WPAC: ATSANI - Post-Tropical

[euro6208]

[cycloneye]

JTWC upgrades to TD.

23W TWENTYTHREE 201029 1200 8.2N 148.4E WPAC 25 1006

[aspen]

I think there’s a high likelihood of the HWRF going sub-900 with Atsani sometime during its life. It already has a 909 mbar peak and it’s only a TD.

[euro6208]

So EURO went haywire in the 00z run and GFS continues to show a powerful typhoon.

Can't wait to see the intensity forecast!

JTWC upgrades to TD.

[cycloneye]

JMA upgrades to TS Atsani.

TS 2020 (Atsani)
Issued at 13:30 UTC, 29 October 2020

<Analysis at 12 UTC, 29 October>
Scale -
Intensity -
Center position N8°00' (8.0°)
E148°25' (148.4°)
Direction and speed of movement N 20 km/h (10 kt)
Central pressure 1000 hPa
Maximum sustained wind speed 18 m/s (35 kt)
Maximum wind gust speed 25 m/s (50 kt)
≥ 30 kt wind area ALL 280 km (150 NM)

<Forecast for 00 UTC, 30 October>
Intensity -
Center position of probability circle N10°10' (10.2°)
E147°00' (147.0°)
Direction and speed of movement NNW 25 km/h (13 kt)
Central pressure 996 hPa
Maximum sustained wind speed 20 m/s (40 kt)
Maximum wind gust speed 30 m/s (60 kt)
Radius of probability circle 85 km (45 NM)

<Forecast for 12 UTC, 30 October>
Intensity -
Center position of probability circle N11°40' (11.7°)
E144°05' (144.1°)
Direction and speed of movement WNW 30 km/h (16 kt)
Central pressure 992 hPa
Maximum wind speed near center 23 m/s (45 kt)
Maximum wind gust speed 35 m/s (65 kt)
Radius of probability circle 120 km (65 NM)

<Forecast for 12 UTC, 31 October>
Intensity -
Center position of probability circle N14°20' (14.3°)
E140°20' (140.3°)
Direction and speed of movement NW 20 km/h (11 kt)
Central pressure 975 hPa
Maximum wind speed near center 35 m/s (65 kt)
Maximum wind gust speed 50 m/s (95 kt)
Radius of probability circle 165 km (90 NM)
Storm warning area ALL 250 km (135 NM)

<Forecast for 12 UTC, 1 November>
Intensity -
Center position of probability circle N16°55' (16.9°)
E136°20' (136.3°)
Direction and speed of movement WNW 20 km/h (12 kt)
Central pressure 965 hPa
Maximum wind speed near center 40 m/s (75 kt)
Maximum wind gust speed 55 m/s (105 kt)
Radius of probability circle 260 km (140 NM)
Storm warning area ALL 370 km (200 NM)

<Forecast for 12 UTC, 2 November>
Intensity Very strong
Center position of probability circle N18°40' (18.7°)
E133°10' (133.2°)
Direction and speed of movement WNW 15 km/h (9 kt)
Central pressure 950 hPa
Maximum wind speed near center 45 m/s (85 kt)
Maximum wind gust speed 60 m/s (120 kt)
Radius of probability circle 370 km (200 NM)
Storm warning area ALL 520 km (280 NM)

<Forecast for 12 UTC, 3 November>
Intensity Very strong
Center position of probability circle N19°25' (19.4°)
E132°25' (132.4°)
Direction and speed of movement NW Slow
Central pressure 950 hPa
Maximum wind speed near center 45 m/s (85 kt)
Maximum wind gust speed 60 m/s (120 kt)
Radius of probability circle 520 km (280 NM)
Storm warning area ALL 650 km (360 NM)

[euro6208]

So much suspense. Their warning graphic not even updated yet for Goni.

[dexterlabio]

Even in their 2015 counterparts, Goni and Atsani were a duo.

[doomhaMwx]

Atsani is contributed by Thailand and means "Lightening flash". A fitting name for this.

[euro6208]

[ElectricStorm]

High chance of back to back Cat 5's in the WPAC. But I think this one *could* become insane if these model runs pan out

[euro6208]

High chance of back to back Cat 5's in the WPAC. But I think this one *could* become insane if these model runs pan out

Last Cat 5 in the WPAC was Halong back in November of last year which peaked at 165 knots. Incredible.

