This is storm MARY that was active in 1974 in the W. Pacific region with maximum winds of 130 km/h.

What was the maximum intensity of the storm?

Max Wind: 130 km/h. Min Pressure: hPa.

storm MARY (1974) - Track and intensity details

Name: storm MARY
Start: 1974-08-10
End: 1974-08-27
Location: W. Pacific

MARY (1974)

Storm Code: 1974222N15149 | Region: W. Pacific
Active from 10/08/1974 to 27/08/1974 (17 days)

130 km/h

1-min Wind (JTWC)

Level 12

126 km/h

10-min Wind (CMA)

Level 12

964 hPa

Min Pressure

8,219 km

Distance

Forecast Agencies

Agency	Max Intensity	Trajectory	Energy	highest_classification
JTWC	130	~	131	7,229	43.49	45.10	Level 12 - Violent Storm
DS824	130	~	131	7,229	43.49	45.10	Level 12 - Violent Storm
TD9636	130	~	129	6,803	43.63	44.91	Level 12 - Violent Storm
TD9635	130	965	131	7,229	43.49	45.10	Level 12 - Violent Storm
WMO (International) (coordinates_only)	~	965	65	8,040	~	~	Undefined
CMA (China)	126	964	129	8,219	47.13	50.31	Level 12 - Violent Storm
HKO (Hong Kong)	111	965	119	6,851	35.64	32.65	Level 11 - Severe Storm
JMA (Japan) (coordinates_only)	~	965	121	7,748	~	~	Undefined

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

130

131

7,229

43.49

45.10

Level 12 - Violent Storm

DS824

130

131

7,229

43.49

45.10

Level 12 - Violent Storm

TD9636

130

129

6,803

43.63

44.91

Level 12 - Violent Storm

TD9635

130

965

131

7,229

43.49

45.10

Level 12 - Violent Storm

WMO (International)
(coordinates_only)

965

8,040

Undefined

CMA (China)

126

964

129

8,219

47.13

50.31

Level 12 - Violent Storm

HKO (Hong Kong)

111

965

119

6,851

35.64

32.65

Level 11 - Severe Storm

JMA (Japan)
(coordinates_only)

965

121

7,748

Undefined

Advanced Meteorological Indices by Agency Automatically calculated from raw data

JTWC RI

Energy
ACE (10⁴ (km/h)²)	43.49	High
PDI (10⁶ (km/h)³)	45.10
Intensification / Weakening
Max Wind Gain/Step	+15 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-24 km/h
Movement & Duration
Avg Movement Speed	18.5 km/h
Tracking Time	390h (16.3 days)
Time as TD+ (≥34kt)	261h (10.9d)
Time as Storm+ (≥64kt)	33h (1.4d)
Peak Intensity & Range
Peak Intensity	14:00 18/08/1974 28.9°N, 128.5°E
Latitude	14.5°N – 37.6°N (23.1°)
Longitude	119.8°E – 152.4°E (32.6°)

DS824 RI

Energy
ACE (10⁴ (km/h)²)	43.49	High
PDI (10⁶ (km/h)³)	45.10
Intensification / Weakening
Max Wind Gain/Step	+15 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-24 km/h
Movement & Duration
Avg Movement Speed	18.5 km/h
Tracking Time	390h (16.3 days)
Time as TD+ (≥34kt)	261h (10.9d)
Time as Storm+ (≥64kt)	33h (1.4d)
Peak Intensity & Range
Peak Intensity	14:00 18/08/1974 28.9°N, 128.5°E
Latitude	14.5°N – 37.6°N (23.1°)
Longitude	119.8°E – 152.4°E (32.6°)

TD9636 RI

Energy
ACE (10⁴ (km/h)²)	43.63	High
PDI (10⁶ (km/h)³)	44.91
Intensification / Weakening
Max Wind Gain/Step	+9 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-7 km/h
Movement & Duration
Avg Movement Speed	17.7 km/h
Tracking Time	384h (16 days)
Time as TD+ (≥34kt)	261h (10.9d)
Time as Storm+ (≥64kt)	36h (1.5d)
Peak Intensity & Range
Peak Intensity	08:00 25/08/1974 26.8°N, 132.7°E
Latitude	14.5°N – 34.5°N (20°)
Longitude	119.8°E – 152.3°E (32.5°)

TD9635 RI

Energy
ACE (10⁴ (km/h)²)	43.49	High
PDI (10⁶ (km/h)³)	45.10
Intensification / Weakening
Max Wind Gain/Step	+15 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-24 km/h
Pressure Variation
Max Pressure Drop/Step	-5 hPa
Max Pressure Drop/24h	-24 hPa	Strong
Max Pressure Rise/Step (weakening)	+8 hPa
Movement & Duration
Avg Movement Speed	18.5 km/h
Tracking Time	390h (16.3 days)
Time as TD+ (≥34kt)	261h (10.9d)
Time as Storm+ (≥64kt)	33h (1.4d)
Peak Intensity & Range
Peak Intensity	14:00 18/08/1974 28.9°N, 128.5°E
Latitude	14.5°N – 37.6°N (23.1°)
Longitude	119.8°E – 152.4°E (32.6°)

