Met. Terminologies and Glossary
|
Type
of system |
Description |
|
Cyclonic Circulation (Cycir) |
Atmospheric wind
flow in upper levels associated with any low pressure system. The wind flow
is counter clockwise in the Northern Hemisphere and clockwise in the Southern
Hemisphere. |
|
Anticyclonic circulation |
Atmospheric wind
flow in upper levels associated with any high pressure system. The wind flow
is clockwise in the Northern Hemisphere and counter clockwise in the Southern
Hemisphere. |
|
Low pressure Area (LOPAR)/ well marked LOPAR |
Area
in the atmosphere in which the pressures are lower than those of the
surrounding region at the same level and is represented on a synoptic chart
by a system of one closed isobar (wind speed on the surface < 17 Knots
(Kts) when the system is at sea or one closed isobar in the radius of 3 Deg.
from the centre over land). |
|
Depression |
Intense
low pressure system represented on a synoptic chart by two or three closed
isobars at 2 hPa interval and wind speed from 17 to 27 Kts at sea and two
closed isobars in the radius of 3 Deg. from the centre over land. |
|
Deep Depression |
Intense
low pressure system represented on a synoptic chart by two or three closed
isobars at 2 hPa interval and wind speed from 28 to 33 Kts at sea and three
to four closed isobars in the radius of 3 Deg. from the centre over land. |
|
Cyclonic Storm |
Intense
low pressure system represented on a synoptic chart by more than four closed
isobars at 2 hPa interval and in which
the wind speed on surface level is in between 34 – 47 Kts. |
|
Severe Cyclonic Strom |
Intense
low pressure system represented on a synoptic chart by more than four closed
isobars at 2 hPa interval and in which the wind speed on surface level is in
between 48 – 63 Kts. |
|
Very Severe Cyclonic Storm |
Intense
low pressure system represented on a synoptic chart by more than four closed
isobars at 2 hPa interval and in which the wind speed on surface level is in
between 64 – 119 Kts. |
|
Super cyclonic storm |
Intense
low pressure system represented on a synoptic chart by more than four closed
isobars at 2 hPa interval and in which the wind speed on surface level is 120
Kts. and above. |
|
Western Disturbance |
Weather
disturbances noticed as cyclonic circulation/trough in the mid and lower
tropospheric levels or as a low pressure area on the surface, which occur in
middle latitude westerlies and originate over the Mediterranean Sea, Caspian
Sea and Black Sea and move eastwards across north India. |
|
Western Depression |
Weather
system, which originate over the Mediterranean Sea, Caspian Sea and Black Sea
and approach northwest India and is defined by two or more closed isobars on
the surface. |
|
Induced low |
Under
the influence of the western disturbance, sometimes a low is developed to the
south of the system called as induced low. |
|
Induced cyclonic circulation |
Under
the influence of the western disturbance, sometimes a cyclonic circulation is
developed to the south of the system called as induced cyclonic circulation. |
|
Trough |
A
line or curve along which the atmospheric pressure is minimum.
Pressure increases on both sides of the line or curve. |
|
Trough in westerlies |
A
moving wave perturbation in mid latitude regions which are present throughout
the year which move from west to east and entire globe. These systems generally affect the northern
parts of India. |
|
Trough in easterlies |
A
moving wave perturbation in the equatorial easterly wave, moving from east to
west. |
|
Easterly Waves |
A
shallow trough disturbance in the easterly current of the tropics, more in
evidence in the upper level winds than in surface pressure, whose passage
westwards is followed by a marked intensification of cloudy, showery
weather. The southern peninsular
region is affected by easterly waves. |
|
Shear line |
A
line or narrow zone across which there is an abrupt change in the horizontal
wind component; a line of maximum horizontal wind shear. |
|
Ridge |
An
elongated area of relatively high atmospheric pressure almost always
associated with and most clearly identified as an area of maximum
anticyclonic curvature of wind flow. |
|
Wind-discontinuity |
A
line across which there is an abrupt change in wind direction |
|
Troposphere |
An
atmospheric layer in which all significant weather phenomena occur. The
troposphere is characterized by decreasing temperature with height. It is the
lowest layer of atmosphere, which may extend upto
8km near poles and 18 km near equator. |
|
Lower troposphere level |
Part
of the troposphere upto 2.1 km above mean Sea level (a.s.l) |
|
Mid troposphere level |
Part
of the troposphere from 2.1 km a.s.l. but below 7.6 km a.s.l |
|
Upper troposphere level |
Part
of the troposphere from 7.6 km a.s.l to a height upto which temperature
decreases with height. |
Forecast
|
Types of forecast |
Description |
|
Nowcasting |
A
short range forecast having a lead time/validity of 3 to 6 hours |
|
Short range forecasts |
Forecasts
having a lead time / validity period of 1 to 3 days |
|
Medium range forecasts |
Forecasts having a lead time /validity
period of 4 to 10 days (However, considered 4-10 days in tropics) |
|
Long range /Extended Range
forecasts |
Forecasts
having a lead time /validity period beyond 10 days (However, considered
beyond 7 days in tropics). Usually
this is being issued for a season. IMD
issues Long Range Forecast for southwest Monsoon rainfall and onset date for
Kerala, Northeast Monsoon Rainfall and Winter precipitation over Northwest
India. |
|
Local
Forecast |
In local forecast, whenever any weather
phenomenon is expected, its intensity, frequency and time of occurrence is
indicated. In the absence of a weather
phenomenon, the local forecast describes anticipated sky conditions. The other parameters for which the local
forecast issued include maximum temperature and/or minimum temperature,
rainfall, wind and special phenomenon.
