Air Masses
The maritime tropical air mass affects Honolulu all year round because Honolulu is surrounded by the Pacific Ocean and is in the tropics. In addition to the maritime tropical air mass, the Hawaiian High is also around all the Hawaiian Islands. Therefore, these conditions are associated with tropical weather consisting of warm and moist temperatures. This explains why Honolulu experiences tropical weather all year round.
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| These are the air masses around the world and it shows how the mT air mass surrounds Hawaii. Source: http://www.bahrainweather.gov.bh/education_air-mass |
Are there Influences of the Mid-latitude Cyclones or the Intertropical Convergence Zone?
Honolulu doesn't experience a mid-latitude cyclone because the Hawaiian High usually deflects it. However, if the Hawaiian High weakens or moves then the cold front of a mid-latitude cyclone can approach the islands5. The cold front would cause the temperature to decrease and cause heavy precipitation5.Generally, the cold front passes the islands during October through April, which would explain why Honolulu receives precipitation during in the winter. In the case of the ITCZ, it moves further north over land than it does over oceans8. For that reason, the ITCZ doesn’t reach Honolulu because it's surrounded by the Pacific Ocean and is further north in the tropic zone.
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| Here you can see the cold front or tail of the mid-latitude cyclone sweeping the islands. Source: https://laulima.hawaii.edu |
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| This shows the ITCZ movement patterns in January and July. In the image, you can see that the ITCZ doesn't move up north enough to pass through the Hawaiian Islands. Source: http://www.bbc.co.uk/education/guides/z9yssbk/revision/2 |
Hurricanes
Although Honolulu doesn’t experience mid-latitude cyclones or the passage of the ITCZ, it does experience hurricanes. The hurricane season in Honolulu is from June to November1. However, hurricanes rarely occur in Hawaii and are generally weakened when they approach the islands1. Hurricanes rarely occur in Hawaii because the ridge from the Hawaiian High protects the islands and deflects the storms7. In the past 50 years, there were five notable hurricanes that damaged the islands. These hurricanes were Hurricane Hiki (1950), Hurricane Nina (1957), Hurricane Dot (1959), Hurricane Iwa (1982), and Hurricane Iniki (1992)3. Hurricane Hiki was the first official hurricane recorded in the islands and was a category 1 hurricane 3, 4. As for the other hurricanes, Hurricane Nina was a category one, Hurricane Dot was a category 4, Hurricane Iwa was a category one, and Hurricane Iniki was a category four 4. Hence, Hurricane Dot and Hurricane Iniki were the most devastating hurricanes. All of these hurricanes caused severe weather conditions, such as storm surges, heavy precipitation, and high-speed gusts of winds. The hurricanes also caused several damages such as destroying homes, toppling trees, and physical injuries.
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| Damages inflicted to houses after a hurricane. Source: http://www.soest.hawaii.edu/met/Faculty/businger/poster/hurricane/ |
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| The damages inflicted by the strong gusts of the wind from the hurricane. Source: http://www.soest.hawaii.edu/met/Faculty/businger/poster/hurricane/ |
Topological Influences
The weather in Honolulu is influenced by orographic lifting because it’s located on the leeward side of the Ko’olau Mountain. As the NE trade winds are forced over the windward side it cools and condenses. Then as the air mass descends on the leeward side, it dries and warms adiabatically. This causes the leeward side to be dry and have less green areas. Even though the air mass is relatively dry on the leeward side, it can still produce a small amount of precipitation. This explains why Honolulu receives small amounts of precipitation and is relatively dry throughout the year. Though, there are times when Honolulu can receive a large amount of precipitation due to the Kona winds. These are “rain-bearing winds that blow over the islands from the SE or SSW in the opposite direction of trade winds” 9. Therefore the dominant wind pattern is reversed and the leeward sides become windward. However, the Kona winds don’t last more than a day or so 9. |
| This is a diagram of Orographic lifting Source: https://laulima.hawaii.edu |
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| This image shows how Honolulu does not have many green areas compared to the windward side of the Koolau Mountain. Source:https://www.google.com/maps/place/Island+of+Hawai'i/ |
Sources
- Climatestoravel.com, (n.d.) Climate-Hawaii. Retrieved from http://www.climatestotravel.com/climate/hawaii
- Furman, T. & Guertin, L. (n.d.). Precipitation and the Inter-Tropical Convergence Zone (ITCZ). Retrieved from https://courseware.e-education.psu.edu/courses/earth105new/content/lesson07/03.html
- Hawaii News Now. (n.d.a). HNN Hurricane Center. Retrieved from http://www.hawaiinewsnow.com/category/190631/hawaii-news-now-hurricane-center
- Hawaii News Now. (n.d.b). Hawaii's Hurricane History. Retrieved from http://www.hawaiinewsnow.com/story/6921152/hawaiis-hurricane-history
- Nullet, D. (n.d.a). Weather Patterns from Migratory Lows. Retrieved from https://laulima.hawaii.edu/access/content/group/2c084cc1-8f08-442b-80e8-ed89faa22c33/book/chapter_6/weather_obs/hawweather_front.htm
- Nullet, D. (n.d.b). Fronts & Midlatitude Cyclones. Retrieved from https://laulima.hawaii.edu/access/content/group/2c084cc1-8f08-442b-80e8-ed89faa22c33/book/chapter_6/fronts.htm
- Thompson, A. (2014). Why Hurricanes Are So Rare in Hawaii. Retrieved from http://www.climatecentral.org/news/why-hurricanes-are-so-rare-in-hawaii-1787
- ThoughtCo. (n.d.). ITCZ: The Intertropical Convergence Zone or ITCZ Brings Convectional Precipitation. Retrieved from https://www.thoughtco.com/itcz-143443
- Tom Barefoot. (2017). What are the Trade Winds in Hawaii?. Retrieved from https://www.tombarefoot.com/hawaii-information/what-are-the-trade-winds-in-hawaii/5324
