Hawaiian Islands weather details & Aloha paragraphs / July 13-14, 2010

July 13-14, 2010

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

Lihue, Kauai –  84
Honolulu, Oahu –  82
Kaneohe, Oahu –  83
Kaunakakai, Molokai – 82
Kahului, Maui – 86
Hilo, Hawaii –   84
Kailua-kona –   82

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

Kapalua, Maui – 82
Lihue, Kauai – 79

Haleakala Crater –    61 (near 10,000 feet on Maui)
Mauna Kea summit – 52 (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 Tuesday afternoon: 

0.21 Kilohana, Kauai  
0.49 aunawili, Oahu
0.07 Molokai 
0.00 Lanai
0.06 Kahoolawe
0.03 Kaupo Gap, Maui
0.32 Kealakekua, Big Island

Marine Winds – Here’s the latest (automatically updated) weather map showing a 1035 millibar high pressure cell far to the northeast, which will keep the trade winds blowing…although lightly into Thursday.

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 webcam 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 webcams 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 begin again until June 1st here in the central Pacific.

 Aloha Paragraphs

 
       The big city of Honolulu…lit up at night
Imageshack 

The trade winds have diminished as expected, with the strongest breezes down near the Big Island Tuesday evening. The trade winds typically blow in the moderately strong category during the summer month of July, although are generally lighter than that now. The winds are weaker now due to several factors, including an out of season retired cold front just to the east-northeast of the Big Island, and an upper level low pressure system near the state. These influences are working together to soften our winds, which will remain lighter than normal through the next couple of days. As this weather map shows, the high is far away, and weighing-in at 1035 millibars. We can also see the curved dashed line to our east-northeast, representing the old cold front, or what we could think of as a cloud band separating lighter winds ahead of it…from stronger winds behind it. Our winds will remain light until later Thursday, at which the cloud band will arrive, bringing a moderately strong surge of fresh trade winds into play then. 

The majority of rainfall that we’ve been seeing for the last couple of weeks at least, has been falling along the windward sides of the islands. None of these windward biased showers have been heavy for a while, while the leeward sides for the most part have remained almost completely dry. As the winds are down now, we’ve moved into what can be considered a modified convective weather pattern, although with still some light to almost moderate trade winds blowing in those more exposed areas. As the daytime heating prompts onshore flowing sea breezes along our sheltered leeward areas, clouds will form in the upslope areas. As the atmosphere remains rather dry and stable now however, afternoon showers will be limited. As the trade winds get stronger, in association with the arrival of the cloud band, we’ll see some increase in showers, migrating back over to the windward sides around later Thursday into Friday. As the trade winds continue to blow through the weekend into early next week…we’ll likely see a fairly normal distribution of windward biased showers continuing.

It’s Tuesday evening as I begin writing this last section of today’s narrative update.  As noted above, we’re in a field of light trade winds. This is being caused mostly by an old cold front to our east and northeast. It is helping to block the stronger trade winds from getting into our area. This will remain the case through most of Thursday, although by late in the day into Friday, our trade winds will rebound nicely. Showers will be restricted to the leeward upslope areas for the most part until then…although not many. The lower elevations of the islands will continue to feel rather muggy, until the refreshing trade winds return relatively soon. ~~~ The daytime heating of the islands caused clouds to form earlier today, than they did on Monday. This in turn held the afternoon air temperatures down some today. The highest temperature around the state today was 86F degrees at Kahului, Maui, which attained 89 degrees yesterday…when more afternoon sunshine prevailed. I would expect another cool morning on Wednesday, perhaps approaching the record for the date in Kahului again. I’m looking up at the Haleakala Crater before I leave Kihei, for the drive home. It’s majorly cloudy up that way, although as was the case yesterday, I don’t see any rain falling. I’ll catch up with you again early Wednesday morning, when I’ll be back online with your next new weather narrative. I hope you have a great Tuesday night until then! One more thing, just as its getting dark, after dinner here in Kula, I walked out on my weather deck and looked around. I found the most wonderful slim crescent moon, with one of the major planets just above it in the western horizon, in perfect alignment. It’s the perfect ending to a near perfect Tuesday! Aloha for now…Glenn.

Interesting:  A single, huge, violent storm that swept across the whole Amazon forest in 2005 killed half a billion trees, according to a new study funded by NASA and Tulane University, New Orleans. While storms have long been recognized as a cause of Amazon tree loss, this study is the first to actually quantify losses from a storm. And the losses are much greater than previously suspected, say the study’s authors, which include research scientist Sassan Saatchi of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The work suggests that storms may play a larger role in the dynamics of Amazon forests than previously recognized, they add.

