE WARNING 243
This affects ocean areas: SUBTROPIC and FORTIES
Tropical Cyclone PAM [935hPa] centre was located near 29.4 South 175.1 East at 150000 UTC.
Position Fair.
Repeat position 29.4S 175.1E at 150000 UTC.
Cyclone is moving southeast 30 knots.
Expect sustained winds of 95 knots close to the centre easing to 85 knots by 151200 UTC and then easing to 75 knots by 160000 UTC with phenomenal sea.
Expect winds over 63 knots within 45 nautical miles of centre.
Expect winds over 47 knots within 150 nautical miles of centre in the sector from north through east to southwest and within 100 nautical miles of centre in the sector from southwest through northwest to north with high to very high sea and moderate to heavy swell.
Expect winds over 33 knots within 310 nautical miles of centre in the northeast quadrant and within 280 nautical miles of centre in the southern semicircle and within 240 nautical miles of centre in the northwest quadrant with very rough sea and moderate to heavy swell.

Forecast position near 34.1S 178.2E at 151200 UTC
and near 37.5S 179.9W at 160000 UTC.

Nev · Unread post by **Nev** » Sun 15/03/2015 17:27

From JTWC this arvo…

WTPS31 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 17P (PAM) WARNING NR 021//
RMKS/
1. TROPICAL CYCLONE 17P (PAM) WARNING NR 021
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
150000Z --- NEAR 29.3S 175.0E
MOVEMENT PAST SIX HOURS - 140 DEGREES AT 31 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
…
REMARKS:
150300Z POSITION NEAR 30.5S 175.9E.
TROPICAL CYCLONE (TC) 17P (PAM), LOCATED APPROXIMATELY 646 NM
SOUTHEAST OF NOUMEA, NEW CALEDONI, HAS TRACKED SOUTHEASTWARD AT
31 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS RAPIDLY DECAYING DEEP CONVECTION WITH AN EXPOSED LOW-
LEVEL CIRCULATION CENTER (LLCC) AND LIMITED CORE CONVECTION.
OVERALL, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE
INITIAL INTENSITY IS ASSESSED AT 100 KNOTS BASED ON DVORAK CURRENT
INTENSITY ESTIMATES OF 102 KNOTS. TC 17P IS FORECAST TO ACCELERATE
SOUTHEASTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE AND IS BEGINNING EXTRA-TROPICAL TRANSITION (ETT) AS IT BEGINS
TO WEAKEN AND INTERACT WITH THE BAROCLINIC ZONE. TC 17P WILL
COMPLETE ETT BY TAU 24 AS IT GAINS FRONTAL CHARACTERISTICS. THERE IS
HIGH CONFIDENCE IN THE JTWC FORECAST BASED ON THE TIGHT AGREEMENT OF
DYNAMIC MODELS THROUGH TAU 24. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
150000Z IS 40 FEET. NEXT WARNINGS AT 151500Z. REFER TO TROPICAL
CYCLONE 18P (NATHAN) WARNINGS (WTPS32 PGTW) FOR TWELVE-HOURLY
UPDATES.//
NNNN

Nev · Unread post by **Nev** » Sun 15/03/2015 19:39

Boarder-line Cat 4 TC Pam now at 950 hPa with central mean-winds to 150 km/h…

MetService - Subtropic high seas forecast

Issued at 7:29pm Sunday 15 Mar 2015

TROPICAL CYCLONE HURRICANE WARNING 246
This affects ocean areas: SUBTROPIC and FORTIES
Tropical Cyclone PAM [950hPa] centre was located near 32.0 South 177.4 East at 150600 UTC.
Position Poor.
Repeat position 32.0S 177.4E at 150600 UTC.
Cyclone is moving southeast 30 knots.
Expect sustained winds of 80 knots close to the centre easing to 70 knots by 151800 UTC and then easing to 50 knots by 160600 UTC. Phenomenal sea easing to high to very high sea and moderate to heavy swell.
Expect winds over 63 knots within 120 nautical miles of centre in the eastern semicircle and within 60 nautical miles of centre in the western semicircle.
Expect winds over 47 knots within 180 nautical miles of centre in the eastern semicircle and within 60 nautical miles of centre in the western semicircle.
Expect winds over 33 knots within 320 nautical miles of centre in the eastern semicircle and within 280 nautical miles of centre in the western semicircle with very rough sea and moderate to heavy swell.

