By Jim Gallagher
mostly sunny today with high temperatures in the low to mid 80's
passing showers in the Windward and Mauka areas and gusty trades from 15 to 25
" Does that brief announcement sound familiar? If not , it's the normal 10
seconds or less of the Maui Weather forecast that you hear on Radio and Television. With
the assistance given us by the Superintendent of the U.S. National Weather Service here on
Maui, this article will try to explain WHY it's almost always that way.
The Northeast Tradewinds here in the Northern Hemisphere (S.E. in So. Hemisphere) get
much of the credit for our good weather. They prevail almost 100% of the time between May
and November and over 60% of the time the rest of the year. The name
"Tradewinds", comes from our early history wherein the exchange of goods and
services between islands and countries was done with sailing ships whose operators, the
"Traders" were very much aware of these winds and used them for the movement of
their goods across the seas. The "Trader's Winds" then became known simply as
Because of a semi-permanent High Pressure area which lies North of the Hawaiian
Islands, these winds are held in a Northeasterly direction bringing great masses of stable
air across the island most of the year. If and when this High Pressure Area moves or
weakens, we are more likely to get the so-called "Kona Winds". The Hawaiian
word, "Kona:, means the leeward side of the Island(s) which is the south or southwest
(sheltered) side and indicates a wind from either of those directions; Kona winds are most
prevalent between November and April. Whereas the Tradewinds bring stable air, the Kona
Winds are more apt to bring unstable, warm, moist, and turbulent air often referred to as
a "Kona Storm".
The "Windward" (un-protected north/northeast ) Side of the Island has direct
exposure to the Tradewinds and thus experiences not only higher winds but more rain and
cooler temperatures which the winds bring with them. Hana, for instance, has an average
annual rainfall of over 75 inches which is, excluding the higher elevations, the wettest
place on Maui. On the other hand the leeward Side of the Island, being protected from
these winds and moisture by the Mountains, receives considerably less rain and higher
temperatures. The highest mountain, Haleakala, gives so much protection to the Kihei -
Wailea - Makena areas that they are semi DESERT regions of the Island. The smaller West
Maui Mountains, give proportionately less protection which results in somewhat higher
rainfall and slightly cooler temperatures in the Lahaina - Kaanapali - Kapalua regions.
The strong Tradewinds which blow through the Valleys and around the ends of the
Mountains produce what Weathermen call the "Eddy Effect" (see map) in Kihei and
other areas. This effect many times will generate an apparent SOUTH wind to the residents
there when, in fact, the Weather Service will confirm that the winds that day are N.E.
Tradewinds! Similar confusion can result in other areas saying they are experiencing
"offshore breezes", when the Tradewinds are actually the prevailing wind.
Since rainfall is our only source of fresh water, these beautiful Hawaiian Islands
would be barren and un-inhabitable without it. The "Wet Season" on Maui is from
November to April, but the Visitor to Maui is usually amazed at the wide variation in
rainfall within only a few miles and the fact that the majority of rain is received in the
late and very early hours of the day - mostly the dark hours, in fact. These phenomena are
a result of both the Wind and the Mountains acting together.
The Tradewinds carry the moisture laden air in the form of Clouds up against the
Mountains which hold them there with the help of the war air raising up from the lower
elevations. Most of the Clouds are too heavy for the Wind to carry them over the Mountains
and so they "sit" on the top until the Sun goes down and allows the air
temperatures to cool. When the air temperature cools sufficiently and no longer raises to
help hold the Clouds on the top of the mountain (the late and early dark hours), the
Clouds "fall" to lower elevations and produce the rain.
At certain points in the Mountains, we have "openings" in the form of
valleys, canyons, etc. and at other points we have lower Mountain elevations than others.