[euro6208]

WDPN32 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI) WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 23W (ASTANI), LOCATED APPROXIMATELY 389 NM
SOUTH-SOUTHEAST OF ANDERSEN AFB, HAS TRACKED NORTHWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS AND RELATIVELY DISORGANIZED SYSTEM, WITH DEEP
CONVECTION FLARING TO THE EAST OF THE BROAD LOW LEVEL CIRCULATION
CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH MODERATE
CONFIDENCE BASED ON A COMBINATION OF ANIMATED 3.9 MICRON SHORTWAVE
INFRARED IMAGERY, SUPPORTED BY A 291155Z ASCAT-B BULLSEYE THAT
SHOWED THE DISORGANIZED AND ASYMMETRIC CIRCULATION TO GOOD EFFECT.
THE INITIAL INTENSITY IS ASSESSED WITH MODERATE CONFIDENCE BASED ON
DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25 KNOTS) FROM BOTH PGTW
AND KNES. THE AFOREMENTIONED ASCAT DATA DID INDICATE 30 KNOT WINDS
WITH SOME ISOLATED 35 KNOT WINDS IN THE SOUTHEAST QUADRANT, HOWEVER
THESE HIGHER WINDS ARE ALL CONFINED TO THE SOUTHERN SIDE OF THE
SYSTEM, WITH ONLY 15-20 KNOT MAXIMUM WINDS ON THE NORTHERN SIDE. DUE
TO THIS ASYMMETRY, THE INITIAL INTENSITY WAS SET AT 25 KNOTS. TD 23W
IS TRACKING JUST A BIT WEST OF DUE NORTH UNDER THE STEERING
INFLUENCE OF AN EXTENSION OF A LARGE, DEEP-LAYER SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST. TD 23W IS TRACKING THROUGH A
GENERALLY FAVORABLE ENVIRONMENT WITH WARM (30 DEG CELSIUS) SSTS,
GOOD WESTWARD AND EQUATORWARD OUTFLOW OFFSETTING MODERATE TO HIGH
(20-25 KNOTS) VWS.
3. FORECAST REASONING.
A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
B. TD 2W IS FORECAST TO TURN TO A MORE NORTHWESTWARD TRACK OVER
THE NEXT 12 HOURS, AS THE STEERING RIDGE REORIENTS SLIGHTLY, AND TO
CONTINUE THIS NORTHWESTWARD TRACK THROUGH TAU 72. AS THE SYSTEM
TRACKS NORTHWESTWARD, IT WILL BEGIN TO BE IMPACTED BY THE OUTFLOW
FROM TY 22W, WITH CONVERGENT UPPER-LEVEL FLOW MOVING DOWN FROM THE
NORTH LIMITING THE AVAILABLE OUTFLOW TO A SINGLE WESTWARD CHANNEL.
THIS, COMBINED WITH MODERATE VWS WILL OFFSET THE VERY WARM (30 DEG
CELSIUS), HIGH OHC WATERS OVER WHICH THE SYSTEM WILL TRACK. BY TAU
48 THE UPPER-LEVEL PATTERN WILL BEGIN TO SHIFT, WITH THE FORECAST
DEVELOPMENT OF AN UPPER-LEVEL ANTICYCLONE JUST EAST OF THE LLCC,
PROVIDING INCREASING DIVERGENT OUTFLOW, AND ALLOWING THE SYSTEM TO
START INTENSIFYING AT A FASTER RATE, INCREASING TO 80 KNOTS BY TAU
72. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36 BUT
CROSS-TRACK SPREAD INCREASES TO 185 NM AT TAU 72 WITH JGSM AND GFS
REPRESENTING THE NORTH AND SOUTH OUTLIERS AT TAU 72. THE JTWC
FORECAST TRACK LIES ALONG THE NORTHERN EDGE OF THE MODEL ENVELOPE
THROUGH TAU 12 TO REFLECT THE NEAR-TERM MOTION, THEN LIES VERY CLOSE
TO THE MULTI-MODEL CONSENSUS THOUGH TAU 72 WITH FAIR CONFIDENCE.
C. BEYOND TAU 72, THE SYSTEM WILL SLOW DOWN WHILE TURNING MORE
NORTHWARD TOWARDS A WEAKNESS A COL AREA THAT DEVELOPS IN A WEAKNESS
IN THE STR TO THE NORTH. AS THE SYSTEM CLOSER TO THE COL REGION, IT
BEGINS TO TAP INTO DUAL-CHANNEL OUTFLOW, ALLOWING IT TO QUICKLY
INTENSIFY FROM TAU 72 TO TAU 96, PEAKING AT 100 KNOTS. THEREAFTER
INTENSITY REMAINS STEADY AS THE SYSTEM MOVES SLOWLY ACROSS AN AREA
OF COOLER WATERS IN THE WAKE OF TY 22W, WHILE OUTFLOW DEGRADES
SIMULTANEOUSLY. NUMERICAL GUIDANCE IS MIXED BEYOND TAU 72, WITH A
BIFURCATION SCENARIO SETTING UP AFTER TAU 96. THE GFS SOLUTION
INCREASES THE STRENGTH OF THE STEERING RIDGE TO THE NORTH AND TRACKS
THE SYSTEM ON A MORE WESTWARD TRACK TOWARDS THE BASHI CHANNEL BEYOND
TAU 120. THE ECMWF AND NAVGEM FAVOR A SLOW TRACK NORTHWARD INTO A
STRONG WEAKNESS IN THE STR, LEADING TO A 320 NM SPREAD AT TAU 120.
THE JTWC FORECAST TRACKS SLOWER AND JUST WEST OF THE MULTI-MODEL
CONSENSUS AND FAVORS THE ECMWF AND NAVGEM SOLUTIONS WITH LOW
CONFIDENCE.//
NNNN

