North Atlantic May Cough up Another Out of Season Tropical Cyclone this Week

Like pretty much everywhere else in the world ocean these days, and due primarily to a rampant injection of greenhouse gasses into the Earth’s atmosphere through fossil fuel burning, the North Atlantic is now considerably warmer than during the 19th and 20th Centuries…

Warming Waters and An Angry Jet Stream

That extra heat provides more available fuel for tropical storm and hurricane formation. It increases the top potential peak intensity of the most powerful storms. And it extends the period in which such tropical cyclones are capable of forming — for sea surface temperatures of at least 70-75 degrees Fahrenheit are often necessary to fuel such systems (please also see the present science on how climate change is impacting tropical cyclones).

(Sea surface temperatures in the North Atlantic now range between 1 and 7 degrees Celsius above average for most regions. These warmer than normal sea surfaces provide more fuel for storms even as they extend the period during which tropical storm and hurricane formation is possible. Image source: Earth Nullschool.)

But it’s worth noting that warm ocean waters are not the only ingredient that add to the potential for the formation and strengthening of these powerful storms. Instability and cloud formation are often necessary to seed such systems. And the more extreme warm and cold temperature anomalies associated with wavier Jet Stream patterns inject exactly this form of instability into the middle latitudes at a higher rate than was witnessed during past decades.

Due to its proximity both to a melting Greenland and to a rapidly warming Arctic, the North Atlantic is particularly vulnerable to the production of powerful swirls of warm and cold air. Warming tropics collide with the cold air producing pools of glacial freshwater melt and the enlarging meanders of the Northern Hemisphere Jet Stream. And it’s the proliferation of these unstable vortices forming over warming waters throughout the North Atlantic that may start to generate a more and more noticeable higher incidence of both out of season cyclones and stronger storm systems.

(A persistent swirl of disorganized clouds in the Central North Atlantic — continuously re-charged by frontal systems sweeping down from Baffin Bay and feeding on warmer than normal sea surface temperatures may become the first tropical cyclone of 2017. If it later forms into a tropical storm, it will become the third out-of-season named storm to form in the Atlantic over the last 15 months. Image source: LANCE MODIS.)

Last year, extremely warm sea surface temperatures combined with this kind of observed instability to spur the formation of Hurricane Alex during January. Tropical storm Bonnie also formed out of season during May. Similar very warm ocean conditions then helped to kick-start the late November formation of Category 3 Hurricane Otto (though November is still technically hurricane season, it’s supposed to be very rare to see so strong a storm form so late in the year).

Possible April Cyclone Underlines Recent High Incidence of Out of Season Storms

Fast forward to April of 2017. According to the National Hurricane Center, there’s now a 30 percent chance that a tropical depression may form in the Central Atlantic over the next 48 hours. Ultimately, such a system could gather into the first Atlantic named storm of 2017 — Arlene. Such an event would mark the third time in just 15 months that the Atlantic basin had produced an out-of-season tropical storm or hurricane.

(A vast majority — 97 percent — of tropical storms and hurricanes in the Atlantic form during hurricane season from June 1 to November 30. That said, human forced climate change may now be in the process of providing more fuel for the formation of out-of-season storms. Image source: North Atlantic Tropical Cyclone Climatology.)

Incidence of out-of-season tropical storms or hurricanes in the Atlantic is rather rare. Over 158 years from 1851 to 2009, perhaps one such system formed, on average, each year. Moreover, these storms primarily formed during May — which by itself produced more out-of-season storms than December through April combined. And a vast majority of these systems were tropical storms — not hurricanes or major hurricanes.

In 2016 and 2017, Alex formed as a hurricane during January — which is practically unheard of. Bonnie formed during late May, which was less unusual but still out-of-season. Otto formed as a category 3 major hurricane during late November — another anomalous event. Meanwhile, if Arlene forms this April it will represent 1 out of only about 20 such systems that formed during the month in the period of 1851 through 2009.

