Hawaiian Islands weather details & Aloha paragraphs / April 28-29, 2011

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

Lihue, Kauai –                    83
Honolulu airport, Oahu –     87 (record for the date: 91 – 1979)
Kaneohe, Oahu –                80
Molokai airport –                 M
Kahului airport, Maui –         86  
Kona airport –                     84
Hilo airport, Hawaii –           83

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

Honolulu, Oahu – 83
Hilo, Hawaii – 78

Haleakala Crater –     50 (near 10,000 feet on Maui)
Mauna Kea summit – 39 (over 13,500 feet on the Big Island)

Precipitation Totals – The following numbers represent the largest precipitation totals Thursday evening:

0.09    Mount Waialeale, Kauai
0.32    Manoa Valley, Oahu
0.00    Molokai
0.00    Lanai 
0.00    Kahoolawe
0.21    West Wailuaiki, Maui
0.37    Kealakekua, Big Island

Marine Winds – Here’s the latest (automatically updated) weather map showing a 1030 millibar high pressure system to the northeast of the Hawaiian Islands. At the same time we find a weak trough of low pressure to our north. Our local trade winds will continue to be light…although stronger locally at times.

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 13,500 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 shining down during the night at times. Plus, during the nights you will be able to see stars, and the sunrise and sunset 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 ended November 30th here in the central Pacific…and begins again June 1st.

 Aloha Paragraphs

Trade winds…with clouds leading
to localized showers at times
 
 
 

Our winds will be light to moderately strong through Friday, easing back some this weekend…then picking up again later next week.  Glancing at this weather map, we find a high pressure system located far to the northeast of the Hawaiian Islands…which is the source of our trades. These trade winds will continue through Friday, maintaining light to moderately strong proportions.  An upper level trough of low pressure edging our way Saturday, lasting into early next week, will cause our trade winds to ease up in strength some. As the trough moves away later in the week…our trade wind speeds will rebound.

Our local winds will remain from the trade wind direction…the following numbers represent the strongest gusts, along with directions Thursday evening:

25 mph       Port Allen, Kauai – NE
24              Honolulu, Oahu – NE 
25              Molokai – NE   
28              Kahoolawe – ENE  
29                Kahului, Maui – NE
14              Lanai Airport 
25              South Point, Big Island – NE 

We can use the following links to see what’s going on in our area of the north central Pacific Ocean Thursday night.  Looking at this NOAA satellite picture we see variable clouds over and around the islands. There are multi-leveled clouds, from high and middle, down to the lower cumulus clouds…with some towering cumulus around the edges. We can use this looping satellite image to see a big stream of high clouds moving by to our south, with a counterclockwise rotating upper level low pressure system far to our east-northeast. Checking out this looping radar image shows some showers falling over the ocean offshore from the islands. There’s a pretty good amount of clouds moving through the islands…carried on the light to moderately trade winds.

Sunset Commentary: Here in Kihei, Maui at around 530pm Thursday evening, skies were partly cloudy, along with a fairly stiff trade wind breeze. The trade wind weather pattern is still well established over the islands Thursday night, as it will be Friday. There is still a small amount of instability over the islands, which should prompt more afternoon clouds and showers over the mountain slopes Friday afternoon. The windward sides, especially at night, will likely see some showers arriving on these trade winds too.

As we push into the upcoming weekend the trade winds will continue to blow, although will lose strength for several days…into next week. Depending upon just how light they become will determine how much of a light winded convective weather pattern we’ll find. If it gets quite light, and with the input of the daytime heating of the islands, we’re apt to find cumulus clouds forming over and around the mountains during the afternoons. These could drop showers, and few of which could be locally quite generous…perhaps even a random thunderstorm over the Big Island slopes.

