WPAC: ATSANI - Post-Tropical

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Re: WPAC: ATSANI - Tropical Storm

#141 Postby NotoSans » Mon Nov 02, 2020 11:03 am

JTWC's intensity estimate has been fairly consistent with ASCAT.
ASCAT does well in this intensity range (25-35kt). The low bias only becomes apparent in mid-range TS. And Atsani is not a tiny system (in fact is is quite broad) that ASCAT is unlikely to undersample.
Last edited by NotoSans on Mon Nov 02, 2020 11:05 am, edited 1 time in total.
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Re: WPAC: ATSANI - Tropical Storm

#142 Postby 1900hurricane » Mon Nov 02, 2020 11:04 am

Ha, was literally about to post the exact same AVN loop from Alex's site. Atsani's status as a TC the last few days has been questionable at best, but it's definitely one again now. Could be ready to make some moves.
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Re: WPAC: ATSANI - Tropical Storm

#143 Postby euro6208 » Mon Nov 02, 2020 8:10 pm

WDPN32 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W
(ATSANI) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 472 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED EASTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY REVEALS THE SYSTEM HAS BECOME QUASI-STATIONARY OVER THE PAST
SIX HOURS, THE CENTRAL CONVECTION IS BECOMING DISPLACED OVER THE
SOUTHERN SEMICIRCLE OF THE SYSTEM, HOWEVER IT CONTINUES TO PARTIALLY
OBSCURE THE LOW LEVEL CIRCULATION (LLC) DECREASING CONFIDENCE IN THE
EXACT POSITION. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE
BASED ON THE LOW-LEVEL BANDING WRAPPING IN TO AN OBSCURED LLC IN THE
EIR LOOP AND A 021721Z AMSR2 89GHZ MICROWAVE IMAGE THAT REVEALS THE
SAME LOW-LEVEL BANDING, BUT THE EXACT CENTER POSITION IS STILL
OBSCURED. THE INITIAL INTENSITY OF 35KTS IS BASED ON THE DVORAK
ESTIMATES OF T2.5/35KTS FROM PGTW AND RJTD. THE ENVIRONMENT IS
FAVORABLE WITH LOW (5-15KT) VERTICAL WIND SHEAR (VWS) AND WARM (29-
30C) SEA SURFACE TEMPERATURES (SST), HOWEVER THE UPPER LEVEL OUTFLOW
IS LIMITED TO SINGLE-CHANNEL EQUATORWARD OUTFLOW. THE CYCLONE IS
CURRENTLY QUASI-STATIONARY LOCATED IN A COL AREA BETWEEN TWO
SUBTROPICAL RIDGES (STR), ONE TO THE EAST-NORTHEAST AND A SECOND TO
THE WEST-NORTHWEST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 23W WILL REMAIN QUASI-STATIONARY THROUGH TAU 48 WITH NO
DOMINANT STEERING MECHANISM AS IT CONTINUES TO SLOWLY MEANDER AROUND
THE COL IT IS CURRENTLY LOCATED NEAR. AROUND TAU 48 THE STR TO THE
EAST-NORTHEAST OF THE SYSTEM WILL BUILD AND TAKE OVER AS THE PRIMARY
STEERING MECHANISM SENDING TS 23W WESTWARD BETWEEN TAUS 48 AND 72. A
FAVORABLE ENVIRONMENT CONSISTING OF LOW (5-15KT) VWS, WARM (28C)
SST, AND DECENT UPPER LEVEL OUTFLOW TO THE WEST WILL PROMOTE STEADY
INTENSIFICATION TO A PEAK OF 65 KTS AT TAU 72. ALTHOUGH THERE HAVE
BEEN INDICATIONS OF THE POTENTIAL FOR RAPID INTESIFICATION THE QUASI-
STATIONARY NATURE OF THE SYSTEM CHURNING UP COOLER WATER BENEATH THE
SURFACE WILL LIKELY INHIBIT THE ABILITY OF THE SYSTEM TO RAPIDLY
INTENSIFY. NUMERICAL MODELS DIVERGE SIGNIFICANTLY WITH VARYING
SOLUTIONS IN THE DURATION OF QS STATE IN THE COL, LENDING LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
C. IN THE EXTENDED TAUS, THE PRIMARY STR WILL STEER TS 23W WEST-
NORTHWESTWARD THROUGH THE LUZON STRAIT, AND INTO THE SOUTH CHINA SEA
(SCS) TURNING TO THE WEST-SOUTHWEST BETWEEN TAUS 96 AND 120. THE
ENVIRONMENT WILL DETERIORATE DUE TO DECREASED DIVERGENCE ALOFT AND
COOLING SST IN THE SCS, WEAKENING THE SYSTEM TO 45KTS BY TAU 120.
NUMERICAL MODELS SIGNIFICANTLY DIVERGE WITH A SPREAD OF 600 NM BY
TAU 120 WITH ECMWF AND UEMN SUGGESTING A RECURVATURE INTO TAIWAN,
LENDING LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST
THAT IS LAID WITH THE MAIN CLUSTER OF THE MODEL ENVELOPE.//
NNNN
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Re: WPAC: ATSANI - Tropical Storm

