This is storm LENA that was active in 1971 in the S. Pacific region with maximum winds of 111 km/h.

What was the maximum intensity of the storm?

Max Wind: 111 km/h. Min Pressure: hPa.

storm LENA (1971) - Track and intensity details

Name: storm LENA
Start: 1971-03-13
End: 1971-03-23
Location: S. Pacific

LENA (1971)

Storm Code: 1971072S13155 | Region: S. Pacific
Active from 13/03/1971 to 23/03/1971 (11 days)

102 km/h

1-min Wind (JTWC)

Level 10

102 km/h

10-min Wind (WELLINGTON)

Level 10

980 hPa

Min Pressure

6,471 km

Distance

Forecast Agencies

Agency	Max Intensity	Trajectory	Energy	highest_classification
JTWC	102	~	109	2,715	11.39	9.34	Level 10 - Severe Storm
DS824	111	980	109	2,754	20.68	18.36	Level 11 - Severe Storm
WMO (International)	74	980	55	6,471	3.29	2.41	Level 8 - Storm
BOM (Australia) (coordinates_only)	~	980	110	2,966	~	~	Undefined
NEUMANN	111	980	102	2,505	19.41	17.34	Level 11 - Severe Storm
TD9636	100	~	106	2,791	9.05	7.69	Level 10 - Severe Storm
WELLINGTON	102	980	126	6,303	24.15	21.79	Level 10 - Severe Storm

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

102

109

2,715

11.39

9.34

Level 10 - Severe Storm

DS824

111

980

109

2,754

20.68

18.36

Level 11 - Severe Storm

WMO (International)

980

6,471

3.29

2.41

Level 8 - Storm

BOM (Australia)
(coordinates_only)

980

110

2,966

Undefined

NEUMANN

111

980

102

2,505

19.41

17.34

Level 11 - Severe Storm

TD9636

100

106

2,791

9.05

7.69

Level 10 - Severe Storm

WELLINGTON

102

980

126

6,303

24.15

21.79

Level 10 - Severe Storm

Advanced Meteorological Indices by Agency Automatically calculated from raw data

JTWC

Energy
ACE (10⁴ (km/h)²)	11.39	Medium
PDI (10⁶ (km/h)³)	9.34
Intensification / Weakening
Max Wind Gain/Step	+6 km/h
Max Wind Gain/24h	+28 km/h
Max Wind Loss/Step	-9 km/h
Movement & Duration
Avg Movement Speed	16.8 km/h
Tracking Time	162h (6.8 days)
Time as TD+ (≥34kt)	103h (4.3d)
Peak Intensity & Range
Peak Intensity	08:00 16/03/1971 -23°N, 154.2°E
Latitude	-24°N – -12.5°N (11.5°)
Longitude	154.1°E – 165.7°E (11.6°)

DS824

Energy
ACE (10⁴ (km/h)²)	20.68	High
PDI (10⁶ (km/h)³)	18.36
Intensification / Weakening
Max Wind Gain/Step	+4 km/h
Max Wind Gain/24h	+28 km/h
Max Wind Loss/Step	-4 km/h
Pressure Variation
Max Pressure Drop/Step	-2 hPa
Max Pressure Drop/24h	-12 hPa
Max Pressure Rise/Step (weakening)	+1 hPa
Movement & Duration
Avg Movement Speed	17 km/h
Tracking Time	162h (6.8 days)
Time as TD+ (≥34kt)	163h (6.8d)
Peak Intensity & Range
Peak Intensity	14:00 15/03/1971 -21.1°N, 154.7°E
Latitude	-24°N – -12.4°N (11.6°)
Longitude	154.1°E – 165.8°E (11.7°)

WMO (International)

