Tropical Cyclone Amos

[Manukau heads obs]

yeah, sorry, I see you did qualify in saying tonight/morning

So what I said was way more accurate than what they had in their recent forecasts.

yeah..so how come arm chair forecasters can be so more onto it?
you would think they would make it a priority to update the forecast after a cyclone speeds up?

[Nev]

Amos managed to just speed past the north coast of American Samoa's main island of Tutuila in the last few hours, rather than down threw it, and a lot sooner than expected. Central pressure up to 973 hPa, but still packing max mean-winds of 150 km/h...

TROPICAL DISTURBANCE ADVISORY NUMBER A18 ISSUED FROM RSMC NADI
Apr 232014 UTC.

SEVERE TROPICAL CYCLONE AMOS CENTRE 973HPA CATEGORY 3 WAS LOCATED
NEAR 13.4S 171.8W AT 231200UTC. POSITION FAIR BASED ON
HIMAWARI-8/GOES IR IMAGERY AND PERIPHERAL SURFACE REPORTS. AMOS
MOVING EAST-SOUTHEAST AT ABOUT 16 KNOTS. MAXIMUM 10-MINUTE AVERAGE
WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 80 KNOTS, EASING TO 70 KNOTS
IN THE NEXT 12 HOURS.
…
DEEP CONVECTION REMAINS PERSISTENT. ORGANISATION GOOD. SYSTEM LIES IN
A MODERATE TO STRONG UPPER DIVERGENCE REGION AND IN A MODERATE
SHEARED ENVIRONMENT. SST AROUND 30 DEGREE CELCIUS. OUTFLOW GOOD TO
THE EAST AND SOUTH. SYSTEM IS BEING STEERED TO THE EAST-SOUTHEAST BY
THE WEST-NORTHWEST DEEP LAYER MEAN WIND FLOW. DVORAK ANALYSIS BASED
ON EMBEDDED CENTRE PATTERN WITH LLCC EMBEDDED IN LG YIELDS DT=4.5.
MET AND PT AGREE. FT BASED ON MET. THUS, YIELDING
T4.5/5.0/W0.5/24HRS.

GLOBAL MODELS MAINTAIN A SOUTHEASTWARD TRACK WITH GRADUAL WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 240600 UTC 14.4S 168.5W MOV ESE AT 06KT WITH 70 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 241800 UTC 14.8S 167.9W MOV SE AT 04KT WITH 65 KT
CLOSE TO CENTRE.

OUTLOOK:
AT 36 HRS VALID AT 250600 UTC 15.1S 167.7W MOV SE AT 02KT WITH 65 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 251800 UTC 15.3S 167.7W MOV S AT 01KT WITH 60 KT
CLOSE TO CENTRE.

THE NEXT TROPICAL DISTURBANCE ADVISORY ON TC AMOS WILL BE ISSUED
AROUND 230200UTC.

