Atmosphere Disturbance Pt 2 Flashcards
hurricane
circular low-pressure center w. steep pressure gradient outward
winds spiral inward
Hurricane formation “ingredients”
1) Needs pre-existing instability (from this latent heat released + fuels hurricane)
2) Need rotation = Coriolis effect SO needs to form at least 3 degrees off equator + cannot cross over equator
3) warm ocean temperatures ~80 degrees F w. depth of 50 meters
4) NO WIND SHEAR
types of tropical disturbances
1) tropical depression, winds 38 mph, closed wind circulation pattern
2) tropical storm, winds 39-73 mph
3) hurricane, winds 74+
hurricane characteristic
converging cyclonic wind pulls in war, moist air
rising air cools adiabatically –> large clouds –> condensation –> tons of rain
condensation releases latent heat, adding to instability of storm + strengthening it
hurricane vs midlatitude cyclone
hurricane has NO fronts, only warm moist air
eye of hurricane
calm center, wind speeds highest at eye wall + most updrafts around eye
weather pattern symmetrical around eye
spiral bands
dense cumulus + cumulonimbus clouds curving in from edge of storm to eyewall
wind shear
changes in wind direction
for hurricane to form, air has to be relatively same temp, to allow air to rise vertically + clouds form via adiabatic cooling
If there’s wind shear –> lose the latent heat so storm won’t increase in size
where do hurricanes form
1) east of Philippines
2) west of southern Mexico + Central America
3) Gulf of Mexico + Caribbean area
where do most hurricanes that hit North America form
west coast of Africa, travels along fetch (vast ocean without landmass) + increases in size before hitting North America
why don’t hurricanes go within 3 degrees of equator + or form in south atlantic
1) Coriolis effect - minimal to nonexistant at equator so hurricanes cannot form there
2) south atlantic - water too cold + too much wind shear
general track of hurricane
1) trade winds affect it –> move east to west
2) may go on east-west path for some time + then curve poleward
3) go up east coast of continents (warm currents there)
Life span of hurricane
average 1 week, max is 4 weeks
WHY? = once it hits land, it’s cut off from its source of warm, moist water
lack of water + colder temps kill it
hurricanes often enmesh into midlatitude cyclones
Saffir Simpson scale
intensity of hurricanes (1 = lowest, 5 = horrific)
measures wind speeds –> relates to pressure gradient
storm surge
wind from hurricane increases water height of waves by ~7.5 m more than normal tide
low pressure eye causes water to bulge an additional 1 m, adding more water
most dangerous part of hurricane