From time to time, these areas allow the wind to carry some rain and cooler temperatures
through or over the Mountains even during the warm, daylight hours of the day. The West
Maui Mountains gets lower as they go north and have some of these openings, allowing more
or less wind and rain to flow through. Thus, we have the explanation of how it can be
raining in Honokowai while dry and sunny in Kaanapali - only 2 miles away. And why the
average annual rainfall in Lahaina is only 14 inches and almost 48 inches just 5 miles
north of there! (Mahinahina)
What about the scarcity of Thunderstorms here in Maui as well as the other Islands? And
why do we only have an average of about 10 thunderstorms a year whereas some areas on the
Mainland have that many within a month or two? The answer is relatively simple.
Thunderstorms are mostly the result of mixing COLD air with warmer air, squall lines,
etc., and we simply don't have that air condition here on Maui. The air temperature
variations are just not enough to produce these storms, except on rare occasions.
Even though Maui and the other Hawaiian Islands are spared most violent weather, we are
none the less susceptible to major earth movements, earthquakes (Lahaina was leveled by
one in 1871),
and the Tsunami effect of same. The Japanese word, "Tsunami"
(soo-nah-me) translates into English as "Long Harbor Wave". The long refers to
both the physical length and the time duration (15-30 minutes) of the wave and the harbor
is used because it is there that the wave is amplified by being confined to a relatively
small area. The Japanese, whose islands have felt this effect for generations, give us
this internationally used name. A Tsunami is often incorrectly referred to as a tidal wave
and as such is a misnomer since it has nothing whatsoever to do with the tides. It is also
completely independent from Hurricanes.
A Tsunami then, is, " a series (up to 5 or more) of high speed traveling ocean waves generated by disturbances associated with earthquakes occurring below or near the ocean floor". In deep water (25,000' to 30,000') they can reach forward speeds of over 600 MPH and in the shoaling water of coastlines, can crest to heights of more than 100 feet! The last major tsunami to hit Maui was March 27, 1964 in the Spreckelsville area with wave heights of 12 feet. There has been five others recorded since 1946 in the Hawaiian Islands. The tsunami of April 1, 1946, which originated in the Aleutian Islands, was the worst natural disaster in Hawaiian history. It took place in Hilo, located on the Big Island, cost 159 lives and did some $25 million in property damage. It was the first tsunami to do any major damage in the state since 1877.
The Tsunami Warning System (Seismic Sea Wave Warning System) has been in operation
since 1948 and the Hawaii Regional Warning System since 1975 are designed to provide
adequate advance warning so as to prevent any recurrence of such a disaster. They advise
however, that there is no warning possible for a tsunami caused by a coastal or
"off-shore" earthquake - and that whenever someone is on the beach or at a
coastline and feels an earth tremor great enough to cause a loss of balance should
immediately head for higher elevations of at least 100 feet + above sea level.
Hurricanes, which are called typhoons east of the International Dateline, are also
known to Hawaii although their incidence is not high and their severity is usually
moderate, except for Hurricane Iniki which devastated the island of Kauai in 1992. A
hurricane is a tropical cyclone with winds over 73 MPH and usually under 150 MPH. Most
hurricanes move from east to west and dissipate long before they ever reach the islands,
but there have been approximately 14 hurricanes recorded within 1500 mile radius of Hawaii
since 1957. None have hit Maui directly. Kauai has sustained the brunt of two direct hits
from hurricanes in 1982 and 1992.
Water Spouts, which occasionally are seen over the waters off Maui, are simply funnel clouds (tornadoes) over water. They are infrequent and usually only minor disturbances since they occur out in the sea or in the channels between the islands.
Because of Maui's location approximately 1,400 miles north of the equator at latitude 25 degrees north and longitude 155 degrees west and "all of the above", we enjoy some of the finest year round weather in the ENTIRE WORLD. Our unique position on the globe gives us natural protection from most inclement, much less violent weather plentiful rainfall and sunlight and cool breezes all year, every year. Is it any wonder we have been called the "Paradise of the Pacific" and that our motto is "Maui No Ka Oi" (Maui is number 1).
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