From Maryland to the Caribbean to Asia, Record-Hot Ocean Waters Give Extreme Weather Potentials a Big Boost

The forecasts began coming in this morning: Heavy rainfall expected over the next two days. Possible flash flooding. Turn around, don’t drown.

These advisories buzzed up from local news media for the DC, Maryland, and Northern Virginia metro areas as a crazy, wavy Jet Stream spawned an upper-level low that’s predicted to gorge on an insane amount of moisture spewing up off the record-hot Atlantic Ocean.

Forecast GFS model guidance shows an upper-level low-pressure system situated over the Great Lakes region in association with a big trough dipping down from the Arctic. Over the next 24 to 48 hours, the low is expected to shift south and east. Becoming cut off from the upper-level flow, the low is then predicted to set up a persistent rainfall pattern over DC, Maryland and Northern Virginia.

noaa-extreme-rainfall-dc-metro-area

(NOAA’s precipitation forecast model shows extreme rainfall predicted for the DC area over the next seven days. Note that record global heat and, in particular, excessively hot sea-surface temperature anomalies off the U.S. east coast are providing an unprecedented amount of fuel for storms. Should such storms fire off, they could produce rainfall totals in excess of those currently predicted. Image source: NOAA.)

Easterly winds are expected to be drawn into the low from a record-hot Atlantic Ocean. These winds will bear upon them an extraordinary burden of atmospheric moisture which has been continuously evaporating up from a very warm Gulf Stream. Such moisture is fuel for powerful rainstorms. Given the destabilizing kick provided by the upper-level low, it is expected to deliver some pretty intense downpours on Wednesday, Thursday and Friday.

NOAA model guidance shows rainfall amounts of 3 to 6 inches over the area for the next five days. However, given the high atmospheric moisture content and the record atmospheric and ocean heat that’s spiking storm energy potentials, there is a possibility for locally higher amounts.

Extreme Ocean Heat Contributes to Severe Weather

As the DC area prepares for what could be another record or near-record rainfall event, various other regions over the Atlantic and on the other side of the world are also facing the possibility of intense weather. Very warm sea-surface temperatures are the common thread that links all these events.

atlantic-ocean-heat

(Hot sea surfaces are loading up the atmosphere with moisture and helping to produce convective updrafts that heighten storm tops. Such are the results of climate change, which has now dumped an extraordinary amount of heat energy into the Earth’s ocean and atmosphere — energy that now provides fuel for both extreme rainfall events and more-intense hurricanes. Image source: Earth Nullschool.)

In the Atlantic Ocean, just off Maryland and DC, sea-surface temperatures running at an amazing 5.7 degrees Celsius above average are helping fuel this week’s possible extreme rainfall event. For reference, ocean temperatures over the course of the 20th century tended to range between 2 C above average to 2 C below average. Any deviation beyond a 2 C departure for any significant length of time was considered pretty out of the ordinary. But off the U.S. east coast over the past couple of years and concurrent with record-hot global temperatures, sea surfaces have regularly hit such high ranges. The heat bleeding off those waters has contributed to a growing number of intense precipitation events.

Possible Strong Cyclone to Form in Caribbean, Track Toward U.S. Coast

Farther south, the Caribbean is also quite hot. Ranging from 1-2 C above average, this region of warmer-than-normal ocean water is about to receive a strong tropical wave running in from the east. Over the next week, this wave is expected to gorge on these hot waters, firing off intense thunderstorms with rising tops around a tightening center of circulation, and developing into a tropical cyclone that could reach hurricane strength by late this week or early next week. Long-range model runs predict all kinds of possible rough weather related to this potential storm for the U.S. east or Gulf coasts or even for the Canadian Maritimes.

florida-hurricane-october-7-ecmwf

(Most recent ECMWF model run shows an extremely powerful 938-millibar hurricane threatening southeast Florida on October 7. If such a storm does form, it will be fueled by hotter-than-normal ocean conditions brought about by human-caused climate change. Image source: Tropical Tidbits.)

One of the most accurate forecast models, the European Centre for Medium-range Weather Forecasting (ECMWF), is pointing toward the possibility of a major hurricane of 938-mb intensity threatening the southeast coast of Florida by October 7. Though such long-range forecasts are highly uncertain so far out, the underlying models are obviously picking up on the potential energy provided by all that ocean heat. The result is a kind of climate roulette — with a few extra bullets in the chambers. In other words, with all that ocean heat laying around, the potential for a big storm is just sitting there, waiting for something big to come along and suck it up. This ongoing, worsening situation could result in some serious added weather consequences over the next ten days or so.

Megi is Third Tropical Cyclone to Impact Taiwan

All across the world this year, big rainfall and related storm events have been popping up. Louisiana alone saw two 30-inch plus rainfall events while nearby Texas got hit again and again and again. This week, major floods in Iowa spurred officials to urge thousands to evacuate. Meanwhile, the recent Ellicott City, Maryland flood has people in the DC area on edge over this week’s potential for very heavy rainfall.

