Hurricanes, or tropical cyclones, form in an environment of little or no vertical wind shear.

Vertical shear (which doesn't have to be throughout the troposphere,
but can also be over a very shallow layer) destroys the convection
around the centre of the tropical cyclone (the 'eye').

For a tropical cyclone to continue to develop, there must be inflow of
warm air at lower levels, and upper level outflow:

The convection provides the 'pathway' for the necessary rising air.

Hurricanes form over very warm waters - sea surface temperatures (SST)
values above about 27 deg C, equator-ward of the sub-tropical
anticyclone belt,

The capture/inflow of water vapour and sensible heat from the tropical
oceans being essential to the physics of the storm.

The storm is warm core, especially in the lower troposphere, with
little overall (synoptic scale) 500-1000 hPa thickness gradient, and
therefore hurricanes have no 'Norwegian model' fronts associated with
them.

Low pressure is primarily due to the contrast between the warm core of
the storm, and the unperturbed tropical environment.

There is some contribution from compressional warming of descending air
within the 'eye' of the storm, and the speed of movement of the storm
is generally less than 15 knots.

(NB: the name 'tropical' should not be taken to mean that these
features only form between the Tropics of Cancer and Capricorn; they
can develop well poleward of the 'tropics' and persist with tropical
characteristics [up to 'Hurricane' category], well into the normally
accepted 'mid-latitudes':

It is the storm structure - as defined above - that is important, not
the exact location of the disturbance.)

http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

000
WWUS74 KLIX 281550
NPWLIX

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1011 AM CDT SUN AUG 28 2005

....DEVASTATING DAMAGE EXPECTED...

..HURRICANE KATRINA...A MOST POWERFUL HURRICANE WITH UNPRECEDENTED
STRENGTH...RIVALING THE INTENSITY OF HURRICANE CAMILLE OF 1969.

MOST OF THE AREA WILL BE UNINHABITABLE FOR WEEKS...PERHAPS LONGER. AT
LEAST ONE HALF OF WELL CONSTRUCTED HOMES WILL HAVE ROOF AND WALL
FAILURE. ALL GABLED ROOFS WILL FAIL...LEAVING THOSE HOMES SEVERELY
DAMAGED OR DESTROYED.

THE MAJORITY OF INDUSTRIAL BUILDINGS WILL BECOME NON FUNCTIONAL.
PARTIAL TO COMPLETE WALL AND ROOF FAILURE IS EXPECTED. ALL WOOD
FRAMED LOW RISING APARTMENT BUILDINGS WILL BE DESTROYED. CONCRETE
BLOCK LOW RISE APARTMENTS WILL SUSTAIN MAJOR DAMAGE...INCLUDING SOME
WALL AND ROOF FAILURE.

HIGH RISE OFFICE AND APARTMENT BUILDINGS WILL SWAY DANGEROUSLY...A
FEW TO THE POINT OF TOTAL COLLAPSE. ALL WINDOWS WILL BLOW OUT.

AIRBORNE DEBRIS WILL BE WIDESPREAD...AND MAY INCLUDE HEAVY ITEMS SUCH
AS HOUSEHOLD APPLIANCES AND EVEN LIGHT VEHICLES. SPORT UTILITY
VEHICLES AND LIGHT TRUCKS WILL BE MOVED. THE BLOWN DEBRIS WILL CREATE
ADDITIONAL DESTRUCTION. PERSONS...PETS...AND LIVESTOCK EXPOSED TO THE
WINDS WILL FACE CERTAIN DEATH IF STRUCK.

POWER OUTAGES WILL LAST FOR WEEKS...AS MOST POWER POLES WILL BE DOWN
AND TRANSFORMERS DESTROYED. WATER SHORTAGES WILL MAKE HUMAN SUFFERING
INCREDIBLE BY MODERN STANDARDS.

THE VAST MAJORITY OF NATIVE TREES WILL BE SNAPPED OR UPROOTED. ONLY THE
HEARTIEST WILL REMAIN STANDING...BUT BE TOTALLY DEFOLIATED. FEW CROPS
WILL REMAIN. LIVESTOCK LEFT EXPOSED TO THE WINDS WILL BE KILLED.

AN INLAND HURRICANE WIND WARNING IS ISSUED WHEN SUSTAINED WINDS NEAR
HURRICANE FORCE...OR FREQUENT GUSTS AT OR ABOVE HURRICANE FORCE...ARE
CERTAIN WITHIN THE NEXT 12 TO 24 HOURS.

ONCE TROPICAL STORM AND HURRICANE FORCE WINDS ONSET...DO NOT VENTURE
OUTSIDE!

This advisory was given around about the time one or two authorities in
Louisiana declared an emergency. There seems to be a dispute over who
said what where and when.

This advisory was given around about the time one or two authorities in
Louisiana declared an emergency. There seems to be a dispute over who
said what where and when.

Bull****. That was a total fabrication.

David O'Grady wrote:

This advisory was given around about the time one or two authorities in
Louisiana declared an emergency. There seems to be a dispute over who
said what where and when.

Bull****. That was a total fabrication.




I saw that advisory posted before the hurricane struck.

..

cloud dreamer wrote:

David O'Grady wrote:

This advisory was given around about the time one or two authorities in
Louisiana declared an emergency. There seems to be a dispute over who
said what where and when.

Bull****. That was a total fabrication.

I saw that advisory posted before the hurricane struck.

There seems to be a dispute over the dispute over who said what, where
and when.

My money is not on the Repubicans.

("Monkey wanna pee pee?"

"No! Naughty monkey wants to play with banana!")