Pacific Tropical Prediction Center - Glossary

Possible Future TC/Cyclone
Any tropical wave or disturbance that is assessed either by numerical models or PTPC to have a chance to develop into a tropical depression or stronger cyclone.

Tropical Disturbance
A significant weather disturbance of tropical origin. A circulation center is generally either very weak or in the process of forming. This would be the class below tropical depressions. These storms go unnumbered (aside from their PFC number).

Tropical Depression
A significant weather disturbance judged to have tropical origin and a significant, closed circulation center (usually judged by microwave imagery in combination with scatterometer data).

Tropical Storm
Traditional classification for tropical cyclones with winds greater than or equal to 34 knots.

Designated tropical classifications
TD	Tropical Depression	<34 kts
TS	Tropical Storm	34 - 47 kts
ST	Severe Tropical Storm	48 - 63 kts
TY	Typhoon 1	64 - 82 kts
TY2	Typhoon 2	83 - 107 kts
TY3	Typhoon 3	>107 kts
Designated non-tropical classifications
SD	Subtropical Depression	any hybrid tropical cyclone with a strength <34 kts
SS	Subtropical Storm	any hybrid tropical cyclone with a strength ≥34 kts
PD	Post-tropical Depression	any transitioning pre-existing tropical or subtropical cyclone less than tropical storm strength
PS	Post-tropical Storm	any transitioning pre-existing tropical or subtropical cyclone of at least tropical storm strength
Non-designated tropical classifications
TX	Tropical Disturbance	any tropical system with a significant, forming center of circulation (intermittent, several gyres)
SX	Subtropical Disturbance
PX	Post-tropical Disturbance
PFC	Possible Future Cyclone	any region of disturbed weather with a significant future chance of becoming a tropical or subtropical cyclone
Non-designated non-tropical classifications
EX	Extratropical Cyclone	a closed extratropical low pressure system
EY	Extratropical Disturbance	a surface extratropical low pressure system
EZ	Shortwave Trough	an upper level extratropical trough of low pressure

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Page last updated: 20130306 21:48 UTC