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windfind
Joined: 18 Mar 1997
Posts: 1901
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 Posted: Mon Aug 01, 2016 11:24 am Post subject: |
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| beallmd wrote: | | While I'm asking questions, let me ask another weather question I've wondered about for a long time. maybe it's simple but I can't figure it out. If hurricanes form and draw their strength from warm water, usually 82 degrees and above, and lose strength and dissipate over water below that temperature such as the northern Atlantic or if they move north in the pacific, how do winter pacific storms form and gather strength? Sometimes they use the term winter hurricanes but obviously that's not right. Thanks |
Hi Bealmd,
Yes it is confusing. Both hurricanes and mid latitude winter storms have strong wind, rain and counter-clockwise spinning winds in the N. hemisphere. But that is about all they have in common.
The causation of hurricanes and regular winter storms is very different
Looking at the first image below... hurricanes start from large thunderstorms in the tropics and if conditions are perfect and the ocean is warm and the air humid enough they merge into a single storm which the Coriolis force turns into a spinning mass of air around an "eye". As humid air spirals into the eye and rises its water vapor condenses. This condensation releases latent energy which heats the air causing it to rise even faster which accelerates the spiraling winds of the hurricane. So a warm ocean provides that basic energy to drive the hurricane. Once over land the hurricane loses its energy source and friction quickly causes the winds to fade. Here is a link with more detail: http://www.ems.psu.edu/%7Enese/ch11sec3.htm
Mid latitude storms like the Bay Area sees in the winter are caused by collision of cooler arctic air masses with warmer mid latitude air masses as you can see in the second image. This causes a front to develop and then a wave at the junction of the cold and warm air masses and a pressure gradient develops. Coriolis force turns this into a spinning mass of air which is usually much larger but weaker than a hurricane. Since the energy driving the storm is different temps of the air masses the winter storm continues over land although its winds are often weakened somewhat by friction with hills etc.
The above a greatly oversimplified but hopefully answers your question.
Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com
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beallmd
Joined: 10 May 1998
Posts: 1154
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| Posted: Mon Aug 01, 2016 3:26 pm Post subject: |
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| Wow, thank you. Well another terrific couple of days at Sherman especially this morning. Last night, Sunday night, was very crowded almost like the old days. Today a few people out at each site. Sacramento temp around 94, very favorable. Strong ebb this morning meant swells shoulder high.
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