Tag Archives: El Nino

4 Facts About California’s “Hellastorm”

California is bracing for a major storm this week. Many schools are closed and residents are hunkering down in preparation for potential flooding. Not to be outdone by the East Coast, which has come up with monikers like “snowmageddon” and “snowpocalypse” for their recent storms, some are referring to it as the “hellastorm.”

Source: twitter.com/AllyNgSF

So, what’s the deal with the so-called “storm of the decade?”

It’s getting rainy and windy on the West Coast.

Estimates this morning are predicting 1 to 5 inches of rain from Northern California up to Washington, 1 to 2 feet of snow in the Sierra Nevada mountains, and wind gusts over 50 miles per hour in the interior regions.

It will happen again.

Storms like these are not uncommon, occurring once every 5 to 10 years. So we could experience another one before the end of the decade.

The drought is partially to blame.

While drought conditions are not a necessity for these types of events, they can increase the impact of flooding because the ground cannot absorb water fast enough. The same can occur when the sustained heavy rain falls on ground is already saturated.

The current rain came all the way from Hawaii.

Storms like this are dependent on many variables. In this case, the excessive rain and snowfall is being driven by the position of the jet stream and what’s known as the Pineapple Express, an atmospheric plume of tropical moisture that flows from the sub-tropics near Hawaii to the U.S. West Coast. It generally occurs during El Nino years, but in this case, forecast El Nino conditions did not fully develop. In other words, it’s a weak one.

UPDATE: Northern California has gotten more than 8 inches of precipitation so far. Sustained winds were forecast to be up to hurricane force (70 to 80 mph) in the local mountains and up to 100 mph in the higher elevations across the Sierra summit. A wind gust to 147 mph was recorded at high altitude peak near Lake Tahoe, that had surfers catching 7-foot waves on the lake!

4 Things You Didn’t Know about Why it’s So Darn Cold!

The U.S. is currently experiencing a bout of cold weather in several regions, raising the question: are we in for another polar vortex winter like the bone-chiller we had last year? And if so, why? Here are four things you might not know about the current extreme cold weather streak in the U.S.

The current cold weather isn’t quite another polar vortex in the U.S. – yet. 

The polar vortex is a region of Arctic air that rotates around the North Pole in the Northern Hemisphere, trapping and containing the frigid air in its circulation. Every now and then, parts of the rotating pocket of cold air break off into smaller pockets that mobilize southward into regions like North America, bringing with them below-normal temperatures and stormy conditions.

Figure 1: General image of the Polar Vortex. Source: Accuweather.

As of now, the U.S. is not experiencing full-blown polar vortex effects; only part of the big Arctic air pocket has been displaced into the U.S., so it is more accurate to say that the country is experiencing an outbreak of Arctic air. Last year, most of the U.S. experienced exceptionally cold and snowy conditions, particularly east of the Rockies, as a result of the polar vortex. Early seasonal outlooks for this winter have indicated that this type of severe weather pattern is unlikely to repeat, though one cannot rule out more Arctic outbreaks like this one.

You can blame Super Typhoon Nuri in Japan.

Many of the world’s largep-scale climate systems and atmospheric patterns are interconnected. You may not know it, but Super Typhoon Nuri, which impacted Japan earlier this month as one of 2014’s strongest tropical cyclones, has played a key role influencing this recent cold air outbreak. Cold air from the polar vortex is separated from warm air by what’s called the polar jet stream; depending on atmospheric conditions, this jet stream can look flat or wavy. Big storms, like Nuri, can alter the jet stream’s shape, pushing parts further north (creating a “ridge”) or south (creating a “trough”) than normal.

Figure 2: Example of a jet stream’s ridges and troughs. Source: Skeptical Science

In Nuri’s case, remnants of the storm pushed part of the polar jet stream north over Alaska, creating a strong ridge. This in turn caused a deep trough to develop over much of the central U.S., making way for Arctic air associated with the polar vortex to flow into the lower 48. It is common for storms to affect the jet stream’s shape, but because Nuri was so intense, it influenced the jet stream enough to trigger a prolonged period of unseasonably chilly weather from North Dakota to New York.

Climate change could have something to do with it. 

Our climate is changing, but there are differing views on how climate change affects the polar vortex. Some posit that a warming climate may lead to more frequent cold air outbreaks due to increased sea ice melting. This would allow more energy to move into the atmosphere and weaken the jet streams, thereby increasing the likelihood of cold Arctic air escaping southward into regions like North America and Europe.

©iStock.com/SeppFriedhuber

Other scientists argue that cold air outbreaks are common and part of the natural variation of the climate. They also suggest that it is extremely hard to link a massive, long-term shift in climate (for example, global warming) to individual weather events. It’s also worth noting that the U.S. takes up less than 3 percent of the Earth’s surface, so even though this region is experiencing cold air outbreaks, there are other parts of the world experiencing record heat at the same time.

Other parts of the country could be in for abnormal weather due to El Niño.

