Hawaiian Islands weather details & Aloha paragraphs / December 17-18, 2010

December 17-18, 2010

Air Temperatures – The following maximum temperatures were recorded across the state of Hawaii Friday afternoon:

Lihue airport, Kauai –       84
Honolulu airport, Oahu –   79
Kaneohe, Oahu –             79
Molokai airport –              83
Kahului airport, Maui –     84
Kona airport –                  81
Hilo airport, Hawaii –        81

Air Temperatures ranged between these warmest and coolest spots near sea level – and on the highest mountain tops…as of 5pm Friday evening:

Kahului, Maui – 80F
Hilo, Hawaii – 75

Haleakala Crater –    50 (near 10,000 feet on Maui)
Mauna Kea summit – 34 (near 14,000 feet on the Big Island)

Precipitation Totals – The following numbers represent the largest precipitation totals (inches) during the last 24 hours on each of the major islands, as of Friday afternoon:

0.02 Omao, Kauai  
0.24 Waianae boat harbor, Oahu
0.00 Molokai 
0.00 Lanai
0.00 Kahoolawe
0.07 Oheo Gulch, Maui
0.01 Honaunau, Big Island

Marine Winds – Here’s the latest (automatically updated) weather map showing weak 1018 millibar high pressure system located just to the east of the state. Our winds will be light from the southeast to southwest Saturday and Sunday.

Satellite and Radar Images: To view the cloud conditions we have here in Hawaii, please use the following satellite links, starting off with this Infrared Satellite Image of the islands to see all the clouds around during the day and night. This next image is one that gives close images of the islands only during the daytime hours, and is referred to as a Close-up visible image. This next image shows a larger view of the Pacific…giving perspective to the wider ranging cloud patterns in the Pacific Ocean. Finally, here's a Looping IR satellite image, making viewable the clouds around the islands 24 hours a day. To help you keep track of where any showers may be around the islands, here’s the latest animated radar image.

Hawaii’s Mountains – Here’s a link to the live web cam on the summit of near 14,000 foot Mauna Kea on the Big Island of Hawaii. The tallest peak on the island of Maui is the Haleakala Crater, which is near 10,000 feet in elevation. These two web cams are available during the daylight hours here in the islands…and when there’s a big moon rising just after sunset for an hour or two! Plus, during the nights and early mornings you will be able to see stars, and the sunrise too…depending upon weather conditions.

Tropical Cyclone activity in the eastern and central Pacific – Here’s the latest weather information coming out of the National Hurricane Center, covering the eastern north Pacific. You can find the latest tropical cyclone information for the central north Pacific (where Hawaii is located) by clicking on this link to the Central Pacific Hurricane Center. Here’s a tracking map covering both the eastern and central Pacific Ocean. A satellite image, which shows the entire ocean area between Hawaii and the Mexican coast…can be found here. Of course, as we know, our hurricane season won't end until November 31st here in the central Pacific.

 Aloha Paragraphs

Generally fine weather Saturday…high cirrus clouds

Winds will be generally light, although trending towards the southeast southwest this weekend. This weather map shows a weak 1018 millibar high pressure system located to the east of the islands Friday night. The orientation of this ridge and the resultant winds, may keep some light volcanic haze around, having come up from the vents on the Big Island. As we get into the weekend, the winds will shift to a more southerly direction. These breezes will stick around until a cold front arrives around Tuesday or so. As this front moves by, and a new high pressure system moves into place, we'll see north to northeast breezes returning, with a relatively cool and dry air mass prevailing for several days…gradually becoming trade winds.

Winds will be light from variable directions, although locally a bit stronger…the following numbers represent the strongest breezes early Friday evening:

16 mph      Port Allen, Kauai
14             Kahuku, Oahu
07             Molokai
21             Kahoolawe
17             Lipoa, Maui
00             Lanai Airport 
27               South Point, Big Island 

There will be a few showers in our area Friday and Saturday, although wetter conditions are expect to arrive Saturday night…into early next week.  This large view satellite image continues to show a large swath of moisture extending up from the deep tropics to our west. Just a bit further west, near the International Dateline, we see a counterclockwise rotating low pressure system. At the same time, glancing down to our southeast we find an area of large thunderstorms. Looking at this next satellite picture, which provides a closer look at our islands, we can see high cirrus clouds to our west through north, which will cover most of the state soon. Finally, checking out this looping radar image we see just a few showers being carried along on the current south to southeast wind flow at the time of this writing…with some moderately heavy showers remaining not far offshore from Niihau and Kauai.