Half a world away today, Typhoon Megi roared ashore in Taiwan as a Category 4 tropical cyclone with top sustained winds of 132 miles per hour. Knocking out power for 3 million people across the island, the storm is now reported to have resulted in 250 injuries and the loss of 4 lives. Meanwhile, as much as 36 inches of rain has fallen over parts of the island.

It’s worth noting that rainfall hasn’t stopped over Taiwan yet, even as the massive circulation of Megi plows toward China — which is likely to receive heavy rainfall from the storm as well.

Like the possible extreme weather events related to very-hot surface waters in the North Atlantic and Caribbean, Megi formed over waters that are 1-3 C hotter than normal. But what’s a bit odd about Megi is that she followed almost in the exact tracks of two other cyclones — one which brushed by just to the north of Taiwan, and another which skirted the island’s south side. Typically, upwelling of cooler waters caused by hurricanes and tropical storms is enough to prevent an immediate follow-on by powerful systems, due to the fact that surface waters tend to be warmer than waters below the surface. But Megi followed these two systems and was able to tap enough ocean heat to reach Category 4 intensity even as it supported a massive outflow.

typhoon-megi-crosses-taiwan

(Typhoon Megi dwarfs Taiwan. Image source: Earth Observatory.)

How did this happen? Well, considering the fact that ocean surfaces in Megi’s path are still 1-2 C hotter than normal, it’s likely that the waters at depth were also much warmer than usual, meaning storm-related upwelling wasn’t able to limit the strength of follow-on storms. This possible new feature of the Western Pacific raises the strange potential for regions to be hit by a train of tropical storms and cyclones, as happened with Taiwan over the past couple of weeks.

Conditions in Context — Record-Hot Ocean, Atmosphere Fuels More Severe Storms

The common link between the forthcoming potential severe weather along the U.S. east coast and the intensity of Typhoon Megi upon following behind two other storms is increased ocean heat. Such heat acts as a kind of energy and moisture engine for more, and more powerful, storms, such as the aforementioned extreme rainfall events and powerful, peak-intensity cyclones. In short, these are aspects of a world undergoing fundamental climate shifts — shifts that continue to ramp up due to the great and ongoing emission of greenhouse gasses into the Earth’s atmosphere.

Links:

Heavy Rain, Flood Threat

GFS Model Guidance by Earth Nullschool

NOAA

Tropical Tidbits

Typhoon Megi Smashes into Taiwan on Path to China

Typhoon Megi Passes Taiwan

Thousands Urged to Evacuate Iowa Floods, Megi’s Threat to Taiwan Escalates

Scientific Hat tip to Dr. Jeff Masters

Hat tip to DT Lange

Hat tip to Colorado Bob

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Bad Climate Outcomes — Atmospheric Warming to Ramp up as PDO Swings Strongly Positive?

Last year, quietly and without much fanfare from the mainstream press, the Pacific Ocean underwent a powerful shift. A shift from a state in which cooler surface waters absorbed atmospheric heat, to a phase in which surface water warming caused ocean heat to be transferred to the world’s already warming airs.

The shift was heralded by a powerful oceanic Kelvin Wave. One that brought warm water up from the depths and spread them across the Pacific Ocean surface. Ever since that time, warm Kelvin Waves have continued to refresh this surface water heat pool.

monster-el-nino

(Major Kelvin Wave that heralded a switch to strongly positive PDO values for the Pacific. Image source: NOAA/ESRL)

And so the Pacific Ocean surface warming continued throughout 2014.

By December, Pacific Decadal Oscillation (PDO) values, a measure directly tied to this warming, hit a new all-time record level of +2.51. That’s the highest and hottest PDO value since record-keeping began in 1900. One that only backed off slightly into January at +2.45 in the preliminary measure.

It’s a major swing in Pacific Ocean surface temperatures to a phase where more heat is dumped into the atmosphere. One that is causing some scientists to warn that a new period of rapid atmospheric warming may just be getting started.

image

(Sea surface temperature anomaly map shows very warm surface waters dominate much of the equatorial, eastern and northern Pacific in a signature that is strongly characteristic of a powerfully positive PDO on Thursday, February 26 2015. Image source: Earth Nullschool. Data Source: Global Forecast Systems Model.)

PDO and The Multi-Decadal Heat Pump

Pacific Decadal Oscillation (PDO) is a periodic change in sea surface temperature states in the Pacific. One that is thought by many oceanic and atmospheric researchers to have a strong influence on global weather and temperature variability.

In the negative state, PDO tends to encourage La Nina events which also coincide with a downswing in global temperatures as the vast Pacific waters take in more heat. In the positive state, PDO tends to encourage El Nino events which result in the great ocean belching heat into the air on a grand scale — pushing atmospheric temperatures higher.