The trade winds will wake up again next week, rebounding into the moderately strong realms likely. This is very typical for the spring months as we know, and will probably remain active through much of the month of May. Late spring into the early summer months are typically some of the driest times of the year. This is why we’re welcoming any precipitation that we can coax our way now through June.  We haven’t seen the word drought being thrown around much lately…although parts of Maui and the Big Island, especially the leeward sections are still drier than normal, while Kauai and Oahu remain in good shape.

~~~ I'll be back early Friday with your next new weather narrative, I hope you have a great Thursday night until then! Aloha for now…Glenn.

Interesting: The nation's 25 most smoggy cities improved air quality over the last year, but half the nation's residents still live with unhealthy levels of air pollution, according to an American Lung Association report released on Wednesday. Weighing the pluses and minuses in U.S. air quality over the past year, the "State of the Air 2011" report concluded that the U.S. Clean Air Act, the federal law aimed at limiting pollution in the nation's skies, is working.

"The progress the nation has made cleaning up coal-fired power plants, diesel emissions and other pollution sources has drastically cut dangerous pollution from the air we breathe," Lung Association President Charles Connor said in a statement. The most dramatic improvement has been controlling ozone, commonly known as smog.

The report found all 25 cities most polluted by ozone had cleaner air than they did last year, Still, the report found that 154.5 million people, just over half the nation's population, live in areas where the air is filled with dangerous levels of ozone and particle pollution, also known as soot.

Cities with the foulest air were broken down into three categories and the worst three in each were Los Angeles, Bakersfield and Visalia, all in California, as most ozone polluted; Bakersfield and Fresno, both in California, and Pittsburgh, Pennsylvania, as most polluted by short-term particle pollution; and Bakersfield, Los Angeles and Phoenix as most polluted by year-round particle pollution. Cities with nation's best overall air quality were Honolulu and Santa Fe, New Mexico, the report said.

Interesting2: China's census shows its population grew to 1.34 billion people by 2010, with a sharp rise in those over 60. Nearly half of all Chinese now live in cities and people over the age of 60 now account for 13.3% of the population, up nearly 3% since 2000. But the figures reveal that China's population is growing more slowly than in the past. That could affect the economy, as the number of potential workers, especially from rural areas, could shrink.

The proportion of mainland Chinese people aged 14 or younger was 16.6%, down by 6.29 percentage points from the last census in 2000. The number aged 60 or older grew to 13.26%, up 2.93 percentage points. When China carried out its first census in 1953 it had a population of 594 million, less than half the current figure.

This census, the first in 10 years, comes after a decade of rapid economic growth that has led to significant social change. The results revealed that almost half of all Chinese – 49.7% of the population – now live in cities, up from about 36% 10 years ago.

Many have been drawn to jobs in China's factories and coastal industrial zones. The census for the first time counted migrant workers where they were living, rather than where they were registered. It found that more than 220 million Chinese had worked away from home for over six months in 2010, almost double the previous figure.

The government's strict controls on family size, including its one-child policy for most urban families, have reduced annual population growth to below 1% percent. The rate is projected to turn negative in coming decades. There has been growing speculation in the country's media about the possibility that the government will ease the policy – introduced in 1980 as a temporary measure to curb surging population growth – and allow more people to have two children.

As it currently stands, most urban couples are limited to one child and rural families to two. The average household now numbers 3.1 people, down from 3.44 a decade ago. Some demographers have said that the limits on family size may now threaten China's economic future, with fewer people left to pay and care for an older population, as well as to work in the factories that have transformed the country into the world's second largest economy.

"The data from this census show that our country faces some tensions and challenges regarding population, the economy and social development," said Ma Jiantang, head of the National Bureau of Statistics. "First, the ageing trend is accelerating, and second the size of the mobile population is constantly expanding."

He said China would have to "actively respond to the new challenges in demographic development". But state-run Xinhua news agency said President Hu Jintao told top party lawmakers on Tuesday that China's family planning policy would remain unchanged and the low birth-rate be maintained.

Interesting3: The salt marshes that rim the shores of Massachusetts's Plum Island estuary, which provide nesting grounds for numerous waterfowl and extremely productive spawning grounds for striped bass and soft-shell clams, have grown by 300 hectares in the last 300 years. That growth, according to a new study, was fueled by post-colonial deforestation and the erosion it caused in areas upstream.

The findings suggests that efforts to maintain or restore salt marshes along the Eastern Seaboard, which have begun to disappear in recent years for a variety of reasons, may be preventing the wetlands from returning to their more natural sizes. In the past century, wetlands in many regions have shrunk dramatically.

San Francisco Bay lost about 20,000 hectares of wetlands during that period, and the Mississippi River delta lost 20 times that amount. Scientists have long presumed that the ongoing loss of wetlands in many areas of the world stems from influences such as rising sea levels and human development of coastal real estate.

In many regions, dams both large and small also contribute to wetland degradation by interrupting the flow of sediment to the sea, thereby depriving the marshes of material that could accumulate and help counteract local erosion.