The latest forecast continues to paint wetter weather starting during the second half of this weekend, with south or southwest Kona winds bringing lots of rain our way… into the first couple of days of the new week. The low pressure area to our west is expected to channel a stream of deep moisture over us with time. Meanwhile, a cold front is forecast to push down through the state at some point around Tuesday or so…keeping the showery weather over the islands. The long and short of all this is that we'll have lots of clouds, and rainfall too, arriving later this weekend, and continuing for two or three days. It hasn’t looked like a flooding situation, although more recently, there is now a chance that some flooding may occur…as the soil becomes saturated by the rains. At the same time, there’s now been indications that we could see some thunderstorms in this mix too.

I'll be heading over to Kahului now, to take in a new film, called The Tourist (2010), starring Angelina Jolie, and Johnny Depp…among others. I've been looking forward to seeing this film, as I like both of these two actors. The synopsis: two strangers find themselves unwittingly thrust into a deadly game of cat and mouse. The critics are being tough on this film, giving it only a C- grade. The viewers are being a bit more generous, giving a B grade. Here's a trailer, just in case you want to give a peek. I'll let you know what I thought when I get back online Saturday morning.

Here in Kihei, Maui at around 540pm, skies are clear, although there is some high cirrus clouds around too.  As noted above we'll got the first half of the weekend to remain dry. This will change to wetter conditions by Sunday, starting first on the Kauai end of the island chain. This rainfall will however work its way down through the rest of the islands Sunday, making for wet conditions, and more challenging driving conditions. I'll have much more to let you know about as we go through the next couple of days, so please stay tuned. I hope you have a great Friday! Aloha for now…Glenn.

Interesting: For a few hours on the night of Dec. 20 to Dec. 21, the attention of tens of millions of people will be drawn skyward, where the mottled, coppery globe of our moon will hang completely immersed in the long, tapering cone of shadow cast out into space by our Earth. If the weather is clear, favorably placed sky watchers will have a view of one of nature's most beautiful spectacles: a total eclipse of the moon.

Unlike a total eclipse of the sun, which is only visible to those in the path of totality, eclipses of the moon can usually be observed from one's own backyard. The passage of the moon through the Earth's shadow is equally visible from all places within the hemisphere where the moon is above the horizon.

The total phase of the upcoming event will be visible across all of North and South America, as well as the northern and western part of Europe, and a small part of northeast Asia, including Korea and much of Japan.

Totality will also be visible in its entirety from the North Island of New Zealand and Hawaii — a potential viewing audience of about 1.5 billion people. This will be the first opportunity from any place on earth to see the moon undergo a total eclipse in 34 months.

This star chart shows where in the sky the upcoming lunar eclipse will appear. And check this NASA lunar eclipse chart to see how visible the eclipse will be from different regions around the world.

Stages of the eclipse

There is nothing complicated about viewing this celestial spectacle.  Unlike an eclipse of the sun, which necessitates special viewing precautions in order to avoid eye damage, an eclipse of the moon is perfectly safe to watch. All you'll need to watch are your eyes, but binoculars or a telescope will give a much nicer view.

The eclipse will actually begin when the moon enters the faint outer portion, or penumbra, of the Earth's shadow a little over an hour before it begins moving into the umbra. The penumbra, however, is all but invisible to the eye until the moon becomes deeply immersed in it.

Sharp-eyed viewers may get their first glimpse of the penumbra as a faint smudge on the left part of the moon's disk at or around 6:15 UT (on Dec. 21) which corresponds to 1:15 a.m. Eastern Time or 10:15 p.m. Pacific Time (on Dec. 20).

