878 mb Storm Off North Florida — The Model Forecast for Irma that no one Wants to See Happen

As the United States struggles to recover from severe damage inflicted by one hurricane made far worse by climate change, another powerful storm is brewing over the hotter than normal waters of the tropical North Atlantic.

As of the 5 PM Atlantic Standard Time statement from the National Hurricane Center, Irma was positioned about 1,100 miles east of the Leeward Islands in the central tropical Atlantic. The storm hosted a small circulation, packing 110 mph winds and a minimum central pressure of 973 mb. Over the next few days, according to the Hurricane Center, Irma is presently expected to reach major hurricane status with 130 mph maximum sustained winds.

(Category 2 Irma in the Central Atlantic seems relatively innocuous. But NHC guidance indicates the potential for Irma to develop into a major hurricane over the next five days. Some of the longer range models, however, are producing some rather worrying forecasts. Image source: National Hurricane Center.)

The Hurricane Center is clear to note that it uncertain at this time if Irma will ultimately threaten the Bahamas or the mainland U.S. But the Center cautions that all interests remain watchful and prepared as the storm could pose a risk over the coming days:

It is much too early to determine what direct impacts Irma will have on the Bahamas and the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

Looking beyond the official forecast, some of the our best long range model runs are putting together some seriously scary predictions for Irma. By next week, the Global Forecast System (GFS) model shows Irma as a 878 mb monster hurricane looming about 300 miles off Florida. 878 mb would represent the lowest pressures ever recorded in a hurricane in the Atlantic (The present strongest Atlantic storm was Wilma at 882 mb. The devastating Labor Day Hurricane hit 892 mb.). And it would almost certainly represent the strongest storm in our records ever to venture so far North. 878 mb roughly corresponds with maximum sustained winds in excess of 170 mph and possibly as high as 200 mph or more. And we’ve never seen something like that threatening the Central Atlantic U.S. East Coast in all of the modern era.

(A storm stronger than Wilma and approaching Tip’s record 870 mb intensity off North Florida and not in the Caribbean? GFS says it’s possible. Let’s hope for the sake of much that is precious and dear to us that this model forecast does not emerge. Image source: Tropical Tidbits.)

The model then slams the storm into Cape Hatteras just after midnight on Monday, September 11 as only a slightly weaker Category 5 range storm at 910 mb. The storm proceeds north into the Hampton Roads area early Monday morning retaining approximate Cat 5 status at 919 mb. After roaring over this highly populated low-lying region, the storm enters the Chesapeake Bay at 934 mb by noon on Monday — in the Category 4 range and still stronger than Hurricane Sandy — before crossing up the Bay and over the D.C. region by evening the same day at 958 mb (approx Cat 3).

To say this would be an absolute worst case disaster scenario for the Mid-Atlantic is an understatement. A storm of this intensity would produce 10-20 foot or higher storm surges, devastating winds, and catastrophic rainfall throughout the Outer Banks, Hampton Roads and on up the Chesapeake Bay. But unlike Harvey, it would be a fast-moving event. More like a freight train than a persistently worsening deluge.

This long range model scenario is not, however, an official forecast. It’s just what the GFS atmospheric computer models are presently spitting out. And such long range predictions from a single model, no matter how reliable, should be taken with at least a pinch of salt. That said, we should certainly, as the NHC recommends, keep our eyes on Irma and keep our response plans ready.

(Sea surface temperatures in the North Atlantic off the Southeast Coast are between 1 and 1.8 C above average. Atmospheric moisture levels are quite high as is instability. So as with Harvey, we have quite a lot more fuel than normal available for a hurricane to feed on. Image source: Earth Nullschool.)

We should also note the context in which this present extreme potential emerges. Ocean surfaces in the North Atlantic off Florida are very warm with temperatures around 30.5 degrees Celsius (87 F) near the Bahamas. This is about 1.8 degrees Celsius above the already warmer than normal climatological average. Atmospheric moisture and instability in this region of the North Atlantic are also quite high. These two conditions provide fuel for hurricanes that do enter this region. They are conditions that are linked, at least in part, to human-caused climate change. And they are similar to the conditions that amplified Harvey’s intensity just prior to landfall.

So though the GFS forecast described above is far from certain, we should absolutely listen to the NHC’s urging for us to pay attention to what could be another dangerous developing storm. One that appears to at least be physically capable of defying previous weather and climate expectations. Let’s just hope it doesn’t.


The National Hurricane Center

Earth Nullschool

Tropical Tidbits

List of Most Intense Tropical Cyclones


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.


The National Hurricane Center

Hurricanes and Climate Change

Earth Nullschool


Extreme Weather Events Linked to Climate Change Impact on Jet Stream

North Atlantic Tropical Cyclone Climatology

Hat tip to Vaughn

Hat tip to Hilary

Hothouse 2090: Category 6 Hurricane A Grey Swansong For Tampa

Tampa. 2090. Late September.

The stiff wind running off the Gulf of Mexico felt like a blast furnace. Ocean surface temperatures near 100 degrees Fahrenheit; air temperatures of 113 F, high humidity, and a smell like rotten eggs added to the overall insufferability. Unpleasant was a better word from a better time. Mere unpleasantness had long since fallen away before the new deadly edge that Nature had adopted.

