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Marine Weather Quiz
Instructor-Mark Howe
MST202
SADDLEBACK COLLEGE
Quiz #5 [Chapt. 12-13]
1.
What are the unique characteristics of an easterly wave?
Travels east to west at regular intervals in the trades.
Acts like a front but not a front; it is not cyclonic.
Has “cloud streets” instead of circular patterns.
2.
Describe the path of a “textbooker” typhoon
in the northern hemisphere. Include the speed
of the storm and the terms used for each direction.
Diagram:
Path – 10 kn, curve – 5 kn, recurve – 40 to 50 kn.
3.
Name three warnings that would tell you you are in the dangerous quadrant of a typhoon in the central
Pacific [No. Hemisphere].
Clocking wind, clocking waves, radio weather predictions.
4.
What generates the heat energy in the “chimney” necessary to power a tropical hurricane?
As warm moist air converges into and rises up and around the eye of the hurricane, it condenses,
releasing latent heat. This heat release increases the convective updraft in the chimney creating more
condensation and latent heat release.
5.
Name three [or more] circumstances which will kill the power of a tropical typhoon.
Any circumstance that reduces the supply of warm moist air.
1. Travel over cooler water.
2. Sucking up cooler air.
3. Making landfall – no more warm water
6.
Describe the importance of “vorticity“ in the formation of a hurricane.
Must have spin to spawn. Without spin (vorticity) a hurricane cannot form.
7.
What are the important factors differentiating the structure of a tropical from an extra-tropical hurricane?
Tropical
Nontropical
8.
Eye
Small
No eye Large
Warm
Cool
Strongest winds at center
moves west
Strongest winds at periphery moves east
Compare and contrast an immature with a mature extra tropical cyclonic frontal system.
Immature is a relatively straight interface between their air masses.
Mature system develops wavelike shape traveling from west to east; warmer high-pressure air on one
side and cooler lower pressure air on the other.
9.
You are on your boat off the Pacific Coast and an extra tropical cyclonic frontal system passes over you.
Describe what you feel and because why.
Assume northern hemisphere in the zone of the westerlies.
As a front approaches you the wind backs to the south (southeast southwest) then as the front passes
over you the wind clocks back to the west (northwest). This is caused by the low pressure to the north
creating a gradient of wind to the south crossing isobars as it passes.
10.
From the previous question, what would be the difference if it had already occluded?
The wind directional shift would be similar but the rain would be heavy and protracted; more rain prior
to and after the passage of the surface front.
11.
What kind of barometric readings would indicate you are in danger of being hammered by a typhoon?
1 mb/hr. drop in pressure: warning of danger
2 mb/hr. drop in pressure: danger
3 mb/hr. drop in pressure: imminent danger
12.
The ITCZ is at 15° north toward the end of August while an easterly wave (EW) is passing to the North.
How could the result to be a tropical storm?
If the ITCZ coincides with the easterly wave passing along the trade belt, the result can be a vortex of
extra low pressure. If this vortex is more than 5° from the equator and deep enough, Coriolis can cause
sufficient vorticity to spawn a tropical storm.
You are sailing in the tropical North Pacific and you sense that the hurricane to your South is beginning
to turn northeast:
13.
What will be the most likely scenario when this happens?
The hurricane is going into its recurve phase and will speed up to a rate of travel of 30 to 50 kn. The
storm will be passing you to your Southeast and you will be on its left shoulder.
14.
What changes (shifts) in wind and waves will you feel to verify your situation?
On the left shoulder you will be feeling a shift in wind from East to North (backing) and large long
waves from the south backing to the southeast.
15.
Are you safer or not when this happens? Why?
The left shoulder is a safer shoulder of a hurricane in the northern hemisphere so if this scenario
continues, that is safer for you.
16.
What direction should you be sailing and at what angle to the wind?
Since you are still in front of the storm you should be making all haste to get as far from its path as
possible, which would be northwest. Since the wind will be from the East, backing to the north, you will
be sailing on a broader reach becoming a beam reach until the storm has passed.