What is the El Niño Southern Oscillation? More conveniently known as ENSO, it is the planet’s largest source of natural climate variability on interannual time scales. ENSO describes the interaction between ocean and atmosphere in the equatorial Pacific, but the results of this interaction are global, and can last for many months. There is a good level of ENSO awareness in our industry, such as that warm phases of the oscillation (El Niño) tend to suppress Atlantic hurricane activity, and that cool phases (La Niña) tend to enhance it. But how was ENSO discovered? And how does it work?
If we’ve learned anything about forecasts and predictions (pick any recent event, sporting, political etc.) they give an indication of the situation, but cannot predict the absolute outcome, and surprises can most definitely happen. We are into the first weeks of the North Atlantic hurricane season, which officially runs for six months from June 1 to November 30, and a variety of forecasting groups and agencies have issued preseason forecasts. Continue reading
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Advances both in the collection of data and computational strength have enabled more precise and comprehensive analytics than were previously possible, thus allowing a more complete and accurate risk profile.
The more you know about risk and exposure, the more they can be managed. Unmanaged or undermanaged, risks, and exposures can become problems and even turn tragic or fatal.
Global insured losses from catastrophes totaled $37 billion in 2015 according to Swiss Re’s most recent Sigma Study. The 2015 figure, at just over half the inflation-adjusted previous 10-year average of $62 billion in insured catastrophe losses, was substantially tied to a quiet Atlantic hurricane season.
“The relatively low level of losses was largely due to another benign hurricane season in the US. El Niño in 2015 contributed to weather patterns deviating from average climate norms,” said the Swiss Re report.
(Re)insurers’ financial results for the past two years have been dotted with the phrase “benign catastrophe losses,” demonstrating how they have benefitted from quiet Atlantic storm conditions producing below-average claims activity.
That period of below-average catastrophe losses for (re)insurers may be coming to an end as researchers and forecasters are pointing toward a more active Atlantic hurricane season for 2016.
When (not if) catastrophe losses do return to their 10-year average, that’s $25 billion across somebody’s balance sheet. What might the 2016 Atlantic hurricane season hold for the U.S. and those who insure it?
With ports lining the U.S. coast from Texas to New York, even one landfall could wreak havoc on marine activities and infrastructure as the country moves into the winter holiday and heating oil seasons.
More Active Season?
While 2015 saw only 11 named storms with just four hurricanes, early indications suggest that the 2016 season will exceed those totals.
An April 14 update from the Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) said that the current El Nino conditions, known to inhibit hurricane activity, are likely to abate.
El Niño is dissipating and NOAA’s Climate Prediction Center is forecasting a 70 percent chance that La Niña—which favors more hurricane activity—will be present during the peak months of hurricane season, August through October.
“Nearly all models predict further weakening of El Niño, with a transition to ENSO-neutral likely during late spring or early summer 2016. Then, the chance of La Niña increases during the late summer or early fall,” the Center said in its update.
The Colorado State University Tropical Meteorology Project issued a forecast that included an estimated 12 named storms and five hurricanes, again greater than observed 2015 totals.
The Weather Company’s Professional Division issued a report stating the 2016 Atlantic Hurricane season would be he most active since 2012. This report forecasts 14 named storms, eight hurricanes, and three major hurricanes, more than the 30-year historical average of 12 named storms, six hurricanes, and three major hurricanes, according to The Weather Channel.
Most recently, NOAA followed its earlier report on El Nino with its annual Atlantic Hurricane Forecast, stating that this year’s hurricane season will see closer to Normal activity after three slow years.
“A near-normal prediction for this season suggests we could see more hurricane activity than we’ve seen in the last three years, which were below normal,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center.
The NOAA forecast predicts a 70% likelihood of 10 to 16 named storms, of which 4 to 8 could become hurricanes and 1 to 4 major hurricanes (Category 3, 4, or 5). In addition to a near-normal season being most likely with a 45% chance, there is also a 30% chance of an above-normal season and a 25% chance of a below-normal season.
Another ominous harbinger was the formation of tropical storm Colin on June 5—the earliest third storm on record in the Atlantic basin. Colin then made landfall on June 6 along Florida’s Big Bend with maximum sustained winds of 50 mph—the first named storm to make landfall in Florida since Andrea in 2013.
