Hawaiian Islands Weather Details & Aloha Paragraphs / April 17-18, 2018

Air Temperatures – The following high temperatures (F) were recorded across the state of Hawaii Tuesday…along with the low temperatures Tuesday:

78 – 71  Lihue, Kauai
82 – 75  Honolulu, Oahu
78 – 72  Molokai AP
82 – 72  Kahului AP, Maui
83 – 73  Kailua Kona
81 – 67  Hilo AP, Hawaii

Here are the latest 24-hour precipitation totals (inches) for each of the islands Tuesday evening:

1.28  Mount Waialeale, Kauai
0.09  Punaluu Stream, Oahu
0.04  Molokai
0.00  Lanai
0.00  Kahoolawe
0.12  West Wailuaiki, Maui
1.20  Honokaa, Big Island

The following numbers represent the strongest wind gusts (mph) Tuesday evening:

29  Port Allen, Kauai
31  Kuaokala, Oahu
35  Molokai
22  Lanai
37  Kahoolawe
32  Maalaea Bay, Maui
25  Waikoloa, Big Island

Hawaii’s Mountains – Here’s a link to the live webcam on the summit of our tallest mountain Mauna Kea (nearly 13,800 feet high) on the Big Island of Hawaii. Here’s the webcam for the Haleakala Crater on Maui. These webcams are available during the daylight hours here in the islands, and at night whenever there’s a big moon shining down. Also, at night you will be able to see the stars — and the sunrise and sunset too — depending upon weather conditions.