Tampa’s streets were packed with vehicles but featured only the rare transient foot and bike traffic. Just 15 minutes’ exposure to the brutal four p.m. heat and humidity could swiftly result in heat stroke as a body’s natural cooling systems were overwhelmed by conditions no human physiology could for long endure. The city had long since grown accustomed to the warnings. Anyone wanting to stay healthy remained indoors, huddling close to the blessed vents blasting machine-cooled, filtered air.

In the heat-scorched streets, elevated many times over to keep above the rising seas, a few diehards still roamed. They sported the latest in cooling accessories — thermal-bleeding fashions were all the rage and had been for at least three decades now. So too were the thin-film sulfur filtration masks, totem-like in their branding and individually styled in patterns of iridescent colors. These were the stylized provisional responses to the gigantic dead zones that regularly painted the Gulf’s waters purple-black with stinking, toxic-gas-spewing bacteria. But today, the waters were sickly green. The stink was merely unbearable and only somewhat unhealthy, thanks to the large and powerful storm now pushing in the bluer off-shore waters and flushing out some of the seaside dead zone.

RCP 8.5

(Under RCP 8.5 warming scenarios, the Earth is transformed into a hotter, more deadly place, capable of supporting storms of never-before-seen intensity. Image source: The European Environmental Agency.)

Great swells churned away – covered in gooey sludge. Some residents thought fondly of the December- to-February tourist season when temperatures fell, the waters cleared and, at times, swimming was safe. But such thoughts were quickly blasted away by the constant warnings now blaring through the local radio. Hot waves capped with frothy green foam were already roaring over the shoals of the old seaside districts and barrier islands before slamming into the defensive ring of sea walls. Ice melt in Greenland and Antarctica had long since forced a retreat from the bay and ocean, pushing an eight-foot rise in sea levels over the 90 years. The near-water residences, once premium real estate, had long since been relegated to tourist homes or the odd air and ocean monitoring station

Tampa Reeling in a Dangerous Climate Zone

Tampa had fared badly, but not so badly as Miami, or the huge chunk of South Florida now covered up by the Gulf and Atlantic Ocean. In the 2030s, large numbers of South Floridians and coastal residents began an exodus northbound and inland. Some stopped in Tampa, staking a claim on the increasingly-expensive higher elevations, but most just kept heading north — past drought-stricken Georgia, through the drying Mid-Atlantic states, and on north, even into Canada. But anywhere they went, there were problems. A big zone from the Mid-Atlantic on south and west was turning into desert. The Mississippi was becoming more and more an intermittent river –practically drying up most summers and then flooding like the dickens during February through April as gigantic storms cycle south out of the Arctic, driving massive swaths of hurricane-force winds before them. The West was even worse, with a large section of four states now experiencing temperatures that make early-century conditions at Death Valley seem tame.

It was tough to find a place of safety and security, much less comfort. Lives were shorter, harder than ever before. People scrambled from place to place. They hoarded food. Most were thin — Renaissance-era voluptuousness was making a comeback. Indoor and underground farming had exploded — saving the lives of millions in the parts of the world that adopted these methods — but the dead oceans, lost farmlands, and increasingly scarce fresh water sources resulted in a cascade of regional and global crises. Needless to say, there were less people. There was basically less of anything living anywhere. All the heating and burning and storming and putrefying had seen to that — the results of two centuries of fossil-fuel emissions that ebbed and flowed but never really stopped growing.

Tampa, like every other city still functioning, had seen her fair share of all this trouble. She was one of the lucky ones — still around, clinging to the higher elevations, still building up her sea walls, making and importing what food she could, finally casting off the corrupt fossil-fuel industries and enabling what economy that remained through all-renewable energy. You couldn’t call it sustainable — that ship had long since sailed. Some day, a big glacial outburst flood somewhere in Antarctica would push seas high enough to devour Tampa whole. Or some day, a giant city-killing storm could scour enough of Tampa from the face of the Earth that the resources and effort necessary to recover would simply become a mountain too high to climb.

Haiyan enhanced

(Under the hothouse-warming scenario that is RCP 8.5, hurricanes will have the potential to substantially exceed the strength of supertyphoons like Haiyan [enhanced satellite image above] which devastated the Philippines. Image source: NOAA.)

Category 6 Hurricane Raptor Sets Sights on Tampa

For Tampa, that day may well be the day after tomorrow, for monster storm Raptor now tore through the blue, green, and purple-black waters of the Gulf of Mexico. Gorging on sea-surface temperatures near 100 F, this enormous stack of lightning-wracked clouds reached 80,000 feet into the atmosphere. It ripped that hot air and moisture up from the surface, casting it in an enormous bellow toward space. In the wall of the resulting funnel, winds howled at 230 miles per hour. Minimum central pressures measured 835 millibars. Wave-height measures from some buoys — those whose sensors hadn’t been slammed into inoperability — were coming in at 100 feet.

A 20-mile-wide swath of these conditions formed an atmospheric axe along the right front quadrant of the storm as it turned toward Tampa. Crossing land, it would produce a 35-foot storm surge topped by 20- to 40-foot breaking waves. In areas not submerged by these churning, toxic waters, the winds would blow as strong as an EF 5 tornado — enough to strip the bark from trees. This combination of conditions would demolish any above-ground structures. The cone of destruction centering at the coast, then ripping 60 to 100 miles inland before the storm finally slaked its rage.