Earlier this year, Hurricane Alex became only the second hurricane on record to form in the month of January, sweeping through The Azores as a tropical storm.
Prepare for the Worst
The insurance sector has been substantially re-shaped since the last large catastrophe loss—by M&A, the influx of new capital—meaning new people, new relationships, even new claims procedures and personnel
It’s an entirely new landscape, entirely untested—how will it respond when a catastrophe hits and claims and losses mount?
From first responders to catastrophe modelers, one piece of advice never changes—be prepared.
That means understanding your exposures and accumulations and owning your own view of risk.
You can’t control or avoid catastrophes, but you can manage and mitigate their effects. Being prepared is the first step.
Sports fans around the world have witnessed impressive winning streaks throughout history. After capturing two consecutive UEFA European Championships (2008, 2012) and a World Cup championship (2010), the Spanish National Football Team entered the 2014 World Cup in Brazil as the top-ranked squad in international competition. The dominant Spaniards were among the international sportsbooks’ favorites to bring home the trophy once again.
Instead, surprising defeats at the hands of the Netherlands and Chile eliminated Spain at the group stage. Spain’s streak of dominance came to a sudden end, marking the earliest World Cup exit for a defending champion since 1950.
From a meteorological perspective, the United States is currently riding its own streak: ten Atlantic hurricane seasons without a major hurricane (category 3 or above) making landfall, the longest such stretch in recorded history. With another hurricane season upon us, many will be keeping a keen eye on the Atlantic this summer to see if this impressive streak will continue.
Global forecasting groups, such as Colorado State University and Tropical Storm Risk, have issued their tropical storm and hurricane activity forecasts for the 2016 Atlantic hurricane season. Christopher Allen of the RMS Event Response team has authored an excellent summary of their forecasts in the RMS 2016 North Atlantic Hurricane Season Outlook published this week on RMS.com.
You can also listen to my summary of the season’s forecasts during my talk to AM Best TV’s John Weber. In summary, most forecasts are predicting anywhere between near-average to above-average activity in the Atlantic basin, reflecting conflicting signals in the key indicators that influence hurricane formation.
Will we have increased hurricane activity?
One factor that may support increased hurricane activity this season is the anticipated state of the El Niño-Southern Oscillation, or ENSO. As reported on this blog several months ago, many ENSO forecasts project a transition out of last year’s historic El Niño phase into a La Niña phase, which is historically more favorable for hurricane development. Wind shear, detrimental to tropical cyclone formation, typically is reduced in the Atlantic basin during La Niña phases of ENSO.
Mid-May 2016 observations and model forecasts of ENSO, based on the NINO3.4 index, through March 2017. Positive values correspond with El Niño, while negative values correspond with La Niña. Source: International Research Institute for Climate and Society
Conversely, some forecasts predict a cooling of Atlantic sea surface temperatures (SSTs), which would oppose any support provided by a forecasted La Niña and reduce the potential for an active hurricane season. This cooling has been driven by a lengthened positive phase of the North Atlantic Oscillation (NAO), which causes stronger than normal trade winds in the tropical North Atlantic and upwelling of deeper cold ocean water near the surface.
February-April 2016 sea level pressure anomalies in the North Atlantic Ocean (hPa, anomalies with respect to 1981-2010 climatology). Anomalously high pressure evident in the Azores and the mid-latitude North Atlantic signals a positive phase of the NAO. Source: National Centers for Environmental Prediction Monthly Reanalysis (Kalnay, E. and Coauthors, 1996: The NCEP/NCAR Reanalysis 40-year Project. Bull. Amer. Meteor. Soc., 77, 437-471).
The Atlantic Multidecadal Oscillation may also be transitioning into a prolonged phase detrimental to tropical cyclone development, a theory often mentioned on this blog, although one that is still debated in the scientific community.
If considered in isolation, La Niña conditions and cooling Atlantic SSTs exert conflicting influences on Atlantic tropical cyclone development. However, forecasts contain key caveats that will ultimately determine this season’s activity:
- Although a transition into a La Niña phase is widely anticipated, a late arrival would limit its ability to support development in the basin.
- Further, forecasts of Atlantic sea surface temperature during August and September, the peak of hurricane season, remain conflicted.
Does the season’s early storm activity signify more activity?
