Update No. 3: Calvin strengthens more, now with maximum sustained winds of 60 mph

Update No. 3 at 2 p.m. July 18: Tropical Storm Calvin has picked up some additional energy, strengthening more since earlier today. The storm is now packing maximum sustained winds of 60 mph as it advances near the Big Island.

As of 2 p.m., the Central Pacific Hurricane Center said Calvin was about 220 miles southeast of Hilo and moving west at 21 mph. Tropical storm-force winds now extend up to 140 miles out from the storm’s center, which is still forecast to pass the islands to the south, very close to the Big Island.

“Wind speeds will steadily increase this afternoon through Wednesday as Tropical Storm Calvin approaches the state,” the National Weather Service forecast office in Honolulu said in its Hawaiʻi area synopsis just before noon Tuesday.

Gusty and potentially damaging winds will be possible across most of the state, with the strongest wind gusts expected over and downwind of terrain. Heavy showers and flash flooding also will be possible because of deep unstable tropical moisture, with the greatest threat of flash flooding expected over windward and southeast portions of the Big Island and windward Maui.

The National Weather Service says the storm will most likely not advance too much farther north unless it experiences additional strengthening.

A tropical storm warning remains in effect for Hawaiʻi County until further notice. A flood watch also remains in effect for all Hawaiian islands through 6 p.m. Wednesday and a high surf warning for east-facing shores of the Big Island and Maui is also in effect through 6 p.m. Wednesday.

Calvin will likely weaken into a tropical depression by Thursday as it continues its westward track.

To see a list of closures, shelters and other emergency information, click here.

The next complete advisory for Tropical Storm Calvin will be at 5 p.m. today.

Update No. 2 at 11 a.m. July 18: Tropical Storm Calvin now has maximum sustained winds of 50 mph, strengthening slightly since this morning, as it continues moving west toward the Big Island at 22 mph.

There have been no significant changes to the storm’s forecasted track since earlier this morning, with Calvin’s center expected to pass to the south, very close to the Big Island, sometime tonight. Impacts from the storm could include flash flooding from heavy rainfall, damaging winds and dangerous high surf.

A tropical storm warning remains in effect for Hawai’i County until further notice. A flood watch also remains in effect for all Hawaiian islands through 6 p.m. Wednesday and a high surf warning for east-facing shores of the Big Island and Maui is also in effect through 6 p.m. Wednesday.

Tropical storm conditions are still likely to begin spreading over Hawai’i County starting this evening. As of 11 a.m., the storm was located about 245 miles east-southeast of Hilo and about 260 miles east-southeast of South Point. Tropical storm-force winds extend up to 115 miles out from Calvin’s center.

Locally strong winds are likely to begin this evening over the Big Island, with north winds shifting to the northeast and east as Calvin moves westward through Wednesday morning. Winds will also become breezy and primarily northeast across the smaller islands outside the cyclone because of strong gradient winds Wednesday and Wednesday night.

It is important to note that the mountainous terrain of the islands can produce localized areas of enhanced winds, even well away from the tropical cyclone center. People on the Big Island should prepare now for tropical storm-force wind impacts.

Heavy rainfall will likely begin this evening on the Big Island, with chances for heavy rain increasing elsewhere in the state through Wednesday as Calvin moves steadily toward the west.

Storm total rainfall amounts of 4 to 8 inches, with maximum amounts of 10 inches, are possible from later today through Thursday, mainly along the windward and southeast flank of the Big Island. Rainfall amounts of 3 to 6 inches are expected in windward areas of Maui and 2 to 4 inches elsewhere in the state. This rainfall could lead to localized flash flooding and mudslides.

Coastal impacts associated with Calvin will include rapidly building surf tonight through Wednesday. Surf may reach as high as 15 feet along east-facing shores of the Big Island, and up to 10 feet along east-facing shores of the other islands.

Swells generated by Calvin are expected to begin spreading across the islands later today, leading to a rapid increase in surf, with high surf expected to continue into Wednesday. This elevated surf will likely cause life-threatening conditions along exposed shorelines.

Although peak surf heights on the Big Island will likely occur around low tide Wednesday morning, some minor overwash and erosion is possible for exposed low-lying coastal areas.

Calvin is expected to remain a tropical storm throughout the next 36 hours, according to the Central Pacific Hurricane Center, before quickly weakening.

“Calvin will likely weaken into a tropical depression by Wednesday and maintain a westward track, moving away from the island chain by Wednesday night,” said the National Weather Service forecast office in Honolulu early Tuesday morning.