WMO (International)

Pressure Variation
Max Pressure Drop/Step	-10 hPa
Max Pressure Drop/24h	-25 hPa	Strong
Max Pressure Rise/Step (weakening)	+20 hPa
Movement & Duration
Avg Movement Speed	20.9 km/h
Tracking Time	384h (16 days)
Peak Intensity & Range
Latitude	15.3°N – 44.3°N (29°)
Longitude	119.8°E – 152.3°E (32.5°)

CMA (China) RI

Energy
ACE (10⁴ (km/h)²)	47.13	High
PDI (10⁶ (km/h)³)	50.31
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+56 km/h	RI
Max Wind Loss/Step	-30 km/h
Pressure Variation
Max Pressure Drop/Step	-6 hPa
Max Pressure Drop/24h	-24 hPa	Strong
Max Pressure Rise/Step (weakening)	+8 hPa
Movement & Duration
Avg Movement Speed	21.4 km/h
Tracking Time	384h (16 days)
Time as TD+ (≥34kt)	270h (11.3d)
Time as Storm+ (≥64kt)	54h (2.3d)
Peak Intensity & Range
Peak Intensity	08:00 18/08/1974 28.6°N, 129.9°E
Latitude	15.7°N – 44.5°N (28.8°)
Longitude	120.2°E – 153°E (32.8°)

HKO (Hong Kong)

Energy
ACE (10⁴ (km/h)²)	35.64	High
PDI (10⁶ (km/h)³)	32.65
Intensification / Weakening
Max Wind Gain/Step	+9 km/h
Max Wind Gain/24h	+46 km/h	Fast
Max Wind Loss/Step	-6 km/h
Pressure Variation
Max Pressure Drop/Step	-5 hPa
Max Pressure Drop/24h	-20 hPa	Strong
Max Pressure Rise/Step (weakening)	+3 hPa
Movement & Duration
Avg Movement Speed	19.4 km/h
Tracking Time	354h (14.8 days)
Time as TD+ (≥34kt)	267h (11.1d)
Peak Intensity & Range
Peak Intensity	14:00 18/08/1974 29°N, 128.6°E
Latitude	15.3°N – 34.7°N (19.4°)
Longitude	119°E – 152.3°E (33.3°)

JMA (Japan)

Pressure Variation
Max Pressure Drop/Step	-5 hPa
Max Pressure Drop/24h	-25 hPa	Strong
Max Pressure Rise/Step (weakening)	+10 hPa
Movement & Duration
Avg Movement Speed	21.5 km/h
Tracking Time	360h (15 days)
Peak Intensity & Range
Latitude	17.8°N – 44°N (26.2°)
Longitude	119.5°E – 153°E (33.5°)

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

🇨🇳 China

WMO

29.12°, 121.52° 1974-08-19 13:39:50

JTWC 87 km/h Level 9

29.33°, 121.94° 1974-08-19 09:46:34

DS824 87 km/h Level 9

29.33°, 121.94° 1974-08-19 09:46:34

TD9636 87 km/h Level 9

29.33°, 121.94° 1974-08-19 09:46:34

TD9635 87 km/h Level 9

29.33°, 121.94° 1974-08-19 09:46:34

CMA 113 km/h Level 11

28.85°, 121.66° 1974-08-19 16:24:11

HKO 74 km/h Level 8

28.72°, 121.52° 1974-08-19 15:27:25

JMA

28.98°, 121.67° 1974-08-19 15:32:52

🇯🇵 Japan

WMO

34.65°, 137.79° 1974-08-26 00:17:55

JTWC 91 km/h Level 10

26.64°, 127.89° 1974-08-24 02:27:28

DS824 91 km/h Level 10

26.64°, 127.89° 1974-08-24 02:27:28

TD9636 89 km/h Level 10

26.54°, 127.91° 1974-08-24 02:33:48

TD9635 91 km/h Level 10

26.64°, 127.89° 1974-08-24 02:27:28

CMA 87 km/h Level 9

26.65°, 127.89° 1974-08-24 02:28:00

HKO 83 km/h Level 9

34.64°, 137.98° 1974-08-25 23:52:58

JMA

26.67°, 127.89° 1974-08-24 01:58:18

Values are interpolated at landfall time and may differ from actual data.

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

MARY (1974)

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Indices Legend

Advanced Meteorological Indices by Agency Automatically calculated from raw data

Advanced Indices Legend

Countries with Direct Landfall

MARY

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MARY (1974)

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Comparison Storms 0

Weather Agencies (8 sources)

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Wind Intensity Chart

Quick Stats

Agency Data Comparison

Indices Legend

Advanced Meteorological Indices by Agency Automatically calculated from raw data

Advanced Indices Legend

Countries with Direct Landfall

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