#144 Postby euro6208 » Tue Nov 03, 2020 5:51 am

Image

WDPN32 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI)
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 396 NM SOUTH
OF KADENA AB, HAS TRACKED SOUTHEASTWARD AT 05 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH
CONVECTION BEGINNING TO ORGANIZE, CURRENTLY FLARING NEAR THE
ASSESSED CENTER POSITION WITH SOMEWHAT WEAKER CONVECTION BEGINNING
TO WRAP INTO THE LLCC. THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ANALYSIS OF THE LOW-LEVEL BANDING FEATURES EVIDENT
BETWEEN THE FLARE UPS OF CONVECTION, SUPPORTED BY EXTRAPOLATION TO A
030718Z SSMIS 91GHZ MICROWAVE IMAGE, SHOWING DEEP CONVECTION TO THE
SOUTH, AND WEAKER CONVECTIVE BANDING WRAPPING UP THE EAST SIDE. THE
INITIAL INTENSITY IS SET AT 35KTS BASED ON MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW, KNES AND
RJTD, AN AUTOMATED DVORAK TECHNIQUE ESTIMATE OF T2.1 AND A SATELLITE
CONSENSUS ESTIMATE OF 40 KNOTS. THE ENVIRONMENT IS OVERALL FAVORABLE
WITH THE SYSTEM COCOONED IN A SMALL POCKET OF LOW (5 KNOTS OR LESS)
VWS, RADIAL OUTFLOW BEING PROVIDED BY A RECENTLY DEVELOPED POINT
SOURCE OVERHEAD, AND WARM (27 TO 28C) SEA SURFACE TEMPERATURES
(SST). THE SYSTEM IS CURRENTLY MOVING SOUTHEAST AS IT MOVES IN A
CLOCKWISE LOOP IN A WEAK STEERING ENVIRONMENT IN A COL AREA BETWEEN
TWO SUBTROPICAL RIDGES (STR), ONE TO THE EAST-NORTHEAST AND A SECOND
TO THE WEST-NORTHWEST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 23W WILL SLOWLY DRIFT FIRST SOUTHEAST, THEN SOUTH, THEN
SOUTHWEST OVER THE NEXT 12-24 HOURS AS IT COMPLETES THE CLOCKWISE
LOOPING MOTION INSIDE THE AFOREMENTIONED COL REGION. BY TAU 24, STR
LOCATED TO THE NORTHEAST WILL BEGIN TO BUILD AND EXTEND WESTWARD,
ACCELERATING TS 23W ONTO A MORE WESTWARD TRACK BY TAU 24, CONTINUING
GENERALLY WESTWARD THROUGH TAU 72, WHEN IT WILL ENTER THE LUZON
STRAIT. SLOW BUT STEADY INTENSIFICATION IS FORECAST THOUGH TAU 72,
UNDER WEAKLY FAVORABLE CONDITIONS OF LOW (5-10 KNOTS) VWS AND
MODERATE UPPER-LEVEL OUTFLOW, BEING SOMEWHAT OFFSET BY THAT FACT
THAT THE SSTS ARE NOT EXCEPTIONALLY WARM AND WILL BE DECREASING AS
THE SYSTEM MOVES WEST. NUMERICAL MODELS ARE IN FAIR AGREEMENT THOUGH
TAU 72, WITH A 140NM SPREAD AT TAU 72, IF THE NVGM SOLUTION IS
DISCOUNTED, AND 270NM IF NVGM IS INCLUDED IN THE GUIDANCE ENVELOPE.
THE NAVGEM SOLUTION IS THE POLEWARD OUTLIER IN THE MULTI-MODEL
CONSENSUS, AND TAKES THE SYSTEM OVER SOUTHERN TAIWAN BEFORE DIVING
IT SHARPLY SOUTH TO REJOIN THE REMAINDER OF THE MODEL TRACKERS BY
TAU 72. IN LIGHT OF THE ERRATIC AND UNLIKELY NORTHWARD MOVEMENT
REPRESENTED BY THIS MODEL, IT IS DISCOUNTED FROM THE CONSENSUS. THE
JTWC FORECAST LIES VERY CLOSE TO THE MULTI-MODEL CONSENSUS SOLUTION
THROUGH TAU 72 WITH FAIR CONFIDENCE.
C. IN THE EXTENDED TAUS, THE PRIMARY STEERING RIDGE WILL REORIENT
TO A MORE SOUTHWEST-NORTHEAST ORIENTATION, PUSHING THE SYSTEM ONTO A
MORE WEST-SOUTHWESTWARD TRACK BY TAU 96. AS THE SYSTEM EXITS THE
LUZON STRAIT, IT WILL COME UNDER INCREASING PRESSURE FROM COOLER,
DRIER NORTHEASTERLY FLOW EXITING THE TAIWAN STRAIT, WHICH COMBINED
WITH INCREASED VWS, DECREASED UPPER-LEVEL OUTFLOW AND MARGINAL SSTS
(27 DEG CELSISUS), WILL STEADILY WEAKEN THE SYSTEM THROUGH TAU 120.
THE CONSENSUS MODELS, WITH THE EXCEPTION OF NVGM, ALL CONCUR ON THE
GENERAL SCENARIO OF A WEAKENING SYSTEM MOVING SOUTHWEST AFTER TAU
96, BUT DIFFER SOMEWHAT ON THE DEGREE OF THE TURN AND THE SPEED OF
THE SYSTEM, CROSS-TRACK SPREAD INCREASING TO 250NM WHILE ALONG-TRACK
SPREAD INCREASES TO 160NM BY TAU 120. THE JTWC OFFICIAL FORECAST
FAVORS THE ECMWF SOLUTION ON THE NORTHERN SIDE OF THE GUIDANCE
ENVELOPE WITH LOW CONFIDENCE.//
NNNN
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Re: WPAC: ATSANI - Tropical Storm