[ElectricStorm]

https://i.imgur.com/GvcHu5F.gif

WDPN32 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI) WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 23W (ASTANI), LOCATED APPROXIMATELY 389 NM
SOUTH-SOUTHEAST OF ANDERSEN AFB, HAS TRACKED NORTHWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS AND RELATIVELY DISORGANIZED SYSTEM, WITH DEEP
CONVECTION FLARING TO THE EAST OF THE BROAD LOW LEVEL CIRCULATION
CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH MODERATE
CONFIDENCE BASED ON A COMBINATION OF ANIMATED 3.9 MICRON SHORTWAVE
INFRARED IMAGERY, SUPPORTED BY A 291155Z ASCAT-B BULLSEYE THAT
SHOWED THE DISORGANIZED AND ASYMMETRIC CIRCULATION TO GOOD EFFECT.
THE INITIAL INTENSITY IS ASSESSED WITH MODERATE CONFIDENCE BASED ON
DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25 KNOTS) FROM BOTH PGTW
AND KNES. THE AFOREMENTIONED ASCAT DATA DID INDICATE 30 KNOT WINDS
WITH SOME ISOLATED 35 KNOT WINDS IN THE SOUTHEAST QUADRANT, HOWEVER
THESE HIGHER WINDS ARE ALL CONFINED TO THE SOUTHERN SIDE OF THE
SYSTEM, WITH ONLY 15-20 KNOT MAXIMUM WINDS ON THE NORTHERN SIDE. DUE
TO THIS ASYMMETRY, THE INITIAL INTENSITY WAS SET AT 25 KNOTS. TD 23W
IS TRACKING JUST A BIT WEST OF DUE NORTH UNDER THE STEERING
INFLUENCE OF AN EXTENSION OF A LARGE, DEEP-LAYER SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST. TD 23W IS TRACKING THROUGH A
GENERALLY FAVORABLE ENVIRONMENT WITH WARM (30 DEG CELSIUS) SSTS,
GOOD WESTWARD AND EQUATORWARD OUTFLOW OFFSETTING MODERATE TO HIGH
(20-25 KNOTS) VWS.
3. FORECAST REASONING.
A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
B. TD 2W IS FORECAST TO TURN TO A MORE NORTHWESTWARD TRACK OVER
THE NEXT 12 HOURS, AS THE STEERING RIDGE REORIENTS SLIGHTLY, AND TO
CONTINUE THIS NORTHWESTWARD TRACK THROUGH TAU 72. AS THE SYSTEM
TRACKS NORTHWESTWARD, IT WILL BEGIN TO BE IMPACTED BY THE OUTFLOW
FROM TY 22W, WITH CONVERGENT UPPER-LEVEL FLOW MOVING DOWN FROM THE
NORTH LIMITING THE AVAILABLE OUTFLOW TO A SINGLE WESTWARD CHANNEL.
THIS, COMBINED WITH MODERATE VWS WILL OFFSET THE VERY WARM (30 DEG
CELSIUS), HIGH OHC WATERS OVER WHICH THE SYSTEM WILL TRACK. BY TAU
48 THE UPPER-LEVEL PATTERN WILL BEGIN TO SHIFT, WITH THE FORECAST
DEVELOPMENT OF AN UPPER-LEVEL ANTICYCLONE JUST EAST OF THE LLCC,
PROVIDING INCREASING DIVERGENT OUTFLOW, AND ALLOWING THE SYSTEM TO
