Trouble in Paradise: Hawaii and Tropical Cyclones

Hawaii – a tropical paradise, full of sun, fun, palm trees, beauty, mountains, volcanoes and more.  But wait…have you ever thought about Hawaii and tropical cyclones?  Although not frequent, tropical cyclones have battered the Hawaiian Islands several times in recent memory.

Do cyclones develop ‘off-season’ in the Atlantic?

Headquarters for the U.S. National Hurricane Center

In the Atlantic, the official dates for the hurricane season are 1 June – 30 November. This certainly doesn’t mean that cyclones only exist during this time frame, yet 97% of all cyclones that have developed have occurred during those months.  While we really won’t know exactly how many cyclones have developed out of season prior to 20th century technological advances, there is evidence of off-season storms in the Atlantic dating back to May of 1771, and more recently tropical storm Beryl in May of 2012. Most cyclones that develop out of season do not typically impact the U.S., but there have been more than handful that have, giving us pause to think what a fickle planet our Earth can be.

Featured Storm – Super Typhoon Fengshen (2002)

Origin and Track of Typhoon Fengshen

Typhoon Fengshen was the strongest storm of the 2002 Pacific typhoon season. It developed on July 13 near the Marshall Islands and rapidly intensified due to its small size. Fengshen went from being a tropical depression to a cyclone in only 6 hours. By July 15, Fengshen was given typhoon status, and after initially moving to the north, it turned toward the northwest. On July 18, the typhoon reached its peak intensity of 185 km/h (115 mph), according to the Japan Meteorological Agency; the Joint Typhoon Warning Center (JTWC) estimated peak winds of 270 km/h (165 mph). Disparities like this between agencies are the driving force behind the creation/purpose of  Cyclone Center, and with your help these dissimilarities can be smoothed out. Your classifications are important to us, so we ask that you please take a moment and provide your input on Typhoon Fengshen to help us determine its peak winds.

Typhoons Fengshen (north) and Fung-Wong (south) undergo the Fujiwhara effect

The JTWC estimated that Fengshen was a super typhoon for five days, which broke the record for longest duration at that intensity. This record would later be tied by Typhoon Ioke in 2006. While approaching peak intensity, Typhoon Fengshen underwent the Fujiwhara effect with Typhoon Fung-wong, causing the latter storm to loop to its south. The Fujiwhara effect is when two nearby cyclonic vortices orbit each other and close the distance between the circulations of their corresponding low-pressure areas. Interaction of smaller circulations can cause the development of a larger cyclone, or cause two cyclones to merge into one.

Fengshen gradually weakened while approaching Japan, and it crossed over the country’s Ōsumi Islands on July 25 as a severe tropical storm. The typhoon swept a freighter ashore, killing four of the 19 crew members aboard. In Japan, Fengshen dropped heavy rainfall that caused mudslides and left $4 million (¥475 million Japanese Yen) in crop damage. After affecting Japan, Fengshen weakened in the Yellow Sea to a tropical depression, before moving across China’s Shandong Peninsula and dissipating on July 28. The typhoon produced strong winds and heavy rain in Japan. A station in Miyazaki Prefecture reported the highest rainfall in Japan with a total of 717 mm (28.2 in). Most of the precipitation fell in a 24 hour period, and the heaviest 1 hour total was 52 mm (2.0 in) in Taira, Toyama. The remnants of Fengshen produced heavy rainfall in northeastern China. The storm affected the capital city of Beijing, becoming the first storm to produce significant impact there since Typhoon Rita in 1972.

– Kyle Gayan is an undergraduate student in Atmospheric Sciences at the University of North Carolina at Asheville and is also a retired USAF Master Sergeant; his 20 years of service was spent exclusively in the weather career field. He recently joined the Cyclone Center team as a classifier and contributor to our social media.

Where did the tropical cyclones go this season?

In short – the western Pacific.

The Atlantic Basin was predicted by many to have an active season. But the season ended November 30th, and it was a very quiet one. There were 13 named storms in the Atlantic, of which two developed into hurricanes.  The Accumulated Cyclone Energy (ACE) Index is used by the National Oceanic and Atmospheric Administration (NOAA) to measure the severity of hurricane seasons.  It considers the intensity and the lifespan of storms.  The 2013 Atlantic season was well below normal; the ACE index came in at 33, about 31% of the 1981-2010 average of 104.

Super Typhoon Dale (1996) was one of our featured storms on Cyclone Center this year.

