This is storm OPAL that was active in 1964 in the W. Pacific region with maximum winds of 315 km/h.

What was the maximum intensity of the storm?

Max Wind: 315 km/h. Min Pressure: hPa.

storm OPAL (1964) - Track and intensity details

Name: storm OPAL
Start: 1964-12-08
End: 1964-12-18
Location: W. Pacific

OPAL (1964)

Storm Code: 1964344N06153 | Region: W. Pacific
Active from 09/12/1964 to 18/12/1964 (10 days)

315 km/h

1-min Wind (JTWC)

Level 17

306 km/h

10-min Wind (CMA)

Level 17

900 hPa

Min Pressure

6,954 km

Distance

Forecast Agencies

Agency	Max Intensity	Trajectory	Energy	highest_classification
JTWC	315	~	59	4,181	281.73	747.64	Level 17 - Super Typhoon
HKO (Hong Kong)	278	900	69	5,513	219.96	516.04	Level 17 - Super Typhoon
DS824	315	~	59	4,181	281.73	747.64	Level 17 - Super Typhoon
TD9635	315	905	59	4,181	281.73	747.64	Level 17 - Super Typhoon
WMO (International) (coordinates_only)	~	900	38	6,399	~	~	Undefined
JMA (Japan) (coordinates_only)	~	900	74	6,305	~	~	Undefined
CMA (China)	306	904	75	6,954	233.78	555.36	Level 17 - Super Typhoon
TD9636	315	~	57	3,903	280.19	744.47	Level 17 - Super Typhoon

Agency

Max Intensity

Trajectory

Energy

highest_classification

Max Wind (km/h)

Min Pressure (hPa)

Number of points

Distance (km)

ACE (10⁴ (km/h)²)

PDI (10⁶ (km/h)³)

JTWC

315

4,181

281.73

747.64

Level 17 - Super Typhoon

HKO (Hong Kong)

278

900

5,513

219.96

516.04

Level 17 - Super Typhoon

DS824

315

4,181

281.73

747.64

Level 17 - Super Typhoon

TD9635

315

905

4,181

281.73

747.64

Level 17 - Super Typhoon

WMO (International)
(coordinates_only)

900

6,399

Undefined

JMA (Japan)
(coordinates_only)

900

6,305

Undefined

CMA (China)

306

904

6,954

233.78

555.36

Level 17 - Super Typhoon

TD9636

315

3,903

280.19

744.47

Level 17 - Super Typhoon

Advanced Meteorological Indices by Agency Automatically calculated from raw data

JTWC RI

Energy
ACE (10⁴ (km/h)²)	281.73	Very High
PDI (10⁶ (km/h)³)	747.64
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+65 km/h	RI
Max Wind Loss/Step	-33 km/h
Movement & Duration
Avg Movement Speed	24 km/h
Tracking Time	174h (7.3 days)
Time as TD+ (≥34kt)	348h (14.5d)
Time as Storm+ (≥64kt)	270h (11.3d)
Peak Intensity & Range
Peak Intensity	02:00 13/12/1964 11.8°N, 129.9°E
Latitude	5.8°N – 17.1°N (11.3°)
Longitude	120.3°E – 153.4°E (33.1°)

HKO (Hong Kong) RI

Energy
ACE (10⁴ (km/h)²)	219.96	Very High
PDI (10⁶ (km/h)³)	516.04
Intensification / Weakening
Max Wind Gain/Step	+24 km/h
Max Wind Gain/24h	+74 km/h	RI
Max Wind Loss/Step	-28 km/h
Pressure Variation
Max Pressure Drop/Step	-8 hPa
Max Pressure Drop/24h	-30 hPa	RI
Max Pressure Rise/Step (weakening)	+13 hPa
Movement & Duration
Avg Movement Speed	27 km/h
Tracking Time	204h (8.5 days)
Time as TD+ (≥34kt)	330h (13.8d)
Time as Storm+ (≥64kt)	270h (11.3d)
Peak Intensity & Range
Peak Intensity	02:00 13/12/1964 11.8°N, 129.9°E
Latitude	6°N – 24.2°N (18.2°)
Longitude	119.7°E – 153.6°E (33.9°)