#145 Postby euro6208 » Tue Nov 03, 2020 5:53 am

TPPN10 PGTW 030923

A. TROPICAL STORM 23W (ATSANI)

B. 03/0900Z

C. 19.82N

D. 128.34E

E. FIVE/HMWRI8

F. T3.0/3.0/D1.0/24HRS STT: D0.5/03HRS

G. IR/EIR

H. REMARKS: 38A/PBO SBC/ANMTN. CNVCTN WRAPS .6 ON LOG10 SPIRAL
YIELDING A DT OF 3.0. MET AND PT AGREE. DBO DT.

I. ADDITIONAL POSITIONS:
03/0718Z 19.85N 128.25E SSMS


YOUNG
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Re: WPAC: ATSANI - Tropical Storm

#146 Postby ElectricStorm » Tue Nov 03, 2020 10:05 am

Remember when we thought this storm was going to become a monster? Yeah, fun times
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Re: WPAC: ATSANI - Tropical Storm

#147 Postby euro6208 » Tue Nov 03, 2020 10:29 am

Weather Dude wrote:Remember when we thought this storm was going to become a monster? Yeah, fun times


Sheared by Goni unfortunately.
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Re: WPAC: ATSANI - Tropical Storm

#148 Postby underthwx » Tue Nov 03, 2020 11:12 am

Is Atsani one of two systems tracking towards Vietnam?
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Re: WPAC: ATSANI - Tropical Storm

#149 Postby underthwx » Tue Nov 03, 2020 11:43 am

Is Atsani forecast to gradually weaken as it moves west?
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Re: WPAC: ATSANI - Tropical Storm

#150 Postby euro6208 » Tue Nov 03, 2020 11:47 am

Image
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Re: WPAC: ATSANI - Tropical Storm