WTPS31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 20P (AMOS) WARNING NR 016//
RMKS/
1. TROPICAL CYCLONE 20P (AMOS) WARNING NR 016
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
231800Z --- NEAR 14.0S 170.4W
MOVEMENT PAST SIX HOURS - 115 DEGREES AT 16 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
…
REMARKS:
232100Z POSITION NEAR 14.2S 170.0W. TROPICAL CYCLONE 20P (AMOS),
LOCATED APPROXIMATELY 25 NM NORTHEAST OF PAGO PAGO, HAS TRACKED EAST-
SOUTHEASTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED IMAGERY CONTINUES TO DEPICT DEEP CONVECTION FORMING A
CENTRAL DENSE OVERCAST OBSCURING THE LOW LEVEL CIRCULATION CENTER. A
231748Z SSMIS 89 GHZ MICROWAVE IMAGE SHOWS A COMPACT SYSTEM WITH THE
DEEP CONVECTION MOSTLY TO THE EASTERN PERIPHERY BUT A SMALL HOOK
FEATURE INDICATING THE CENTER OF THE SYSTEM, LENDING MODERATE
CONFIDENCE TO THE INITIAL POSITION. THE CURRENT INTENSITY IS
ASSESSED AT 90 KNOTS IN CONGRUENCE WITH SUBJECTIVE DVORAK CURRENT
INTENSITY ESTIMATES FROM PGTW/KNES/NFFN. TC AMOS SPED UP OVER THE
PAST SIX HOURS WHILE CONTINUING TO TRACK EAST-SOUTHEASTWARD UNDER
THE STEERING INFLUENCE OF A NEAR-EQUATORIAL RIDGE (NER) LOCATED TO
THE NORTHEAST. BASED ON RECENT SURFACE OBSERVATIONS AND ASSESSMENTS
OF AVAILABLE SATELLITE AND MICROWAVE IMAGERY, THE CENTER OF TC AMOS
IS ASSESSED TO HAVE PASSED VERY NEAR AMERICAN SAMOA AT APPROXIMATELY
231730Z AND CONFIRMS THE INCREASE IN TRACK SPEED. HOWEVER, THE
FORECAST PHILOSOPHY AND OVERALL TRACK REMAIN ESSENTIALLY UNCHANGED.
THE AFOREMENTIONED NER WILL REMAIN THE PRIMARY STEERING INFLUENCE
THROUGHOUT THE FORECAST PERIOD. HOWEVER, TRACK SPEED IS EXPECTED TO
DECREASE RAPIDLY OVER THE NEXT 24 HOURS DUE TO AN ANTICIPATED,
TEMPORARY WEAKENING OF THE STEERING RIDGE. AFTER TAU 72, TRACK SPEED
INCREASES AS THE NER STRENGTHENS AGAIN. TC AMOS HAS MAINTAINED
STRONG POLEWARD OUTFLOW INTO THE BASE OF AN UPPER LEVEL TROUGH OVER
THE PAST TWELVE HOURS, ENABLING THE SYSTEM TO MAINTAIN INTENSITY
DESPITE INCREASING VERTICAL WIND SHEAR (VWS). HOWEVER, THE SYSTEM
HAS PEAKED IN INTENSITY AND A GRADUAL WEAKENING IS ANTICIPATED
THROUGH THE ENTIRE FORECAST PERIOD DUE TO INCREASING VWS AND A
REDUCTION IN OUTFLOW AS THE UPPER LEVEL TROUGH EXITS THE AREA AFTER
TAU 24. NUMERICAL MODELS ARE GENERALLY IN GOOD AGREEMENT REGARDING
THE OVERALL FORECAST SCENARIO WITH INCREASING UNCERTAINTY REGARDING
TRACK SPEED AND INTENSITY BEYOND TAU 36 RESULTING IN LOW CONFIDENCE
IN THE FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 231800Z IS
30 FEET. NEXT WARNINGS AT 240300Z, 240900Z, 241500Z AND 242100Z.//
NNNN

[Nev]

Came across this BoM Obs website for Apia, which shows a sharp drop in pressure at around 1230Z this morning. SE gusts of about 45 kt (85 km/h) peaked a little earlier at around 1100Z…

Apia Temp & Pres. Obs ℅ BoM - Apr 23 (UTC).png

Apia Wind Obs ℅ BoM - Apr 23 (UTC).png

Note times are in UTC.
Add 13 hrs for Apia, Samoa time, and subtract 11 hrs for Pago Pago, American Samoa time...

[Nev]

Amos weakened quite a bit today and was downgraded to Cat 2 by RSMC this evening, with a central pressure of 985 hPa and max winds of 90 km/h…

TROPICAL DISTURBANCE ADVISORY NUMBER A20 ISSUED FROM RSMC NADI
Apr 240746 UTC.

SEVERE TROPICAL CYCLONE AMOS CENTRE 985HPA CATEGORY 2 WAS LOCATED
NEAR 14.3S 169.7W AT 240600UTC. POSITION FAIR BASED ON
HIMAWARI-8/GOES IR IMAGERY AND PERIPHERAL SURFACE REPORTS. AMOS
MOVING SOUTHEAST AT ABOUT 08 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS
NEAR THE CENTRE ESTIMATED AT ABOUT 50 KNOTS.

EXPECT WINDS OVER 47 KNOTS WITHIN 10 NAUTICAL MILES OF CENTRE.
EXPECT WINDS OVER 33 KNOTS WITHIN 35 NAUTICAL MILES OF CENTRE.

LLCC WEAK WITH CONVECTION DISPLACED TO THE EAST. ORGANISATION HAS
DECREASED IN PAST 24 HOURS. SYSTEM LIES IN A MODERATE TO STRONG UPPER
DIVERGENCE REGION AND IN A MODERATE SHEARED ENVIRONMENT. SST AROUND
30 DEGREE CELCIUS. OUTFLOW GOOD TO THE SOUTH. SYSTEM IS BEING STEERED
TO THE SOUTHEAST BY THE NORTHWEST DEEP LAYER MEAN WIND FLOW. DVORAK
ANALYSIS BASED ON SHEAR PATTERN WITH LLCC ABOUT 3/4 DEGREE FROM
STRONG T GRADIENT YIELDS DT=3.0. MET=3.5 AND PT=3.0. FT BASED ON DT.
CI HELD HIGHER DUE TO CI RULES FOR WEAKENING. THUS, YIELDING
T3.0/3.5/W2.0/24HRS.