Forecasts predicting above-average basin activity are understandable, given the early activity observed prior to the season’s official start. Tropical Storms Bonnie and Colin both formed before the second week in June, bringing heavy rainfall to South Carolina and the Gulf coast of Florida, respectively. Bonnie and Colin followed Hurricane Alex, the first January hurricane since 1938.
Bonnie’s formation marked the first time since 2012 that two named storms developed before June 1, the official start of hurricane season. The 2012 season ended with 19 total named storms, the third-most on record, including Superstorm Sandy, which caused more than $18 billion in insured losses.
Would the industry be prepared for the next major hurricane landfall? According to Fitch, the answer is yes: insurers and reinsurers in 18 coastal U.S. states would be equipped to handle one major event this season, although this resiliency has not been recently tested. More worrying, though, are the prospects of a large tail event or even multiple landfalling events, which may be supported by the right combination of oceanic and atmospheric influences.
With the hurricane season now officially underway, we will watch, wait and see how the season’s activity unfolds over the next few months. What is certain, though, is that streaks are made to be broken. It’s just a matter of when.
It’s not often that you see an Atlantic hurricane making headlines in January. Subtropical Storm Alex was named by the National Hurricane Center on January 13, 2016 and strengthened into a hurricane one day later. Although Alex ultimately exhibited a short lifespan and caused minimal damage, the storm has the scientific and risk management communities talking about what it might mean for the 2016 hurricane season and the near-term state of the basin.
In October, we discussed the below-average rate of landfalling hurricanes in recent Atlantic seasons, the influence of the Atlantic Multidecadal Oscillation (AMO) on basin activity phase shifts, and how shifts are reflected within the RMS Medium Term Rates (MTR) methodology.
In response to recent quiet seasons, scientists hypothesized about a possible shift in Atlantic hurricane frequency, one that would end the observed active Atlantic hurricane regime that began around the mid-1990s. Central to these discussions was commentary published in the October 2015 edition of Nature Geosciences, suggesting that AMO is entering a negative phase detrimental to Atlantic cyclogenesis.
However, recent peer-reviewed research highlights how sensitive the historical record is to the precise definitions used for hurricane activity. An article soon to be published in the Bulletin of the American Meteorological Society argues that the definition of the recent “hurricane drought,” based on the number of U.S. major landfalling hurricanes, may be arbitrary. This research finds that small adjustments to intensity thresholds used to define the drought, as measured by maximum winds or minimum central pressure, would shorten the drought or eliminate it completely.
In its most recent annual review of the Atlantic basin, RMS recognized that the anticipated atmospheric conditions for the upcoming season present a unique challenge. The latest forecasts suggest that the influence of the El Niño-Southern Oscillation (ENSO), another key indicator of hurricane frequency, may oppose the influence of a negative AMO.
ENSO represents fluctuating ocean temperatures in the equatorial Pacific that influence global weather patterns. El Niño, or a warm phase of ENSO, is associated with increased Atlantic wind shear that historically inhibits tropical cyclone development in the basin. La Niña, or a cool phase of ENSO, is associated with decreased Atlantic wind shear that historically supports tropical cyclone development.
Illustrations of the three main phases of the El Niño-Southern Oscillation. Source: Reef Resilience
ENSO has played an important role in influencing tropical cyclone activity in recent Atlantic hurricane seasons, particularly in 2015. Last season, the basin experienced one of the strongest El Niño phases on record, which contributed to below-average activity and well-below normal Accumulated Cyclone Energy (ACE), an index quantifying total seasonal duration and intensity. .
Looking ahead, the latest ENSO forecasts predict a shift out of the current El Niño phase over the next few months towards a more neutral or even a La Niña phase. The extent to which these conditions impact hurricane activity for 2016 is still to be determined; however, these conditions historically support above average activity.
Mid-February 2016 observations and model forecasts of ENSO, based on the NINO3.4 index, through December 2016. Positive values correspond with El Niño, while negative values correspond with La Niña. Sharp shifts from El Niño to La Niña are not unprecedented: La Niña conditions quickly followed the very strong El Niño of 1997-98. Source: International Research Institute for Climate and Society
The concurrence of potential changes in both the AMO and ENSO represent a unique period for 2016:
- A negative AMO phase may act to suppress Atlantic hurricane activity in 2016.