Taller Storms Climate Change

(Increasing global temperatures enlarges the zone in which storms can form, heightening cloud tops. Taller warm-air updrafts more heavily laden with moisture increases storm potential energy. In this way, climate change increases top potential storm intensity. Overshooting cloud top image provided by: Commons/NOAA.)

Similar nasty storms had helped to render the Persian Gulf region uninhabitable. Cairns, Australia had been ripped apart by such a beast five years earlier. The Phillipines, Taiwan, coastal China and Japan were visited ever more frequently by the monster category 4, 5, and 6 systems. And the thing barreling toward Tampa was among the strongest of a deadly new breed that meteorologists were now calling city killers.

The threat was not lost on residents. Those unresponsive to storms and extreme weather didn’t have a very high life expectancy. Roadways leading out of Tampa became packed with traffic. Inbound lanes were designated outbound. Trains, planes, hyperloops, and buses were all packed to the gills with those fleeing the path of Raptor. Lower populations after the migrations and mid-to-late Century crashes, in part, made the flight easier. As did the increased responsiveness. But the size of the storm swath, lower road and track resiliency due to the heat ahead of the storm, the more toxic air blowing off the ocean, and the increased population densities due to suburban abandonment created its own evacuation nightmares.

Higher populations of older persons suffering from increased rates of dementia and frailer organ systems due to toxin accumulation and disease proliferation were also less mobile. Moving this vulnerable group required a major effort on the part of Tampa volunteers and emergency responders. But after suffering decades of increased losses, lives and personal relationships were often considered all-the-more precious as people nostalgically clung to what connections remained or fought a crushing sense of fear and isolation by increasingly working to help others. The great ages of excess that preceded this period had left deep and enduring marks on the psyches of the people who’d survived through those times. And a quiet, defiant, never-again mentality had begun to emerge. In the face of such loss of beauty and safety, people were not only determined to live, they were determined to make the most of what meager lives remained to them by caring. By adding art and color to a world increasingly denuded of beauty. And by, most of all, attempting to preserve life.

The flight of Tampa’s populace from before the storm was, therefore, far more responsive, far more vigorous, than the responses of previous generations. And a vast majority heeded the warnings and left. As a result, the city became an empty shell with only about a hundred thousand die-hards and emergency personnel remaining.

With the big evacuation pulse now running inland and northbound, and with sections of Orlando evacuating while other portions hunkered down, the first outliers of Raptor began to encounter the coast. The green-white froth on the swells grew more vivid — almost looking neon in the light of dawn. Off-shore, an angry black stack of clouds thrown off from Raptor’s outer bands rushed toward shore. Gale-force gusts and a large accompanying swell pummeled Tampa’s seawalls and streets. The down-drafts and the first falling rain drove temperatures lower — into 90s (F). But the sensation was still one of oppressive heat due to the near 100 percent humidity.

The Storm Rushes In

Winds continued to rise and, over the next few hours, hot, driving rain steadily wrapped the Tampa region in a kind of stinking, hissing, steam. The continuously lifted sea walls and dikes never quite kept up with sea level rise. So even the early outliers of Raptor were enough to generate floods of putrid, green waters rushing through the lower-lying streets. Bridges and roads were quickly cut off and those remaining in town, and especially those on the newly dubbed Petersburg Island, were quickly cut off. Those poor souls remaining would have to face Raptor on their own and without the aid and comfort of an increasingly necessary emergency response force.

Current Tampa Bay Topographical Map

(Current Tampa Bay topographical map provided by the US Geological Survey. Under the 8 feet of sea level rise by 2090, most of the green sections would be below sea level. 8 feet of sea level rise plus 35 feet of storm surge plus 30-40 foot breaking waves would generate flooding in event some of the higher elevation areas [orange to brown]. Note that elevations in the map above are listed in meters. Image source: USGS.)

Raptor was moving rather swiftly and by early evening the storm’s eye wall was beginning to approach the coast. Off-shore, a great mound of water like a tsunami ran up from the waters of the shallow Gulf. Still taller waves rose atop it. Some of the rogue peaks stretched 150 feet above the base sea level. The net effect was one of an intense green-white mass taller than the tops of most buildings roaring in from the Ocean. The mass drowned St. Petersburg in a foundering break-water. It roared into Tampa Bay, and there it lifted the remaining ships and boats and hurled them bodily into buildings, across the shore line, and into rapidly flooding streets. Waters rushed into Tampa and on inland — in some places continuing for 10-20 miles before the great pulse of water was finally slaked by elevation.

Southwest winds rose up into a sound like a freight train. Debris was hurled into a great cloud over the flooded city. Everything from bits of sand and dirt, to paint chips, to flinders of bark from the few hardy trees remaining, to as large as vehicles and wall sections was lifted and hurled with lethal force. The churning vortex of 150 to 230 mph winds created a wall of moving air full of this shrapnel. Tampa was engulfed in a loud and angry blackness full of giant waves and flying teeth. In the above-water sections, it was impossible to see more than 10 feet outside clearly. And tens of thousands of structures were quickly ground down to their foundations by the combination of violent water and air.