But in some areas, the 20th-century shrinkage of wetlands may simply be a return toward normal coverage, argue Matthew Kirwan, a geomorphologist with the U.S. Geological Survey in Charlottesville, Virginia, and colleagues. They draw that conclusion from their study of the Plum Island estuary reported in the May issue of Geology.

By carbon-dating peat samples taken in 2006 from more than a dozen places in those marshes, Kirwan and his colleagues found that 3 centuries ago the wetlands covered only about 2/3 their current area. Mainly during the 1700s and 1800s, the salt marshes expanded atop a temporary bounty of sediment delivered to the estuary's shores as a result of human-induced erosion, the researchers contend.

The area was first settled in the 1630s, and by 1700 at least three of the rivers flowing into the estuary powered sawmills and gristmills—evidence of the substantial deforestation and agricultural activity taking place in the watershed, Kirwan notes.

Interesting4: The US has born the brunt of two spates of tornadoes in the past month. Between 14 and 16 April, storms swept through several states, with North Carolina the hardest hit. In the past few days a new wave has struck. Alabama's governor Robert Bentley said today that 131 people were confirmed dead in the state, and the number is expected to rise. New Scientist explains what is happening.

How many tornadoes have there been? There have probably been 600 in April, according to Harold Brooks of the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma. That is more than any month since records began in 1950. What is causing the onslaught? For a tornado to form, cold air must sit above warm, moist air, and the wind needs to go in different directions at different heights, creating shear forces.

"One thing that brings those things together is a strong jet stream," says Brooks, "especially if it comes from the west or south-west, over the Rockies." That is exactly what has been happening throughout April. The jet stream has dipped south over the south-western US, sending strings of storms over the southern states for weeks on end. According to Brooks, such a sustained pattern happens only two or three times a century.

Is it over? NSSL's forecasters think the stormy weather is likely to calm down over the next few days as the warm, moist air currently trapped over the southern states moves away and conditions become less favourable for tornadoes. But the laboratory is unsure what will happen next week: its different models are forecasting different outcomes. Is climate change to blame? There's no way of knowing for sure.

There have been claims that tornado numbers have increased over the past few decades, but because records are less reliable further back in time, we cannot be sure. "Some ingredients that are favourable to tornadoes will increase in a warming world, others will decrease," Brooks says. How that will balance out is anyone's guess.

Interesting5: Some climate models suggest that a warming future could herald more intense storms like those that ripped through the Southeast on Wednesday night. But that doesn't mean the southern storms and tornadoes were a manifestation of climate change, climate scientists say. That's because teasing out the influence of climate on weather takes time.

"The impacts of climate change on any weather events will likely only be seen in the statistics — more rainfall that occurs in intense bursts, more overall water vapor, more heat waves, less cool nights," Gavin Schmidt, a climate scientist with NASA's Goddard Institute for Space Studies, wrote in an email to LiveScience.

"But the combination of events that lead to the tornado swarms we've seen are both rare and complex, and to ask climate scientists to pronounce definitively on them the instant they happen is just asking for trouble." The death toll from this week's line of storms has topped 200, making it likely the deadliest tornado outbreak since 1974.

Even in severe storms, tornados are relatively rare, said Morris Weisman, a senior scientist at the National Center for Atmospheric Research in Boulder, Colo. Long-lasting, rotating thunderstorms called supercell storms are the breeding grounds for severe tornadoes, Weisman told LiveScience, but only about 25 percent of supercell storms result in a tornado.

Ingredients for the perfect storm To form, supercell storms require two atmospheric ingredients — warm, moist air near the surface colliding with cooler air high in the atmosphere, and a vertical windshear, or a change in speed and direction of wind with height. When warm, moist air from the Gulf of Mexico collides with vertical windshear caused by a strong jetstream, supercells form.

The question for climate scientists, then, is whether climate change will make it more likely for these two atmospheric ingredients to clash into one another. While there are no models precise enough to predict the birth of individual storms, climate researchers can use computer simulations to find out if the weather conditions that cause storms are likely to occur.

In one 2007 study, Purdue University climate researcher Robert Trapp found that in a climate change scenario considered likely by the Intergovernmental Panel on Climate Change, there would be increases in storm-friendly conditions in some areas, including the Southeast. "We primarily saw that regions that already experience severe weather would see an amplification of the frequency" of those conditions, Trapp told LiveScience. The increase held regardless of season.

Measuring tornado trends Estimating climate effects on tornadoes is particularly difficult, Trapp said, because they aren't as well recorded as other weather disasters such as hurricanes. Many of Wednesday's tornadoes occurred in daylight in populated areas, Trapp said, but nighttime tornadoes in rural spots may not get entered into the record. He and his colleagues are working to figure out the real trends using more objective numbers.

"We're investigating ways of trying to recreate and correct for biases using Doppler weather radar data," Trapp said. "We're also doing something similar with computer models." To show for certain that climate affects storms events, researchers will need to take that unbiased data and compare it across decades, Trapp said.

In the meantime, meteorologists are working to understand the conditions that trigger a tornado in a supercell. Researchers know the warning signs to look for, Weisman said, and they even know where tornadoes are likely to appear (the southwest flank of a storm, he said). But exactly what turns a given rotating storm into a tornado-spawning monster is still up in the air, Weisman said. "A tornado is a very chaotic animal," he said. "Getting that last detail — that last little step — is very difficult."