START INTENSIFYING AT A FASTER RATE, INCREASING TO 80 KNOTS BY TAU
72. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36 BUT
CROSS-TRACK SPREAD INCREASES TO 185 NM AT TAU 72 WITH JGSM AND GFS
REPRESENTING THE NORTH AND SOUTH OUTLIERS AT TAU 72. THE JTWC
FORECAST TRACK LIES ALONG THE NORTHERN EDGE OF THE MODEL ENVELOPE
THROUGH TAU 12 TO REFLECT THE NEAR-TERM MOTION, THEN LIES VERY CLOSE
TO THE MULTI-MODEL CONSENSUS THOUGH TAU 72 WITH FAIR CONFIDENCE.
C. BEYOND TAU 72, THE SYSTEM WILL SLOW DOWN WHILE TURNING MORE
NORTHWARD TOWARDS A WEAKNESS A COL AREA THAT DEVELOPS IN A WEAKNESS
IN THE STR TO THE NORTH. AS THE SYSTEM CLOSER TO THE COL REGION, IT
BEGINS TO TAP INTO DUAL-CHANNEL OUTFLOW, ALLOWING IT TO QUICKLY
INTENSIFY FROM TAU 72 TO TAU 96, PEAKING AT 100 KNOTS. THEREAFTER
INTENSITY REMAINS STEADY AS THE SYSTEM MOVES SLOWLY ACROSS AN AREA
OF COOLER WATERS IN THE WAKE OF TY 22W, WHILE OUTFLOW DEGRADES
SIMULTANEOUSLY. NUMERICAL GUIDANCE IS MIXED BEYOND TAU 72, WITH A
BIFURCATION SCENARIO SETTING UP AFTER TAU 96. THE GFS SOLUTION
INCREASES THE STRENGTH OF THE STEERING RIDGE TO THE NORTH AND TRACKS
THE SYSTEM ON A MORE WESTWARD TRACK TOWARDS THE BASHI CHANNEL BEYOND
TAU 120. THE ECMWF AND NAVGEM FAVOR A SLOW TRACK NORTHWARD INTO A
STRONG WEAKNESS IN THE STR, LEADING TO A 320 NM SPREAD AT TAU 120.
THE JTWC FORECAST TRACKS SLOWER AND JUST WEST OF THE MULTI-MODEL
CONSENSUS AND FAVORS THE ECMWF AND NAVGEM SOLUTIONS WITH LOW
CONFIDENCE.//
NNNN

That seems pretty conservative, although first advisories for any agency usually are. I really hope this recurves, as every big storm in 2020 has hit land. I want one that I can root for to become an all-out monster lol

[aspen]

Tons of OHC in its path.

[Hayabusa]

[aspen]

Globals have been trending weaker with Atsani, likely due to the outflow from the far stronger than anticipated Goni. However, once Goni is out of the picture, outflow-caused shear won’t be an issue.

[Hayabusa]

Big change in 18Z keeps it weak until it nears the Philippines

[1900hurricane]

Pretty notable bifurcation after tau 120 with the 12Z EPS. The system stays generally weak until then, but then encounters either a north or west split. Looks like the west splits get an opportunity to become strong while north splits move out of the tropics largely uneventfully.