Also affecting this winter’s temperatures is the weak central El Niño being forecast; this series of climatic changes happens when the tropical Pacific Ocean, particularly the central and eastern regions, becomes warmer than average. As the ocean gets warmer with respect to its average temperature, the stronger the El Niño signal. El Niño often results in changes to precipitation and temperature patterns throughout the world, including North America, and especially in the winter.

The most common impact is wetter-than-average conditions along the Gulf Coast, warmer-than-average conditions in the Northern Rockies and Pacific Northwest, drier-than-average conditions in the Ohio Valley, and, to a lesser extent, wetter-than-average conditions in California and the southwestern U.S. The weak El Niño forecast means that these impacts are possible, but not likely to be extreme.

What to expect this 2014-2015 Europe Winter Windstorm Season

When it rains in Sulawesi it blows a gale in Surrey, some 12,000 miles away? While these occurrences may sound distinct and uncorrelated, the wet weather in Indonesia is likely to have played some role in the persistent stormy weather experienced across northern Europe last winter.

Weather events are clearly connected in different parts of the world. The events of last winter are discussed in RMS’ 2013-2014 Winter Storms in Europe report, which provides an in-depth analysis of the main 2013-2014 winter storm events and why it is difficult to predict European windstorm hazard due to many factors, including the influence of distant climate anomalies from across the globe.

Can we predict seasonal windstorm activity during the 2014-2015 Europe winter windstorm season?

As we enter the 2014-2015 Europe winter windstorm season, (re)insurers are wondering what to expect.

Many consider current weather forecasting tools beyond a week to be as useful as the unique “weather forecasting stone” that I came across on a recent vacation.

I am not so cynical; while weather forecasting models may have missed storms in the past and the outputs of long-range forecasts still contain uncertainty, they have progressed significantly in recent years.

In addition, our understanding of climatic drivers that strongly influence our weather, such as the North Atlantic Oscillation (NAO), El Niño Southern Oscillation (ENSO), and the Quasi-Biennial Oscillation (QBO) is constantly improving. As we learn more about these phenomena, forecasts will improve, as will our ability to identify trends and likely outcomes.

What can we expect this season?

The Indian dipole is an oscillation in sea surface temperatures between the East and West Indian Ocean. It has trended positively since the beginning of the year to a neutral phase and is forecast to remain neutral into 2015. Indonesia is historically wet during a negative phase, so we are unlikely to observe the same pattern that was characteristic of winter 2013-2014.

Current forecasts indicate that we will observe a weak central El Niño this winter. Historically speaking this has led to colder winter temperatures over northern Europe, with a blocking system drawing cooler temperatures from the north and northeast.

The influence of ENSO on the jet stream is less well-defined but potentially indicates that storms will be steered along a more southerly track. Lastly, the QBO is currently in a strong easterly phase, which tends to weaken the polar vortex as well as westerlies over the Atlantic.

Big losses can occur during low-activity seasons

Climatic features like NAO, ENSO, and QBO are indicators of potential trends in activity. While they provide some insight, (re)insurers are unlikely to use them to inform their underwriting strategy.

And, knowing that a season may have low overall winter storm activity does not remove the risk of having a significant windstorm event. For example, Windstorm Klaus occurred during a period of low winter storm activity in 2009 and devastated large parts of southern Europe, causing $3.4 billion in insured losses.

Given this uncertainty around what could occur, catastrophe models remain the best tool available for the (re)insurance industry to evaluate risk and prepare for potential impacts. While they don’t aim to forecast exactly what will happen this winter, they help us understand potential worst-case scenarios, and inform appropriate strategies to manage the exposure.

2014 Atlantic Hurricane Season Update: Not Quite 2004

The 2014 Atlantic Hurricane Season is already half over, and with only five named storms in the books and El Niño conditions likely by late fall, all signs are pointing to a below-average season.

Over the last six weeks, organizations like Colorado State University (CSU) and the National Oceanic and Atmospheric Administration (NOAA) updated their seasonal outlooks with similar or slightly reduced numbers, attributing them to a variety of oceanic and atmospheric conditions acting to suppress activity, including cooler than normal sea surface temperatures, higher than normal sea level pressures, and stronger than normal wind shear.

Interestingly, the suppressed activity is not being attributed nearly as much to El Niño conditions as originally thought. Despite high likelihoods that the equatorial Pacific would warm to El Niño levels by late summer, observed El Niño Southern Oscillation (ENSO) conditions were neutral during the July and August period, according to the International Research Institute for Climate and Society.

Such observations have certainly impacted ENSO forecasts for the remainder of 2014 into 2015. As of September 4, the likelihood for El Niño conditions to form during the period from September to November dropped to 55% from a convincing 74% probability back in May. Despite this material reduction, most of the ENSO prediction models still forecast the onset of El Niño by early Fall, peaking during Northern Hemisphere winter 2014-2015 and lasting into the first few months of 2015.

Barring any late season surge in activity, this year will be a far cry from the busier seasons of the past, most notably the 2004 season. Like this year, 2004 was also impacted by weak, neutral El Niño conditions. However, the 2004 season was impacted by a rare type of storm known as Modoki El Niño in which unfavorable hurricane conditions are produced in the Pacific instead of the Atlantic Ocean, resulting in above average activity in the Atlantic.

