GEOL 106 Lecture Notes - Lecture 37: Maximum Sustained Wind, World Meteorological Organization, Sea Surface Temperature
26 May 2018
School
Course
Professor
[Type here]
NAMING CYCLONES
- only small percentage are given names: identify where they form or to track their movement
- extratropical cyclones: sometimes named for the geographic area where they form (e.g. Alberta
Clippers)
- all tropical depressions that develop into tropical storms and hurricanes are given individual names
by government forecasting centres
o established by international agreement through World Meteorological Organization
WMO
o standardized naming system adopted by WMO replaced other practices
- official name is assigned once the maximum sustained winds of tropical depression exceed 63 km/hr
and it becomes a tropical storm
o names are assigned sequentially each year from previously agreed upon list for region in
which storm forms
o naming helps forecasters keep track of multiple storms moving across ocean at same time
- Atlati oea: aes oe fro 1 of 6 alphaetial lists of alteratig e’s ad woe’s aes
o each list has 21 names derived from English, Spanish or French
o 6 lists are used in rotation: e.g. 2014 list will be used again in 2020 and 2026
- names of especially damaging hurricanes: Katrina, Rita, Ivan, Charley → retired from rotating lists
- 2005: number of tropical storms and hurricanes in Atlantic Ocean, exceeded list for that year
o more than 21 tropical storms and hurricanes formed in Atlantic Ocean in single year
o NWS forecasters went to their backup plan of assigning letters of Greek alphabet to
additional storms
10.2 Cyclone Development and Movement
- tropical and extratropical cyclones:
o differ in their characteristics
o differ in their development
o some tropical cyclones transform into extratropical cyclones if they encounter upper level
low pressure trough as they weaken over land or over cooler seawater at higher latitudes
TROPICAL CYCLONES
- tropical cyclone: large thunderstorm complex rotating around an area of low pressure that has formed
over warm tropical or subtropical ocean water
o tropical depressions and tropical storms: low intensity tropical cyclones
o hurricanes: high intensity tropical cyclones
▪ tropical cyclone must have sustained winds of at least 119 km/hr
▪ require tremendous amounts of heat to develop and generally form only where
sea surface temperature is at least 26 degrees
- most hurricanes start out as tropical disturbance
o tropical disturbance: large area of unsettled weather that is typically 200 – 600 km in
diameter and ha organized mass of thunderstorms that persists for more than 24 hours
o tropical disturbance is associated with elongated area of low pressure called a trough
o air in disturbance has weak partial rotation caused by Coriolis effect
o tropical disturbances form in variety of ways, including lines of convection similar to squall
lines, upper level troughs of low pressure, remnants of cold fronts, and easterly waves of
converging and diverging winds that develop in tropics
find more resources at oneclass.com
find more resources at oneclass.com