On the other side of the planet, in comparison to the Atlantic Basin, the western Pacific appears to be the ‘hot spot’ this season for strong tropical cyclones. The western Pacific has seen 31 storms, 13 being typhoons (in this region, hurricanes are called typhoons). This makes the western Pacific season slightly above the 1981-2010 average of 26 named storms. The ACE index for the Western Pacific, however,  stands at 268.3 – about 88% of the 1981-2010 average of 302.

Typhoons such as Lekima, Usagi, Fransico and of course Super Typhoon Haiyan(Yolanda) will be recorded in the 2013 history book.  A super typhoon is a typhoon whose winds exceed 150 mph, equivalent to a Category 4 or 5 hurricane on the Saffir-Simpson scale.

What has contributed to the strong activity seen in the western Pacific this season? A combination of the right ingredients is the answer. A tropical cyclone needs favorable conditions, such as moisture, warm sea surface temperatures, and lack of wind shear in the upper atmosphere in order to aid development. Based on the activity in the western Pacific, it is likely that those conditions were present much of the season.

The 2013 tropical cyclone season was bittersweet for many; those in the Atlantic were glad for a quiet season while many in the western Pacific were forced to make preparations all season. Our prayers are with those affected by these forces of nature.

Visit Cyclone Center to classify many storms including those past storms that formed in the western Pacific, such as: Supertyphoon Dale (1996), Super Typhoon Herb (1996), Typhoon Faxai (2001), Super Typhoon Mike(1990) and more.

– Davanna G. Saunders is an undergraduate student in Atmospheric Sciences at the University of North Carolina at Asheville.  She recently joined the Cyclone Center team as a classifier and contributor to our social media.

Hurricane Katrina and the Intensifying Coastal Threat

This week Cyclone Center introduces Hurricane Katrina (2005) as one of our featured storms.  This is the 8th anniversary of Katrina’s assault on the northern Gulf of Mexico coast.  The city of New Orleans, despite a massive system of protective levees and pumps, lost over 1500 souls, almost all from drowning when water flooded about 80% of the city.  Since then,  millions of dollars have been spent on the repair and upgrade of the levee system in and around metro New Orleans.  Are they ready for the next one?

“We’ll be absolutely ready for it,” said U.S. Army Corps communications officer Wade Habshey in a recent Discovery News article. “What we have in place now can withstand a Katrina-level storm.”

New Orleans flooding caused by 60 kt. winds, 10-14 ft. storm surge. Category-5 values: 140 kt winds, 25-35 ft. storm surge.

But what exactly is a “Katrina-level” storm?  Winds in downtown New Orleans rarely exceeded minimal hurricane force at the peak of the event.  Storm surge and the strongest winds from the weakening Katrina were focused well to the east in coastal Mississippi.  And yet levees failed, water flooded significant portions of the city, and over 1,500 perished.

An even bigger concern in the long-term are geological changes occurring in the area; coastal portions of Louisiana are sinking into the ocean as climate-forced sea levels continue to rise and land areas sink.  This exacerbates the threat of  hurricanes for a region that experiences one on average every couple of years.  Many climate scientists now believe that hurricanes will be stronger on average in the future as the ocean, which provides the fuel for the storms, continues to warm.

What more should be done?  Government officials exude confidence that the improvements to the levy system will hold up, but we’ve heard that story before.  Claims were made soon after Katrina that the levee system was designed to withstand a Category-3 storm , not something like “Katrina’s strength”.  We’ve already seen that Katrina wasn’t even a hurricane in New Orleans – what happens when a real Category-4 or 5 storm hits the area?  We can only hope that residents will have left, because it’s a very good bet that there will be little dry land to stand on.

– Chris Hennon is part of the Cyclone Center Science Team and Associate Professor of Atmospheric Sciences at the University of North Carolina at Asheville

New Developments on Tropical Cyclones and Climate Change

One of the goals of the Cyclone Center project is provide a more definitive answer on how tropical cyclones (TCs) have been responding to the dramatic changes that our climate is undergoing.  It is difficult for meteorologists to determine how strong tropical cyclones are getting because we rarely observe them directly, relying primarily on satellite data to give us a decent estimate of the wind speeds.  But as you can imagine, it is very hard to determine the maximum winds in a hurricane when you are in the hurricane itself, let alone flying more than 22,000 miles above it!  Our record of tropical cyclones is by no means nailed down.