|
Welcome to the Southwest Indian Ocean
Tropical Cyclone page of Hurricane Alley.
The information source used for the graphs presented on this page is the
"Best Track" files from the Joint Typhoon Warning Center.
Current Tropical
Activity ---
From the Joint Typhoon Warning
Center
REGION 13
- FAQ--
SOUTHWEST INDIAN OCEAN
Areal coverage - area south of
0° and between 90°E and the east coast
of Africa.
Names for the
2007/2008 season
Season - October
through April Average number
of tropical cyclones in a year -- 9.68
Average number of tropical cyclones in a
"normal season" -- 9.11
Most active month -- January - average
2.45 storms/year
Most active period -- January through March -
78.04% of all storms
Most storms in a single season -
18 in 1965
Fewest storms in a single season --
6 on several occasions
The graphs below have been created using the "best
track" data from 1945 to 2000 courtesy of JTWC. Click on the graph to enlarge.
| Tropical Cyclones by Year |
Tropical Cyclones by Month |
Tropical Cyclone Probability by Month |
Tropical Cyclone Frequency Per Month |
 |
 |
 |
 |
Cyclone rating designation process --
MSW Averaging Period: 10 minutes
Tropical Disturbance - term is used for
all tropical weather
disturbances from weak ill-defined systems to fairly well-
defined systems with MSW up to 27 kts (Beaufort Force 6 -
Dvorak T2.0) which would be classified as tropical depressions
by many TCWC's. Regular bulletins are issued for the stronger
tropical disturbances.
Tropical Depression - MSW in range of
28-33 kts (Beaufort Force 7 -
Dvorak T2.5)
Moderate Tropical Storm - MSW in range
of 34-47 kts/ Dvorak rating
of T3.0 - weak T3.5
Severe Tropical Storm - MSW in range of
48-63 kts/ Dvorak rating
of strong T3.5 - T4.0
Tropical Cyclone - MSW in range of
64-89 kts/ Dvorak rating of
T4.5 - T5.5
Intense Tropical Cyclone - MSW in range
of 90-115 kts/ Dvorak
rating T6.0 - T7.0
Very Intense Tropical Cyclone - MSW
exceeding 115 kts/ Dvorak
rating T7.5 - T8.0
The WMO's RSMC for the South Indian region is the TCWC on the French
island of La Reunion; however, names are actually assigned by the
sub-regional centres on Mauritius (east of 55E) and Madagascar (west of
55E). The La Reunion TCWC employs a conversion factor of 0.88 to
convert the 1-minute MSW Dvorak scale to an equivalent 10-minute
average scale. TCWC = Tropical Cyclone Warning Center
MSW = Mean Surface Wind
JTWC = Joint Typhoon Warning Center
| 
