December 31, 2020

This Is Your World Today | December 31, 2020

Today is the 366th day of the longest year we've been through in a long time. Fires, floods, tornadoes, excessive heat, bitter cold, massive snows, and hurricanes upon hurricanes upon hurricanes—and that's just the weather. It's hard to find beauty amid the chaos, but it's there if you know where to look.

If you're a longtime reader (hi!), you might remember that I used to write "Here's Your World Today" posts in a previous blogging life. I originally started those posts as filler to get through quiet days, but it turned into an enjoyable (but short-lived) series to gawk at happenings around the world. In that spirit, and 'cause goodness knows we could use it, here's a loosely affiliated sequel: This Is Your World Today.

A: Today's big weathermaker in the United States is this blobular (totally a word) winter storm in the southeast. It's producing severe thunderstorms along the northern Gulf Coast, complete with an enhanced risk for tornadoes across parts of Louisiana and Mississippi. The cold side of the storm will bring snow and ice to communities from Texas north through the Midwest. Temperatures will briefly jump into the 60s along the East Coast before the system's cold front sends things back down to a more reasonable level for the beginning of January.

B: It's tough to see the Great Lakes through the clouds—but they're part of the reason there are clouds there in the first place. It's been such a (relatively) warm couple of months in the eastern United States that there's hardly any ice on the Great Lakes. The latest analysis from NOAA showed that just 2.2 percent of the Great Lakes were covered by ice. Ice cover percentages are usually in the double digits by this point in the winter.

C: A strong cold front moving over relatively warm waters of the Atlantic Ocean is a recipe for brilliant streets of cumulus clouds. These are always a sight on satellite imagery. They form as air warms up near the surface of the ocean, forming cumulus clouds as its rises and gets organized into rows (or "streets") by the prevailing winds. 

D: The Amazon's hot and humid climate affords us the opportunity to admire thousand-mile fields of cumulus clouds. Particularly active days will see raucous thunderstorms blow up over the Amazon, raging and randomly scooting around until the instability of the day wanes after sunset. 

E: Actinoform clouds (a close-up is seen at the top of this post) are a near-daily occurrence in the southern Pacific Ocean. These marine clouds take on a radial pattern, kind of developing littles spokes and trippy chains as they form over frigid waters. These clouds weren't discovered until weather satellites first spotted them—it's hard to see their shape from below—and it's still a bit of an open question why these clouds take on their distinctive shape. Some of the clouds over the northern Atlantic in "C" above are also actinoform clouds.

F: It's the sun! Well, the sun's reflection. Each day for about the next six months, the sun's reflection on the ocean surface will tick a little higher in latitude. Maximum sunlight reached its southernmost extent over the Tropic of Capricorn on last week's winter solstice. It's always cool to watch the sun's reflection glisten across the oceans in long satellite loops. (The loops are too sizeable to upload here, unfortunately.)

G: This swirling low-pressure system in the Bering Sea is the strongest storm in that part of the world in years. The system's central pressure dropped to a staggering 921 mb on Thursday, which is about as low as you'd expect in a powerful category four or category five hurricane. I explained on Forbes yesterday how this storm got so strong—and why it's so different from a hurricane.

H: Hey, look, Hawaii! Very pretty. It's always interesting to look at the islands on satellite imagery because it's obvious which way the winds are blowing. Moist winds blowing out of the northeast dry out as they pass over the islands, leaving clear skies downwind.

[All satellite images from NOAA.]

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December 24, 2020

A Boisterous Windstorm Will Usher In A Frigid Christmas Across Much Of The Eastern U.S.

A coast-to-coast storm will reach its peak tonight as it shoves its way across the eastern United States, bringing some combination of dangerously strong winds, severe thunderstorms, flooding rains, and heavy snow to everyone from the southern tip of Florida to the northern reaches of Maine. This storm will be highly disruptive in many areas as it pushes through.

As we've seen out west already, a strong pressure gradient will lead to ripping winds as the system strengthens. The low already produced heavy snow and intense winds across much of the north-central part of the country. Intense winds buffeted communities in the Rockies and on the Plains earlier this week. A significant portion of Minnesota and Iowa endured blizzard conditions during the day on Thursday, whiteout conditions that made driving a fool's errand and simply walking around without getting disoriented just about as difficult.

More snow will fall as the system tracks east. The greatest snowfall totals—read: the greatest chance for a white Christmas—will fall in the Ohio Valley and the Appalachians. Some areas could see a decent li'l snowstorm, with totals exceeding half a foot in higher elevations of West Virginia. Lake effect snow on the eastern shores of the Great Lakes will bring a fresh blanket to communities that are plenty acclimated to those conditions.

Farther east, it'll be rain, storms, and wind. Ugly stuff any time of the year, but just brutal for Christmas Eve. Even though people shouldn't be traveling (NUDGE NUDGE), people will travel anyway, and those folks—hopefully not you, my loving and health-conscious reader—should pay attention to the weather and make plans to quickly get to safety if they roll up on dangerous storms or flash flooding.