It is valid for a radius of 50 km around the
station and is updated 4 times in a day. |
Seasons
|
Winter Season Pre Monsoon Season
Southwest Monsoon Season Northeast Monsoon Season |
January – February March – May June
- September October
- December |
Sky
Conditions
|
Reported
in terms of Octa wherein the sky is divided into 8 equal parts |
|
|
Clear sky |
0 Octa |
|
Mainly clear |
1-2 Octa of sky covered |
|
Partly cloudy |
3-4 Octa of sky covered |
|
Generally cloudy |
5-7 Octa of sky covered |
|
Cloudy |
> 7 Octa of sky covered |
Weather
phenomena
|
Types |
Description |
|
One or two spells of rain |
In a 24 hrs time, rainfall occurring with a
frequency of 1-2 spells. |
|
A few spells of rain |
In a 24 hrs time, rainfall occurring with a
frequency of more than 2 spells but with well defined dry spells in between. |
|
Intermittent rain |
In a 24 hrs time, rainfall occurring with a
frequency more than that defined in “A Few Spells” but is discontinuous and
without presenting the character of a shower. |
|
Drizzle |
Liquid precipitation in the form of
water drops of very small size (by convention, with radius of water drops
between about 100 and 500 µm). |
|
Rain |
Liquid precipitation in the form of
water drops of radius between about 500 and 2500 µm. |
|
Shower |
Solid or liquid precipitation from a
vertically developed cloud is designated a shower and is distinguished from
the precipitation, intermittent or continuous, from layer clouds. Showers are
often characterized by short duration and rapid fluctuations of intensity (by
convention, with radius of water drops more than |
|
Hail |
Solid precipitation in the form of balls or
pieces of ice (hailstones) with diameters ranging from 5 to 50 mm or even
more. |
|
Thunderstorm |
One or more sudden electrical discharges
manifested by a flash of light (Lightning) and a sharp rumbling sound
(thunder). |
|
Duststorm |
An ensemble of particles of dust or
sand energetically lifted to great heights by a strong and turbulent wind. Surface visibility is reduced to low
limits; the qualification for a synoptic report is visibility below 1000 m. |
|
Mist |
Mist is a phenomenon of small droplets suspended in air |
|
Dew |
Condensation of water vapour on a
surface whose temperature is reduced by radiational cooling to below the
DEW-POINT of the air in contact with it |
|
Fog |
Fog is a phenomenon of small droplets suspended in air
and the visibility is less than one
kilometer |
|
Frost |
Frost
occurs when the temperature of the air in contact with the ground, or at
thermometer-screen level, is below the freezing-point of water (‘ground
frost’ or ‘air frost’, respectively). The term is also used of the icy
deposits which may form on the ground and on objects in such temperature
conditions (glaze, hoar-frost). |
|
Haze |
Haze is traditionally an
atmospheric phenomenon where dust, smoke and other dry particles obscure the
clarity of the sky. |
|
Smog |
Smoke and fog together reduce the
visibility |
|
Squally weather |
Squally weather is meant to cover
occasional or frequent squalls with rain or persistent type of strong gusty
winds (mean wind speed not less than 20 knot) accompanied by rain. Such
conditions are associated with low pressure systems or onset and
strengthening of monsoon. |
|
Visibility |
The greatest distance that prominent object
can be seen and identified by unaided, normal eyes. |
Rainfall
The latest practices followed are summarised
below:
Spatial Distribution of
Rainfall
|
Distribution |
No. of Places |
Description |
|
Isolated |
One or two Places |
<25% of area
or less gets rainfall |
|
Scattered |
At a few Places |
(26–50)% of area
gets rainfall |
|
Fairly Widespread |
At many Places |
(51–75)% of area
gets rainfall |
|
Wide spread |
At Most place |
(76–100)% of area
gets rainfall |
|
Dry |
- |
No station reported rainfall |
Intensity
of Rainfall
|
Descriptive