Forecast position near 35.6S 179.9E at 151800 UTC
and near 38.4S 177.6W at 160600 UTC.
This warning cancels and replaces warning 243.

Vertigo · Unread post by **Vertigo** » Sun 15/03/2015 20:09

Nev, can they really still call it a TC now that its most probably going cold-core? Im sure they dont base the classification purely on wind speed and central pressure.

Nev · Unread post by **Nev** » Sun 15/03/2015 20:34

I'm not an expert, but she still has plenty of convection, particularly in eastern quadrants of her LLCC, which looks to flared in recent hours. So yes, I'd say she's still warm cored, but currently undergoing ETT.

Willoughby · Unread post by **Willoughby** » Sun 15/03/2015 21:43

Yeah she's well extratropical now... But still packing a punch.

Here are some advanced dvorak technique numbers from a couple of agencies:

Satellite Services Division - NOAA:

TXPS21 KNES 150621
TCSWSP

A. 17P (PAM)

B. 15/0532Z

C. 31.3S

D. 176.1E

E. THREE/MTSAT

F. EXTRATROPICAL

G. IR/EIR/VIS/SSMI

H. REMARKS...EXTRATROPICAL TRANSITION IS CURRENTLY UNDERWAY. THIS WILL
BE THE FINAL BULLETIN.

I. ADDL POSITIONS

15/0322Z 30.6S 175.3E SSMI

...TURK

Joint Typhoon Warning Center:

TPPS10 PGTW 150643

A. TROPICAL CYCLONE 17P (PAM)

B. 15/0532Z

C. 31.70S

D. 176.40E

E. FIVE/MTSAT

F. T3.5/4.5/W2.0/24HRS STT: W0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 40A/PBO SBC/ANMTN. CNVCTN SHEARED 34NM FROM LLCC
YIELDING A DT OF 3.5. PT YIELDS A 3.0, WHILE MET YIELDS A 5.0.
DBO DT.

I. ADDITIONAL POSITIONS:
15/0057Z 30.17S 175.02E AMS2
15/0204Z 30.37S 175.22E TRMM
15/0322Z 30.78S 175.52E SSMI

CHAPPOTIN

Uni. of Wisconsin/CIMSS ADT chart:

17PP[1].GIF

Orion · Unread post by **Orion** » Sun 15/03/2015 23:04

"HAS TRACKED SOUTHEASTWARD AT
31 KNOTS OVER THE PAST SIX HOURS"

- she'd have a "bone in her teeth" at that rate. Remarkable.

Nev · Unread post by **Nev** » Mon 16/03/2015 06:26

Ok, so for the record, the last time Pam was classified by MetService (TCWC Wellington) as a TC was around 7pm NZDT on Sunday when about 500 km NE of Cape Reinga.

Latest Warning/Advice from MS...

MetService - Subtropic high seas forecast

Issued at 1:34am Monday 16 Mar 2015

STORM WARNING 249
This affects ocean areas: SUBTROPIC FORTIES and PACIFIC
AT 151200UTC
Low 960hPa, former Cyclone PAM, near 34S 179E moving southeast 20kt.
1. Within 240 nautical miles of low in sector from north through east to west: Clockwise 55kt.
2. Outside area 1 and within 480 nautical miles of low: Clockwise 35kt.
Storm and gale areas moving with low.
This warning cancels and replaces warning 246.

