[talk-ph] Typhoon Wind Speeds

Mark Cupitt markcupitt at gmail.com
Thu Dec 12 00:15:01 UTC 2013


Hi All

Whilst looking at our areas and the overlaid track of the Typhoon, I was
reminded of some information that I thought I would share with all
concerned. I was reminded of this by one of our team members.

In the Northern Hemisphere, Typhoons rotate in a Counter Clockwise
Direction, so the actual wind on the ground has to be factored with the
speed of travel of the typhoon itself. The faster the speed over ground of
the typhoon, the more wind that will be added or subtracted over the ground
depending on what position within the circulation a specific point is.

To illustrate

Typhoon is travelling East to West at 15 knots with wind speeds of 150
knots.
Because of the counter clockwise rotation, the actual winds North of the
track will be wind-speed + the speed over ground of the typhoon, in our
example, 150 + 15 = 165 knots
On the south side of the track, it will be the reverse as we subtract the
travel of the typhoon from the wind speed as it is travelling "with" the
typhoon, in our example 150 - 15 = 135 knots.
Now this may seem insignificant, but realize that the difference between
the north side of the track and south side is actually 30 knots. This can
make a significant difference in damage assessment.

The strongest adjustments will be at 90 degrees to each side of the track
with no adjustment on the actual track location itself, and proportionally
in between the two positions.

The Southern hemisphere is simply the reverse.

When prioritizing mapping efforts, the initial areas to focus on would be
90 degrees to the north of the track in the Northern hemisphere and 90
degrees south of track in the Southern Hemisphere to look for the areas
with the most likely damage

The faster the typhoon is travelling over the ground, the greater this
effect is.

Hope this is useful

Regards

Mark Cupitt

"If we change the world, let it bear the mark of our intelligence"

See me on LinkedIn <http://ph.linkedin.com/in/markcupitt>

*See me on StackExchange <http://gis.stackexchange.com/users/17846/mark-c>*

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