Term used |
Rainfall amount in mms |
|
No Rain |
0.0 |
|
Very
light Rain |
0.1- 2.4 |
|
Light
Rain |
2.5 – 7.5 |
|
Moderate
Rain |
7.6 – 35.5 |
|
Rather Heavy |
35.6 – 64.4 |
|
Heavy
Rain |
64.5 – 124.4 |
|
Very
Heavy Rain |
124.5 – 244.4 |
|
Extremely
Heavy Rain |
≥ 244.5 |
|
Exceptionally Heavy Rain |
When the amount is a value near about the highest
recorded rainfall at or near the station for the month or season. However, this
term will be used only when the actual rainfall amount exceeds 12 cm. |
Weekly/Seasonal Rainfall Distribution on regional scale
Excess
|
Percentage departure of realised rainfall from normal rainfall is +
20% or more. |
|
Normal |
Percentage
departure of realised rainfall from normal rainfall is between - 19 % to + 19
%. |
|
Deficient |
Percentage
departure of realised rainfall from normal rainfall is between – 20 % to - 59
%. |
|
Scanty |
Percentage departure of realised rainfall from normal rainfall is
between – 60 % to - 99 %. |
|
No rain |
Percentage departure of realised rainfall from normal rainfall is–
100 % |
Rainfall distribution on All India
scale
|
Normal |
percentage departure of realised rainfall is within ± 10 % of the
Long Period Average |
|
Below Normal |
percentage departure of realised rainfall is < -10% of the Long
Period Average |
|
Above Normal |
percentage departure of realised rainfall is > 10% of the Long
Period Average |
|
All India Drought Year |
When the rainfall
deficiency is more than 10% and when 20 to 40% of the country is under
drought conditions, then the year is termed as All India Drought Year |
|
All India Severe Drought Year |
When the rainfall
deficiency is more than 10% and when the spatial coverage of drought is more
than 40% it is called as All India Severe Drought Year |
Monsoon
"MONSOON" has originated from the Arabic word “MAUSIM” which means season. It is most often applied to the seasonal
reversals of the wind direction along the shores of the Indian Ocean,
especially in the Arabian Sea, that blow from the southwest during one half of
the year and from the northeast during the other half.
Onset
& Advance of Monsoon
The guidelines
followed for declaring the onset of monsoon over Kerala and its further advance
over the country are enlisted below:
Onset
over Kerala
a)
Rainfall
If after 10th May, 60% of the available 14 stations enlisted*, viz.
Minicoy, Amini,Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery,Kannur,
Kasargode and Mangalore report rainfall of 2.5 mm or
more for two consecutive days, the onset over Kerala be declared on the 2nd
day, provided the following criteria are also in concurrence.
b) Wind field
Depth of westerlies should be maintained upto 600 hPa, in the box equator
to Lat. 10ºN and Long. 55ºE to 80ºE. The zonal wind speed over the area bounded by Lat. 5-10ºN,
Long. 70-80ºE should be of the order of 15 – 20 Kts.
at 925 hPa. The source of data can be RSMC wind
analysis/satellite derived winds.
3. Outgoing Longwave
Radiation (OLR)
INSAT derived OLR value should be below 200 wm-2 in the box
confined by Lat. 5-10ºN and Long. 70-75ºE.
Further Advance of Monsoon over the
Country
a)
Further advance is declared based on the occurrence of rainfall over
parts/sectors of the sub-divisions and maintaining the spatial continuity of
the northern limit of monsoon, further advance is declared.
The following auxiliary features are also looked
into:
b) Along
the west coast, position of maximum cloud zone, as inferred from the satellite
imageries is taken into account.
c) The satellite water vapour imageries are
monitored to assess the extent of moisture incursion.
Northern Limit of Monsoon (NLM)
Southwest monsoon normally sets in over Kerala
around 1st June. It advances northwards, usually in surges, and
covers the entire country around 15th July. The NLM is the northern
most limit of monsoon upto which it has advanced on
any given day.