DS824 RI

Energy
ACE (10⁴ (km/h)²)	281.73	Very High
PDI (10⁶ (km/h)³)	747.64
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+65 km/h	RI
Max Wind Loss/Step	-33 km/h
Movement & Duration
Avg Movement Speed	24 km/h
Tracking Time	174h (7.3 days)
Time as TD+ (≥34kt)	348h (14.5d)
Time as Storm+ (≥64kt)	270h (11.3d)
Peak Intensity & Range
Peak Intensity	02:00 13/12/1964 11.8°N, 129.9°E
Latitude	5.8°N – 17.1°N (11.3°)
Longitude	120.3°E – 153.4°E (33.1°)

TD9635 RI

Energy
ACE (10⁴ (km/h)²)	281.73	Very High
PDI (10⁶ (km/h)³)	747.64
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+65 km/h	RI
Max Wind Loss/Step	-33 km/h
Pressure Variation
Max Pressure Drop/Step	-8 hPa
Max Pressure Drop/24h	-31 hPa	RI
Max Pressure Rise/Step (weakening)	+4 hPa
Movement & Duration
Avg Movement Speed	24 km/h
Tracking Time	174h (7.3 days)
Time as TD+ (≥34kt)	348h (14.5d)
Time as Storm+ (≥64kt)	270h (11.3d)
Peak Intensity & Range
Peak Intensity	02:00 13/12/1964 11.8°N, 129.9°E
Latitude	5.8°N – 17.1°N (11.3°)
Longitude	120.3°E – 153.4°E (33.1°)

WMO (International) RI

Pressure Variation
Max Pressure Drop/Step	-20 hPa
Max Pressure Drop/24h	-75 hPa	RI
Max Pressure Rise/Step (weakening)	+20 hPa
Movement & Duration
Avg Movement Speed	29.2 km/h
Tracking Time	219h (9.1 days)
Peak Intensity & Range
Latitude	6.1°N – 28.5°N (22.4°)
Longitude	120.4°E – 151.8°E (31.4°)

JMA (Japan) RI

Pressure Variation
Max Pressure Drop/Step	-10 hPa
Max Pressure Drop/24h	-40 hPa	RI
Max Pressure Rise/Step (weakening)	+10 hPa
Movement & Duration
Avg Movement Speed	28.8 km/h
Tracking Time	219h (9.1 days)
Peak Intensity & Range
Latitude	6.3°N – 27.1°N (20.8°)
Longitude	120.3°E – 152.7°E (32.4°)

CMA (China) RI

Energy
ACE (10⁴ (km/h)²)	233.78	Very High
PDI (10⁶ (km/h)³)	555.36
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+54 km/h	Fast
Max Wind Loss/Step	-19 km/h
Pressure Variation
Max Pressure Drop/Step	-8 hPa
Max Pressure Drop/24h	-30 hPa	RI
Max Pressure Rise/Step (weakening)	+8 hPa
Movement & Duration
Avg Movement Speed	31.3 km/h
Tracking Time	222h (9.3 days)
Time as TD+ (≥34kt)	438h (18.3d)
Time as Storm+ (≥64kt)	234h (9.8d)
Peak Intensity & Range
Peak Intensity	08:00 12/12/1964 9.5°N, 133.7°E
Latitude	6.3°N – 29.4°N (23.1°)
Longitude	120.1°E – 152.7°E (32.6°)

TD9636 RI

Energy
ACE (10⁴ (km/h)²)	280.19	Very High
PDI (10⁶ (km/h)³)	744.47
Intensification / Weakening
Max Wind Gain/Step	+15 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-33 km/h
Movement & Duration
Avg Movement Speed	23.2 km/h
Tracking Time	168h (7 days)
Time as TD+ (≥34kt)	342h (14.3d)
Time as Storm+ (≥64kt)	264h (11d)
Peak Intensity & Range
Peak Intensity	08:00 13/12/1964 12.2°N, 128.8°E
Latitude	6.1°N – 17.1°N (11°)
Longitude	120.3°E – 151.8°E (31.5°)

