Second Exam

1
Second Exam

• Average 72.8, median 74.5, high 100, low 32
• Approximate TENTATIVE grading
• 82 A
• 72-81 B
• 62-71 C
• 52-61 D
• 51lt F
• Will put up a key on WebCT soon.

2
Check our math!!!
(apparently, getting a Ph.D. doesnt guarantee
that you can add)
3
Review Question
Q. If the air temperature at sea level were
23C, what would the air temperature be at a
height of 2 kilometers under average conditions?
A. The environmental lapse rate is 6.5C per
kilometer, which means on average temperature
decreases by 6.5C every 1000 meters, so the
answer is 23 (2x6.5) 10C
4
Review Question
Q. Least three basic mechanisms of energy
transfer. Which mechanism is least important to
meteorology?

• A.
• Conduction
• Convection
• Radiation

• Conduction

5
Review Question
Q. What are isotherms and what is their purpose?
A. Isotherms are lines that connect points of
equal temperature, generally trend east to west
and show decreasing temperature
poleward. Isotherms illustrate latitudinal
shifting of temperatures caused by the seasonal
migration of the Suns vertical rays and also
the presence of ocean currents.
6
Easterly Wave Development
cold Canary current kills most disturbances
Forecasters look to the west coast of Africa to
see the hint of hurricane formation.
An easterly wave which lead to Hurricane Bertha
7
Hurricane Formation and Decay

• By WMO agreement, tropical cyclones are given
  terms which correspond to their strength, as
  measured by wind speed.
• Tropical Depression sustained winds less than 61
  kilometers per hour (37 mph). Given numbers
  like TD 11.
• Tropical Storm sustained winds are between 61
  and 119 kilometers per hour (37 and 74 mph).
  Tropical storms are given names.
• Hurricane sustained winds are at least 119
  kilometers per hour (75 mph)

8
Hurricane Decay

• Because hurricanes are heat engines fueled by
  condensation of
• water vapor, the loss of water vapor will result
  in a rapid
• decrease in storm strength. In addition, a
  hurricane needs upper
• level support to maintain vertical balance and
  rapid rotation.
• Three events cause hurricanes to lose strength
• move over waters that cannot supply warm, moist
  tropical air
• move onto land
• reach a location where the large-scale flow aloft
  is unfavorable
• A hurricane can reinvigorate itself if the the
  supply of warm, moist
• air returns or if upper level conditions once
  again become conducive
• to rapid rotation.

9
Hurricane Destruction
The amount of damage caused by a hurricane is
dependent on many things (population, warning
time, etc). The most significant factor is the
strength of the storm itself.
Saffir-Simpson scale was established to rank the
relative intensities of hurricanes (1 least
severe- 5 most severe).

• Damage caused by hurricanes can be divided into
  three
• classes
• storm surge
• wind damage
• inland freshwater flooding

10
Storm Surge
Storm surge is a dome of water 65-80 kilometers
(40-50 miles) wide that sweeps across the coast
near the point where the eye makes land fall.
Storm surge is caused by the pileup of water
because of strong onshore winds. Stronger to
the right of where the eye makes landfall.
11
Storm Surge
Winds are stronger and storm surge is larger on
the right side of the storm.
12
Storm surge was tremendous in The Great Galveston
Hurricane of 1900
A typical block in Galveston after the storm
The scene at 21st and O Avenue on Sunday morning
September 9, 1900
The ruins of St. Patrick's Catholic Church
13
Wind Damage
For higher category hurricanes, wind damage can
be a significant destructive force related to
hurricanes. Wind damage is typically more
widespread than storm surge, but less severe (if
the structures in the path of high winds are
strong enough to withstand the force of the
winds). Flying debris can be a very damaging and
dangerous result of strong winds.
14
(No Transcript)
15
Wind Damage
Winds associated with a Northern Hemisphere
hurricane advancing toward the coast.
16
Inland Flooding
Storm surge and strong winds are typically
associated with coastal areas, however, inland
flooding can extend hundreds of miles from the
coast and several days after the storm has lost
its hurricane status (winds lt75 mph). Hurricane
Agnes was a good example of a hurricane which
caused significant inland flooding. While Agnes
was only a category 1 storm on the Saffir-Simpson
scale more than 2 billion dollars in damage
related to the hurricane (most of the severe
flooding was in Pennsylvania). It is
interesting to note that Agnes was an overall
good thing economically as farmers in the
southeast received much needed rain for crops.
17
Inland flooding due to hurricanes can be
extensive as rainfall from a hurricane sometimes
can be measured in tens of inches.
Note that this is nowhere included in the
Saffir-Simpson scale.
18
Saffir-Simpson scale?

• While wind is an important part of a hurricane,
  rating hurricanes by wind alone is not a good
  indicator of how much damage the hurricane might
  do.
• Hurricane Mitch was a very strong hurricane, but
  more importantly, it landed in Central America
  and did not move, preferring to dump all its rain
  in one spot!