Update 8 a.m. July 18: Tropical Storm Calvin is now 330 miles east-southeast of Hilo and continues to move at 22 mph toward the Big Island with maximum sustained winds of 45 mph and gusts higher, according to the National Hurricane Center.

A full update on the progress of the storm will be released at 11 a.m.

Original post: Tropical Storm Calvin is expected to begin impacting the Big island tonight, with rainfall of 4 to 8 inches and possibly 10 inches mainly on the windward areas. Hawaiʻi County could experience flash flooding and mudslides.

As of 5 a.m. Tuesday, Calvin was 390 miles east-southeast from Hilo and moving at 22 mph toward the Big Island with maximum sustained winds of 45 mph and higher gusts, according to the National Hurricane Center.

The storm is expected to pass over, or just south of the Big Island tonight through Wednesday night — then pass well south of the other Hawaiian Islands.

This places the islands in the windier and wetter part of Calvin’s circulation. Tropical-storm-force winds extend outward up to 105 miles from the center.

North winds will shift to the northeast and east as Calvin moves westward through Wednesday morning. Winds will primarily be northeasterly over the smaller islands, strongest Wednesday and Wednesday night. It is important to note that the mountainous terrain of the islands can produce localized areas of enhanced winds, even well away from the tropical cyclone center.

Calvin will bring rapidly building surf tonight through Wednesday. Surf may reach as high as 15 feet along east-facing shores of the Big Island, and up to 10 feet along east-facing shores of the other islands. Although peak surf heights on the Big Island will likely occur around low tide Wednesday morning, some minor overwash and erosion is possible for exposed low-lying
coastal areas.

Deep convection has been developing near Calvin Tuesday morning, which may slow the weakening trend today. Calvin is forecast to gradually weaken from tonight through Thursday.

Residents and visitors should complete any last minute preparations today during the daylight hours before the storm strikes. For information about how to get ready, click here.

Swells generated by Calvin are expected to begin spreading across the main Hawaiian Islands later today and tonight. This will lead to a rapid increase in surf along east facing shores,
with high surf continuing into Wednesday. This elevated surf will likely cause life-threatening conditions along exposed shorelines.

Potential Impacts:

Wind: Protect against hazardous wind having possible limited impacts across the Hawaiian islands. Potential impacts include:

• Damage to porches, awnings, carports, sheds, and unanchore mobile homes. Unsecured lightweight objects blown about.
• Many large tree limbs broken off. A few trees snapped or uprooted, but with greater numbers in places where trees are shallow rooted. Some fences and roadway signs blown over.
• A few roads impassable from debris, particularly within urban or heavily wooded places. Hazardous driving conditions on bridges and other elevated roadways.
• Scattered power and communications outages.

Surge: Protect against locally hazardous surge having possible limited impacts across portions of windward and southeast Big Island. Potential impacts in this area include:

• Localized inundation with storm surge flooding mainly along immediate shorelines and in low-lying spots, or in areas farther inland near where higher surge waters move ashore.
• Sections of near-shore roads and parking lots become overspread with surge water.
• Driving conditions dangerous in places where surge water covers the road.
• Moderate beach erosion. Heavy surf also breaching dunes, mainly in usually vulnerable locations. Strong rip currents.
• Minor to locally moderate damage to marinas, docks, boardwalks and piers. A few small craft broken away from moorings.

Elsewhere across the Hawaiian islands, little to no impact is anticipated.

Flooding raing: Protect against dangerous rainfall flooding having possible significant impacts across mainly windward and southeastern portions of the Big Island. Potential impacts include:

• Moderate rainfall flooding may prompt several evacuations and rescues.
• Rivers and tributaries may quickly become swollen with swifter currents and overspill their banks in a few places, especially in usually vulnerable spots. Small streams, creeks, canals, arroyos, and ditches overflow.
• Flood waters can enter some structures or weaken foundations.
• Several places may experience expanded areas of rapid inundation at underpasses, low-lying spots, and poor drainage areas. Some streets and parking lots take on moving water as storm drains and retention ponds overflow.
• Driving conditions become hazardous. Some road and bridge closures.

Prepare for locally hazardous rainfall flooding having possible
limited impacts across other Hawaiian Islands from Kaua’i to Maui.

Tornadoes: Protect against a tornado event having possible limited impacts
across the Hawaiian islands. Potential impacts include:

• The occurrence of isolated tornadoes can hinder the execution of emergency plans during tropical events.
• A few places may experience tornado damage, along with power and communications disruptions.
• Locations could realize roofs peeled off buildings, chimneys toppled, mobile homes pushed off foundations or overturned, large tree tops and branches snapped off, shallow-rooted trees knocked over, moving vehicles blown off roads, and small boats pulled from moorings.