Lecture 8 10/29/12
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Review Last Lecture
CH 11 Hurricanes
Hurricane Sandy!
Review Mid Term
Video Dessert: Infrared satellite imagery for the
west coast of the US at 4 different scales
• Due Dates:
• Mid Term III 11/19/12
• CH 6-11
• Lecture 7-10
• Research Paper/Video Presentation 11/26/12
REVIEW SLIDES:
Simplified model depicting the life cycle of an ordinary thunderstorm
that is nearly stationary. (Arrows show vertical air currents. Dashed
line represents freezing level, 0°C isotherm.)
REVIEW SLIDES:
A simplified model describing air motions and other features
associated with an intense multicell thunderstorm that has a tilted
updraft. The severity depends on the intensity of the storm’s
circulation pattern.
Thunderstorms Video
http://www.youtube.com/watch?v=bOfOA3PTghM&feature=related
REVIEW SLIDES:
The generalized charge
distribution in a mature
thunderstorm.
REVIEW SLIDES:
The development of a lightning stroke. (a) When the negative charge near the bottom of the
cloud becomes large enough to overcome the air’s resistance, a flow of electrons — the
stepped leader — rushes toward the earth.
(b) As the electrons approach the ground, a region of positive charge moves up into the air
through any conducting object, such as trees, buildings, and even humans. (c) When the
downward flow of electrons meets the upward surge of positive charge, a strong electric
current — a bright return stroke — carries positive charge upward into the cloud.
Chapter 11
Hurricanes
• Intense storm of tropical origin with winds
greater than 64 kts; typhoon, cyclone,
tropical cyclone
• Eye
• Eyewall
• Spiral rain band
• Anticyclonic divergence
• Latent heat
Hurricane Elena over the Gulf of Mexico about 130 km (80 mi) southwest of
Apalachicola, Florida, as photographed from the space shuttle Discovery during
September, 1985. Because this storm is situated north of the equator, surface
winds are blowing counterclockwise about its center (eye). The central pressure
of the storm is 955 mb, with sustained winds of 105 knots (121 mi/hr) near its
eye.
intensifying tropical cyclone
air pressure drops rapidly as you approach the eye of the storm
surface winds normally reach maximum strength in the region of the eyewall
A model that shows a vertical view of air motions and clouds in
a typical hurricane in the Northern Hemisphere. The diagram is
exaggerated in the vertical.
The cloud mass is Hurricane Katrina’s eyewall, and the clear area is
Katrina’s eye photographed inside the eye on August 28, 2005,
from a NOAA reconnaissance (hurricane hunter) aircraft.
Hurricane Katrina in 3-D
The cutaway view shows
concentric bands of heavy
rain (red areas inside the
clouds) encircling the eye.
Notice that the heaviest
rain (largest red area)
occurs in the eyewall.
The isolated tall cloud
tower (in red) in the
northern section of the
eyewall indicates a cloud
top of 16 km (52,000 ft)
above the ocean surface.
Such tall clouds in the
eyewall often indicate that
the storm is intensifying.
Hurricane Formation and Dissipation
• Why Does The Storm Die Out?
– Cold water, land
• Hurricane Stages of Development:
• Tropical Disturbance
• Tropical Depression (22-34kts)
• Tropical Storm (35-64kts)
• Hurricane (> 65kts)
Visible satellite image showing four tropical systems, each in a
different stage of development.
A hurricane moving
northward will
have higher
sustained winds on
its eastern side
than on its western
side. The boxed
area represents the
region of strongest
winds.
The total number of hurricanes and tropical storms (red shade) and
hurricanes only (yellow shade) that have formed during the past 100
years in the Atlantic Basin—the Atlantic Ocean, the Caribbean Sea, and
the Gulf of Mexico. (NOAA)
Regions where tropical storms form (orange shading), the names given
to storms, and the typical paths they take (red arrows).
Hurricane Sandy
• Video of Infrared imagery of Hurricane
Sandy from the National Weather Service
east_coast_IR_20121028_1700.avi
• Forecasts
• Hazards (wind, rain, storm surge, flooding)
• River Gages: http://water.weather.gov/ahps2/index.php?wfo=akq
National Hurricane Center (NHC) satellite imagery Sunday 10/28/12
These graphics show
probabilities of
sustained (1-minute
average) surface wind
speeds equal to or
exceeding 34 kt...39
mph (tropical storm
force).
These wind speed
probability graphics are
based on the official
National Hurricane
Center (NHC) track,
intensity, and wind radii
forecasts, and on NHC
forecast error statistics
for those forecast
variables during recent
years.
http://google.org/crisismap/2012-sandy
This is the forecast for rainfall from Hurricane Sandy after 120 hours.