Aloha Paragraphs

A trough west…high pressure north of the state

Towering cumulus to the west and southwest

Partly to mostly cloudy…lots of high cirrus clouds

A few showers…over the islands and offshore
Looping image

 

~~~ Hawaii Weather Narrative ~~~

 

Small Craft Advisory…Most coasts and channels Maui County and the Big Island

Flash Flood Watch…all islands / starting Thursday morning

Winter Storm Watch…Big Island summits / starting Thursday morning

 

Broad Brush Overview: High pressure to the north of the state will maintain moderate to strong trades through early next week. A typical trade wind shower pattern is expected through Wednesday, falling mostly along the windward and mountains. Deep moisture will increase as an old cold front drops southward into the islands Wednesday night through Friday…while an upper level trough passes overhead. This is expected to result in an increase in shower activity across the entire state, with some locally heavy rainfall and thunderstorms possible Thursday and Thursday night. Deep moisture will begin to decrease Friday night, as the upper trough and frontal remnants shift south of the area, with a more typical trade wind pattern returning over the weekend into early next week.

Details: With no significant forcing mechanism, other than orographic lift along the slopes of the mountains, provided by the trades interacting with the terrain…a typical trade wind shower regime should prevail. Low clouds and showers will focus primarily over windward and mountain areas, particularly during the overnight and early morning hours, with a stray shower spilling leeward from time to time. Considerable high cirrus cloud cover is expected to prevail through the period, resulting in mostly cloudy conditions across the state.

Moderate to strong trade winds will prevail, as a ridge of high pressure remains in place well to the north of the state through Friday. The models show an old cold front pushing southward into the islands Wednesday night, lingering through Thursday night. Aloft, the upper level low currently well to the west of the Kauai, is expected to shift eastward Wednesday night. This feature will approach from the west Thursday, then slowly shift southeastward through the island chain Thursday night and Friday…before exiting to the south of the state Friday night.

Trade wind showers are expected to increase in coverage and intensity Wednesday night, with the potential for some locally heavy rain and thunderstorms Thursday and Thursday night. Given the recent heavy rainfall and saturated soils, model trends will need to be monitored closely over the next few days. Showers will be most prevalent over windward and mountain areas, although given the moist and unstable airmass expected then, leeward areas will see more regular showers as well.

Looking Ahead: The deep tropical moisture will exit to the south of the state Saturday. Upper level ridging will build southeastward over the islands as well, bringing more stable conditions back. Overall, we can look for typical trade wind weather, with bands of clouds and showers occasionally moving across the islands through early next week. This incoming moisture will favor windward areas, with a few showers reaching the leeward sides from time to time. Some high clouds will likely continue to pass overhead through the period, although it appears that they will remain thin enough to allow more sunshine during the days.

Here’s a wind profile of the Pacific Ocean – Closer view of the islands / Here’s the vog forecast animation / Here’s the latest weather map

Marine environment details: A ridge of high pressure located far north of the islands, will continue to provide trade winds into the weekend. The strong trades have resulted in a small craft advisory (SCA) for all waters. The trades will be trending slightly softer and into the moderate to locally strong range Wednesday, and that will lead to the scaling down in coverage of the SCA to most of the waters around Maui County and the Big Island. This is due to the ridge weakening temporarily Wednesday only to rebound Friday resulting in a strengthening of the trades for the weekend.

The strong and gusty trades combined with a northeast swell has lead to High Surf Advisory level surf for the east facing shores of all islands. Due to the windy trades, water conditions will continue to be rough.

A small south swell is expected to arrive and remain through mid-week. A series of swells from the south and south-southwest may arrive later in the week or during the weekend.

The north and west facing shores will find a series of northwest swells arriving during the next week. The first  is slated for Wednesday, peaking late Wednesday night. This swell will reinforced by a slightly larger northwest swell Thursday. This swell will peak Friday morning. A slow decline will follow, well into the weekend. The third in the series arrives Sunday night, peaking Monday.

 

World-wide Tropical Cyclone activity

Here’s the latest Pacific Disaster Center (PDC) Weather Wall Presentation

>>> Atlantic Ocean:

>>> Caribbean Sea:

>>> Gulf of Mexico:

Here’s a satellite image of the Caribbean Sea…and the Gulf of Mexico

Here’s the link to the National Hurricane Center (NHC)

>>> Eastern Pacific:

Here’s a wide satellite image that covers the entire area between Mexico, out through the central Pacific…to the International Dateline.

Here’s the link to the National Hurricane Center (NHC)

>>> Central Pacific:

Here’s a link to the Central Pacific Hurricane Center (CPHC)

>>> Northwest Pacific Ocean: No active tropical cyclones

>>> North and South Indian Oceans / Arabian Sea: No active tropical cyclones

Here’s a link to the Joint Typhoon Warning Center (JTWC)


Interesting: As World Warms, America’s Invisible ‘Climate Curtain’ Creeps East – A climate boundary divides the United States — and it’s on the move.

During the late 19th century, land management officials conceived of the invisible boundary along the 100th meridian (a longitudinal line), which runs north to south, to mark the beginning of the U.S.’s Great Plains region. The invisible border bisects all of North America.

But the 100th meridian is also a boundary between two profoundly different climates: eastern humidity and western dryness. And scientists have noticed an alarming trend. The border is shifting, with the arid conditions on the west slowly expanding eastward, nudging the boundary by about 140 miles from its original position.

The American geologist and explorer John Wesley Powell visited and reported on the 100th meridian in 1878, arguing that the U.S. government should establish irrigation strategies to compensate for drier conditions to the west of the boundary, researchers explained in a new study. Powell wrote that he observed changes in landscape and scenery along the boundary as he traveled from east to west, seeing the lush greenery and flowers give way to ground that “gradually becomes naked,” calling it “a wonderful transformation,” the study authors reported.

But is the actual boundary as dramatic as Powell described? To find out, scientists examined data on soil moisture, crop and vegetation cover, precipitation, and atmospheric conditions that shape the distribution of water across the continent. The researchers discovered that Powell’s evaluation of the 100th meridian as “an arid-humid divide” was highly accurate and that this division is still strongly evident, with effects on the types of crops that can succeed on either side of the divide.

For example, wetter conditions favor corn, which makes up 70 percent of the crops grown to the east of the border. However, agriculture in the drier west is dominated by wheat, which grows well under arid conditions, according to the study.

Along the boundary, soil moisture showed “a sharp transition,” as did the type of vegetation likely to grow there in the absence of human activity, the scientists noted.

North America’s geography and the interplay of global wind patterns explain why eastern regions are wetter than the plains. During the winter, storms that brew in the Atlantic Ocean carry moisture inland, but they can’t travel far enough to soak the west. And during the summer months, when moisture moves northward from the Gulf of Mexico, winds carry that moisture to the east, so the west again comes up short.

Meanwhile, much of the moisture that originates in the Pacific Ocean stops at the Rocky Mountains, before it reaches the Great Plains.

But this boundary is changing, according to data collected since around 1980 and described in the two-part study published March 21 in the journal Earth Interactions. Dry conditions are expanding, shifting the border to the 98th meridian, around 140 miles east, researchers explained in the study’s second part.

The shift can be explained by changing precipitation patterns and higher average temperatures that make moisture evaporate from the soil more rapidly than in the past, the study said.

Both parts of the study highlight the different conditions that have long existed side by side along this unseen border, suggesting the ways climate shaped colonization and agriculture in North America. But as climate change continues to heat up our planet, human communities and farms may need to adjust to long-term changes in conditions — and potential crop failure — should dryness continue to encroach into eastern lands, the study said.