The most notable U.S. hurricanes during the 2004 season were Hurricanes Charley, Frances, Ivan, and Jeanne. These four events damaged an estimated 2 million properties in Florida – approximately one in five houses – and caused more than $20 billion in insured losses throughout the U.S.

The strongest system to hit land that season was Hurricane Charley. The storm made landfall on the southwest coast of Florida on August 13 as a Category 4 hurricane, causing nearly $15 billion in economic damages – one of the most destructive hurricanes in U.S. history.

Just over three weeks later, Hurricane Frances, a large, slow-moving, but less-intense system made landfall on the east coast of Florida as a Category 2 storm with peak winds of 105 mph.

In early September, Hurricane Ivan developed just south of where Frances formed, intensifying quickly. Moving through warm ocean waters, the storm reached Category 5 strength three separate times before making landfall as a Category 3 hurricane along the Mississippi/Alabama border.

When Hurricane Jeanne made landfall in Stuart, Florida on September 26, it marked the second time in history that one state was impacted by four hurricanes in one season.

At this point 10 years ago, nine named storms had already formed in the basin, with six reaching hurricane status. In total, 2004 saw 15 named storms, nine of which became hurricanes, including 6 that reached major hurricane status (Category 3+).

While this hurricane season shares some common characteristics with the 2004 season, so far, 2014 has been relatively quiet while 2004 was the second costliest Atlantic hurricane season in history.

2014 Atlantic Hurricane Season Outlook: Are the Tides Beginning to Turn?

The 2014 Atlantic Hurricane Season officially kicked off this week (June 1), running through November 30. Coming off a hurricane season with the lowest number of hurricanes in the Atlantic Basin since 1983, will 2014 follow suit as a less active season? If so, is the Atlantic Basin officially signaling a shift out of an active phase of hurricane activity? Or will we revert back to the above-average hurricane numbers and intensities we’ve grown accustomed to over most of the last 20 years? And regardless of the season’s severity, what should be done to prepare?

Forecasting the 2014 Hurricane Season

Most forecasts to date, including those of Colorado State University and the National Oceanic and Atmospheric Administration (NOAA), are calling for an average to below-average season in terms of the number of named storms (8–13), hurricanes (3–6), and major hurricanes (0–3). The same holds true for the overall intensity forecasts, where projected seasonal values of Accumulated Cyclone Energy (ACE) range from just 55 to 84, compared to the average overall seasonal ACE of 101.8.

So what’s driving this outlook? Most forecasting organizations are attributing it to two major atmospheric drivers that have been known to suppress hurricane activity: the strong likelihood of an El Niño event developing this summer into the peak part of the season from July through October, and below-average sea surface temperatures in the Atlantic Basin’s Main Development Region (MDR).

Model forecasts for El Niño/La Niña conditions in 2014. El Niño and La Niña conditions occur when sea surface temperatures in the equatorial central Pacific are 0.5°C warmer than average and 0.5°C cooler than average, respectively.

Model forecasts for El Niño/La Niña conditions in 2014. El Niño and La Niña conditions occur when sea surface temperatures in the equatorial central Pacific are 0.5°C warmer than average and 0.5°C cooler than average, respectively.

El Niño conditions create stronger-than-normal upper-level winds, which inhibit storms from forming and maintaining a favorable structure for intensification. Similarly, below-average ocean temperatures in the MDR essentially reduce the energy available to fuel storms, making it difficult for them to develop and intensify.

However, low activity does not always translate into a decrease in landfalling hurricanes. Also, all it takes is one landfalling event to cause catastrophic losses. For example, 1992 was a strong El Niño year, yet Hurricane Andrew made landfall in Florida as a Category 5 storm, eventually becoming the fourth most intense U.S. landfalling hurricane recorded, and the fourth costliest U.S. Atlantic hurricane. Of course, while a landfalling storm like Andrew may have occurred during the last significant El Niño year, there’s no guarantee it will happen this season. The U.S. has not experienced a major landfalling hurricane since Hurricane Wilma in August of 2005. This eight-year drought is the longest in recorded U.S. history.

Preparing for Hurricane Season

Whether or not the 2014 Atlantic hurricane season is active, it is imperative to monitor and prepare for impending storms effectively to help reduce the effects of a hurricane disaster.

The NOAA National Hurricane Center provides several tips and educational guides for improving hurricane awareness, including forecasting tools that assess the potential impacts of landfalling hurricanes. This year, NOAA also offers an experimental mapping tool, as well as other new tools, to help communities understand their potential storm surge flood threat.

The RMS Event Response team provides real-time updates for all Atlantic hurricanes, among other global hazards, 24 hours a day, seven days a week. Similarly, when it comes to preparation, along with the essentials, such as bottled water, canned foods, and battery-powered flashlights, consider purchasing these ten items.

Are you ready for the 2014 Atlantic Hurricane season?