GLOBAL MODELS MAINTAIN A SOUTHEASTWARD TRACK WITH GRADUAL WEAKENING.


FORECASTS :
AT 12 HRS VALID AT 241800 UTC 14.9S 168.7W MOV ESE AT 06KT WITH 45 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 250600 UTC 15.3S 167.9W MOV ESE AT 05KT WITH 40 KT
CLOSE TO CENTRE.

OUTLOOK:
AT 36 HRS VALID AT 251800 UTC 15.8S 167.3W MOV SE AT 04KT WITH 35 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 260600 UTC 16.4S 167.0W MOV SE AT 03KT WITH 30 KT
CLOSE TO CENTRE.

[NZ Thunderstorm Soc]

Nice to see that it didn't affect Samoa, so much, as what was forecasted earlier.

[Nev]

Amos was downgraded to Cat 1 by RSMC Nadi earlier this morning and now looks to have since gone extratropical since, with convection completely sheared…

TROPICAL CYCLONE AMOS CENTRE 995HPA CATEGORY 1 WAS LOCATED NEAR 14.1S
169.5W AT 241200UTC. POSITION FAIR BASED ON HIMAWARI-8/GOES IR
IMAGERY AND PERIPHERAL SURFACE REPORTS. AMOS MOVING EAST-SOUTHEAST AT
ABOUT 05 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE
ESTIMATED AT ABOUT 40 KNOTS.

EXPECT WINDS OVER 33 KNOTS WITHIN 30 NAUTICAL MILES OF CENTRE.

LLCC POORLY ORGANISED. DEEP CONVECTION WEAKENING IN PAST 6 HOURS AND
DISPLACED TO THE EAST OF LLCC. ORGANISATION HAS DECREASED
SIGNIFICANTLY IN PAST 24 HOURS. SYSTEM LIES IN A MODERATE UPPER
DIVERGENCE REGION AND IN A MODERATE SHEARED ENVIRONMENT. SST AROUND
30 DEGREE CELCIUS.SYSTEM IS BEING STEERED TO THE EAST-SOUTHEAST BY
THE WEST-NORTHWEST DEEP LAYER MEAN WIND FLOW. DVORAK ANALYSIS BASED
ON SHEAR PATTERN WITH LLCC LESS THEN 1 1/4 DEGREE FROM STRONG T
GRADIENT YIELDS DT=2.0. MET=3.5 AND PT=2.5. FT BASED ON PT. CI HELD
HIGHER DUE TO CI RULES FOR WEAKENING. THUS, YIELDING
T2.5/3.0/W2.5/24HRS.

GLOBAL MODELS MAINTAIN A EAST-SOUTHEASTWARD TRACK WITH FURTHER
WEAKENING.

FORECASTS :
AT 12 HRS VALID AT 250000 UTC 14.5S 168.8W MOV ESE AT 04KT WITH 35 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 251200 UTC 14.9S 168.3W MOV ESE AT 03KT WITH 30 KT
CLOSE TO CENTRE.

OUTLOOK:
AT 36 HRS VALID AT 260000 UTC 15.3S 167.9W MOV SE AT 04KT WITH 30 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 261200 UTC 15.7S 167.5W MOV SE AT 03KT WITH 25 KT
CLOSE TO CENTRE.