#151 Postby euro6208 » Wed Nov 04, 2020 5:30 am

Image


WDPN32 PGTW 040900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI)
WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 379NM SOUTH OF
KADENA AB, HAS TRACKED NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT
THE SYSTEM HAS BECOME QUASI-STATIONARY, WITH THE LOW LEVEL
CIRCULATION CENTER (LLCC) OBSCURED BY FLARING DEEP CONVECTION. THE
INITIAL POSITION IS PLACED WITH ONLY FAIR CONFIDENCE DUE TO THE
OBSCURED LLCC, WITH A 040458Z AMSR2 89 GHZ MICROWAVE IMAGE LENDING
SUPPORT TO THE INITIAL POSITION. THE INITIAL INTENSITY IS
ASSESSED WITH FAIR CONFIDENCE ON AN ANALYSIS OF THE PGTW DVORAK
CURRENT INTENSITY ESTIMATE OF T3.0 (45 KNOTS), AN ADVANCED DVORAK
TECHNIQUE (ADT) ESTIMATE OF T3.2 AND A SATELLITE CONSENSUS ESTIMATE
OF 46 KNOTS. TS 23W LIES IN AN OVERALL FAVORABLE ENVIRONMENT, WITH
LOW (5-10 KNOTS) OF EASTERLY VWS, GOOD EQUATORWARD AND POLEWARD
OUTFLOW AND WARM (28 TO 29 DEG CELSIUS) SSTS. INITIAL MOTION HAS
BEEN ERRATIC OVER THE PAST 12 HOURS IN A WEAK STEERING ENVIRONMENT,
AND IT APPEARS AS IF THE CENTER IS CURRENTLY LOOPING BACK TO THE
NORTH AND WEST BASED ON ANIMATED VISIBLE IMAGERY.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. WHILE THE NEAR-TERM MOTION REMAINS ERRATIC, ANALYSIS OF THE
DEEP-LAYER MEAN FLOW IN THE GLOBAL MODELS AND 500MB ANALYSIS
INDICATE THAT THE STR TO THE NORTHEAST HAS ALREADY BEGUN TO BUILD
WESTWARD, WITH RIDGING FORECAST TO BUILD WEST OVER TAIWAN AND
EASTERN CHINA BY TAU 24, EFFECTIVELY ELIMINATING THE COL REGION IN
WHICH TS 23W CURRENTLY IS ENSCONCED, PUSHING THE SYSTEM ONTO A
WESTWARD TRACK BY TAU 12. AS THE RIDGE BECOMES MORE ENTRENCHED TO
THE NORTH, TS 23W WILL ACCELERATE WHILE CONTINUING WESTWARD THROUGH
TAU 72. THE SYSTEM IS FORECAST TO STEADILY INTENSIFY TO A PEAK OF 65
KNOTS BY TAU 48 UNDER GENERALLY SUPPORTIVE CONDITIONS OF LOW (5 TO
15 KNOTS) VWS, SINGLE CHANNEL DIVERGENT WESTWARD OUTFLOW AND
RELATIVELY WARM (28 TO 29 DEG CELSIUS). DYNAMIC MODEL GUIDANCE IS IN
VERY GOOD AGREEMENT THROUGH 72, WITH THE NOTABLE EXCEPTION OF
NAVGEM, WHICH CONTINUES TO SHOW AN UNREALISTIC NORTHWESTWARD TRACK
TOWARDS TAIWAN. THE JTWC FORECAST LIES ALONG THE NORTHERN EDGE OF
GUIDANCE ENVELOPE THROUGH TAU 24 IN LIGHT OF THE NEAR-TERM
NORTHWESTWARD MOVEMENT, THEN NEAR THE MULTI-MODEL CONSENSUS SOLUTION
THROUGH TAU 72 WITH FAIR CONFIDENCE.
C. IN THE EXTENDED TAUS, THE SYSTEM WILL ENTER THE NORTHERN
PORTION OF THE SOUTH CHINA SEA BY TAU 72 ON A GENERALLY WESTWARD
TRACK AS STRONG TROPICAL STORM. HOWEVER, THE COMBINATION OF
INCREASED VWS, CONVERGENT UPPER-LEVEL FLOW, THE ENTRAINMENT OF
DRIER, COOLER AIR FROM THE NORTH, AND COOLER SSTS WILL COMBINE TO
STEADILY WEAKEN THE SYSTEM THROUGH TAU 120. AS THE SYSTEM WEAKENS,
AND VORTEX BECOMES WEAKER, IT WILL COME UNDER THE STEERING INFLUENCE
OF THE LOW TO MID-LEVEL FLOW FROM THE NORTHEAST, PUSHING THE SYSTEM
ONTO A SOUTHWESTWARD TRACK AFTER TAU 72. TS 23W IS FORECAST TO MAKE
LANDFALL ALONG THE SOUTHERN VIETNAMESE COASTLINE JUST PRIOR TO TAU
120 AS A WEAK TROPICAL STORM, BEFORE CONTINUING TO TRACK INLAND
TOWARDS THE SOUTHWEST. DYNAMIC MODEL GUIDANCE IS IN OVERALL GOOD
AGREEMENT, WITH CROSS-TRACK SPREAD INCREASING TO 185 NM BY TAU 120.
NOTABLY, THE NAVGEM AND ECMWF MODELS TAKE THE SYSTEM POLEWARD
TOWARDS THE TAIWAN STRAIT AND LOSE THE VORTEX BY TAU 96, WHICH IS
SKEWING THE MULTI-MODEL CONSENSUS FURTHER TO THE NORTH. THE JTWC
FORECAST DISCOUNTS THESE TWO MODELS, AND LIES ALONG THE SOUTHERN
SIDE OF THE CONSENSUS ENVELOPE. HOWEVER, IN VIEW OF THE UNCERTAINTY
IN THE EXACT TIMING OF THE TURN SOUTHWARD, THERE IS LOW CONFIDENCE
IN THIS PORTION OF THE FORECAST TRACK.//
NNNN
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Re: WPAC: ATSANI - Tropical Storm

