| 5. Meaning of terms used for regional exchange |
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A |
B |
C |
D |
E |
F |
G |
H | I | J | K |
L |
M |
N | O | P | Q |
R |
S |
T |
U |
V |
W |
X | Y |
Z
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| TERM |
MEANING |
| Average
wind speed |
Speed
of the wind averaged over the previous 10
minutes (mean surface wind) as read from the
anemogram or the 3 minutes mean determined
with the non-recording anemometer or estimated
wind at sea by mariners using the Beaufort
scale. |
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|
| Bulletin |
Cyclone
warning bulletin |
| |
|
| Central
pressure of a tropical cyclone |
Surface
pressure at the center of the tropical cyclone
as measured or estimated. |
| |
| Centre fix of the tropical
cyclone |
The
estimated location of the center of a tropical
cyclone. |
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| Centre of the tropical cyclone |
The
center of the cloud eye, or if not discernible,
of the wind/pressure center. |
| |
| Confidence
in the center position |
Degree
of confidence in the center position of a
tropical cyclone expressed as the radius of
the smallest circle within which the center
may be located by the analysis.
- Position good implies a radius
of 30 nautical miles (55 kilometres) or
less.
- Position fair, a radius of
30 to 60 nautical miles (55 to 110 km)
and
- Position poor, a radius of
greater than 60 nautical miles (110 km).
|
| |
| Cyclone |
Tropical
cyclone |
| |
| Cyclone warning bulletin |
A priority
message for exchange of tropical cyclone information
and advisories. |
| |
|
Direction
of movement
of the tropical cyclone |
The
direction towards which the center of the
tropical cyclone is moving. |
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|
| Extra-tropical
cyclone |
Low-pressure
system which develops in latitudes outside
the tropics. |
| |
| Eye of the tropical cyclone |
The
relatively clear and calm area inside the
circular wall of convective clouds, the geometric
center of which is the center of the tropical
cyclone. |
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|
| Gale force
wind |
Average
surface wind speed of 34 to 47 knots. |
| |
| Gale warning |
Meteorological
message intended to warn those concerned of
the occurrence or expected occurrence of average
wind speed in the range of 34 to 47 knots,
or wind force 8 or 9 in the Beaufort scale. |
| |
| Gust |
Instantaneous
peak value of surface wind speed. |
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|
| Low
pressure area |
Region
of the atmosphere in which the pressures are
lower than those of the surrounding region
at the same level. (On the weather map, the
low pressure area is denoted with the capital
L within the innermost isobar without showing
the center position.) |
| |
|
| Maximum sustained
wind |
Maximum value of the average wind speed at the surface. |
| |
| Mean wind speed |
Average
wind speed. |
| |
|
Reconnaissance
aircraft center fix
of the tropical cyclone,
vortex fix |
The
location of the center of a tropical cyclone
obtained by reconnaissance aircraft penetration. |
| |
|
| Severe
tropical storm |
A tropical
cyclone with the maximum sustained winds of
48 knots (24.5 m/s, 89 km/h) to 63 knots (32.6
m/s, 117 km/h) near the center. |
| |
| Speed of
movement of the tropical cyclone |
Speed
of movement of the center of the tropical
cyclone. |
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| Storm force wind |
Average
surface wind speed of 48 to 63 knots. |
| |
| Storm surge |
The
difference between the actual water level
under the influence of a meteorological disturbance
(storm tide) and the level which would have
been attained in the absence of the meteorological
disturbance (i.e. astronomical tide).
(Storm surge results mainly from the shoreward
movement of water under the action of wind
stress. A minor contribution is also made
by the hydrostatic rise of water resulting
from the lowered barometric pressure). |
| |
| Storm tide |
The
actual sea level as influenced by a weather
disturbance. The storm tide consists of the
normal astronomical tide and the storm surge. |
| |
| Storm warning |
Meteorological
message intended to warn those concerned of
the occurrence or expected occurrence of average
wind speeds in the range of 48 to 63 knots
or wind force 10 to 11 in the Beaufort scale. |
| |
| Sub-tropical cyclone |
A low
pressure system, developing over sub-tropical
waters which initially contains few tropical
characteristics. With time the sub-tropical
cyclone can become tropical. |
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|
| Sustained wind speed |
Average wind speed. Average period of one, three
or ten minutes is depending upon the regional practices. |
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| Tropical cyclone |
Generic
term for a non-frontal synoptic scale cyclone
originating over tropical or sub-tropical
waters with organized convection and definite
cyclonic surface wind circulation.
(The term is also used for a storm in the
South-West Indian Ocean in which the maximum
of the sustained
wind speed * is estimated to be in the
range of 64 to 90 knots and in the South Pacific
and South-East Indian Ocean with the maximum
of the sustained over 33 knots.) |
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| Tropical
cyclone advisory |
A priority
message for exchanging information, internationally,
on tropical cyclones. |
| |
| Tropical depression |
A tropical
cyclone with the maximum sustained winds of
33 knots (17.1 m/s, 61 km/h) or less near
the center. |
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| Tropical disturbance |
A non-frontal
synoptic scale cyclone originating in the
tropics or sub-tropics with enhanced convection
and light surface winds. |
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| Tropical storm |
A tropical
cyclone with the maximum sustained winds of
34 knots (17.2 m/s, 62 km/h) to 47 knots (24.4
m/s, 88 km/h) near the center. |
| |
| Tropical wave |
A trough
or cyclonic curvature maximum in the trade
wind easterlies or equatorial westerlies.
The wave may reach maximum amplitude in the
lower middle troposphere, or may be the reflection
of an upper-troposphere cold low or equatorial
extension of a mid-latitude trough. |
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| Typhoon |
A tropical
cyclone with the maximum sustained winds of
64 knots (32.7 m/s, 118 km/h) or more near
the center. |
| |
| Typhoon force wind |
Average
surface wind speed of 64 knots or more. |
| |
| Typhoon warning |
Meteorological
message intended to warn those concerned of
the occurrence or expected occurrence of the
mean wind speed of 64 knots (32.7 m/s, 118
km/h) or higher, or wind force 12 in the Beaufort
scale. |
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| Visual
storm signals |
Visual
signals displayed at coastal points to warn
ships of squally winds, gales and tropical
cyclones. |
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| Weather warning |
Meteorological
message issued to provide appropriate warnings
or hazardous weather conditions. |
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| Zone of disturbed
weather |
A zone
in which the pressure is low relative to the
surrounding region and there are convective
cloud masses which are not organized. |
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