Advanced Indices Legend

ACE: Accumulated Cyclone Energy - measures total storm activity

PDI: Power Dissipation Index - measures potential destructiveness

RI: Rapid Intensification - when wind increases >=30 kt/24h or pressure drops >=30 hPa/24h

Countries with Direct Landfall

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Index	Meaning	Formula / Condition	Classification
ACE Accumulated Cyclone Energy	Accumulated Cyclone Energy. Measures the total energy generated by the storm during its lifetime. Only counts reports with wind ≥ 35 kt (TS level or higher).	`ACE = Σ(V_max²) / 10&sup4;` Unit: 10⁴ kt²	< 2: Low 2-6: Medium 6-15: High ≥ 15: Very High
PDI Power Dissipation Index	Power Dissipation Index. More sensitive than ACE to extremely strong storms due to using cubic power. Reflects potential destructive power.	`PDI = Σ(V_max&sup³;) / 10&sup6;` Unit: 10⁶ kt³	Higher value = greater cumulative destructive power
RI Rapid Intensification	Rapid Intensification - storm strengthens suddenly in a short time. Very dangerous as it is difficult to forecast and causes surprise for prevention efforts.	Wind increase ≥ 30 kt/24h or Pressure drop ≥ 30 hPa/24h	Has RI or Fast increase (≥20kt)
Max wind gain/step	Maximum wind increase between 2 consecutive reports (usually 6 hours apart). Shows the fastest local intensification rate.	`max(V_i+1 - V_i)` Unit: kt (km/h)	Positive value = storm strengthening
Max wind gain/24h	Maximum wind increase in a 24-hour window. Main criterion for determining Rapid Intensification (RI).	`max(V_t+24h - V_t)` RI if ≥ 30 kt/24h	≥ 30kt: RI ≥ 20kt: Fast
Max wind loss/step	Maximum wind weakening between 2 consecutive reports. Shows at which stage the storm weakened fastest.	`max(V_i - V_i+1)` Unit: kt (km/h)	Positive value = storm weakening
Max pressure drop/step	Maximum pressure drop between 2 consecutive reports. Pressure decrease = storm center strengthening. Reflects local deepening rate.	`max(P_i - P_i+1)` Unit: hPa	Higher value = faster strengthening
Max pressure drop/24h	Maximum pressure drop in a 24-hour window. Important index for evaluating explosive deepening / explosive intensification.	`max(P_t - P_t+24h)` Explosive if ≥ 30 hPa	≥ 30hPa: RI ≥ 20hPa: Strong
Max pressure rise/step	Maximum pressure rise between 2 consecutive reports. Pressure increase = storm weakening. Large value indicates rapid weakening (due to terrain interaction, landfall, etc.).	`max(P_i+1 - P_i)` Unit: hPa	Higher value = faster weakening
Average moving speed	Average moving speed of the storm center during the entire monitoring period by that agency.	`V_avg = S_total / T_total` Unit: kt (km/h)	Slow-moving storms (<15 km/h) usually cause prolonged heavy rain
Monitoring duration	Total time from first report to last report of that agency.	`T = t_end - t_start` Unit: hours (days)	Different agencies may monitor for different durations
TS+ Duration	Total hours with average wind ≥ 34 kt (Tropical Storm level or higher). Reflects how long the storm maintained significant intensity.	Average wind ≥ 34 kt	Longer storm = greater total damage
TY+ Duration	Total hours with average wind ≥ 64 kt (Typhoon level or higher). Storms maintaining this level longer have much greater destructive power.	Average wind ≥ 64 kt	Longer time at Typhoon level = more dangerous
Peak Intensity	Time and location (lat, lon) when the storm reached maximum wind according to each agency. Helps identify where the storm was strongest.	V_max = max(V_i)	Peak location helps assess danger for nearby areas
Latitude / Longitude	Spatial range of activity by latitude and longitude. Shows whether the storm affected area is wide or narrow.	min-max(lat), min-max(lon)	Large range = long trajectory, wide impact

Index

Meaning

Formula / Condition

Classification

ACE
Accumulated Cyclone Energy

Accumulated Cyclone Energy. Measures the total energy generated by the storm during its lifetime. Only counts reports with wind ≥ 35 kt (TS level or higher).