WTPS31 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 20P (AMOS) WARNING NR 019//
RMKS/
1. TROPICAL CYCLONE 20P (AMOS) WARNING NR 019
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
241200Z --- NEAR 13.7S 169.5W
MOVEMENT PAST SIX HOURS - 090 DEGREES AT 07 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
…
REMARKS:
241500Z POSITION NEAR 13.7S 169.3W.
TROPICAL CYCLONE 20P (AMOS), LOCATED APPROXIMATELY 79 NM EAST-
NORTHEAST OF PAGO PAGO, HAS TRACKED EASTWARD AT 07 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT SATELLITE
FIXES FROM PGTW, KNES, AND PHFO, A 240844Z AMSU IMAGE, AND A 240932Z
AMSU IMAGE. THERE IS LOW CONFIDENCE IN THE INITIAL POSITION DUE TO
THE INCREASINGLY INDISTINCT SIGNATURE OF THE LOW LEVEL CIRCULATION
CENTER. THE INTENSITY OF 40 KNOTS IS BASED ON A CONSENSUS OF
SUBJECTIVE DVORAK FINAL T-NUMBER AND CURRENT INTENSITY ESTIMATES
FROM MULTIPLE REPORTING AGENCIES, AND IS ALSO CONSISTENT WITH THE
PREVIOUSLY-OBSERVED WEAKENING TREND. TC 20P CONTINUES TO RAPIDLY
WEAKEN IN RESPONSE TO PERSISTENT VERTICAL WIND SHEAR AS IT TRACKS
EASTWARD ALONG THE PERIPHERY OF NEAR-EQUATORIAL RIDGING SITUATED TO
THE NORTH AND EAST. THE CYCLONE IS NOW EXPECTED TO DISSIPATE BELOW
THE WARNING THRESHOLD INTENSITY OF 35 KNOTS BY TAU 24 AS PERSISTENT
SHEAR CONTINUES TO IMPACT THE SYSTEM. NUMERICAL MODELS ARE IN GOOD
AGREEMENT WITH THE OVERALL FORECAST SCENARIO. THE CURRENT FORECAST
TRACK LIES NEAR, BUT SLIGHTLY TO THE EAST OF, THE MULTI-MODEL
CONSENSUS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 241200Z IS 14 FEET.
NEXT WARNINGS AT 242100Z, 250300Z AND 250900Z.//

[Nev]

Ex-TC Amos was declared extratropical around midday today our time. And JTWC issued their Final Advisory earlier this morning.

GALE WARNING 047 ISSUED FROM RSMC NADI Apr 250020 UTC.

TROPICAL DEPRESSION 17F EX-TC AMOS CENTRE 998HPA WAS ANALYSED NEAR 14.8S 168.5W
AT 242300 UTC. POSITION GOOD. EX-TC AMOS MOVING EAST-SOUTHEAST AT 06 KNOTS.
EXPECT CLOCKWISE WINDS UPTO 35 KNOTS WITHIN 075 TO 150 NAUTICAL MILES AWAY FROM
CENTRE IN THE SECTORS FROM NORTH THROUGH EAST TO SOUTHEAST.

AREA OF GALES MOVING WITH DEPRESSION.

WTPS31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 20P (AMOS) WARNING NR 020//
RMKS/
1. TROPICAL CYCLONE 20P (AMOS) WARNING NR 020
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
241800Z --- NEAR 14.3S 168.4W
MOVEMENT PAST SIX HOURS - 120 DEGREES AT 12 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
REPEAT POSIT: 14.3S 168.4W
---
FORECASTS:
12 HRS, VALID AT:
250600Z --- 15.5S 166.8W
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
---
REMARKS:
242100Z POSITION NEAR 14.6S 168.0W. TROPICAL CYCLONE 20P (AMOS),
LOCATED APPROXIMATELY 134 NM EAST OF PAGO PAGO, AMERICAN SAMOA, HAS
TRACKED EAST-SOUTHEASTWARD AT 12 KNOTS OVER THE PAST SIX HOURS.
ANIMATED INFRARED AND VISIBLE IMAGERY DEPICT A VERY SHEARED SYSTEM
WITH A BROAD BAND OF CIRRUS CLOUDS OBSCURING ANY VIEW OF THE LOW
LEVEL CIRCULATION CENTER (LLCC). A 241720Z SSMIS 91 GHZ MICROWAVE
IMAGE SHOWED A BROAD, ELONGATED AND INDISTINCT CIRCULATION. THE
INITIAL POSITION IS PLACED BETWEEN THE PGTW AND KNES FIX POSITIONS
WITH LOW CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS
BASED ON A CONSENSUS OF SUBJECTIVE DVORAK FINAL T-NUMBER AND CURRENT
INTENSITY ESTIMATES FROM MULTIPLE REPORTING AGENCIES, AND IS ALSO
CONSISTENT WITH THE PREVIOUSLY-OBSERVED WEAKENING TREND. TC 20P
CONTINUES TO RAPIDLY WEAKEN IN RESPONSE TO PERSISTENT WESTERLY
VERTICAL WIND SHEAR (VWS) AS IT TRACKS GENERALLY EAST-SOUTHEASTWARD
ALONG THE PERIPHERY OF A NEAR-EQUATORIAL RIDGE. DISSIPATION OF THE
CYCLONE IS IMMINENT AS PERSISTENT SHEAR CONTINUES TO IMPACT THE
SYSTEM, PREVENTING REINTENSIFICATION. 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 241800Z IS 18 FEET.//

Earlier track-maps...