And the Final Advisory from JTWC earlier this morn…

WTPS31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 17P (PAM) WARNING NR 022//
RMKS/
1. TROPICAL CYCLONE 17P (PAM) WARNING NR 022
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
151200Z --- NEAR 33.3S 178.3E
MOVEMENT PAST SIX HOURS - 140 DEGREES AT 20 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
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
RADIUS OF 050 KT WINDS - 085 NM NORTHEAST QUADRANT
085 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 160 NM NORTHEAST QUADRANT
160 NM SOUTHEAST QUADRANT
140 NM SOUTHWEST QUADRANT
140 NM NORTHWEST QUADRANT
REPEAT POSIT: 33.3S 178.3E
---
FORECASTS:
12 HRS, VALID AT:
160000Z --- 37.0S 179.9W
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
151500Z POSITION NEAR 34.2S 178.8E.
TROPICAL CYCLONE 17P (PAM), LOCATED APPROXIMATELY 572 NM EAST-
SOUTHEAST OF KINGSTON IS., HAS TRACKED SOUTHEASTWARD AT 20 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED IR SATELLITE IMAGERY
DEPICTS RAPIDLY DECAYING DEEP CONVECTION WITH A PARTIALLY EXPOSED
LOW-LEVEL CIRCULATION CENTER AND LIMITED CORE CONVECTION, WITH THE
MAJORITY OF THE CONVECTION ON THE EASTERN SIDE. THIS IS CONFIRMED
WITH A 151246Z GPM IMAGE WHICH SHOWS THE SYSTEM TAKING ON FRONTAL
CHARACTERISTICS. THE SYSTEM IS EXPECTED TO COMPLETE EXTRA-TROPICAL
TRANSITION BY TAU 12 AS IT BECOMES FULLY ENVELOPED IN THE BAROCLINIC
ZONE. THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST BASED ON THE
TIGHT AGREEMENT OF DYNAMIC MODELS. THIS IS THE FINAL WARNING ON THIS
SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL
BE CLOSELY MONITORED FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 151200Z IS 40 FEET. REFER TO TROPICAL CYCLONE 18P
(NATHAN) WARNINGS (WTPS32 PGTW) FOR TWELVE-HOURLY UPDATES.//
NNNN

Nev · Unread post by **Nev** » Mon 16/03/2015 21:16

Thought this ir/vis sat-pic from around 6:30pm on Sunday NZDT might also be of interest. It shows the partially exposed LLCC (red 'x' at 176.1E 31.3S) and the main upper convection being sheared to east…

tgsnoopy · Unread post by **tgsnoopy** » Tue 17/03/2015 07:35

Nev wrote:Ok, so for the record, the last time Pam was classified by MetService (TCWC Wellington) as a TC was around 7pm NZDT on Sunday when about 500 km NE of Cape Reinga.

I understood it was downgraded at about 1.30am Monday morning.

Nev · Unread post by **Nev** » Tue 17/03/2015 08:40

tgsnoopy wrote:
Nev wrote:Ok, so for the record, the last time Pam was classified by MetService (TCWC Wellington) as a TC was around 7pm NZDT on Sunday when about 500 km NE of Cape Reinga.
I understood it was downgraded at about 1.30am Monday morning.

Yes, MS's 1:34am warning with the downgrade was included with my above comment.

(Also gratefully posted in the NZ thread by tunster just minutes after it was issued.)

Vertigo · Unread post by **Vertigo** » Tue 17/03/2015 21:42

That pic is great, Nev. Thats precisely the time I noted it was interacting with a jetstream.

Nev · Unread post by **Nev** » Thu 19/03/2015 18:32

Thought this was interesting - TC's can leave a 'scar' across the ocean in the form of cooler SST's…

'Pam's long lasting scar' - Swellnet

TC Pam Track v. SST's ℅ Swellnet.png

jamie · Unread post by **jamie** » Thu 19/03/2015 19:10

Awesome. I suppose it's due to the mixing of deeper water with big waves and swells?

Nev · Unread post by **Nev** » Thu 19/03/2015 19:44

Yes, along with high rainfall. Mixing the deeper water also allows it to extract even more thermal energy.

Orion · Unread post by **Orion** » Sat 21/03/2015 20:47

Fascinating.

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