ACE = Σ(V_max²) / 10&sup4;
Unit: 10⁴ kt²

< 2: Low
2-6: Medium
6-15: High
≥ 15: Very High

PDI
Power Dissipation Index

Power Dissipation Index. More sensitive than ACE to extremely strong storms due to using cubic power. Reflects potential destructive power.

PDI = Σ(V_max&sup³;) / 10&sup6;
Unit: 10⁶ kt³

Higher value = greater cumulative destructive power

RI
Rapid Intensification

Rapid Intensification - storm strengthens suddenly in a short time. Very dangerous as it is difficult to forecast and causes surprise for prevention efforts.

Wind increase ≥ 30 kt/24h or Pressure drop ≥ 30 hPa/24h

Has RI or
Fast increase (≥20kt)

Max wind gain/step

Maximum wind increase between 2 consecutive reports (usually 6 hours apart). Shows the fastest local intensification rate.

max(V_i+1 - V_i)
Unit: kt (km/h)

Positive value = storm strengthening

Max wind gain/24h

Maximum wind increase in a 24-hour window. Main criterion for determining Rapid Intensification (RI).

max(V_t+24h - V_t)
RI if ≥ 30 kt/24h

≥ 30kt: RI
≥ 20kt: Fast

Max wind loss/step

Maximum wind weakening between 2 consecutive reports. Shows at which stage the storm weakened fastest.

max(V_i - V_i+1)
Unit: kt (km/h)

Positive value = storm weakening

Max pressure drop/step

Maximum pressure drop between 2 consecutive reports. Pressure decrease = storm center strengthening. Reflects local deepening rate.

max(P_i - P_i+1)
Unit: hPa

Higher value = faster strengthening

Max pressure drop/24h

Maximum pressure drop in a 24-hour window. Important index for evaluating explosive deepening / explosive intensification.

max(P_t - P_t+24h)
Explosive if ≥ 30 hPa

≥ 30hPa: RI
≥ 20hPa: Strong

Max pressure rise/step

Maximum pressure rise between 2 consecutive reports. Pressure increase = storm weakening. Large value indicates rapid weakening (due to terrain interaction, landfall, etc.).

max(P_i+1 - P_i)
Unit: hPa

Higher value = faster weakening

Average moving speed

Average moving speed of the storm center during the entire monitoring period by that agency.

V_avg = S_total / T_total
Unit: kt (km/h)

Slow-moving storms (<15 km/h) usually cause prolonged heavy rain

Monitoring duration

Total time from first report to last report of that agency.

T = t_end - t_start
Unit: hours (days)

Different agencies may monitor for different durations

TS+ Duration

Total hours with average wind ≥ 34 kt (Tropical Storm level or higher). Reflects how long the storm maintained significant intensity.

Average wind ≥ 34 kt

Longer storm = greater total damage

TY+ Duration

Total hours with average wind ≥ 64 kt (Typhoon level or higher). Storms maintaining this level longer have much greater destructive power.

Average wind ≥ 64 kt

Longer time at Typhoon level = more dangerous

Peak Intensity

Time and location (lat, lon) when the storm reached maximum wind according to each agency. Helps identify where the storm was strongest.

V_max = max(V_i)

Peak location helps assess danger for nearby areas

Latitude / Longitude

Spatial range of activity by latitude and longitude. Shows whether the storm affected area is wide or narrow.

min-max(lat), min-max(lon)

Large range = long trajectory, wide impact

OPAL (1964)

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OPAL (1964)

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Advanced Meteorological Indices by Agency Automatically calculated from raw data

Advanced Indices Legend

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