Re: OT: interesting global warming quote found elsewhwere

In <704b132f-cb4b-42ed-9fdb-ffcc4c9841ab@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
bill.sloman@xxxxxxxx wrote:
On Jul 27, 2:14 pm, d...@xxxxxxxxxxxxxx (Don Klipstein) wrote:
In <246d2b98-79c2-4b77-814a-63d950028...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,

bill.slo...@xxxxxxxx wrote:
On Jul 25, 4:22 pm, d...@xxxxxxxxxxxxxx (Don Klipstein) wrote:
In <c0c8b408-ea13-4cbd-82f1-80c4700c8...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,

  I expect that the LA-SD region of California with such extreme warming
would run into a hurricane problem a little worse than Acapulco has to
deal with now.  And that the SF area and West Coast North America will
only worsen to about what LA and SD deal with now.

As far as the frequency of hurricanes go you may be right. The
intensity of the hurricanes - with much larger areas of hot ocean to
track over before they hit land - is a different question.

  The ocean off CA is still not going to be nearly as hot as the tropical
oceans.  The hurricanes will weaken when approaching CA, the way they now
do once past about 35 or so degrees N going up the East Coast.

The mechanism proposed was lots of intense hurricans over a much wider
belt arond the equator - as you'd expect, since hurricans grow where
the sea surface temperature is over about 26.5C

  That is not a critical temperature carved in stone.  Should the middle
and upper troposphere in hurricane formation areas also warm, then the
critical sea surface temperature for hurricane formation will aslo rise -
probably by a small amount.  Also keep in mind that the tropics will warm
less than the globe as a whole.

But give the hurricanes a bigger playground to grow in, and they can
get bigger and stronger before they hit the coast.

  Furthermore, keep in mind that the hurricane uptick of the last decade
or so is in significant part not from global warming but from the Atlantic
multidecadal oscillation.

Agreed. But that's about the frequency, not the intensity.

  Intensity also.  The multidecadal oscillation affects temperatures of
the Carribean and the Gulf Stream and the Gulf Loop Current.

- that mixed the
surface layers of the tropical oceans much more thoroughly - and
deeply than they are mixed at the moment, putting a lot wmore warm
water into the cean currents flowing towards the poles.

  That one is a more serious concern, to the extent there is an increase
of hurricane activity that is independent of the multidecadal oscillations
of the Atlantic and Pacific oceans.  That can melt away sea ice in polar
and near-polar regions - for now in/near the Arctic, since most tropical
cyclones are in the northern hemisphere.

With enough intense hurricans around, the coast of California would
not be a good place to build a conventional house.

  I would advise coastal Southern CA to be advised that in a few centuries
they may get what Acapulco gets now.

But with stronger winds and heavier rainfall.

  I doubt it - the ocean for hundreds of miles offshore CA would be a lot
cooler than the tropical oceans, so hurricanes would weaken when
approaching CA.  As for frequency - I was even counting on westerly winds
turning them towards the shore.

  How bad would it be if LA and San Diego become more like Acapulco and SF
becomes like San Diego or a degree or two warmer than San Diego is now?

Better analogies would be Galverston and New Orleans.

  How do you see coastal California getting that bad?  The climate
forecast models that made more sense to me have LA and SD hardly worse
than Acapulco (besides sea level higher) even if we warm up our planet to
what it was like in the Cretaceous Age.

  The worst I see for coastal CA if the world gets that warm is having to
move a couple hundred meters uphill - which is not far.  

Probably not far enough to cope with storm surges

  A Cat-5 hurricane storm surge is generally 6-9 meters.

Cat-6?

  If Cat-6 is invented, such storms would only exist where there is
extremely warm water to sustain them.

or a long enough track over water at or above 26.5C - you can trade
distance against surface water temperature, so long as the surface
water temperature stays abobe 26.5C

27 degree C water will not grow a hurricane into a Cat-5 and will
not keep a Cat-5 at Cat-5.

  Ever hear of a Cat-4 or 5 hitting New England or Nova Scotia?  The
strongest hurricanes do weaken when they get away from the warmest water.

Hurricanes weaken when the sea surface temperature falls below 26.5C
- warmer water drives them harder, but the cut-off point is an
absolute temperature, set by the vapour pressure of water over the sea
surface.

Very strong hurricanes become weaker hurricanes when the water is barely
or hardly over 26.5 degrees C. They remain hurricanes but they will lose
some of their strength.

One example is Rita of 2005, which was Cat-5 when it was over the Gulf
Loop Current which then had a temperature around 29.5 or 30 degrees C or
so. Rita weakened while approaching the coast in large part from running
into water that was more like 27.5 degrees C or so once stirred up.
Wilma later in 2005 did not make landfall at Cat-5 strength. That storm
did not recover to its peak strength after an eyewall replacement cycle
largely because it moved onto water not quite as hot as it was over when
it reached record intensity. Wilma made landfall on Cozumel and the
Mexico mainland as a Cat-4.

Most Cat-5 hurricanes (so far) do not stay at Cat-5 strength until
landfall but weaken when they hit conditions able to sustain a hurricane
but at less strength - and usually the main reason is water that is cooler
though above 26.5 degrees C. Eyewall replacement cycles complicate this,
but many Cat-5 storms have time to fully recover from an eyewall
replacement cycle but fail to reach their prior strength when over water
that is exceeding 26.5 degrees C by a smaller extent.

Also, that 26.5 degree C figure will vary with what temperatures in the
upper troposphere do. The temperature at, say, the 200 or 150 millibar
level in the tropics tends to be fairly constant, but will warm if there
is widespread major warming in the regions of the tropics where there is a
lot of convection to the upper troposphere.

Move the isotherms further from the equator, and the tracks
become longer, and more northerly coastlines will be exposed to
maximally intense hurricanes.

- Don Klipstein (don@xxxxxxxxx)
.

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