Withdrawal of SW Monsoon
a)
Withdrawal from extreme north-western parts of the country is not
attempted before 1st September.
b)
After 1st September:
The following major synoptic features are
considered for the first withdrawal from the western parts of NW India.
i) Cessation
of rainfall activity over the area for continuous 5 days.
ii) Establishment of anticyclone in the lower
troposphere (850 hPa and below)
iii) Considerable reduction in moisture content
as inferred from satellite water vapour imageries and tephigrams.
Further Withdrawal from the Country
i) Further
withdrawal from the country is declared, keeping the spatial continuity,
reduction in moisture as seen in the water vapour imageries and prevalence of
dry weather for 5 days.
ii) SW
monsoon is from the southern peninsula and hence from the entire country only
after 1st October, when the
circulation pattern indicates a change over from the southwesterly
wind regime.
Criteria for Declaring Onset of
Northeast Monsoon
For
declaring onset of Northeast Monsoon following criteria are considered:
(1)
Withdrawal of south west Monsoon upto 15º
N.
(2) Onset of persistent surface easterlies over
Tamil Nadu coast.
(3)
Depth of easterlies upto
850 hpa over Tamil Nadu coast.
(4)
Fairly widespread rainfall over the
coastal Tamil Nadu and adjoining areas.
(5) Onset
is not to be declared before 10th October even, if the conditions
described above exist.
Activity/
strength of Northeast Monsoon
The
monsoon activity over a subdivision is described as below.
Weak Monsoon:
Rainfall less than half of
the normal.
Normal Monsoon:
Rainfall
half to less than one and a half (1½) times the normal.
Active Monsoon:
i) Rainfall 1½ to 4 times the normal.
ii) Rainfall
in atleast two stations should be 3 cm in Coastal
Tamil Nadu and south
coastal Andhra Pradesh and 2 cm elsewhere.
Iii)
Rainfall in that sub-division should be
fairly widespread or widespread.
Vigorous Monsoon :
i) Rainfall
exceeding 4 times the normal.
Ii) Rainfall
in atleast two stations should be 5 cm in Coastal
Tamil Nadu and south coastal Andhra Pradesh and 3 cm elsewhere.
Iii) Rainfall
in that sub-division should be fairly widespread or widespread.
Strength of Southwest Monsoon
Descriptive term over the Sea
Description
of monsoon condition over the sea is based on wind speed (in knots) reported or
inferred to be existing.
Weak monsoon Upto
12 knots
Moderate monsoon 13 to 22
knots
Strong monsoon 23 to 32 knots
Vigorous
monsoon 33
knots and above.
Descriptive term over land area
Weak
monsoon
Rainfall
less than half of the normal.
Normal
monsoon
Rainfall
half to less than 1½ times the normal (mention of ‘normal’ monsoon may not be
necessary in general).
Active/ strong monsoon
|
i) |
Rainfall 1 ½ to 4 times the normal. |
|
ii) |
The rainfall in at least two
stations should be 5 cm, if that sub-division is along the west coast and 3
cm, if it is elsewhere. |
|
iii) |
Rainfall in that sub-division should
be fairly widespread to widespread. |
Vigorous monsoon
|
i) |
Rainfall more than 4 times the
normal. |
|
ii) |
The rainfall in at least two
stations should be 8 cm if the sub-division is along the west coast and 5 cm
if it is elsewhere. |
|
iii) |
Rainfall in that sub-division should
be fairly widespread or widespread |
Subdued Monsoon activity
1.
Whenever, a country
wide dry spell continues for more than 3 days and is expected to continue for atleast 2 more days, the description of monsoon is given as
‘weak or subdued monsoon for the country as a whole.
2.
Information on
prolonged dry spells/ subdued activity over the Met. Subdivisions are also
included in the bulletins issued by Regional Meteorological Centres and
Meteorological Centres, if such a spell is persisting for 2 or more days and is
expected to continue.
3. Monsoon
activity for a sub-division might be considered subdued if the rainfall
realised is less than ½ the normal.
Temperature
Description
of 24 hrs temperature changes.
Maximum temperature
(a)
When the normal maximum temperature of a station is 40º
C or below.
Nomenclature Past 24 hours change
Little
change -1º
C to 1º
C
Rise/
fall 2º
C
Appreciable
rise/ fall 3º
C to 4º
C
Marked
rise/ fall 5º
C to 6º
C
Large
rise/ fall 7º
C or more
(b)
When the normal maximum temperature of a station is more than 40º C.
