Here are two good articles on why we rarely get hurricanes. We are protected by the TUTT -- Tropical Upper Tropospheric Trough
The two articles have a slightly different take on the water temperature aspect, but both agree that the upper atmosphere flow is key to stopping hurricanes, and that when we do get hurricanes it is because the TUTT is out of position or some other circumstances combine to survive in spite of it.
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www.weather.com/blog/weather/8_13056.html
"Why is Hawaii so rarely hit by a hurricane?
The answer is actually very simple and unrelated to sea water temperatures around the islands. Those water temperatures are warm enough to maintain at least a category 4 hurricane. It turns out that average upper level winds across Hawaii in summer are from the southwest at 40-60 mph!
The reason is the Tropical Upper Tropospheric Trough (called TUTT for short) rules the high levels of our weather atmosphere there and creates winds typically too fast for development of a hurricane and too fast for an approaching hurricane from the east to remain a hurricane. That is why quite a few remnant tropical circulations go by south, north, or occasionally through the islands, but rarely does a tropical storm or hurricane reaches them.
But paradise is not always paradise. Hawaii is vulnerable when a strong hurricane develops to the southwest, then moves north when the TUTT is displaced slightly north of its normal location. This is by far most common in El Nino years. The last time this happened was in 1992 when CAT 4 Hurricane Iniki struck Kauai, in 1982 when Hurricane Iwa nearly hit Kauai, and back in 1957 when Hurricane Nina came close to Kauai. All of these were El Nino years.
Interestingly there are very rare occasions when Hawaii can be struck by a hurricane coming from the east or southeast. The most common scenario for this to happen is from a hurricane at very low latitudes that suddenly takes a northwest or north-northwest track toward the islands. This track gives the shortest duration encounter with the TUTT before reaching Hawaii, and hence the least amount of time to weaken beneath high wind shear. The last time this happened was the year of Hawaii's statehood, 1959, when CAT 1 hurricane Dot struck Kauai, coming out of the south-southeast after having a track from east to west.
So remember in Hawaii "king TUTT" rules the skies and keeps Hawaii a paradise, at least most of the time.
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Why does Hawaii get so few hurricanes? Hans Rosendal, retired meteorologist, provides the answer:
The reasons for the lack of hurricanes in Hawaii are several. We usually don't quite have sea surface temperatures warm enough (about 82 degrees) and deep enough warm surface waters to sustain the development of hurricanes. If we get up to 80 degrees now and then in August and September, that is about max. We therefore have to import the few hurricanes that we do get.
Secondly, the upper wind flow over our region usually features westerlies which is very detrimental to keeping a hurricane approaching from the east from being sheared off. In countless cases we have been 'saved' by this upper flow pattern as storms move into our region and fall apart due to it being sheared. What is needed is easterlies at both the surface and aloft so the entire column of air can move along without ventilating out the latent heat derived from the convection which in turn cause the pressure drops and wind increases.
In the case of Iniki in 1992 (an El Nino year), we had an unusual flow pattern with less vertical wind shear and other things working to sustain the health of the storm. Just like living beings, a hurricane goes through a life cycle. Since Iniki formed on this side of 140W longitude about two or three days prior to it hitting Kauai on 9-11, it was a healthy and growing youngster by the time it moved into our area. The health of storms also depend on what is going on, often far away from the storm.
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The track of Iniki northward after passing south of the Big Island was forecast quite well and the hurricane watch was issued the afternoon before on 9/10 as we realized that the storm would not pass as far west of Kauai as earlier thought. We did not get the full 36 hour lead time, we strive for. I worked on the initial issuance of the watch, so I remember it well.
http://www.petergelsey.com/hurricanes.doc
, which in turn originates from Greek tuph#333;n (#932;#965;#966;#974;#957