Previous research had attributed a peak in tree mortality in 2005 solely to a severe drought that affected parts of the forest. The new study says that a single squall line (a long line of severe thunderstorms, the kind associated with lightning and heavy rainfall) had an important role in the tree demise. Research suggests this type of storm might become more frequent in the future in the Amazon due to climate change, killing a higher number of trees and releasing more carbon to the atmosphere.

Tropical thunderstorms have long been suspected of wreaking havoc in the Amazon, but this is the first time researchers have calculated how many trees a single thunderstorm can kill, says Jeffrey Chambers, a forest ecologist at Tulane University and one of the authors of the paper. The paper has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

Previous studies by a coauthor of this new paper, Niro Higuchi of Brazil’s National Institute for Amazon Research (INPA), showed the 2005 tree mortality spike was the second largest recorded since 1989 for the Manaus region in the Central Amazon. Also in 2005, large parts of the Amazon forest experienced one of the harshest droughts of the last century. A study published in the journal Science in 2009 pointed to the drought as the single agent for a basin-wide increase in tree mortality. But a very large area with major tree loss (the region near Manaus) was not affected by the drought.

"We can’t attribute [the increased] mortality to just drought in certain parts of the basin–we have solid evidence that there was a strong storm that killed a lot of trees over a large part of the Amazon," Chambers says. From Jan. 16 to 18, 2005, a squall line 620 miles long and 124 miles wide crossed the whole Amazon basin from southwest to northeast, causing several human deaths in the cities of Manaus, Manacaparu, and Santarem. The strong vertical winds associated with the storm, blowing up to 90 miles per hour, uprooted or snapped in half trees that were in their path. In many cases, the stricken trees took down some of their neighbors when they fell.

The researchers used a combination of Landsat satellite images, field-measured tree mortality, and modeling to determine the number of trees killed by the storm. By linking satellite data to observations on the ground, the researchers were able to take into account smaller tree blow downs (less than 10 trees) that otherwise cannot be detected through satellite images.

Looking at satellite images for the area of Manaus from before and after the storm, the researchers detected changes in the reflectivity of the forest, which they suspected were indicative of tree losses. Undisturbed forest patches appeared as closed, green canopy in satellite images. When trees die and fall, a clearing opens, exposing wood, dead vegetation, and surface litter. This so-called "woody signal" only lasts for about a year in the Amazon. In a year, vegetation re-grows and covers the exposed wood and soil. This means the signal is a good indicator of recent tree deaths.

After seeing disturbances in the satellite images, the researchers established five field sites in one of the blow down areas, and counted the number of trees that had been killed by the storm; researchers can usually tell what killed a tree from looking at it. "If a tree dies from a drought, it generally dies standing. It looks very different from trees that die snapped by a storm," Chambers says. In the most affected plots, near the centers of large blow downs, up to 80 percent of the trees had been killed by the storm.

By comparing their field data and the satellite observations, the researchers determined that the satellite images were accurately pinpointing areas of tree death, and they calculated that the storm had killed between 300,000 and 500,000 trees in the area of Manaus. The number of trees killed by the 2005 storm is equivalent to 30 percent of the annual deforestation in that same year for the Manaus region, which experiences relatively low rates of deforestation.

The team then extrapolated the results to the whole Amazon basin. "We know that the storm was intense and went across the basin," Chambers says. "To quantify the potential basin-wide impact, we assumed that the whole area impacted by the storm had a similar level of tree mortality as the mortality observed in Manaus." The researchers estimate that between 441 and 663 million trees were destroyed across the whole basin. This represents a loss equivalent to 23 percent of the estimated mean annual carbon accumulation of the Amazon forest.

Squall lines that move from southwest to northeast of the forest, like the one in January 2005, are relatively rare and poorly studied, says Robinson Negron-Juarez, an atmospheric scientist at Tulane University, and lead author of the study. Storms that are similarly destructive but advance in the opposite direction (from the northeast coast of South America to the interior of the continent) occur up to four times per month. They can also generate large forest blow downs (contiguous patches of wind-toppled trees), although it’s infrequent that either of these two types of storms crosses the whole Amazon.

"We need to start measuring the forest perturbation caused by both types of squall lines, not only by the ones coming from the south," Negron-Juarez says. "We need that data to estimate total biomass loss from these natural events, which has never been quantified." Chambers says that authors of previous studies on tree mortality in the Amazon have diligently collected dead-tree tolls, but information on exactly what killed the trees is often lacking, or not reported.

"It’s very important that when we collect data in the field, we do forensics on tree mortality," says Chambers, who has been studying forest ecology and carbon cycling in the Amazon since 1993. "Under a changing climate, some forecasts say that storms will increase in intensity. If we start seeing increases in tree mortality, we need to be able to say what’s killing the trees."