#152 Postby euro6208 » Wed Nov 04, 2020 7:33 am

Interesting. EURO wants to deepen this down to 977 mb before a possible Taiwan landfall.
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Re: WPAC: ATSANI - Severe Tropical Storm

#153 Postby Hayabusa » Wed Nov 04, 2020 7:42 am

STS 2020 (Atsani)
Issued at 12:45 UTC, 4 November 2020

<Analysis at 12 UTC, 4 November>
Scale -
Intensity -
Center position N20°10' (20.2°)
E128°40' (128.7°)
Direction and speed of movement NW Slow
Central pressure 994 hPa
Maximum wind speed near center 25 m/s (50 kt)
Maximum wind gust speed 35 m/s (70 kt)
≥ 30 kt wind area ALL 280 km (150 NM)
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Re: WPAC: ATSANI - Tropical Storm

#154 Postby ElectricStorm » Wed Nov 04, 2020 7:25 pm

Man this is one weird looking storm on IR...
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Re: WPAC: ATSANI - Tropical Storm

#155 Postby euro6208 » Wed Nov 04, 2020 8:34 pm

Peak increase to 70 knots.

WDPN32 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI)
WARNING NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 391
NM SOUTH OF KADENA AB, HAS TRACKED WEST-SOUTHWESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS SPIRAL BANDS OF CONVECTION
WRAPPING INTO A LOW LEVEL CIRCULATION CENTER (LLCC) THAT IS
OBSCURED BY DENSE CONVECTION OVER THE CENTER OF THE SYSTEM.
THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED
ON THE LOW LEVEL CIRCULATION FEATURES IN THE EIR LOOP AS
WELL AS IN A 041718Z ATMS 165 GHZ IMAGE. THE INITIAL
INTENSITY OF 50 KTS IS PLACED WITH FAIR CONFIDENCE BETWEEN
MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T3.5
(55 KTS, PGTW) AND T3.0 (45 KTS, RJTD) AND IN AGREEMENT
WITH A CIMSS ADVANCED DVORAK TECHNIQUE CURRENT INTENSITY
ESTIMATE OF T3.3 (51 KTS). THE ENVIRONMENT IS FAVORABLE FOR
INTENSIFICATION WITH LOW (5-10) KTS VERTICAL WIND SHEAR
(VWS), WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURES AND
ROBUST POLEWARD AND MODERATE EQUATORWARD OUTFLOW ALOFT. THE
STEERING ENVIRONMENT HAS IMPROVED OVER THE LAST 6 HOURS AND
THE SYSTEM IS NOW TRACKING WEST-SOUTHWESTWARD ALONG THE
PERIPHERY OF THE SUBTROPICAL RIDE POSITIONED TO THE
NORTHEAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 23W HAS BEGUN ITS WESTWARD MOVEMENT AS THE STR TO THE
NORTHEAST BUILDS IN TO THE NORTH, AND IT IS FORECAST THAT THE
SYSTEM WILL ACCELERATE ALONG THIS GENERAL WEST-NORTHWEST
MOTION THROUGH TAU 48. THE SYSTEM IS FORECAST TO GRADUALLY