These conditions covered a region stretching for 20 miles along the coast. With Raptor making landfall near Largo, this swath covered the mouth of Tampa Bay, St. Petersburg, Lealman, and Pinellas Park. With the storm running across the northern bay to make a second landfall about ten miles south and east of Safety Harbor, most of Tampa proper was affected by this zone. The raging storm surge, concentrated by the Bay and pulled along the arch of the storm’s vortex peaked to extreme heights where the bay narrowed into Tampa. And large sections of the nearby city simply drowned.

Then the storm passed inland, dumping torrential rain and cutting an 80 mile long, 20 mile wide swath of destruction through Central Florida. The wall of airborne shrapnel picked up more and more debris as it went. A few travelers on the road were forced to hunker down at a nearby recharging station’s convenience store — which subsequently collapsed. Their ordeal, recorded by portable devices which caught the hours-long images of flying cars, bits of transmission towers and other debris so damaged as to be rendered into an unrecognizable black grit across the sky, became a part of one more ‘new most violent’ storm record. A testimony to the worsening hazards and losses of the time.

As the next day dawned and rescue and disaster relief aircraft entered the storm zone, the epic destruction was more fully revealed. Observers from airplanes pointed out the swirling impressions upon the stripped land. One pilot noted that it looked like a thousand tornadoes had all gotten into a line 20 miles long and then run north and east inland. Another simply stated that it looked like the land had been pounded barren by the vast fists an angry god. Over a million structures had suffered at least moderate damage. Over 200,000 had been blown or knocked by waves down to their foundations. Despite the effective evacuation, the death count was tremendous. More than 35,000 in the Tampa region and points inland immediately lost their lives to the storm. Another 60,000 were estimated to have perished in the aftermath as a failure to restore power in time resulted in exposure to killing heat and near-shore airborne toxins. Considering comparable storm, fire or drought losses in three other US cities that year and the inevitable coming multi-meter sea level rise, government officials decided to add Tampa to the growing list of communities that would never be rebuilt.

Conditions in Context – Global Warming Increases the Top Potential Strength of the Most Powerful Storms

In 2016, Earth’s atmosphere isn’t yet capable of producing a storm like Raptor. But in a not-too-distant future, a 5-degree (Celsius) rise in global temperatures pushed on by 900 parts per million of atmospheric CO2 would result in heightened levels of heat and moisture fueling a great deal of instability. The Earth’s atmosphere would still be taking in huge amounts of heat at its top. The glaciers would likely be unzipping and sending out hordes of icebergs riding a pulse of cold surface water. As ever-more-dominant heat goes to war with dying cold, the amazing temperature differentials spawn equally terrible storms.

Seventy-four years from now, under business as usual warming scenarios, the tropics and subtropics are likely to be hundreds of miles to the north of their current geography. Rising troposphere heights will bring ever-taller thunderstorms. When these storms manage to organize into hurricanes, the results have the potential to be dramatically more powerful than today’s comparatively tame storms. Category 3, 4, and 5 storms would be more frequent. And a new category — 6 – may be needed for storms whose maximum sustained winds exceed a range near 200 miles per hour and whose minimum central pressure hits lower than around 880 mb (a range that starts out a bit more powerful, on balance, than the strongest storms that are capable of forming today).


The above scenario is a climate fiction portrayal of a potential category 6 hurricane impacting Tampa in the 2090s. The scenario incorporates recent scientific studies pointing toward projected increases in hurricane intensity due to human-forced warming of the Earth’s oceans and atmosphere. In particular, the work of Dr. Jeff Masters on emerging Grey Swan hurricanes driven by climate change proved very helpful in providing a groundline basis for potential category 6 hurricane strength and impacts. And it is worth noting that Dr. Masters is highlighting scientific work showing that under business as usual human warming it is possible that storms of never-before-seen intensity will hit the Tampa region.

The storm in this scenario, Raptor, is nearly as strong as the storm produced by one of the climate models Dr. Masters references. This extremely powerful storm hit Tampa in a physical computer model assessing hurricane strength under business as usual warming. The modeled storm achieved 235 mph maximum sustained winds and an 830 mb minimum pressure. It’s worth noting that we have no record of a storm of this strength ever forming on Earth. But, under greenhouse gas loads and temperatures that continued fossil fuel burning will establish by the end of this century, the Earth atmosphere becomes capable of supporting such extreme events.

To this point, it is absolutely also worth referencing Dr. James Hansen’s seminal Storms of My Grandchildren while making the very clear statement that the atmospheric brew we are pumping out will make never before seen monster storms a terrible and dangerous aspect of the world our children and grandchildren will inherit and try to survive in.

Tampa Bay Florida LANCE MODIS

(Tampa, Florida, seen in the center of this July 2016 satellite image, is currently one of many cities facing serious threats posed by human-caused climate change. Whether Tampa or any of these other cities survive depends on how well human beings respond and on how much we lessen the coming damage by reducing fossil fuel emissions now. RCP 8.5 is a bad climate scenario. The only problem is that all we have to do to get there is simply continue to burn oil, gas, and coal. Image source: LANCE MODIS.)