All things being equal, this natural variability would pan out — marking upswings and downswings in a global average. However, human fossil fuel burning and related greenhouse gas emissions have bent this curve upward by trapping more and more heat in the lower atmosphere. So the case is now that during positive PDO phases, in which more El Ninos occur, atmospheric warming has tended to ramp drastically higher. And, consequently, during negative PDO phases, atmospheric warming has tended to merely slow down even as oceanic warming sped up.

You can see this speeding up and slowing down in the below graphic provided  by Weather Underground:

PDO vs global temperature change Weather Underground

(Global temperature change since 1900 vs phases of positive PDO [1925 to 1945 and 1975 to 1998] and negative PDO [1945 to 1975 and 1998 to 2014]. Image source: Weather Underground. Data Source: NOAA.)

In the era during which global temperatures have been increasingly driven by human greenhouse gas emissions, four phases of PDO have been recorded. Two were positive, two were negative.

In the first positive PDO phase during 1925 through 1945, global average temperatures jumped upward by about 0.5 degrees F (+0.25 F per decade). This initial surge in atmospheric warming abated as global temperatures remained roughly steady during the negative PDO period of 1945 to 1975 (+/- 0 F per decade). But by 1975, PDO values were positive again and the period through 1998 showed a rapid warming of about 0.8 F over 23 years (+0.4 F per decade). After the super El Nino of 1998, PDO values again trended negative as atmospheric warming continued at a somewhat slower pace of about +0.15 F per decade.

Global Warming and Related Ills to Ramp Up?

This underlying trend should be cause for serious concern.

The first issue is that we see warming now during negative PDO decades where we only saw cooling or zero warming before. Given the present rate of warming in the range of +0.15 F per decade during periods in which the Pacific Ocean is taking on atmospheric heat, one could expect the next positive PDO phase to see decadal warming in the range of +0.55 F or higher (or by about 1 C in 20-30 years).

Such a rapid pace of warming could challenge the fabled 2 C ‘point of no return’ before 2050 (for reference, we are at about +0.85 C above 1880s values now). And it is for this reason that some scientists are now starting to sound alarm bells.

In the recent Weather Underground commentary penned by Jeff Masters, Kevin Trenberth, an NCAR scientist and one of the world’s foremost experts on ocean temperature dynamics, noted:

“I am inclined to think the hiatus [in global temperature increases] is over, mainly based on the PDO index change. If one takes the global mean temperature from 1970 on, everything fits a linear trend quite well except 1998.”

NOAA global surface temperature anomalies

(Global surface temperature anomalies. Image source: NOAA.)

Though Trenberth does not explicitly spell out the potential for an overall warming acceleration, he does point toward a return to the +0.29 F per decade trend line seen since 1970. Meanwhile, Matthew England of the University of South Wales warned in the same Weather Underground commentary that any post ‘hiatus’ warming would be likely to be very rapid.

Dr. Michael Mann, a climate scientist of considerable fame both due to his Hockey Stick tree ring study and due to his ongoing success fighting off smear campaigns launched by climate change deniers, recently put together climate model assessments that showed world temperatures exceeding the 2 C threshold by 2036 under business as usual greenhouse gas emissions. To reach such a high reading so soon would require in excess of 1 degree Fahrenheit warming over each of the next two decades. And such a rate of warming would be very rapid indeed, unprecedentedly rapid and well outside the linear trend line from 1970.

Michael Mann today made related comments at Realclimate on the more recent oscillations in Pacific Ocean sea surface temperature:

There is the possibility that internal, natural oscillations in temperature may have masked some surface warming in recent decades, much as an outbreak of Arctic air can mask the seasonal warming of spring during a late season cold snap. One could call it a global warming “speed bump”. In fact, I have… Given the pattern of past historical variation, this trend will likely reverse with internal variability, instead adding to anthropogenic warming in the coming decades. That is perhaps the most worrying implication of our study, for it implies that the “false pause” may simply have been a cause for false complacency, when it comes to averting dangerous climate change.

To these points, it is worth noting that any rate of warming above 0.3 F (0.2 C) per decade is extraordinary and terrifying. Such a rate is enough to achieve post ice age warming of 4 C in merely 2 centuries where it took 10,000 years to achieve such warming before. Warming at 0.4, 0.6 or 1 F per decade would be both drastic and devastating to current climates, geophysical stability, weather stability, glacial stability, water security, food security, and ocean health. In the current world, already warmed by about 0.85 C above 1880s levels any acceleration to current warming is a rather bad outcome on top of an already dangerous situation.

Links:

Are We Entering a New Period of Rapid Global Warming?

Climate Oscillations and the Global Warming Faux Pause

NOAA’s National Climate Data Center

NOAA’s Earth Systems Research Lab

Monster El Nino Emerging From the Depths?

Far Worse Than Being Beaten With a Hockey Stick: Michael Mann Climate Model Shows 2 C Warming by 2036

Global Warming Speed Bump? The Answer May be Blowing in the Wind.

Earth Nullschool

Global Forecast Systems Model

Hat Tip to Colorado Bob

Hat Tip to Bassman

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