INTENSIFY TO 70 KTS BY THIS TIME DUE TO CONTINUED LOW (10-15
KTS) VWS, WARM SST AND UPPER LEVEL SUPPORT. AFTER TAU 48, THE
SYSTEM WILL SLOW SOMEWHAT AS THE STR WEAKENS SLIGHTLY AND
REORIENTS TO A MORE SOUTHWEST TO NORTHEAST ORIENTATION. BY TAU 72
THE PRIMARY STEERING MECHANISM WILL SHIFT TO THE STR LOCATED
OVER CENTRAL CHINA, WHICH WILL SERVE TO SHIFT THE TRACK MORE
SOUTHWESTWARD. THIS NEW TRACK WILL BRING THE SYSTEM INTO HIGH
(30-35 KTS) VWS WHICH WILL WEAKEN THE SYSTEM INTENSITY TO 45
KTS BY TAU 72. NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT, HOWEVER NAVGEM AND AFUM DIVERGE SIGNIFICANTLY FROM
THE MULTI-MODEL CONSENSUS. SPECIFICALLY, NAVGEM DRIVES THE
VORTEX NORTHWARD WHILE AFUM BRINGS THE SYSTEM SOUTH TOWARDS
LUZON. AS SUCH, THIS INITIAL PORTION OF THE JTWC FORECAST
TRACK IS PLACED WITH GOOD CONFIDENCE AND IS LAID SLIGHTLY
SOUTH OF THE JTWC MULTI-MODEL CONSENSUS IN ORDER TO OFFSET THE
UNREALISTIC TRACKS FROM THESE MODELS.
C. IN THE EXTENDED TAUS, THE SYSTEM WILL ENTER THE NORTHERN
PORTION OF THE SOUTH CHINA SEA BY TAU 72 ON A GENERALLY WEST-
SOUTHWESTWARD TRACK ALONG THE SOUTHEAST PERIPHERY OF THE STR
OVER CENTRAL CHINA. SIMULTANEOUSLY, THE COMBINATION OF
INCREASED VWS, CONVERGENT UPPER-LEVEL FLOW, ENTRAINMENT OF
DRIER AIR FROM THE NORTH, AND COOLER SSTS WILL COMBINE TO
STEADILY WEAKEN THE SYSTEM TO 30 KTS BY TAU 96. AS THE SYSTEM
WEAKENS, IT WILL COME UNDER THE STEERING INFLUENCE OF THE LOW
TO MID-LEVEL FLOW FROM THE NORTHEAST, LEADING TO A
SOUTHWESTWARD TRACK THAT WILL LEAD TO LANDFALL AFTER TAU 96
ALONG THE SOUTH CENTRAL COAST OF VIETNAM. INTERACTION WITH THE
UNDERLYING TERRAIN WILL LEAD TO FURTHER WEAKENING AND FULL
DISSIPATION OVER LAND BY TAU 120. AFTER DISCOUNTING THE
AFOREMENTIONED NAVGEM AND AFUM OUTLIERS, THERE REMAINS GOOD
AGREEMENT IN NUMERICAL MODEL SOLUTIONS AND AS SUCH THE JTWC
FORECAST TRACK IS PLACED WITH GOOD CONFIDENCE ALONG THE
MULTI-MODEL CONSENSUS THROUGH THE REMAINDER OF THE FORECAST
PERIOD.//
NNNN
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Re: WPAC: ATSANI - Tropical Storm

#156 Postby ElectricStorm » Thu Nov 05, 2020 12:43 am

0z HWRF takes it to 976mb before a landfall in far S Taiwan
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Re: WPAC: ATSANI - Tropical Storm

#157 Postby doomhaMwx » Thu Nov 05, 2020 11:13 am

Looks to have weakened instead of intensify. It has become convectively anemic and those numerous 50kt flags found by ASCAT in the morning (~01Z) are now gone on the ~11Z pass.