The most noticeable part of this eclipse will come when the moon begins to enter the Earth's dark inner shadow (called the umbra). A small scallop of darkness will begin to appear on the moon's left edge at 6:33 UT (on Dec. 21) corresponding to 1:33 a.m. EST or 10:33 p.m. PST (on Dec. 20).

The moon is expected to take 3 hours and 28 minutes to pass completely through the umbra. The total phase of the eclipse will last 72 minutes beginning at 7:41 UT (on Dec. 21), corresponding to 2:41 a.m. EST or 11:41 p.m. PST (on Dec. 20).  

At the moment of mid-totality (8:17 UT/3:17 a.m. EST/12:17 a.m. PST), the moon will stand directly overhead from a point in the North Pacific Ocean about 800 miles west of La Paz, Mexico.

The moon will pass entirely out of the Earth's umbra at 10:01 UT/5:01 a.m. EST/2:01 a.m. PST and the last evidence of the penumbra should vanish about 15 or 20 minutes later.

Color and brightness in question

During totality, although the moon will be entirely immersed in the Earth's shadow, it likely will not disappear from sight. Rather, it should appear to turn a coppery red color, a change caused by the Earth's atmosphere bending or refracting sunlight into the shadow.

Since the Earth's shadow is cone-shaped and extends out into space for about 844,000 miles, sunlight will be strained through a sort of "double sunset," all around the rim of the Earth, into its shadow and then onto the moon.

However, because of the recent eruptions of the Eyjafjallajökull volcano last spring and the Merapi volcano in Indonesia in October, one and possibly even two clouds of ash and dust might be floating high above the Earth.

As a result, the moon may appear darker than usual during this eclipse; during totality, parts of the moon might even become black and invisible.

A careful description of the colors seen on the totally eclipsed moon and their changes is valuable.  The hues depend on the optical equipment used, usually appearing more vivid with the naked eye than in telescopes. The French astronomer Andre-Louis Danjon introduced the following five-point scale of lunar luminosity ("L") to classify eclipses:

L = 0:  Very dark eclipse, moon almost invisible, especially in mid-totality.
L = 1:  Dark eclipse, gray or brownish coloration, details distinguishable only with difficulty.
L = 2:   Deep red or rust-colored eclipse, with a very dark central part in the shadow, and outer edge of the umbra relatively bright.
L = 3:   Brick red eclipse, usually with a bright or yellow rim to the shadow.
L = 4: Very bright copper-red or orange eclipse, with a bluish very bright shadow rim.

Examine the moon at mid-totality and also near the beginning and end of totality to get an impression of both the inner and outer umbra.  In noting an L observation, state the time and optical means (naked eye, binoculars or telescope) that is used.

At mid-totality, from rural locations far from city lights, the darkness of the sky is impressive.  Faint stars and the Milky Way will appear, and the surrounding landscape will take on a somber hue.  As totality ends, the eastern edge of the moon begins to emerge from the umbra, and the sequence of events repeats in reverse order until the spectacle is over.

Fringe effects

Interestingly, from most of New Zealand, a slice of northeast Australia, Papua, New Guinea, southwest Japan and Korea, the moon will rise during totality on the evening of Dec. 21. Because of low altitude and bright evening twilight, observers in these locations may not see much of the moon at all until it begins to emerge from out of the Earth's shadow.

Conversely, much of the United Kingdom and parts of western and northern Europe will see the moon set during totality on the morning of Dec. 21. Because of low altitude and bright morning twilight, observers in these locations may not see much of the moon at all after it slips completely into the Earth's shadow.

Past and future

The last total lunar eclipse occurred on Feb. 20 to Feb. 21, 2008 and was visible from most of the Americas, as well as Europe, much of Africa and western Asia. In 2011, there will be two total lunar eclipses.  The first, on June 15, will be visible primarily from the Eastern Hemisphere and will have an unusually long duration of totality lasting one hour and 40 minutes.

Another total lunar eclipse will occur on Dec. 10 and will be visible over the western half of North America before moonset.  For the next total lunar eclipse that will be visible across all of North America, we must wait until April 14 to April 15, 2014.