The scenario also takes into account various broader Earth System changes such as potential sea level rise due to melting glaciers, increased disruption of food and water supplies, loss of ocean health and increased anoxia and related water and local air toxicity (due to warming and increased nutrient run-off into the world ocean), model simulations and understandings of the increasing prevalence of extreme land and ocean surface heat and 2 meter humidity (wet bulb temperatures increasing into the lethal range of 35 C+), and expanding drought, disease and extreme weather zones.

This particular event and context follows closely to conditions projected under the IPCC’s business as usual fossil fuel emissions or RCP 8.5 warming scenario. For the purpose of this exercise, I have added climate conditions to the business as usual case that I see as plausible given that level of warming. Some of these additions are based on my own interpretation of scientific efforts that are currently not fully settled. However, I feel the overall portrayal is likely at least relatively accurate given various model projections and how the Earth System appears to have changed in response to past warming events.

It’s worth noting that RCP 8.5 does not assume zero renewable energy adoption. It simply assumes that fossil fuels will remain the dominant source of energy with consumption growing through the end of the 21st Century. As such it results in a catastrophic warming scenario over a less than one century time-frame. But such a warming would be achieved over longer time-frames so long as human carbon emissions are not rather swiftly brought to zero, Earth System feedbacks are strong enough, or elevated atmospheric greenhouse gas levels are not drawn down. Conditions similar to RCP 8.5 at 2100 could be achieved by approximately 500 ppm CO2 by around 2500. A reality that increases the necessary urgency of our current mitigation responses. Lower level warming and emissions scenarios are still dangerous, but do not result in the higher levels of harm evident in RCP 8.5.

Human impacts in the scenario such as loss of lives and lifespan reduction are based on my own understanding of how human beings are likely to adapt to such situations and how multiplied environmental stresses are likely to start to overwhelm human population growth in net by middle-to-end Century under the RCP 8.5 scenario. The writing above assumes that the civil system surrounding Tampa and this section of the United States remains at least partially intact due to cooperative effort on the part of individuals living in society at the time. Such a response is hopeful, but it is not guaranteed.

Record Hot Atlantic Basin to Fuel Brutish 2016 Hurricanes?

Last week, Gulf of Mexico sea surface temperatures off Tampa Bay were outrageously hot. On July 10, the ocean temperature measure hit 93 degrees Fahrenheit (34 Celsius). By the 11th, temperatures had warmed still more. And by the 12th, ocean surfaces had hit a sweltering 95 F (35 C).

Tampa bay water temperatures

(NOAA shows extreme sea surface temperatures at Old Port in Tampa, FL. Hat tip to Michael Lowry.)

It’s pretty rare that you see ocean waters anywhere on Earth become so hot. And when you do, it’s often in places like the Red Sea or the Persian Gulf — not the Gulf of Mexico. But in the new world driven to increasingly extreme warmth by human fossil fuel emissions, the potential heat bleeding off of ocean surfaces has jumped by quite a bit.

And it’s not just true with Tampa Bay. According to Michael Lowry, a hurricane specialist at The Weather Channel, the whole of the Gulf of Mexico recorded its hottest average daily July sea surface temperature this month at 86.3 F (30.1 C).

Atlantic Basin Sees Record July Heat

The record ocean heat extends still further. National Hurricane Center storm specialist Eric Blake earlier today noted that, for July, the entire Atlantic Basin west of longitude 60° W is the hottest it’s ever been during any hurricane season, including the record storm year that was 2005. In other words, a huge zone of ocean stretching from the far eastern edge of the Caribbean, encompassing all of the Gulf of Mexico and running up the entire eastern seaboard of the US and on to just east of Bermuda is now seeing the hottest July ocean temperatures experienced in our modern records.

Record Hot Atlantic Basin Sea Surface Temperatures

(Sea surface temperatures hit record ranges for the western North Atlantic during recent days. CDAS image via Eric Blake.)

Overall ocean surface temperatures range from 0.5 to 1 C above average for the Caribbean, 0.5 to 2.5 C above average for the Gulf of Mexico and 1 to 6 C above average for the coastal US Atlantic. These temperatures compare to an already hotter-than-normal 1981-to-2010 average, so departures from the 20th-century average would be even greater.

Record Ocean Heat to Strengthen 2016 Atlantic Hurricanes?

Hot ocean temperatures are fuel for the powerful storms we call hurricanes. But it’s not the only ingredient. Low-pressure formation at the surface, a lift in the atmosphere, high pressure aloft, widely available moisture, and a lack of wind shear are all atmospheric assists that aid in storm formation. So far during July, a dearth of these other factors has resulted in no storms as of yet for the month.

2016, however, has already seen four named tropical storms — including the odd winter Hurricane Alex and three tropical storms which spun up during June. And given the extreme ocean surface heat in the Northwestern Atlantic, some agencies are beginning to call for the potential for more and possibly powerful storms on the way.

According to The Weather Network:

The main driving elements for hurricane formation in the Atlantic are the SST values present in the Atlantic itself, the predicted wind shear conditions in the region, and the SST pattern found in the Pacific related to the timing of the transition from El Niño to La Niña in the equatorial Pacific Ocean. Model predictions anticipate that the second part of this 2016 season will be more active as La Niña intensifies in the Pacific and becomes one of the main drivers of activity for the Atlantic.