- A neutral or La Niña ENSO phase may act to enhance Atlantic hurricane activity in 2016.
These signals also have a range of potential implications on the RMS MTR forecast. Thus, RMS will spend the upcoming months closely engaging both the scientific community and market regarding this unique state of the basin and its potential forward-looking implications on hurricane activity. Modelers will evaluate the influence and sensitivities of new data, new methods, and new science on the MTR forecast. During this time, RMS will communicate results and insights to the broader market across a variety of mediums, including at Exceedance in May.
This post was co-authored by Jeff Waters and Tom Sabbatelli.
The northwest Pacific is the most active tropical cyclone basin in the world, having produced some of the most intense and costly cyclone events on record. The 2015 typhoon season has been particularly active due to this year’s strong El Niño conditions.
Sea surface temperature in the equatorial Pacific Ocean. El Niño is characterized by unusually warm temperatures in the equatorial Pacific. (NOAA)
The unpredictable nature of the El Niño phenomenon, which affects the genesis and pathway of tropical cyclones, and the complexity of tropical cyclone systems underscore the need to fully understand typhoon risk—particularly in Japan where exposure concentrations are high. Catastrophe models, such as the forthcoming RMS® Japan Typhoon Model, using a basin-wide event set to model the three key correlated perils—wind, inland and coastal flood—are more effective in enabling firms to price and manage the ever-evolving exposures that are at risk from this multifaceted peril.
The Significance of September
Peak typhoon season in the northwest Pacific basin is between July and October, but it’s September that typically sees the highest number of strong category 3-5 typhoons making landfall: eight of the top ten greatest insured losses from northwest Pacific tropical cyclones since 1980 all occurred in September.
In September, during El Niño years, Guam is significantly more susceptible to a higher proportion of landfalls, and Japan and Taiwan experience a slight increase due to the genesis and pathway of tropical cyclones. While wind is the primary driver of tropical cyclone loss in Japan, inland and coastal flooding also contribute substantially to the loss.
In September 1999, Typhoon Bart caused $3.5 billion in insured losses due to strong winds, heavy rainfall, and one of the highest storm surges on record at the time. The height of the storm surge reached 3.5 meters in Yatushiro Bay, western Japan, and destroyed coastal defences, inundating vast areas of land.
Five years later in September 2004, Typhoon Songda caused insured losses of $4.7 billion. Much of the loss was caused by rain-related events and flooding of more than 10,000 homes across South Korea and Japan in the Chugoku region, western Honshu.
Table 1 Top 10 Costliest Tropical Storms in Asia (1980-2014):
|Date||Event||Affected Area||Maximum Strength (SSHWS)||Insured Loss ($mn)|
|Sept, 1991||Mireille||Japan||Cat 4||6,000|
|Sept, 2004||Songda||Japan, South Korea||Cat 4||4,700|
|Sept, 1999||Bart||Japan, South Korea||Cat 5||3,500|
|Sept, 1998||Vicki||Japan, Philippines||Cat 2||1,600|
|Oct, 2004||Tokage||Japan||Cat 4||1,300|
|Sept 2011||Roke||Japan||Cat 4||1,200|
|Aug – Sept, 2004||Chaba||Japan, Russia||Cat 5||1,200|
|Sept, 2006||Shanshan||Japan, South Korea||Cat 4||1,200|
|Sept, 2000||Saomai||Japan, South Korea, Guam, Russia||Cat 5||1,100|
|Sept, 1993||Yancy||Japan||Cat 4||980|
September 2015 – A Costly Landfall for Japan?
This September we have already seen Tropical Storm Etau, which brought heavy rains to Aichi Prefecture on Honshu Island causing immense flooding to more than 16,000 buildings, and triggered dozens of landslides and mudslides.
The increased tropical cyclone activity in the northwest Pacific this year has been attributed to an El Niño event that is forecast to strengthen further. Two factors linked to El Niño events suggest that this September could still see a costly landfall in Japan:
- El Nino conditions drive the formation of tropical cyclones further eastward, increasing the travel times and distances of typhoons over water, giving rise to more intense events.
- More northward recurving of storms produces tropical cyclones that track towards Japan, increasing the number of typhoons that could make landfall.
Combined, the above conditions increase the number of strong typhoons that make landfall in Japan.
