OBX Wave Report Jan 25 — Surf Set to Build as a Storm Rolls In

Small waves in the range of 0-2 feet are set to build to 2-8+ feet later today as a massive frontal system sweeps in bringing gale force winds and possible thunderstorms.

OBX Wave Report Jan 24 — 1-2 Foot With Another Gale on The Way

A storm gathering over Texas is expected to kick up gale force winds and stormy conditions for the Outer Banks starting late Wednesday. Meanwhile, today, waves across the Outer Banks are in the range of 1-2 foot. Following December’s bomb cyclone, numerous fronts and yesterday’s hurricane force gust at Jennette’s Pier, a larger analysis of Winter of 2022-2023 weather trends for the Outer Banks is included for added local and regional context.


Ellicott City Flood — 1,000 Year Event Looks a Lot Like One of the Rain Bombs of Climate Change

We live in a strange new world, one in which the familiar is all mixed up with the radically altered. Such was the case this weekend when a weather pattern that was pretty normal for summer spawned a single thunderstorm that produced a once-in-a-thousand-years flood event in Ellicott City.

Normal Weekend, Typical Weather Pattern, Abnormal Conditions

On Saturday, my wife and I readied to trek out to Shenandoah National Park for a happily-anticipated summer camping trip. As we headed out the door, the weather pattern looked mostly normal for summer, if a little stormy. A high-pressure system out over the ocean was pulling in moisture off its waters and drawing warm air up from the south. A low over western Pennsylvania and a warm frontal boundary over Maryland created instability in a big zone of convection from Northern Virginia on through to Connecticut. Overall, it was a pretty typical pattern that would probably have produced some moderate-to-strong late-afternoon thunderstorms back in the 20th century. Back then, it was far less likely that a similar pattern would have produced a 1,000 year flood event.

Extreme Ocean Heat 2

(Extremely warm sea surface temperatures on the weekend of July 30-31 helped to fuel the record rainfall event over Elicott City, Maryland. Sea surface temperature anomaly map provided by: Earth Nullschool.)

However, conditions were not normal, not the same as they were back during a time when human fossil-fuel emissions hadn’t forced the world to warm by 1.2 degrees Celsius above 1880s levels. In the new world in 2016, the ocean high-pressure system was circulating over record warm sea surfaces that were 3-5 C hotter than late 20th-century averages. And because of this, the ocean was bleeding off a whole hell of a lot more moisture than it typically would. Any storms that fired in that very wet air mass would, as a result, tend to pump out a lot more rain than is typical.

A Wet Atmosphere Crackling with Unusual Energy

As my wife and I made our way toward the Blue Ridge Mountains and down Interstate 66 and Route 211, large, energetic cumulus clouds sprouted all around us. Wafted in the hot, unstable air, many tops punched up through the troposphere, spreading out into the characteristic anvil shapes of thunderstorms.

Light streamed down between these big, wet beasts. For a while, as we made our way up to the campground, set up our gear, and took a hike along a local rock scramble, we were fortunate — able to enjoy our day despite the loud rumbles and roars of thunder echoing up from the valleys or off the nearby mountainsides in the steamy, moisture-choked air.

Available Rainfall Saturday

(A massive amount of atmospheric moisture fueled powerful thunderstorms on Saturday, July 30 from the Appalachians of northwestern Virginia to the Baltimore City region. One of these storms dumped more than 4.5 inches of rain on Ellicott City, Maryland Saturday in just one hour. Image source: Terp Weather.)

At about 3,000 feet in elevation, these conditions were a bit odd for Shenandoah National Park which typically experiences milder weather. Temperatures were around 80 degrees Fahrenheit (about 5-6 F hotter than average), and the level of atmospheric moisture was amazing. Great, steamy clouds kept rolling up the mountainsides. They made the air heavy and full of shapes dancing with light and shadow, seeming to give it the character of some alive thing sprouting a thousand wet heads and arms.