As a result of the combined extreme Atlantic Basin heat and the predicted emergence of La Niña conditions in the equatorial Pacific, some hurricane monitors are upping the number of storms predicted for 2016. Colorado State is now forecasting 15 named storms as opposed to its earlier 13. However, its prediction for the number of major hurricanes has remained the same at two, with one affecting the US.

Predicted tropical wave

(Models predict what appears to be a very healthy tropical wave emerging off the west coast of Africa by July 28. If a tropical cyclone results that tracks into record warm western Atlantic waters, peak storm intensity near the US could be quite extreme. Hat tip to meteorologist Ryan Maue for the ECMWF infrared forecast capture.)

However, predicted warm-water formation in the Pacific off Mexico could dampen Atlantic storms by pushing in more dry air and developing a higher degree of wind shear than is typical during a La Niña year. In addition, large African dust flows currently over the tropical Atlantic also may tend to suppress storm formation.

Given the ambiguous conditions noted above, the situation still appears to be a bit of a crapshoot. That said, those extreme sea surface temperatures near the US will likely continue to ramp up through August. And that’s a situation that creates a potential where storms approaching the US rapidly intensify as they hit those record-hot waters. Overall, it’s a pretty dicey environment for forecasters and one that has been wagged in no small amount by conditions related to human-forced warming.



National Hurricane Center


The Weather Network

Michael Lowry

Ryan Maue

Eric Blake

Hat tip to DT Lange

Hawaii in a Sea of Storms: Abnormally Warm Pacific To Serve Up Unprecedented Double Cyclone Strike?

Hawaii in a Sea of Storms

(Iselle [center frame] and Julio [right frame] take aim on Hawaii [upper left] in most recent LANCE MODIS satellite shot.)

The Northern Pacific has been a very hot place this year. Above the Equator and stretching from Asia to the West Coast of North America, very few regions have witnessed below normal temperatures. And numerous very large hot zones continue to dominate off of Central and North America, between Alaska and Russia, and near Japan.

Overall, Pacific Ocean temperatures today are an excessive +0.93 degrees C above the, already hotter than normal, 1979 to 2000 average. And this extra heat, fueled by global warming, provides energy for the propagation of tropical cyclones well outside of their traditional ranges.

For Hawaii, this means falling under threat of two cyclone strikes within the period of as many days.

Hot Pacific Waters Projected to Spawn More Hawaiian Storms

Cyclone strikes in Hawaii are rare. The last time the island state was pummeled by a tropical storm was during the 1992 El Nino. But now it is threatened by not one, but two hurricanes. It is an event that is unprecedented in the entire satellite record. In other words, we’ve never seen this before.

Pacific SST Anomaly August 6

(Global sea surface temperature anomaly on August 6, 2014, shows an extreme +1.11 C positive temperature departure for the globe and a very strong +0.93 positive temperature departure for the North Pacific. Current science shows that warming ocean waters are extending the northward ranges of tropical cyclones, bringing regions like Hawaii under increasing threat. Image source: University of Maine.)

A shift in hurricanes toward Hawaii wasn’t entirely unexpected, however.

In 2013, Hiroyuki Murakami, from the International Pacific Research Center at the University of Hawaii at Mano together with a team of ocean and atmospheric researchers produced a report for Nature entitled Projected Increases in Cyclones Near Hawaii. The study modeled expected increases in Pacific Ocean surface temperature driven by human-caused climate change in the region near Hawaii. What it discovered was a marked increase in storm formation near Hawaii due to warming waters and related atmospheric changes.

The paper notes:

A key factor in projecting climate change is to derive robust signals of future changes in tropical cyclone activity across different model physical schemes and different future patterns in sea surface temperature. A suite of future warming experiments (2075–2099), using a state-of-the-art high-resolution global climate model1, 2, 3, robustly predicts an increase in tropical cyclone frequency of occurrence around the Hawaiian Islands.

Change in tropical cyclones

(Change in tropical cyclone frequency between now and 2075-2090 according to model projections produced in the Murakami Paper. Image source: Nature. See Also: Climate Change May Increase Number of Hawaiian Hurricanes)

What these researchers might not have expected was that a very warm Pacific during 2014 might well provide a prelude to what their models were predicting.

Iselle and Julio Barreling On In

For forecasts now show that Hawaii may well be in for a dose of double trouble — an extended period of stormy conditions starting early Friday and possibly not letting up until Monday as the unheard of storm pair barrels on in.

As of the most recent advisory, 85 mph hurricane Iselle was located about 650 miles to the east and southeast of Hilo. Iselle’s present and projected motion toward the west and northwest at around 15 miles per hour is expected to bring the storm, at a strong tropical storm intensity, over Hawaii’s Big Island by Friday. The storm is then projected to pass near the eastern islands before tracking back out into the open Pacific.

Coming directly behind Iselle, Julio is located about 1600 miles east-southeast of Hilo and packs maximum sustained winds of 75 miles per hour. The storm is also expected to weaken to strong to moderate tropical storm status before passing over or near the Hawaiian Island Chain along a track just to the north of Iselle’s path. This would bring the storm near the islands on Sunday, just two days after Iselle.

Threat Cones

(Threat cones for Iselle, Julio and Genevieve, all developing in an unusual region near the Central Pacific. Image source: NOAA.)