Damaging Typhoons Don’t Just Occur In September
Damaging typhoons don’t just occur in September or El Niño years – they can happen under any conditions.
Of the ten costliest events, only Typhoon Mireille in 1999 and Typhoons Songda, Chaba, and Tokage, all of which made landfall in 2004, occurred during El Niño years
Look out for more information on this topic in the RMS paper “Effects of the El Niño Southern Oscillation on Typhoon Landfalls in the Northwest Pacific”, due to be published in October.
The idea of a “super” El Niño has become a hot topic, with many weighing in. What’s drawing all of this attention is the forecast of an unusually warm phase of the El Niño Southern Oscillation (ENSO). Scientists believe that this forecasted El Niño phase could be the strongest since 1997, bringing intense weather this winter and into 2016.
Anomalies represent deviations from normal temperature values, with unusually warm temperatures shown in red and unusually cold anomalies shown in blue. Source: NOAA
It’s important to remember the disclaimer “could.” With all of the information out there I thought it was a good time to cull through the news and try to separate fact from fiction regarding a “super” El Niño. Here are some of the things that we know—and a few others that don’t pass muster.
Fact: El Niño patterns are strong this year
Forecasts and models show that El Niño is strengthening. Meteorologist Scott Sutherland wrote on The Weather Network that there is a 90 percent chance that El Niño conditions will persist through winter and an over 80 percent chance that it will still be active next April. Forecasts say El Niño will be significant, “with sea surface temperatures likely reaching at least 1.5oC (2.7oF) above normal in the Central Pacific – the same intensity as the 1986/87 El Niño (which, coincidentally also matches the overall pattern of this year’s El Niño development).”
A “strong” El Niño is identified when the Oceanic Niño Index (ONI), an index tracking the average sea surface temperature anomaly in the Niño 3.4 region of the Pacific Ocean over a three-month period, is above 1.5oC. A “super” El Niño, like the one seen in 1997/98, is associated with an ONI above 2.0oC. The ONI for the latest May-June-July period was recorded as 1.0oC, identifying El Niño conditions present as of “moderate” strength with the peak anomaly model forecast consensus around 2.0oC.
Fiction: A “super” El Niño is a cure-all for drought plaguing Western states
Not necessarily. The conventional wisdom is that a “super” El Niño means more rain for drought-ravaged California, and a potential end to water woes that have hurt the state’s economy and even made some consider relocation. But, we don’t know exactly how this El Niño will play out this winter.
Will it be the strongest on record? Will it be a drought buster?
Some reports suggest that a large pool of warm water on the northeast Pacific Ocean and a persistent high-pressure ridge over the West Coast of the U.S., driven by dry, hot conditions, could hamper drought-busting rain.
The Washington Post has a good story detailing why significant rain from a “super” El Niño might not pan out for the Golden State.
And if the rain does come, could it have devastating negative impacts? RMS’ own Matthew Nielsen recently wrote an article in Risk and Insurance regarding the potential flood and mudslide consequences of heavy rains during an El Niño.
Another important consideration is El Niño’s impact on the Sierra snow pack, a vital source for California’s water reserves. Significant uncertainty exists around when and where snow would fall, or even if the warm temperatures associated with El Niño would allow for measureable snow pack accumulation. Without the snow pack, the rainwater falling during an El Niño would only be a short-term fix for a long-term problem.
Fact: It’s too early to predict doomsday weather
There are a vast number of variables needed to produce intense rain, storms, flooding, and other severe weather patterns. El Niño is just one piece of the puzzle. As writer John Erdman notes on Weather.com, “El Niño is not the sole driver of the atmosphere at any time. Day-to-day variability in the weather pattern, including blocking patterns, forcing from climate change and other factors all work together with El Niño to determine the overall weather experienced over the timeframe of a few months.”
Fiction: A “super” El Niño will cause a mini ice age
This theory has appeared around the Internet, on blogs and peppered in social media. While Nature.com reported some similarities between ice age and El Niño weather patterns to an ice age more than a decade ago you can’t assume we’re closing in on another big chill. The El Niño cycle repeats every three to 10 years; shifts to an ice age occur over millennia.
What other Super El Niño predictions have you heard this year? Share and discuss in the comments section.
