WPAC: NANGKA - Post-Tropical

[euro6208]

Pretty good chance this will become a Cat 1 before landfall

Nope

[ElectricStorm]

Pretty good chance this will become a Cat 1 before landfall

Nope

Yeah nope that didn't happen... Didn't even hit the 60kts initially forecast

[aspen]

Pretty good chance this will become a Cat 1 before landfall

Nope

Yeah nope that didn't happen... Didn't even hit the 60kts initially forecast

It’s a Pacific system during a La Niña year. It was bound to under-achieve like 75% of everything that’s formed in the WPac and EPac.

[NotoSans]

Lowest MSLP recorded in Hainan Island was 987.7mb. No buoy, oil rig and weather station at offshore islands recorded storm-force winds, and max radar velocity was around 55kt only.

[euro6208]

WDPN33 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (NANGKA)
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (NANGKA), LOCATED APPROXIMATELY 183 NM
EAST-SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
17 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE SYSTEM HAS ACCELERATED THROUGH THE
ISLAND OF HAINAN AND EXITED INTO THE GULF OF TONKIN WITH MINOR
DEGRADATION. CONVECTION WRAPPING INTO A DEFINED LOW LEVEL
CIRCULATION (LLC) HAS QUICKLY RESUMED ALTHOUGH THE MAIN FEEDER BAND
HAS SEVERED AND REMAINED IN THE SOUTH CHINA SEA. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE LLC FEATURES IN
THE EIR LOOP AND A COMPOSITE RADAR LOOP FROM CNA. THE INITIAL
INTENSITY OF 45KTS IS BASED ON THE HIGH END OF AGENCY DVORAK
ESTIMATES OF T2.5/35KTS TO T3.0/45KTS. ENVIRONMENTAL ANALYSIS
INDICATES THE SYSTEM IS IN A GENERALLY FAVORABLE ENVIRONMENT WITH
LOW (10-15KT) VERTICAL WIND SHEAR, DIVERGENT WESTWARD OUTFLOW, AND
WARM (30C) SST. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY
OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS NANGKA WILL TRACK WESTWARD UNDER THE STR THROUGH THE GULF
OF TONKIN AND MAKE A FINAL LANDFALL OVER NORTHERN VIETNAM NEAR TAU
18. THE FAVORABLE ENVIRONMENT WILL FUEL A SECONDARY PEAK TO 50KTS BY
TAU 12; AFTERWARD, LAND INTERACTION WILL RAPIDLY ERODE THE SYSTEM TO
DISSIPATION BY TAU 36 AFTER IT DRAGS ACROSS THE RUGGED TERRAIN OF
VIETNAM AND LAOS. NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.//
NNNN

[euro6208]

WTPN33 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL STORM 18W (NANGKA) WARNING NR 011//
RMKS/
1. TROPICAL STORM 18W (NANGKA) WARNING NR 011
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
140600Z --- NEAR 20.2N 106.5E
MOVEMENT PAST SIX HOURS - 285 DEGREES AT 11 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
RADIUS OF 034 KT WINDS - 135 NM NORTHEAST QUADRANT
110 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
070 NM NORTHWEST QUADRANT
REPEAT POSIT: 20.2N 106.5E
---
FORECASTS:
12 HRS, VALID AT:
141800Z --- 20.4N 104.8E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
VECTOR TO 24 HR POSIT: 260 DEG/ 07 KTS
---
24 HRS, VALID AT:
150600Z --- 20.2N 103.3E
MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
VECTOR TO 36 HR POSIT: 255 DEG/ 06 KTS
---
36 HRS, VALID AT:
151800Z --- 19.9N 102.1E
MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
---
REMARKS:
140900Z POSITION NEAR 20.2N 106.1E.
14OCT20. TROPICAL STORM 18W (NANGKA), LOCATED APPROXIMATELY 59 NM
SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 11
KNOTS OVER THE PAST SIX HOURS. MULTISPECTRAL SATELLITE IMAGERY
INDICATES THE SYSTEM HAS BECOME SHEARED, WITH THE OUTER LOW-LEVEL
BANDS ON THE EAST SIDE BECOMING EXPOSED OVER THE PAST FEW HOURS,
WHILE MID-LEVEL ROTATION IS EVIDENT OVER EASTERN VIETNAM. THE
INITIAL POSITION IS PLACED WITH MODERATE CONFIDENCE BASED ON
ANALYSIS OF THE OUTER BANDS, WITH SUPPORT FROM A 140619Z AMSR2 37
GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS
BASED ON MULTI-AGENCY DVORAK INTENSITY ESTIMATES OF T3.0 FROM PGTW
AND T2.0 FROM RJTD, SUPPORTED BY AN ADVANCED DVORAK TECHNIQUE
ESTIMATE OF T2.3. THE SYSTEM HAS MADE LANDFALL SOUTH OF HAIPHONG,
VIETNAM AND WILL CONTINUE TRACKING INLAND WHILE DISSIPATING OVER THE
MOUNTAINOUS TERRAIN OF NORTHWEST VIETNAM AND NORTHERN LAOS OVER THE
NEXT 36 HOURS. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT
TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED
FORSIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 140600Z
IS 13 FEET.//
NNNN