19
Detecting and Tracking Hurricanes
North Atlantic hurricanes develop in the trade
winds which explains why these storms move east
to west at 15 mph. Hurricanes almost always
curve poleward and are deflected into the
westerlies which increases their forward motion
up to a maximum of about 60 mph. However, on a
finer scale, all hurricanes have irregular
paths, which makes prediction of their movement
challenging.
20
Detecting and Tracking Hurricanes
The greatest single advance in tools used for
observing tropical cyclones has been the
development of meteorological satellites.
Satellites allow us to detect tropical storms and
have significantly improved monitoringyou can
see em days away!
21
Hurricane Allen in 1980 ( a rare category 5 storm)
22
well defined eye
Hurricane Allen in 1980 ( a rare category 5 storm)
23
Hurricane Allen in 1980 ( a rare category 5 storm)
24
Aircraft reconnaissance
Aircraft reconnaissance represents the second
important source of information about
hurricanes. Experimental flights were conducted
in the 1940s and will be used for the
forseeable future because of the detailed
information they provide. Much information of
hurricane structure has been obtained by the P3
WP-3A Orions
WWII patrol bomber, the PB4Y Privateer
Early Aircraft
Current Aircraft
25
Radars and Buoys make up the third and fourth
tools used to study and observe hurricanes.
A network of radar units in the Gulf of Mexico
and Atlantic coastal regions give continuous
coverage of tropical storms within 150 miles of
the coast.
Buoys represent the only means of making nearly
continuous direct measurements of surface
conditions over the ocean.
26
Hurricane Watches and Warnings
A hurricane watch is an announcement aimed at
specific coastal areas that a hurricane poses a
possible threat, generally within 36 hours.
VERY different from a tornado watch! A
hurricane warning is issued when sustained winds
of 74 mph or higher are expected within a
specified coastal area in 24 hours or less.
27
(No Transcript)
28
NOAA Hurricane site
http//www.nhc.noaa.gov/
29
Hurricane Season

• Hurricane season June 1 November 30
• When water temperatures near the equator are over
  80ºF
• Ordinary year
• 9.6 tropical storms A.K.A. named storms
• 5.9 hurricanes
• 2.3 major hurricanes (category 3-4-5)

30
Upcoming Hurricane Season

• http//hurricane.atmos.colostate.edu/Forecasts/200
  3/april2003/
• 12 tropical storms
• 8 hurricanes
• 3 major storms

31
1950-2000 Averages

• 1) Named Storms (NS) 9.6
• 2) Named Storm Days (NSD) 49.1
• 3) Hurricanes (H) 5.9
• 4) Hurricane Days (HD) 24.5
• 5) Intense Hurricanes (IH) 2.3
• 6) Intense Hurricane Days (IHD) 5.0

32
This year

• The recent upturn in Atlantic basin hurricane
  activity which began in 1995 is expected to
  continue through 2003. We anticipate an
  above-average probability for Atlantic basin
  tropical cyclones and U.S. hurricane landfall.

33
Predictors ALL above normal

• Azores high is weaker than usual, meaning higher
  water temperatures than usual
• Other indicators point to a shift from El Nino to
  La Nina conditions, and warmer Atlantic
  temperatures in general.

34
Similar seasons

• There were four hurricane seasons since 1949
  with characteristics similar to what we have
  observed through March 2003 and what we
  anticipate will occur in the summer/fall 2003
  period. These best years are 1952, 1954, 1958 and
  1998. We expect that the 2003 seasonal hurricane
  conditions will be slightly above the average
  values for these four years.

35
Global Warming?

• Various groups and individuals have suggested
  that the recent large upswing in Atlantic
  hurricane activity (since 1995) may be in some
  way related to the effects of increased man-made
  greenhouse gases such as carbon dioxide (CO2).
  There is no reasonable scientific way that such
  an interpretation of this recent upward shift in
  Atlantic hurricane activity can be made.

36
and now the bad news

• "A remarkable upturn in Atlantic Basin hurricane
  activity has occurred the past seven years," Gray
  said. "We believe we have entered a new,
  multi-decadal era for increased storm activity,
  particularly an increase in the number of major
  hurricanes, which will likely last another two or
  three decades."

37
no wait, theres more

• Beyond the past seven years, the United States
  also has seen a significant decrease in major
  hurricane landfalls over the past
  three-and-a-half decades. According to Gray, this
  pattern has resulted from a rare combination of
  multi-decadal global circulation changes and pure
  luck and cannot be expected to continue.

38
oh yeah, one more.

• "We should anticipate the century-long landfall
  climatology to eventually right itself and must
  expect a large increase in landfalling hurricanes
  in the coming years," Gray said. "With exploding
  growth in coastal populations and property
  values, we must be prepared for levels of
  hurricane damage many, many times greater than
  has occurred in the past three decades."
• (ouch)

39
Next week

• Hurricane primer handout