While the Atlantic hurricane season is expected to be below average this year, the North Pacific is smashing records. Fuelled by the strengthening El Niño conditions, the Accumulated Cyclone Energy (ACE)—used to determine how active a season is by measuring the number of storms, their duration and their intensity—continues to set unprecedented highs for the 2015 season. According to Dr. Philip Klotzbach, a meteorologist at Colorado State University, the North Pacific ACE is 30% higher for this time of year than at any other time since 1971.
To date, there have been 12 named Northwest Pacific storms, of which three have strengthened to Category 5 super-typhoon status, and two have strengthened to Category 4 typhoon. Typhoon Maysak was the first of the super-typhoons to develop and is reportedly the strongest known storm to develop so early in the season—it eventually passed over the northern Philippines in late March as a tropical depression. Super-Typhoons Noul and Dolphin followed in quick succession in May, with Noul scraping the northern tip of the Philippines, and Dolphin tracking directly in-between the islands of Guam and Rota.
China is recuperating after getting hit by Typhoons Linfa and Chan-Hom only days apart. Linfa made landfall on July 9, bringing strong winds and heavy rainfall to Hong Kong and southern China’s Guangdong province. Two days later, Chan-Hom brought tropical storm-force winds and heavy rainfall to Taiwan and the Japanese Ryukyu Islands before briefly making landfall as a weak Category 2 storm over the island of Zhujiajian in the Zhejiang province. Prior to landfall, Chan-Hom was anticipated to pass over Shanghai, but swung northeast and missed China’s largest city by 95 miles. Despite this near-miss, Chan-Hom still stands as one of the strongest typhoon to have passed within 100 miles of the city in the past 35 years.
Typhoon Nangka, the first typhoon to hit Japan this season, intensified to a Category 4 storm before ultimately making landfall as a Category 1 storm over the Kochi Prefecture on Shikoku Island, Japan. Although Nangka’s strength at landfall was weaker than originally forecast, the high level of moisture within the system caused significant rainfall accumulations, leading to widespread flooding and the threat of landslides. While there was an initial fear of storm surge in Osaka Bay, there has been limited damage reported.
This record-breaking season has been strongly influenced by the strengthening El Niño conditions, which can be characterised by several physical factors including warmer sea surface temperatures, a higher number of Category 3-5 typhoons, and a greater proportion of typhoons that follow recurring or northward tracks—all of which have been evident so far this year.
With El Niño conditions expected to continue intensifying the storms to come, this season highlights the necessity for a basin-wide multi-peril model, connected through an event-based approach and correlated geographically through a basin-wide track set. These will be featured in the new Japan typhoon model, due out next year, followed by the South Korea and Taiwan typhoon models. The RMS China typhoon models currently models typhoon wind, inland flood and surge for a correlated view of risk.
As El Niño conditions continue to bolster the Northwest Pacific typhoon season, RMS will be monitoring the situation closely. In September, RMS will be releasing a white paper on ENSO in the West Pacific that will provide further insight into its affects.
RMS recently released its 2015 North Atlantic Hurricane Season Outlook. So, what can we expect from this season, which is now underway?
2015 season could be the 10th consecutive year without a major landfalling hurricane over the United States.
The 2014 season marked the ninth consecutive year that no major hurricane (Category 3 or higher) made landfall over the United States. Although two named storms have already formed in the basin so far this year, Tropical Storm Ana and Tropical Storm Bill, 2015 looks to be no different. Forecast groups are predicting a below-average probability of a major hurricane making landfall over the U.S. and the Caribbean in the 2015 season.
The RMS 2015 North Atlantic Hurricane Season Outlook highlights 2015 seasonal forecasts and summarizes key meteorological drivers in the Atlantic Basin.
Forecasts for a below-average season can be attributed to a number of interlinked atmospheric and oceanic conditions, including El Niño and cooler sea surface temperatures.
So what factors are driving these predictions? A strong El Niño phase of the El Niño Southern Oscillation (ENSO) is a large factor, as Jeff Waters discussed previously.
Another key factor in the lower forecast numbers is that sea surface temperatures (SSTs) in the tropical Atlantic are quite a bit cooler than previous years. SSTs higher than 80°F (26.5°C) are required for hurricane development and for sustained hurricane activity, according to NOAA Hurricane Research Division.