The big thermals and thunderstorms were supported by hotter temperatures into the 90s (F) down in the valleys. And the storms were taller, bearing more moisture, engorged by a hot atmosphere whose temperatures and water vapor levels are now probably unlike anything seen in at least the past 115,000 years — conditions that would have devastating effect just a couple of hours later and about 100 miles to the east in Ellicott City.

Returning to camp, as we prepared for a hearty dinner of tempeh and veggie pasta, thunder from the southwest grew ever closer and a rolling wave of cloud seemed to spill in through the trees, spreading mist and heavy rain over everything nearby. In just a few minutes, we were scrambling into our vehicle and watching as torrents of rain streamed down, transforming the mountaintop campground into a world of rushing water.

Thunderstorm Dumps More Rain on Ellicott City than Any of the Past Deluges or Hurricanes in its History

At about the same time that my wife and I were scrambling for cover, another massive thunderstorm was bearing down on Ellicott City, Maryland. The storm hit one of the densest pockets of atmospheric moisture in that big bleed off the record-hot Atlantic Ocean and just exploded. Packed with all that unusual and heat-fueled moisture, the storm then began to dump its amazing and unprecedented torrents on this historic town of 65,000 just 20 miles to the west of Baltimore. In only 60 minutes this massive thunderstorm managed to unload 4.5 inches of rainfall. Two-hour rainfall totals approached six inches.

(Restaurant-goers in Ellicott City watch in shock as the street below floods and sends vehicles hurtling past. Video source: Ellicott City Flash Flood.)

Streets were rapidly flooded as the Patapsco River rose to a record 14 feet and leaped over its banks. The main road running through the center of town became a four-to-six-foot-deep torrent that hurtled vehicles along its path or into buildings. First responders scrambled to rescue more than a hundred motorists who were suddenly stranded in the flash flood. Tragically, two people lost their lives.

The force of the flood was so energetic that not only were many of the historic buildings in town damaged, but some had their very foundations torqued off-center, twisted by the great energy of the sudden flood waters churning through town. The Maryland government has declared a state of emergency, but it is uncertain how long it will take to make repairs or how much that is irreplaceable has been lost in the flood.

Two 100+ Year Flood Events For Ellicott City in the Past Five Years

The Washington Post’s Capital Weather Gang appropriately notes that Ellicott City is a pretty vulnerable place for floods:

It’s a highly vulnerable spot, an urbanized strip along the bottom of a deep valley through which the Patapsco River flows. This place, historic Ellicott City, Md., has seen plenty of serious floods: 1868, 1923, 1952. More recently, the remnants of Hurricane Agnes (1972) left an extreme high-water mark, measured in many feet. The Great Mid-Atlantic Flood of June 2006, once again drowned parts of the town.

And another big flood back in 2011 pushed the Patapsco River to 11 feet, prompting a local art gallery to build a 20-inch-high flood barrier. But the unforeseen flood that roared into Ellicott this past Saturday was the worst among all of these. As a result, most protections and flood barriers previously erected were quickly overwhelmed.

Phoenix Macroburst 2

(Dramatic microburst over Phoenix, Arizona on July 21, 2016. Each degree Celsius of warming increases the atmosphere’s water vapor content by about seven percent. This increase, along with other factors such as intensified convection and rising cloud tops, escalates the frequency of extreme rainfall events like the July 30, 2016 Ellicott City flood. Image source: GGferg.)

Two-inch-per-hour rainfall amounts are usually enough to completely overwhelm most drainage infrastructure, overtop banks, and turn streets into rivers. Ellicott City saw nearly six inches of rainfall in two hours and 4.56 inches of rainfall in just one. Such events are typically seen as quite rare (100-year events or more) and building codes do not often account for them. Managing so much water is a major engineering challenge and requires a great deal of investment. Spending so much money on flood defense systems for a storm that might happen in 100 years or 1,000 years can sometimes seem like a waste at the time.