[euro6208]

WDPN32 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI)
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY 297 NM
SOUTH-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED NORTH-
NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY DEPICTS A BROAD AREA OF GENERALLY
DISORGANIZED DEEP CONVECTIVE ACTIVITY. A 291610Z AMSR2 89 GHZ PASS
SUGGESTS THE LOW LEVEL CIRCULATION CENTER (LLCC) MAY BE
CONSOLIDATING AROUND A DEVELOPING VERTICAL TOWER NEAR THE CENTER OF
THE CONVECTIVE MASS, WHILE ACTIVITY ALONG THE NORTHERN PERIPHERY
APPEARS LINEAR AND NOT WRAPPING. THE CIMSS 850 MB VORTICITY PRODUCT
ALSO DEPICTS THE CURRENT STRUCTURE ASYMMETRY. THERE IS A HIGH DEGREE
OF UNCERTAINTY IN THE INITIAL PLACEMENT AS THE LLCC IS NOT FIRMLY
ESTABLISHED AND MAY SHIFT. THE INITIAL POSITION IS BASED ON FIXES
FROM PGTW AND RJTD, AND THE AFOREMENTIONED AMSR2 DATA. THE INITIAL
INTENSITY IS ASSESSED AT 25 KTS BASED ON SUBJECTIVE DVORAK
ESTIMATES. THE AMSR2 WIND SPEED PRODUCT INDICATES AN ISOLATED AREA
OF 30 TO 34 KNOT WINDS TO THE EAST, HOWEVER, AN EARLIER SCAT PASS
AND CURRENT STRUCTURE ANALYSIS INDICATES THESE ISOLATED HIGHER WINDS
ARE NOT REPRESENTATIVE OF THE SYSTEM’S OVERALL DEVELOPMENT AT THIS
TIME. UPPER LEVEL ANALYSIS INDICATES MODERATE (15-20 KNOT) VERTICAL
WIND SHEAR OVER THE SYSTEM MAY BE HAMPERING DEVELOPMENT, HOWEVER,
THIS IS PARTIALLY OFFSET BY DIVERGENCE OVER THE LLCC. 30 TO 31
DEGREE CELSIUS SEA SURFACE TEMPERATURES ARE VERY FAVORABLE. TD 23 IS
CURRENTLY TRACKING GENERALLY NORTHWESTWARD ALONG A RIDGE OF HIGH
PRESSURE TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TD 23W IS FORECAST TO CONTINUE ITS PIVOT TO A MORE
NORTHWESTWARD TRACK OVER THE NEXT 12 HOURS, AS THE STEERING RIDGE
REORIENTS SLIGHTLY, AND IS FORECAST TO CONTINUE THIS NORTHWESTWARD
TRACK THROUGH TAU 72. AS THE SYSTEM TRACKS NORTHWESTWARD, IT WILL
BEGIN TO BE IMPACTED BY THE OUTFLOW FROM TY 22W, WITH CONVERGENT
UPPER-LEVEL FLOW MOVING DOWN FROM THE NORTH LIMITING THE AVAILABLE
OUTFLOW TO A SINGLE WESTWARD CHANNEL. THIS, COMBINED WITH MODERATE
VWS WILL OFFSET THE VERY WARM (30 DEG CELSIUS) WATERS TO LIMIT THE
SYSTEM’S INTENSIFICATION THROUGH TAU 48. AFTER TAU 48 THE UPPER-
LEVEL PATTERN WILL BEGIN TO SHIFT AND PROVIDE INCREASING DIVERGENT
OUTFLOW ALLOWING THE SYSTEM TO START INTENSIFYING AT A FASTER RATE,
INCREASING TO 80 KNOTS BY TAU 72. THE JTWC FORECAST TRACK IS PLACED
WITH HIGH CONFIDENCE THROUGH TAU 48 AND LIES SLIGHTLY SOUTH OF THE
MULTI-MODEL CONSENSUS TO ACCOUNT FOR JGSM, WHICH IS FAR TO THE NORTH
OF THE REMAINDER OF THE MODELS AT TAU 48. HOWEVER, NUMERICAL MODEL
GUIDANCE DIVERGES MORE AFTER TAU 48 LEADING TO MODERATE CONFIDENCE
BETWEEN TAUS 48-72 WITH CROSS-TRACK SPREAD INCREASING TO 250 NM AT
TAU 72 WITH AFUM AND GFS REPRESENTING THE NORTH AND SOUTH
OUTLIERS.//
NNNN

[aspen]

HWRF is up and running for Atsani. The 18z run doesn’t show RI until day 4, and it’s now showing a small eye like Goni.