Nomenclature Past 24 hours change
Little
change -1o
C to 1 o C
Rise/
fall 2º
C
Marked
rise/ fall 3º
C to 4º
C
Large
rise/ fall 5º
C or more
Minimum temperature
(a)
When the normal minimum temperature of a station is 10º C or more.
Nomenclature Past 24 hours change
Little
change 1º
C to -1º C
Fall/
rise 2º
C
Appreciable
fall/ rise 3º C
to 4º C
Marked
fall/ rise 5º
C to 6º C
Large
fall/ rise 7º
C or less
(b)
When the normal minimum temperature of a station is less than 10º
C.
Nomenclature Past 24 hours change
Little
change 1º
C to -1º C
Fall/
rise 2º
C
Marked
fall/ rise 3º
C to 4º C
Large
fall/ rise 5º
C or less
Criteria for Heat Wave:
Heat wave
need not be considered till maximum temperature of a station reaches at least
40º C for
Plains and at least 30º C for
Hilly regions.
a)
When normal maximum temperature of a station is less than or equal
to 40º
C
Heat Wave Departure from normal is 5º C to 6º C
Severe Heat Wave Departure from normal is 7º C or more
b)
When
normal maximum temperature of a station is more than 40º C
Heat Wave Departure from normal is 4º C to 5º C
Severe Heat Wave Departure from normal is 6º C or more
c)
When actual maximum temperature remains 45ºC or more irrespective of normal maximum temperature, heat wave
should be declared.
Hot day
In the northern plains of the country,
dust in suspension occurs in many years for several days, bringing minimum
temperature much higher than normal and keeping the maximum temperature around
or slightly above normal. Sometimes increase in humidity also adds to this
discomfort. Nights do not get cooled and become uncomfortable. To cover this
situation, hot day concept has
been introduced as given below:
Whenever, the maximum temperature
remains 40ºC or more and minimum temperature is 5º C or more above normal, it
may be defined as Hot Day,
provided it is not satisfying the heat wave criteria given above.
Criteria for describing Hot Day for coastal stations
When
maximum temperature departure is 5º C or more from normal, Hot Day may be described irrespective
of the threshold value of 40º C. If the threshold value of 40º C is
reached Heat Wave may be
declared.
When
a station satisfies both the Heat Wave and Hot Day criteria, then Heat Wave
should be given higher priority and be declared.
Hot Wind
Hot
wind reduces moisture causing dehydration and a prolonged exposure may prove to
be fatal.
The
phenomena of Loo over the
plains of northwest India is very well known. It is also described in the
Weather bulletins and appropriate warnings are being issued at present.
Criteria for Cold Wave
Wind
chill factor plays an important role and brings down the actual minimum
temperature depending upon the wind speed. The actual minimum temperature of a
station is reduced to “wind chill effective minimum temperature (WCTn)” based
on wind chill factor (Reference : WMO No. 331/ Tech
note No. 123 on “The assessment of human bio-climate. A
limited review of physical parameters, 1972).
For declaring “Cold Wave” and “Cold Day” WCTn is
used.
If
WCTn is 10°C or less, then only the conditions for cold wave are considered.
a)
When normal minimum temperature is equal to 10°C or more.
Cold Wave : Departure from
normal is -5°C to -6°C.
Severe Cold Wave :
Departure from normal is -7°C or less
b)
When normal minimum temperature is less than 10°C.
Cold Wave : Departure from
normal is -4°C to -5°C.
Severe Cold Wave : Departure from normal is -6°C or less.
When
WCTn is 0°C or less, Cold Wave is declared irrespective of normal minimum
temperature of the station. However, this criteria is
not applicable for those stations whose normal minimum temperature is below
0°C.
Cold Wave conditions for
coastal stations
For
coastal stations the threshold value of minimum temperature of 10ºC is rarely
reached. However, the local people feel discomfort due to wind chill factor
which reduces the minimum temperature by a few degrees depending upon the wind
speed. The “Cold Day” concept
is used following the criteria given below:
Criteria for describing “Cold Day”
for coastal stations
i) Actual minimum temperature of a station
is reduced to WCTn.
ii) This WCTn is used to declare “Cold Wave” or “Cold Day”.
iii) When minimum temperature departure is -5ºC
or less over a station, “Cold Day” is
described irrespective of threshold value of 10ºC
iv) However, when a threshold of
10ºC is reached “Cold Wave” is
declared.
v) When a station satisfies both the Cold
Wave and Cold Day criteria, then Cold Wave has a higher priority and has to be
declared.
