WHERE DOES WIND COME FROM?

“Understanding the winds on Maui will give you the knowledge necessary to select your ride site, and anticipate the changing winds. Here in the Maui Wind Report I have given you some of the basics and general concepts of wind and some specifics you will find on Maui” Ride Safe and have fun”. Aloha, David Dorn.

Maui Factor: Maui is not like other places. Maui is perhaps more extreme than most people are expecting. Always treat Nature and the elements here with respect. Be humble and do not underestimate the weather here. Mother Nature is the boss, so do not push your luck no matter how long you have waited to sail or surf here. There are going to be days when you should NOT go out. There will always be conditions too tough even for the biggest expert, never forget that. Maui factor usually also means that you will not be as good as you think you are, the first time you ride here. So start out conservatively and take the time to learn about local conditions. Pay your dues, be respectful, and be prepared to be humbled. With the right attitude and approach, you will better appreciate and ultimately enjoy the uniqueness that Maui has to offer. **Read More Local Information Below at the Bottom of this Page.

Windward / Leeward Diagram. Image courtesy Kitesafe.comWindward and Leeward: Maui is an island and there are two main areas for wind, windward side gets the onshore wind, and the leeward gets the offshore wind. Of course there are more subtle variations, but knowing this fundamental fact can save your life. Offshore winds can be very dangerous in a kayak, SUP or any small boats including windsurfers and kiters. Even surfers and people floating on air mattresses are at risk. Also experienced sailors and outrigger canoe paddlers can get into trouble in offshore winds. There are hundreds of rescues and interventions each year for watercraft blown away from shore. Windward areas are no picnic either, strong winds intersect the shoreline, and the wind can blow unwary sailors onto land. The wind also interacts with the landforms on shore and create eddies and severe gustiness, so take care.

Maui Wind Combinations: Maui winds are a combination of prevailing trade winds (aka “trades”),  combined with local wind effects caused by Maui’s geography, and thermal Seabreezes etc. Less often we have winds that are generated by low pressure systems (storm activity) examples: Kona winds and tropical storms. The wind on Maui will be very specific to each different area. The wind on one side of the island can be blowing in the opposite direction from the wind on the other side. Depending on the activity you have planned, you may be seeking out the windiest spot, or trying to shelter from the wind for a surf session or picnic.

Check out this page link for all the Current Wind Forecast for North Shore Maui.

Weather Maps: Here is the weather map. Global weather patterns affect our local weather. Distant storms produce surf, and massive pressure systems create our winds. We can see these features on the Weather Map and make predictions about the wind and weather.  These predictions are for the generalized (Tradewind) airflow across the larger area for example: the state, and local wind effects (rain/venturi/clouds/etc.) need to be considered. For More info about Weather Maps..

For safety reasons you should always be aware of: extreme weather, severe weather, and any marine warnings. Check the weather reports before going to the beach, so you will have a good idea what to expect when you get there.  On this page, we have brought together most of the information that is useful to check the weather every day. Click here for a general description of the monthly averages that will give you an overview of seasonal variations. On this Maui Wind page, we have wind information, wind patterns, Local Wind effects. Links to: moon phase, tide times, the current Weather map for the Northern pacific, and some global weather data. We also have some descriptions of local weather patterns. See our Surf Report page for more info on Surf Forecasts, Wave heights, swell maps, tidal info and much more. Once you get up the accurate wind picture, you will have a better understanding, and and expectation of the conditions you will encounter at the beach. May your ocean experience be a safe and enjoyable one.

What creates wind Convection Wind What are Tradewinds What are Kona Winds What are wind effects
Sea Breeze Surface Pressure Global Winds Valley Venturi Tropical Storms
Hurricane Season Winter Winds Spring Winds Summer Winds Fall Winds
What is a convection Wind? A convection wind is caused by uneven heating of the earth’s surface. A “seabreeze” is an example of a convection wind effect, when the land heats faster than the ocean, and the air above the land is heated and subsequently rises and creates a low pressure over the land, Then the cooler air over the water descends and flows toward the land. Seabreeze causes the wind to blow toward the land.

Sea Breeze: The sea breeze is a local wind where the land heats faster than the ocean, creating a temperature differential. The uneven heating of the surface in turn affects the temperature and dynamics of the air. The sea-breeze effect is strongest in the middle of the day, and lessens at dusk and dawn. The sea-breeze effect can reverse at night to become a night breeze or land breeze.

Sea Breeze, www.actionsportsmaui.com

What creates wind ? A convection wind is caused by uneven heating of the earth’s surface. The Air above the surface is heated and begins to rise. Air over colder areas becomes denser and falls.
Surface Pressure: The rising air causes a low pressure area at the surface. The cooler air descending causes a high pressure to form. At the surface the air moves from a high towards a low. This creates the horizontal air flow, which is wind.

Surface Pressure,  www.actionsportsmaui.com

What are the cause of Global Winds?

Maui Wind Report, image copyright www.actionsportsmaui.com

Because the earth is a sphere, Incoming Sunlight hits the surface at the equatorial regions more directly, and the polar regions at a low indirect angle. This causes the equator to heat more than the poles.

Maui Wind Report, image copyright www.actionsportsmaui.com

The hotter surface at the equator heats the air above it. The Hot air rises and moves outward towards the poles. The cooler polar air descends and moves towards the equator along the surface. This creates surface winds. This atmospheric circulation is called the convection cycle.