Colorado State University (CSU)’s June 1st forecast is calling for 8 named storms, 3 hurricanes, and 1 major hurricane this season, with an Accumulated Cyclone Energy (ACE) index—used to express activity and destructive potential of the season—of 40. This is well below the 65- and 20-year averages, both over 100.
However, all it takes is one significant event to cause significant loss.
Landfalls are difficult to predict more than a few weeks in advance, as complex factors control the development and steering of storms. Despite the below-average number of storms expected in the 2015 season, it only takes one landfalling event to cause significant loss. Even if the activity and destructive energy of the entire season is lower than previous years, factors such as location and storm surge can increase losses.
For example, Hurricane Andrew made landfall as a Category 5 storm over Florida in 1992, a strong El Niño year. Steering currents and lower-than-expected wind shear directed Andrew towards the coastline of Florida, making it the fourth most intense landfalling U.S. hurricane recorded. Hurricane Andrew also holds the record for the fourth costliest U.S. Atlantic hurricane, with an economic loss of $27 billion USD (1992).
Sometimes, a storm doesn’t even need to be classified as a hurricane at landfall to cause damage and loss. Though Superstorm Sandy had Category 1 hurricane force winds when it made landfall in the U.S., it was no longer officially a hurricane, having transitioned to an extratropical storm. However, the strong offshore hurricane force winds from Sandy generated a large storm surge, which accounted for 65 percent of the $20 billion insured losses.
While seasonal forecasts estimate activity in the Atlantic Basin and help us understand the potential conditions that drive tropical cyclone activity, a degree of uncertainty still surrounds the exact number and paths of storms that will form throughout the season. For this reason, RMS recommends treating seasonal hurricane activity forecasts with a level of caution and to always be prepared for a hurricane to occur.
Today the insurance industry gears up for the start of another hurricane season in the Atlantic Basin. Similar to 2014, most forecasting agencies predict that 2015 will yield at- or below-average hurricane activity, due largely in part to the anticipated development of a strong El Niño phase of the El Niño Southern Oscillation (ENSO).
Unlike 2014, which failed to see the El Niño signal that many models projected, scientists are more confident that this year’s ENSO forecast will not only verify, but could also be the strongest since 1997.
Earlier this month, the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) reported weak to moderate El Niño conditions in the equatorial Pacific, signified by above-average sea surface temperatures both at and below the surface, as well as enhanced thunderstorm activity.
According to the CPC and the International Research Institute for Climate and Society, nearly all forecasting models predict El Niño conditions—tropical sea surface temperatures at least 0.5°C warmer than average—to persist and strengthen throughout 2015. In fact, the CPC estimates that there is approximately a 90% chance that El Niño will continue through the summer, and better than a 80% chance it will persist though calendar year 2015.
Model forecasts for El Niño/La Niña conditions in 2015. El Niño conditions occur when sea surface temperatures in the equatorial central Pacific are 0.5°C warmer than average. Source (IRI)
Not only is the confidence high for the tropical Pacific to reach El Niño levels in the coming months, several forecasting models predict possible record-setting El Niño conditions this fall. Since 1950, the record three-month ENSO value is 2.4°C, which occurred in October-December 1997.
Even if conditions verify to the average model projection, forecasts suggest at least a moderate El Niño event will take place this year, which could affect many parts of the globe via atmospheric and oceanic teleconnections.
Impacts of El Niño conditions on global rainfall patterns. Source (IRI)
In the Atlantic Basin, El Niño conditions tend to increase wind speeds throughout the upper levels of the atmosphere, which inhibit tropical cyclones from forming and maintaining a favorable structure for strengthening. It can also shift rainfall patterns, bringing wetter-than-average conditions to the Southern U.S., and drier-than-average conditions to parts of South America, Southeast Asia, and Australia.
Despite the high probability of occurrence, it’s worth noting that there is considerable uncertainty with modeling and forecasting ENSO. First, not all is understood about ENSO. The scientific community is still actively researching its trigger mechanisms, behavior, and frequencies. Second, there is limited historical and observational data with which to test and validate theories, hence the source of ongoing discussion amongst scientists. Lastly, even with ongoing model improvements, it remains a challenge for climate models to accurately capture the complex interactions of the ocean and atmosphere, leading to small initial errors that can amplify quickly in the long term.
Regardless of what materializes with El Niño in 2015, it is worth monitoring because its teleconnections could impact you.