Flash flood watches are in effect for a vast swath of the eastern United States, stretching from Tennessee to New England's border with Canada. It's not going to be a tremendous amount of rain, but a few inches of rain will fall quickly—that's a problem on its own, but many of these areas still have snow on the ground from last week's storm, so between existing snowpack, rapid snow melt, and clogged storm drains, some areas could deal with flash flooding.

Severe thunderstorms will be an issue closer to the coast. I went into detail about the threat over at my Forbes column on Wednesday afternoon. There's an enhanced risk for severe weather in parts of eastern North Carolina and Virginia on Thursday afternoon and evening. That's a pretty significant risk for this region this late in the year.

Any thunderstorms that form have the potential to produce damaging wind gusts and tornadoes, especially in the discrete storms that form ahead of the cold front. These individual thunderstorms ahead of the main line have the greatest chance of developing into supercells capable of producing tornadoes.

This storm will likely be remembered for its wind. It's going to be windy. Wiiindy. The wind will follow the track of the low-pressure system from the Mid-South straight through New England on Friday. Widespread wind gusts of 40 to 50 MPH will be the norm across many eastern states, with higher gusts likely in thunderstorms, higher elevations, and communities close to coastlines.

Wind alerts scattered around from Texas to Maine in anticipation of widespread gusty winds. Gusts greater than 60 MPH could be common in parts of New England, which will easily knock out power. Widespread power outages are going to be difficult for power crews to get a handle on, so there's a good chance that many communities will spend Christmas without electricity as a result of this storm.

Make sure you're prepared for a power outage. Keep flashlights (actual, physical flashlights) and plenty of batteries to keep them going for at least several days. Gather some non-perishable, ready-to-eat food and water so you don't scramble to find something to eat if you can't cook anything, keeping in mind that McDonald's and Pizza Hut probably won't have power either. And please be mindful of candles and fireplaces as you try to see and keep warm.

It's going to be tough to keep warm in many areas. That cold front is a doozy. Temperatures plummeted 30-40°F in many areas in the central U.S. High temperatures will struggle to climb above freezing in many parts of the east on Christmas.

Here's the National Weather Service's high temperature forecast for Friday. Some of these high temperatures in New England will occur not long after midnight, plummeting through the morning and day after the cold front passes through. (Temperatures will be quite nice on the Plains, though, as a ridge builds in behind the big storm.)

And here's their low temperature forecast for Friday night:

Brr. The chilly air makes it all the way to southern Florida, which won't escape this burst of cold air without a morning in the mid 40s. 

It's not going to linger for too long—temperatures will slowly moderate after this weekend—but it's going to stick around just long enough to remind you that we're in the throes of winter now.

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December 15, 2020

A Significant Winter Storm Will Plaster The Mid-Atlantic And Northeast This Week

Gird your loaves and invest in milk futures: a snowstorm's comin'. A big one, in fact. Parts of the Mid-Atlantic and Northeast are getting ready for the season's first big-time snowstorm. Some areas will see more snow than they've seen in two years—of course, that's not as impressive as it sounds considering last winter's snows were a dud in the Mid-Atlantic. As we see with so many coastal storms, the precise track of the storm will determine whether you get blanketed by snow or shrouded by bitter disappointment.

The Setup

A trough in the jet stream will drive the formation of the low-pressure system that will become our mid-week winter storm. A low-pressure system will develop in the Carolinas on Tuesday night and move up the coast through Thursday. The system will have plenty of moisture and cold air to work with, so there's not much wishy-washiness about whether or not the system will produce big snowfall totals. There's going to be a sharp cutoff between blockbuster snows and a nuisance, so the ultimate track of the storm will make a big difference on who sees huge snows or a cold rain.

The Timing

Rain will begin over the southeast on Tuesday night and Wednesday morning as the low-pressure system starts to develop. The storm will pick up intensity in a hurry as it approaches the Mid-Atlantic, which is when wintry precipitation will start on the northern side of the storm.

Freezing rain will likely begin in western North Carolina and parts of western Virginia on Wednesday morning and afternoon. Temperatures will eventually climb above freezing across areas expecting freezing rain, so the question will be how long it takes the subfreezing air at the surface to erode. The longer it sticks around, the thicker the crust of ice will grow. It shouldn't be a big ice storm, but any crust of ice is dangerous when there's ice on the roads and if tree limbs or power lines snap under the weight. Temperatures should—should!—climb above freezing by late afternoon across most areas expecting ice.

Farther north, the snow will begin on Wednesday afternoon west of D.C. and spread north through the afternoon and evening hours. Precipitation will taper off on Thursday morning from west to east. 

The Track

Six runs of the GFS model showing how tiny shifts in the storm's position can move around the rain/snow line. SOURCE:

Track track track. Track? Track. Okay, I got that word out of my system. It'll be like Edith and the cling peaches. Won't say that word again.

The structure of coastal storms like this is usually pretty textbook. The rain/snow line follows close to the tra—uh, path—of the center of the low-pressure system, so you wind up with rain to the south/east and snow to the north/west. You get a pretty heavy shield of snow to the northwest of the low that accounts for the greatest snowfall totals. If that line sets up near I-95, you wind up with those memorable storms that immobilize big cities for an entire week.