Maui Wind Report, image copyright www.actionsportsmaui.com

The Rising and falling air form a series of smaller cells that create wind bands. The areas where the air is rising or falling have less wind. The area between the rising or falling air will have more horizontal air flow (wind).

Maui Wind Report, image copyright www.actionsportsmaui.com

The surface winds in the northern hemisphere are deflected to the right by the Coriolis force as they move across the surface. The Coriolis force is a result of the earth’s rotation.

 

Maui Wind Report, image copyright www.actionsportsmaui.com

The Equatorial Low at the Equator has almost no wind, this area is also known as the Doldrums or the ITCZ (Inter-Tropical Convergence Zone). The areas north and south of the equatorial Low are the trade-wind zones with the Tropical Easterlies. Trade-winds in the northern hemisphere blow from the North-East, Trade-winds in the southern hemisphere blow from the South-East.

Maui Wind Report, image copyright www.actionsportsmaui.com

Maui Hawaii at 20.8 degrees north, is located in the trade-wind zone in the northern hemisphere. So winds are generally from the Northeast. The bands of wind shift slightly north in the summer and south in the winter. In the summer the trade winds are situated better relative to the Hawaiian islands for wind sports.

 

What are Trade winds? In summer the trade wind weather predominates. Trades blow from the NE to ENE direction and provide the comfortable climate and wind powered activities that we enjoy here in the islands. In summer 9 out of 10 days have trade winds. Trades usually bring fair weather to the central valley and south side of the island. But trades do bring regular showers to the windward sides of all the islands and on Maui especially toward Hana, Haiku and upcountry. We do have the rain-forests and waterfalls to prove it. Showers are especially frequent in overnight and in the mornings. There may be spells of lighter winds but Hawaii has a high number of windy days.
What are Kona Winds? Kona winds are often accompanied by rain and thunderstorms. Hawaii experiences about three Kona storms per year. It is possible to windsurf and kite in these southerly Kona wind conditions but it is definitely not recommended during the intense parts of any storms. Kona storms can produce heavy rains, flooding, waves and storm surge. Localized flooding can cause flash floods, which are extremely dangerous to people and vehicles.
Surfing in Kona Winds: In Kona winds huge plumes of spray to peel of the crest of waves. Some expert windsurfers may venture out at Ho’okipa an Lanes, but there is a real possibility of getting blow out to sea. The strength of the Kona offshore winds may be masked close to shore because of wind shadow of the land and trees at the shoreline. So you should never attempt to surf the north shore during a strong Kona.
Wind Effects: What are wind effects? Wind effects are the interaction of the wind and the surfaces that it passes over. Mountains will block or bend the wind, bays will spread the wind and valleys can squeeze the wind. Wind is forced to go up over and around. The wind is altered by these interactions, whether temporarily or permanently. Understanding the wind effects will give you a better understanding of the actual wind in a specific area.

Wind Shadows: Wind shadows occur on the downwind side of any object. The wind is blocked by the object and creates an area of little or no wind on the downwind side. Examples: The mountains on Maui create huge shadows that protect the leeward sides from the trade-winds. Headlands and trees also create wind shadows on their downwind sides. The wind in the “shadow zone” can also be turbulent or even the reverse direction from the prevailing wind.

 

Venturi Effect: A “Venturi” is an area where the wind is squeezed into a narrow place. The wind speed will increase in the narrow area. Examples: This can be caused by mountains forcing wind through a narrow valley, or by the wind squeezing between two buildings,  or wind blowing past a point of land. The Venturi effect on Maui is noticeable on the north shore, especially at Kanaha Beach Park,

Maui Wind Report, image copyright www.actionsportsmaui.comValley Island Venturi: Maui is called the valley island, because its twin volcanoes have created a valley that runs NE to SW. This large valley acts as a funnel to concentrate the trade winds making them stronger. Maui’s valley is a natural wind tunnel that makes it the windiest Hawaiian island. There are also Venturi effects between the islands where the wind is forced to squeeze into a narrow channel. The Maalaea Bay on the south shore experiences the Bay effect.

Bay Effect: is where the wind spreads out and reduces its speed and diverges outward in its direction. During the trade winds, the Ma’alaea Bay experiences a Bay Effect, and during a Kona wind the Kahului Bay experiences the same effect.

Wind Shadows: On Maui there are two large areas on Maui that experience significant wind shadows. The Lahaina area, and the westside are usually protected from the trade winds by the West Maui Mountains (at 5,500 feet high), and the Wailea – Makena area on the south side (protected by 10,000 foot high Mt. Haleakala).

Tropical Storms: Depending on its location and strength, a tropical cyclone is referred to by many other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge as well as spawning tornadoes. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding.
Hurricane Season: Hurricanes are rare but the hurricane season is from June to November. The last major hurricane to hit Hawaii was Iniki, which severely damaged Kauai in September 1992.

Quotes from our WeatherBlog

The Wind Prediction: We predict the wind based on our own interpretation of the forecast wind tables, and other factors, like the “Kanaha Observed Deviation” or Forecast factor (see below). This gives us an adjusted expectation of the expected wind which is what we do daily (sometimes hourly).

Forecast Factor: There is a consistent difference (deviation) between the forecast wind at Kanaha and the actual “observed” wind. This can be up to 30-50 percent differential. The observed wind is generally 30-50 more than the forecast wind. Example; yesterday was calling for 8-9 and ended up being 15-19mph.

 

 For more information on Maui’s Current Wind Graphs click here.