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Re: WPAC: ATSANI - Tropical Storm

#158 Postby aspen » Thu Nov 05, 2020 12:45 pm

This really busted HARD. Now it won’t even become a Category 1. Remember how quickly the models had this develop into a MH-equivalent typhoon?

Goni’s RI and outflow really took their toll on Atsani.
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Re: WPAC: ATSANI - Tropical Storm

#159 Postby euro6208 » Thu Nov 05, 2020 10:07 pm

WDPN32 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) WARNING
NR 031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 23W (ATSANI), LOCATED APPROXIMATELY 265 NM
SOUTH OF TAIPEI, TAIWAN, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS BUILDING CONVECTION THAT IS NOW OBSCURING A LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH
GOOD CONFIDENCE BASED ON LOW LEVEL SPIRAL BANDS THAT WRAP INTO THE
LLCC IN THE MSI LOOP AS WELL AS A MICROWAVE EYE FEATURE PRESENT IN
A 052308Z SSMIS 37 GHZ IMAGE. THE INITIAL INTENSITY IS ASSESSED AT
45 KTS WITH FAIR CONFIDENCE BASED ON A DVORAK CURRENT INTENSITY
ESTIMATE OF T3.0 (45 KTS) FROM PGTW AND RJTD AS WELL AS A 052241Z
CIMSS SATELLITE CONSENSUS INTENSITY ESTIMATE OF 45 KTS. TS ATSANI
IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTHEAST AND THROUGH A FAVORABLE
ENVIRONMENT WITH WARM (27-28 CELSIUS) SEA SURFACE TEMPERATURES
(SST), ESTABLISHED POLEWARD AND EQUATORWARD OUTFLOW ALOFT AND LOW
(10-15 KTS) VERTICAL WIND SHEAR (VWS).
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 23W IS EXPECTED TO TRACK GENERALLY WEST-NORTHWESTWARD
THROUGH TAU 24 AS IT TRANSITS ALONG THE SOUTHWESTERN PERIPHERY OF
THE STR. DURING THIS TIME, THE SYSTEM SHOULD INTENSIFY TO 55 KTS BY
TAU 12 DUE TO PERSISTENT FAVORABLE ENVIRONMENTAL CONDITIONS.
AFTERWARDS, INCREASING VWS WILL BEGIN TO IMPACT THE SYSTEM CAUSING
IT TO BEGIN TO GRADUALLY WEAKEN. AFTER TAU 24, THE SYSTEM IS
EXPECTED TO TURN TO A WEST-SOUTHWESTWARD TRACK AS A STR POSITIONED
OVER CENTRAL CHINA TAKES OVER AS THE PRIMARY STEERING MECHANISM.
THIS STEERING MECHANISM SHIFT WILL CAUSE THE SYSTEM TO THEN SHIFT TO
A SOUTHWESTWARD TRACK AFTER TAU 36 WHEREUPON IT WILL BEGIN TO WEAKEN
TO 30 KTS BY TAU 48 AS IT BEGINS TO DISSIPATE OVER WATER. THE SYSTEM
WILL THEN FURTHER WEAKEN DUE TO CONTINUED HIGH (30+ KTS) VWS AND
FULLY DISSIPATE OVER WATER BY TAU 72. NUMERICAL MODEL GUIDANCE IS IN
TIGHT AGREEMENT THROUGH TAU 36, HOWEVER TRACK AND INTENSITY GUIDANCE
DIVERGES SIGNIFICANTLY THEREAFTER. THIS UNCERTAINTY IN MODEL GUIDANCE
IS LIKELY DUE TO THE TIMING AND MAGNITUDE OF THE RIDGE REORIENTATION
AND YIELDS OVERALL POOR CONFIDENCE IN THE JTWC FORECAST TRACK WHICH
IS PLACED NEAR THE JTWC MULTI-MODEL CONSENSUS.//
NNNN
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Re: WPAC: ATSANI - Tropical Storm

#160 Postby mrbagyo » Thu Nov 05, 2020 10:24 pm

Lo and behold, it now looks decent on radar

 https://twitter.com/EarthUncutTV/status/1324525949140922368


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