Heat wave/ Cold Wave and hot Day/ Cold Day are area
specific phenomena. Therefore they are described for a Met. Sub-division or a
part thereof, when at least two stations satisfy the criteria
Winds
|
Wind |
Air in motion is called wind which is haracterized by direction and speed. The direction of the wind is the direction
from which the wind approaches the station (Example Northerly wind – Wind
approaching the station from North) |
|
Gales |
A gale is a very strong wind (34 knots or more) |
|
Squall |
A sudden increase of wind speed by atleast
3 stages on the Beaufort Scale, the speed rising to force 6 or more, and
lasting for atleast one minute is called a squall |
|
Gust |
A rapid increase in the strength of the
wind relative to the mean strength at the time. The wind speed should be at
least 17 knots or more |
Nomenclature for different
parts of the day
|
Early hours of (date) |
0000 – 0400 hrs, IST |
|
Early morning |
0400 – 0600 hrs. IST |
|
Morning |
0400 – 0800 hrs. IST |
|
Forenoon |
0800 – 1200 hrs. IST |
|
Around noon |
1100 – 1300 hrs. IST |
|
Afternoon |
1200 – 1600 hrs. IST |
|
Evening |
1600 – 2000 hrs. IST |
|
Night |
2000 – 2400 hrs. IST |
Terminology used for state of Sea
|
Descriptive term |
Height in Metres |
Wind speed in knots (kmph) |
Beaufort scale |
|
Calm (
glassy) |
0 |
0 |
0 |
|
Calm
(rippled) |
0 - 0.1 |
1 - 3 ( 2 - 6) |
1 |
|
Smooth (waveless) |
0.1 - 0.5 |
4 - 10 ( 7 - 19 ) |
2 - 3 |
|
Slight |
0.5 - 1.25 |
11 - 16 (20 - 30 ) |
4 |
|
Moderate |
1.25 - 2.5 |
17 - 21 ( 31 - 39) |
5 |
|
Rough |
2.5 - 4.0 |
22 - 27 (41 - 50) |
6 |
|
Very
rough |
4.0 - 6.0 |
28 - 33 (52 - 61) |
7 |
|
High |
6.0 - 9.0 |
34 - 40 (63 - 74) |
8 |
|
Very
high |
9.0 - 14.0 |
41 - 63 (76
- 117) |
9 - 11 |
|
Phenomenal |
Over 14 |
64 or above (119 or above) |
12 |
The
Dvorak technique
The Dvorak technique is a method using enhanced Infrared and/or
visible satellite imagery to quantitatively estimate the intensity of a
tropical system. Cloud patterns in satellite imagery normally show an
indication of cyclogenesis before the storm reaches
tropical storm intensity. Indications of continued development and/or weakening
can also be found in the cloud features. Using these features, the pattern
formed by the clouds of a tropical cyclone, expected systematic development,
and a series of rules, an intensity analysis and forecast can be made. This
information is then standardized into an intensity code.
“T”
classification of Cyclonic Storm
|
T. Number / C.I. Number |
Wind speed in knots |
Wind speed in kmph |
D p |
Classification of cyclonic disturbance |
Wind criteria in knots |
Wind criteria in kmph |
|
T1.0 |
|
|
|
Low |
<17 |
<31 |
|
T1.5 |
25 |
46.3 |
3 |
Depression |
17-27 |
31-49 |
|
T2.0 |
30 |
55.6 |
4.5 |
Deep Depression |
28-33 |
50-61 |
|
T2.5 |
35 |
64.9 |
6.1 |
Cyclonic Storm |
34-47 |
62-88 |
|
T3.0 |
45 |
83.4 |
10.0 |
|||
|
T3.5 |
55 |
101.9 |
15.0 |
Severe Cyclonic Storm |
48-63 |
89-117 |
|
T4.0 |
65 |
120.5 |
20.9 |
Very Severe Cyclonic Storm |
64-119 |
119-221 |
|
T4.5 |
77 |
142.7 |
29.4 |
|||
|
T5.0 |
90 |
166.8 |
40.2 |
|||
|
T5.5 |
102 |
189.0 |
51.6 |
|||
|
T6.0 |
115 |
213.1 |
65.6 |
|||
|
T6.5 |
127 |
235.4 |
80.0 |
Super Cyclonic Storm |
120 and above |
222 and above |
|
T7.0 |
140 |
259.5 |
97.2 |
|||
|
T7.5 |
155 |
287.3 |
119.1 |
|||
|
T8.0 |
170 |
315.1 |
143.3 |