Energy
ACE (10⁴ (km/h)²)	3.29	Low
PDI (10⁶ (km/h)³)	2.41
Intensification / Weakening
Max Wind Gain/Step	+19 km/h
Max Wind Gain/24h	+19 km/h
Max Wind Loss/Step	-19 km/h
Pressure Variation
Max Pressure Drop/Step	-7 hPa
Max Pressure Drop/24h	-12 hPa
Max Pressure Rise/Step (weakening)	+7 hPa
Movement & Duration
Avg Movement Speed	26.2 km/h
Tracking Time	247h (10.3 days)
Time as TD+ (≥34kt)	72h (3d)
Peak Intensity & Range
Peak Intensity	08:00 19/03/1971 -21.5°N, 161.7°E
Latitude	-39.1°N – -12.8°N (26.3°)
Longitude	154.2°E – 200.7°E (46.5°)

BOM (Australia)

Pressure Variation
Max Pressure Drop/Step	-2 hPa
Max Pressure Drop/24h	-12 hPa
Max Pressure Rise/Step (weakening)	+3 hPa
Movement & Duration
Avg Movement Speed	18.3 km/h
Tracking Time	162h (6.8 days)
Peak Intensity & Range
Latitude	-24°N – -12.4°N (11.6°)
Longitude	154.1°E – 167.8°E (13.7°)

NEUMANN

Energy
ACE (10⁴ (km/h)²)	19.41	Medium
PDI (10⁶ (km/h)³)	17.34
Intensification / Weakening
Max Wind Gain/Step	+4 km/h
Max Wind Gain/24h	+37 km/h	Fast
Max Wind Loss/Step	-4 km/h
Pressure Variation
Max Pressure Drop/Step	-2 hPa
Max Pressure Drop/24h	-13 hPa
Max Pressure Rise/Step (weakening)	+2 hPa
Movement & Duration
Avg Movement Speed	16.7 km/h
Tracking Time	150h (6.3 days)
Time as TD+ (≥34kt)	151h (6.3d)
Peak Intensity & Range
Peak Intensity	14:00 15/03/1971 -21°N, 155.1°E
Latitude	-24°N – -12.4°N (11.6°)
Longitude	154.2°E – 163.8°E (9.6°)

TD9636

Energy
ACE (10⁴ (km/h)²)	9.05	Medium
PDI (10⁶ (km/h)³)	7.69
Intensification / Weakening
Max Wind Gain/Step	+6 km/h
Max Wind Gain/24h	+26 km/h
Max Wind Loss/Step	-4 km/h
Movement & Duration
Avg Movement Speed	17.9 km/h
Tracking Time	156h (6.5 days)
Time as TD+ (≥34kt)	89h (3.7d)
Peak Intensity & Range
Peak Intensity	07:00 16/03/1971 -22.9°N, 154.2°E
Latitude	-24°N – -13.6°N (10.4°)
Longitude	154.1°E – 167.8°E (13.7°)

WELLINGTON

Energy
ACE (10⁴ (km/h)²)	24.15	High
PDI (10⁶ (km/h)³)	21.79
Intensification / Weakening
Max Wind Gain/Step	+6 km/h
Max Wind Gain/24h	+28 km/h
Max Wind Loss/Step	-6 km/h
Pressure Variation
Max Pressure Drop/Step	-2 hPa
Max Pressure Drop/24h	-10 hPa
Max Pressure Rise/Step (weakening)	+2 hPa
Movement & Duration
Avg Movement Speed	27.6 km/h
Tracking Time	228h (9.5 days)
Time as TD+ (≥34kt)	186h (7.8d)
Peak Intensity & Range
Peak Intensity	20:00 14/03/1971 -17.8°N, 156.1°E
Latitude	-39.1°N – -15.1°N (24°)
Longitude	-179.7°E – 179°E (358.7°)

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

Storm did not make landfall

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

LENA (1971)

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Advanced Meteorological Indices by Agency Automatically calculated from raw data

Advanced Indices Legend

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Advanced Meteorological Indices by Agency Automatically calculated from raw data

Advanced Indices Legend

Countries with Direct Landfall

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