It’s worth mentioning that a third storm, Genevieve, has also developed in the mid-Pacific within about 1,000 miles of the Hawaiian chain — also in a rather rare region for tropical cyclone formation. Genevieve, however, is not expected to threaten the islands as it tracks westward, taking a long journey toward Asia.

Conditions in Context

These three cyclones generated over warm waters near the central equatorial Pacific. The storms emerged from a convective pattern in a region that typically only shows robust storm development during El Nino.

Though El Nino is not officially ongoing, atmospheric conditions over the past few weeks have become more favorable even as a new warm Kelvin Wave appears to be forming in the waters of the Western Pacific. NOAA still forecasts a weak to moderate El Nino for 2014, but conditions, though somewhat more favorable, remain murky.

Sea surface temperatures in the region of Hawaii

(Current sea surface temperatures in the region of Hawaii are a in rather warm and mostly above average range from 26 to 28 C [80 to 83 F], more than enough to sustain powerful tropical cyclones. Generally, water temperatures above 75 F are needed for tropical cyclone formation and strengthening. The primary limiters to both Eselle’s and Julio’s strength remains wind shear, which is expected to reduce both storms to tropical storm status over the coming days. Even so, Hawaii is in for an ongoing period of unprecedented weather. Image source: National Hurricane Center.)

It’s worth noting that a rash of storms in this region is unprecedented in the satellite era and is especially odd considering that ENSO remains neutral. It is very likely that the outbreak is in some way related to the larger Pacific Ocean warming trend associated with human-caused climate change acting together with an El Nino-like development trend.

UPDATE: Due to warm surface waters in the region of Hawaii and somewhat more favorable than expected atmospheric conditions, Iselle is expected to make landfall on the big island of Hawai’i near Hawaii City later today. Expected maximum sustained winds at the time of landfall are near 75 miles per hour.

Hurricane tracking from NOAA brings the storm directly over the Big Island at around midnight after which the storm is predicted to skirt Maui and Oahu:

NOAA Hurricane Track Iselle

(NOAA’s most recent projected storm track for Iselle. Image source: National Hurricane Center.)


Double Trouble: Hawaii Braces For Hurricanes Iselle and Julio

Climate Change May Increase Number of Hawaii Hurricanes

Projected Increases in Cyclones Near Hawai


University of Maine


National Hurricane Center

Hat tip to Eleggua


Storms of My Grandchildren Rising: Hurricane Amanda Sets Record as Strongest Eastern Pacific Ocean Cyclone in May

Category 5. Only the most powerful of the most powerful storms on Earth reach this ominous peak. It’s a designation that occurs when hurricanes achieve a highly destructive wind strength greater than 156 mph. Usually relegated to late season storms that form and strengthen when the ocean surface temperature is at its hottest, it is a very, very, very rare event to see any storm approach Cat 5 status at the start of hurricane season.

Water temperatures are typically not high enough to support such a monster event so early.

But this Sunday, just six months after the Western Pacific spawned Typhoon Haiyan, the most powerful storm ever to strike the land, the three-day-old hurricane Amanda raged to just shy of Cat 5 status in the Eastern Pacific. Peaking at a maximum sustained wind speed of 155 mph, the storm teetered at the edge of highest intensity category even as it roared its way into the record books as the mightiest storm ever recorded for this region of the world in May.

Hurricane Amanda May 25

(Hurricane Amanda at strong Category 4 status on May 25. Image source: LANCE-MODIS.)

By comparison, the storm Amanda beat out, Adolph, was also a rather recent event, forming on May 25 of 20o1 and reaching a peak intensity of 145 mph on May 29th.

Hot, Deep Water

Hurricane season in the Eastern Pacific starts on May 15. Amanda began to gather just four days after, as a tropical disturbance, on May 19th. The storm gradually gained strength as it drifted north and west into extraordinarily warm waters that ranged from 1 to 3.6 C above typical temperatures for this time of year. By Sunday, May 25, the storm had exploded to just shy of category five status.

Extreme heat intensity fueling Amanda came from a Pacific Ocean exploding with warmth. The equatorial Pacific was just tipping into the hot ocean surface event that is El Nino even as overall Pacific anomalies ranged near 0.8 C above the, already hotter than normal, 1979 to 2000 average. The net result was that Amanda was fueled by sea surface temperatures in the range of 27 to 30 degrees Celsuis with hurricane-supporting warmth pushing as far as 50 meters into the depths. As a result, cool ocean water upwelling through Ekman pumping had far less effect on this storm than is typical for early in the season when the sun’s rays usually have not pushed warmth so deep.

Ocean surface anomaly May 28

(Today’s ocean surface temperature anomaly at +1.13 C on May 28th. Global Ocean surface temperature anomalies have been in the record range of +1 C above 1979-2000 values all throughout May. Hot ocean surface temperatures of this kind is hyperfuel for hurricanes. It is no accident that the record storm that was Amanda formed in the visible hot pool off the west coast of Mexico. Image source: University of Maine.)

Hurricanes are nothing if not ocean heat and moisture engines. The storms feed on hot air rising off the ocean surface, and their cyclonic action churns the waters below them eventually limiting their intensity as the strongest storms dredge into cooler waters. But with human warming, both the ocean surface as well as the waters far below show ever increasing heat potentials. This heat is nothing if not high-efficiency energy for oceanic, warm core cyclones.