However, in a world warmed by climate change, such floods are happening with greater frequency. A 100 to 1,000 year flood may happen every five years or so in some locations (as has been the case with Ellicott for 2011 and 2016). The atmosphere is loaded more and more with both heat and moisture. The troposphere is taller due to the heat. The oceans are warmer and bleed more moisture. All these factors combine to make even pop-up storms more intense and to generate the 100 and 1,000 year events with a higher frequency in the present day. And as the world continues to warm, such severe storms will become ever more common.


Ellicott City Gets Rainfall Expected Only Once in a Millenium

Two Dead, 100 Rescued as Ellicott City Flood Causes Tremendous Devastation

Ellicott City Flash Flood

Earth Nullschool

How an Off-the-Charts Flood Ravaged Ellicott City


Terp Weather

Hat tip to Colorado Bob

Hat tip to DT Lange

Hat tip to Greg

Hat tip to Griffin

Jet Stream Tattered By Climate Change Brings New Bout of Worst Storms On Record For North-Central US


(Mangled Jet Stream on June 20th, 2014 together with cut-off upper air low threatens record-shattering storms and flood events across a multi-state region from the Dakotas to Minnesota to Iowa and Nebraska over the coming days. Image source: Earth Nullschool. Data source: NOAA.)

If you wanted an example of a Jet Stream mangled by human-caused climate change, you couldn’t find a better one than today’s tangle of upper level winds swirling over North America.

It’s a chaotic maelstrom of split flows, colliding storm tracks, blocking highs, and cut-off upper air lows. A barrel of snakes pattern that’s become ever-more-common since Arctic sea ice plummeted to staggering volume lows of nearly 80 percent less than 1979 levels at end summer of 2012. A loss that opened wide the gates for warm air to flood northward and confuse the hot-cold dividing line that drives this key weather governor.

Over the past week, we’ve seen what amounts to a mess of storms mostly locked in place. A Pacific Ocean flow squeezed between a blocking high off California and an upper level low south of Alaska drew a train of moisture trailing all the way across the Pacific into a hungry cut-off low that had stalled along the border between Canada and the US. Drifting slowly east to west, west to east, the low gorged on the synoptic moisture feed, dumping record rainfall after record rainfall over the Dakotas, Minnesota, Nebraska and Iowa.

100 Year Records Shattered

By the 16th of June, with just slightly more than half the month passed, Sioux Falls South Dakota had crushed its all-time record rainfall for any month by more than 2.5 inches. The previous record of 9.42 inches set in 1898 catapulting to a staggering 13.04 inches by early this week. And with the storm track writhing overhead the rains for the region just kept coming. By yesterday, the twin cities region in Minnesota had rocketed to its second wettest June on record amidst massive rainfall-driven landslides and region-wide preparations for Mississippi River flooding. At 10.33 inches measured rainfall so far, with storms still popping overhead, and with 11 days still remaining in the month, it appears the area may well be set to shatter the previous rainfall record of 11.67 inches set back in 1874.

(Record flooding along the Big Sioux River in Iowa and South Dakota as witnessed yesterday by Storm Chasers.)

All the massive rainfall has built up quite a pulse of flood water that is now moving down major river systems and threatens record flooding events throughout a multi-state region from the Dakotas to Minnesota to Iowa to Nebraska. Residents are being called to aid in sand bagging and other flood mitigation operations as rivers keep rising through numerous regions. According to a report today in the Christian Science Monitor:

“In Iowa, South Dakota, and Nebraska, officials are asking volunteers to build sandbag barriers and other fortifications in advance of the brunt of the storm – but politicians and emergency workers are conceding that their efforts, in some areas, may not be enough.

In South Dakota, workers have begun turning a major Interstate exchange bridge into a temporary levee. While officials there say that will mitigate the flood in many locales, Governor Dennis Daugaard (R) said he expects parts of North Sioux City, S.D., to be underwater by the end of the week.”