This shows the overall
chance that storm
surges will be greater
than 2 feet above
normal tide levels
during the 3 days after
10/28/12.
The graphic is based upon an
ensemble of Sea, Lake, and
Overland Surges from
Hurricanes (SLOSH) model runs
created using the current
National Hurricane Center (NHC)
official hurricane advisory. Storm
surge probabilities depend on
the historical accuracy of NHC's
forecasts of hurricane track, and
wind speed, and an estimate of
storm size.
http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/205341.shtml?gm_psurge#contents
This shows the overall
chance that storm
surges will be greater
than 6 feet above
normal tide levels
during the 3 days after
10/28/12.
http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/205341.shtml?gm_psurge#contents
Measured
Projected
BONUS SLIDE
http://www.nhc.noaa.gov/text/refresh/MIATCPAT3+shtml/290247.shtml
Example: DISCUSSION AND 48-HOUR OUTLOOK
-----------------------------AT 1100 PM EDT...0300 UTC...THE CENTER OF HURRICANE SANDY WAS LOCATED NEAR
LATITUDE 34.5 NORTH...LONGITUDE 70.5 WEST. SANDY IS MOVING TOWARD THE NORTHEAST
NEAR 14 MPH...22 KM/H. A TURN TOWARD THE NORTH IS EXPECTED DURING THE NEXT
SEVERAL HOURS...WITH A TURN TOWARD THE NORTHWEST EXPECTED ON MONDAY. ON THE
FORECAST TRACK... THE CENTER OF SANDY WILL MOVE OVER THE COAST OF THE MIDATLANTIC STATES LATE MONDAY OR MONDAY NIGHT.
MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH...120 KM/H...WITH HIGHER GUSTS. SANDY IS
EXPECTED TO TRANSITION INTO A FRONTAL OR WINTERTIME LOW PRESSURE SYSTEM PRIOR TO
LANDFALL. HOWEVER...THIS TRANSITION WILL NOT BE ACCOMPANIED BY A WEAKENING OF
THE SYSTEM...AND IN FACT...A LITTLE STRENGTHENING IS POSSIBLE DURING THIS PROCESS.
SANDY IS EXPECTED TO WEAKEN AFTER MOVING INLAND.
HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 175 MILES... 280 KM...MAINLY TO THE
SOUTHWEST OF THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO
520 MILES...835 KM. A NATIONAL OCEAN SERVICE STATION AT THE WILLOUGHBY DEGAUSSING
STATION NEAR NORFOLK NAVAL STATION VIRGINIA RECENTLY REPORTED SUSTAINED WINDS OF
45 MPH...72 KM/H...WITH A GUST TO 53 MPH...85 KM/H. A WEATHERFLOW STATION AT
THIMBLE SHOALS VIRGINIA RECENTLY REPORTED SUSTAINED WINDS OF 44 MPH...70
KM/H...AND A WIND GUST OF 52 MPH...83 KM/H.
THE MINIMUM CENTRAL PRESSURE BASED ON AIR FORCE RESERVE AND NOAA HURRICANE
HUNTER AIRCRAFT DATA IS 950 MB...28.05 INCHES.
BONUS SLIDE
Video Dessert: Infrared Satellite Imagery of the west
coast of the US at 4 different scales:
pacific_IR_28_km_20121028_1700.avi
pacific_IR_14_km_20121028_1700.avi
pacific_IR_4_km_20121028_1700.avi
pacific_IR_2_km_20121028_1700.avi
BONUS SLIDE
This shows storm surge height
in feet, above normal tide
levels, such that there is an N
percent chance of exceeding
it, where N ranges from 10 to
90 in intervals of 10 percent.
The 10 percent exceedance
height, for example, is the
storm surge height, above
normal tide levels, such that
there is a 10 percent chance
of exceeding it.
This graphic is based upon an
ensemble of Sea, Lake, and Overland
Surge from Hurricanes (SLOSH) model
runs using the National Hurricane
Center (NHC) official advisory and
account for track, size, and intensity
uncertainty from historical errors.
http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/205341.shtml?gm_esurge#contents
BONUS SLIDE
A tropical wave
(also called an
easterly wave)
moving off the
coast of Africa
over the Atlantic.
The wave is
shown by the
bending of
streamlines—
lines that show
wind flow
patterns. (The
heavy dashed
green line is the
axis of the ridge.)
The wave moves
slowly westward,
bringing fair
weather on its
western side and
rain showers on
its eastern side.
BONUS SLIDE
Hurricane Formation and Dissipation
Hurricane movement
 General track: west, northwest, northeast
Topic: Hurricanes and Mid-latitude Storms
 Hurricane warm core low
 Mid-latitude cold-core low
 Arctic hurricanes
 Hurricane + upper level trough = mid-latitude
cyclone