Global Warming Heat Engine — Lengthens Storm Season, Generates More Powerful Cyclones

Amanda’s anomalous intensity was, thus, no accident. Instead, it was directly related to the extreme ocean heating that is an attribute of human-caused warming. The danger here is not only for more intense storms and for more intense storms coming earlier and earlier in the year, it is also for a general lengthening of the period during which these powerful storms emerge. The risk, therefore, is that hurricane season will extend deeper into the Spring and further into Fall for both the Eastern Pacific and the Atlantic. And during this ever-growing storm year the higher heat values increase the likelihood of monster storms reaching and exceeding category five strength.

The currently explosive Western Pacific may well foreshadow events for other regions of the world. That volatile storm zone already sees some seasons featuring year-round hurricanes and tropical storms. And the already intense cycle there is also likely to strengthen as the oceans continue to warm.


Dr. Jeff Masters: Amanda Peaks as Strongest May Pacific Cyclone on Record


Abnormally Hot Pacific Ocean Explodes Haiyan into 195 mph Monster

University of Maine




NASA’s Brown Ocean Hurricane: Global Warming Amps Up Hydrological Cycle to Produce Cyclones that Strengthen over Land

New Cyclone Dynamics

(Image source: NASA)

A new report produced by NASA raises the possibility that global warming may be enhancing the potential for what it’s calling Brown Ocean Cyclones. In such events, record rainfall and heat over land produce hot, moist conditions that may give rise to Cyclones that increase in strength even after they make landfall.

A typical hurricane or tropical weather system usually rapidly loses strength once it comes into contact with land. The storms are fueled by a kind of heat and moisture engine. Warm, moist air over oceans hotter than 75 degrees provide big kicks to these storms as they roar across large stretches of ocean. Drier land masses provide less heat and moisture content to feed storms so they usually fade after crossing the coast.

But, over the past three decades, researchers noticed a strange phenomenon — storms that strengthened over land. In one example a 2007 tropical storm named Erin crossed over Texas and Oklahoma. As she turned north into a region that had recently encountered record flooding and rainfall, Erin strengthened, maintaining tropical storm intensity for far longer than meteorologists had predicted.

Erin 2007

Tropical Storm Erin in 2007 was a warm-core TCMI, which can deliver much more rainfall than their extratropical counterparts. The newly described storm type derives energy over land from the evaporation of abundant soil moisture.
Image Credit:
NASA Goddard/Hal Pierce, SSAI


(Image source: NASA)


Researchers later found that Erin had derived its energy from a high rate of soil evaporation in the regions it traversed after it made land-fall.

According to the NASA press release:

Andersen and Shepherd [the report’s authors] show that a brown ocean environment consists of three observable conditions. First, the lower level of the atmosphere mimics a tropical atmosphere with minimal variation in temperature. Second, soils in the vicinity of the storms need to contain ample moisture. Finally, evaporation of the soil moisture releases latent heat, which the team found must measure at least 70 watts averaged per square meter. For comparison, the latent heat flux from the ocean averages about 200 watts per square meter.

The new research found that of 45 storms that maintained or increased strength after they made landfall, 16 did so under the conditions described above. These conditions resulted in a new category for inland storms — tropical cyclone maintenance and intensification events or TCMIs.

Added Cyclone Intensity, Duration and Frequency from Human Caused Warming

Though NASA scientists do not mention the potential for global warming to create and enhance the occurrence of such storms, it is important to examine if the forces set in place by human caused warming and climate change will result in greater instances of such storms. To this point, global warming increases the evaporation and rainfall driven hydrological cycle by 8% for each degree Celsius of atmospheric warming (Lawrence Livermore). And as this new type of inland cyclone is driven by the intensity of evaporation and heat forcing (70 watts per meter squared or more) over land, then meta analysis would seem to indicate a greater risk for such events as Earth heats up and churns more moisture into the atmosphere.

Doing some, rather basic, math we find that a 4 degree Celsius warming creates a 32% intensification in the hydrological cycle, resulting in a greatly increased likelihood that tropical systems moving over land will encounter conditions consistent with TCMIs. This new risk adds to the likely increased frequency of storm hybridization events, like Sandy, where meandering flows in the Jet Stream (caused by Northern Hemisphere sea ice loss) encounter tropical systems to create monstrous Frankenstorms.

So we have not one, but two indirect methods where global warming may intensify or extend the duration of tropical cyclones.

Perhaps more ominous, global warming also provides a direct means through which storms are both induced to form over longer periods during the year and are given added fuel for intensification. This amplification of the ocean heat engine that drives powerful storms comes from the increasing temperature of the ocean surface through human-caused warming. In such cases, both the added atmospheric and ocean warmth and the increased hydrological cycle come directly into play resulting both in the potential for stronger storms and for an increased period of time in which tropical cyclones can form throughout the year.

The end result may be hurricane seasons that last from April or May to November or December in which storms with access to added fuel to feed their intensity may increasingly link up with Arctic weather systems to blow up into massive storms or persist or even strengthen for long periods over land.

These are important risks to consider as the Earth warms and the heat and moisture engine that drives these powerful storms continues to intensify.



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