But even if we don’t get a tropical cyclone in the middle of the North Atlantic during April of 2017, it’s becoming increasingly obvious that conditions have changed. That forecasters now need to be more alert for out-of-season tropical cyclones and to the various new weather phenomena that are now being precipitated by a warming climate.

Links:

The National Hurricane Center

Hurricanes and Climate Change

Earth Nullschool

LANCE MODIS

Extreme Weather Events Linked to Climate Change Impact on Jet Stream

North Atlantic Tropical Cyclone Climatology

Hat tip to Vaughn

Hat tip to Hilary

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Ocean Temperature Anomaly Hits Extraordinary +1.12 C Above Average Reading on April 22, All Australian Weather Models Now Predict El Nino for 2014

With the ever-more certain approach of El Nino, the world ocean surface is starting to radiate more and more heat.

Over the past four days, GFS assessments have shown positive temperature anomaly values in excess of +1 degrees Celsius (C) above the, already hotter than normal, 1979 to 2000 average (which was, itself, about .5 C above the low averages seen during the period of 1880 to 1920). With each new dawn, readings ramped higher and, by today, those temperatures had spiked to an extraordinary +1.12 C hotter than ‘normal’ for the entire global ocean system.

TS_anom_satellite1 April 22

(Global oceans hit extreme +1.12 surface temperature anomaly. Data from NOAA’s Global Forecast Systems model visually depicted by the University of Maine’s Climate Reanalyzer.)

The equatorial Pacific region hovered near El Nino values with readings of +.44 to +.45 C approaching the El Nino threshold of +.5 C. It is worth noting that the Eastern Equatorial Pacific has consistently shown below average temperatures during recent years as strong trade winds drove both upwelling of cooler waters and atmosphere-to-ocean heat transfer. Meanwhile, the Western Pacific spiked to much hotter than normal readings as heat content just kept piling up in a broad zone east of the Philippines.

Extraordinary high temperature departures have also cropped up across other regions. The Northern Hemisphere, for example, showed an extraordinary +1.56 temperature anomaly for April 22. This exceptional reading was fed by extreme northern ocean temperatures in the Barents Sea above the Arctic Circle at +4-5 C above the 1979 to 2000 average and a very warm pool in the Pacific Ocean south of Alaska ranging from 1.5 to 2.5 C hotter than normal.

Aside from these zones of extreme heat, almost all Northern Hemisphere waters now display hotter than average temperatures.

All Australian Models Now Show El Nino

These excessively high global ocean temperature readings come on the same day that the Australian Bureau of Meteorology (BOM) issued new findings showing that every climate model run by that agency now predicts El Nino for 2014. The BOM notes:

The likelihood of El Niño remains high, with all climate models surveyed by the Bureau now indicating El Niño is likely to occur in 2014. Six of the seven models suggest El Niño thresholds may be exceeded as early as July.

At issue is the fact that reversals of the trade wind, known as west wind back-bursts (WWB), are currently ongoing both east of the Solomon Islands and in the Central Pacific Ocean. Real-time observation of western Pacific wind flow through composite weather model data shows a broad field of westerly winds of about 5-15 mph velocity centered at 1.7 degrees South, 156 degrees East. A second cyclonic circulation north of Tahiti at 2.9 North, 139 West in the mid Pacific Ocean has also generated a 5-15 mph west wind.

Overall, these counter trade wind flows help to push down-welling warm water in the Western Pacific eastward, spreading hot waters across the surface and amplifying the force of what, during March, was the most powerful Kelvin Wave on record. Factors that bring with them the potential for an extraordinarily powerful monster El Nino for 2014-2015, continued positive ocean surface temperature extremes, and major weather disruptions associated with both human warming and the global tilt toward the warm extreme that is El Nino.

Links:

Climate Reanalyzer

BOM ENSO Wrap-up

El Nino’s Arrival Seen by All Models

Real Time Global Surface Wind Data

Monster El Nino Emerging From the Depths

Potential For El Nino Spikes as Record Pacific Ocean Heat Content Continues to Emerge

Hat Tip to Colorado Bob

 

 

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