Storms Expected to Continue

Today a frontal boundary sweeping out from our upper air low is bringing rains to the Great Lakes and Central Plains region. Meanwhile, behind the front, instability and moisture flow beneath the low continue to result is a high risk for severe thunderstorms accompanied by strong winds, torrential downpours, hail and frequent lightning. Severe storm risks are most extreme for areas of southeastern Nebraska, western Iowa, northern and western Minnesota, and eastern North Dakota.

Already, satellite imagery shows strong storms and accompanying high cloud tops popping up over Nebraska with more likely to follow as afternoon and evening progresses.

Conditions in Context: How Climate Change Intensifies Droughts/Storms

Multiple news agencies are now gathering reports of record storm events throughout the affected multi-state region. Recording agencies and residents alike note a dramatic increase in both the frequency of record events and in their intensity.

Storm precipitation intensity is a measure of how much rain, snow, sleet or hail falls from a given storm over a given period. And what we have seen is an increasing number of record hourly rainfall events in which precipitation totals measure 1 to 2 inches or more within a 60 minute span. Such intense events rapidly overwhelm infrastructure, flood roads, and burst river banks, creating a dangerous situation that often results in numerous water rescues. And both local and national climate reports have marked a major increase in both precipitation and precipitation intensity over the past two decades for regions such as Iowa.

In the context of human-caused climate change, frequency of intense storm events is increased due to rising atmospheric moisture loading. Overall, for each 1 degree C increase in temperature, the hydrological cycle increases by about 7% in intensity. The current .8 C rise since 1880 has resulted in about a 6% increase in the rate of evaporation and of rainfall. So in regions where heat and dryness tend to take hold, the soils tend to dry out faster, tipping into drought conditions far more rapidly and seeing an overall intensification and lengthening of droughts. And in regions where storms do form, they tend to dump far more rainfall than they used to.


(Global warming intensifies thunderstorms by adding convective energy, increasing atmospheric moisture, and expanding the troposphere. As a result, thunderstorm cloud heights increase resulting in more intense rain and hail events. Image source: National Weather Service.)

Changes in the Jet Stream due to loss of sea ice in the Northern Hemisphere also tends to result in more persistent weather patterns. The Jet Stream tends to meander more, spinning off more cut off lows that linger over regions creating instability and rough weather for longer periods. High amplitude waves tend to also form as more warm air invades the higher Latitudes. In the ridges, powerful high pressures tend to dominate. And once these highs establish, they can be very difficult to move. Beneath these blocking highs, droughts proliferate due to the extreme length of dry periods and due to the intensified rate of evaporation. We see such an event now in the 15+ month long blocking high that has so greatly impacted California and the ongoing drought there.

Lastly, increasing convection and a thickening, hotter atmosphere tend to spike storm intensity. In areas where moisture and heat are both high, the explosive rate of evaporation tends to rapidly form storms with very high cloud tops. These cloud tops, now sometimes pushing 50,000 or 60,000 feet pack in more moisture and can generate very intense rainfall events over shorter periods than we are used to.

In these ways, climate change forms an ideal brew for perfect thunderstorms and perfect droughts. With temperatures expected to spike to +2 C or great anomalies over the coming century, we can look forward to extreme weather continuing to intensify with both record rainfalls and record droughts dominating with ever-increasing frequency.




Weather Underground: Record Rainfall in Sioux Falls South Dakota

Twin Cities: Flood Preparation Begins as Record Rainfall Sends Mississippi Rising

Global Warming to Spawn More Severe Thunderstorms

Warming Planet Could Spawn Bigger, Badder Thunderstorms

How Climate Change Wrecks the Jet Stream, Amps up the Hydrological Cycle and Spawns Severe Weather

Hat Tip to Colorado Bob

Hat Tip to TodaysGuestis


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