Since precipitation type and totals are so heavily dependent on the storm's motion, getting it right is crucial to the forecast. If the storm moves 20 miles to the right or to the left of what was forecast, the rain/snow line and shield of heavy snow will follow suit. That could result in surprises and disappointments.

Right now, it's likely that any jog in the storm's motion would be a northerly jog, which would push the heaviest snowfall totals north.

The Snow

Speaking of surprises and disappointments, check out that tremendous cutoff between lots of snow and not much at all. That's why even a tiny shift in the storm's motion could result in a tremendous difference in snowfall amounts for these densely populated communities.

Right now, the National Weather Service's forecast calls for more than a foot of snow from northwestern Virginia to southern Connecticut, which is a vast swath of real estate at risk of seeing a great deal of snow. The greatest totals are likely in central Maryland, eastern Pennsylvania, northern New Jersey, and the Hudson Valley in New York—these areas could see more than a foot-and-a-half of snow by the end of the storm.

Again, it won't take much for that sharp cutoff in totals to nudge a dozen or two miles to the right or to the left, which could have big implications for densely populated communities along I-95. When you're preparing for a storm, it's always best to prepare for the worst so you're ready no matter what happens.

The Weather Prediction Center's new Winter Storm Severity Index (WSSI) shows major to extreme impacts across areas expecting more than a foot of snow. The greatest disruptions are likely in eastern Pennsylvania and northern New Jersey, where a combination of deep snow on the ground and the weight of the snow on trees, power lines, and flat roofs could cause major issues.

Across the hardest hit areas, travel will be all but impossible during and immediately after the storm. It could take several days for crews to reach residential areas. Hopefully the fact that travel is at a minimum and work/school is predominately conducted at home these days will make it easier for crews to safely clear the roads in a reasonable amount of time.

Now that most trees have lost their leaves and the snow isn't going to be particularly wet, there shouldn't be a widespread risk for power outages, but this much snow built up on power lines and tree limbs could lead to some power outages.

It's likely that the snowpack will stick around for a while after the storm—it doesn't look like there are any significant warmups on the way for the eastern states.

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December 4, 2020

The Season's First Big Nor'easter Could Bring A Foot Of Snow To Interior New England

The first significant nor'easter of the season will bring heavy snow to parts of New England this weekend. It's got everything: a sharp cutoff in totals, uncertain snow amounts, and small changes in the storm's path having a big impact on what ultimately happens. Hey, at least we're not talking about hurricanes anymore, right?

The storm that will become the nor'easter—which, by the way, doesn't have a name, since we don't name winter storms in the United States—will get its act together tonight over the southeastern states. Precipitation will begin as heavy rain and thunderstorms in the Carolinas as the low-pressure system organizes and starts to move toward the coast.

Here's what to expect.

Rain And Severe Thunderstorms

Heavy rain and thunderstorms will begin to overspread the Carolinas tonight through early Saturday morning. Not only will the rain be quite heavy at times—with a quick inch or so of rain possible—but there's a possibility for severe thunderstorms in eastern North Carolina.

The Storm Prediction Center issued a slight risk for severe weather across the far eastern portion of the state through Saturday morning, with a marginal risk extending westward into the Piedmont Triad.

The greatest risk will be damaging wind gusts of 60 MPH, but tornadoes are possible, especially in the slight risk area in eastern N.C. There will be enough wind shear on the eastern side of the developing nor'easter that discrete thunderstorms ahead of the main line could rotate and produce tornadoes.

Elsewhere, it's just a heavy rain threat. Precipitation will fall as rain across most inland and coastal areas until you reach deep into New England. Even areas that could see snow at the end of the storm, such as Boston and Portland, will see rain for most of the storm.

The heaviest totals are likely along the coast—Cape Cod could see up to two inches of rain by the end of the storm. This isn't a blockbuster rain event, but it could cause some flooding issues, especially where any storm drains are clogged by fallen leaves.


Plenty of cold air over interior New England will ensure that the northwestern side of the storm will produce the first decent snowstorm of the year for the region. The latest forecast from the National Weather Service calls for more than half a foot of snow through much of Massachusetts, Vermont, New Hampshire, and Maine, with the greatest totals likely from northern New Hampshire northward into Quebec. Augusta, Maine, could see more than a foot of snow by the end of the storm.

Precipitation will begin as rain on Saturday, quickly changing over to snow as the evening wears on. Snow will continue through Sunday afternoon as the storm pulls away into Atlantic Canada. There's a decent chance that rain will end as snow near the coast, possibly bringing a light blanket of snow to Boston.

The first big snow of the year is a big deal no matter where you live because it takes a little while to acclimate yourself to shoveling, walking, and driving in the stuff. The Weather Prediction Center's new Winter Storm Severity Index (WSSI) calls for minor to moderate impacts across the region, mostly for a combination of snow amounts and the "snow load," which is the weight of wet snow on trees, power lines, and roofs. This is going to be a wet snow, so that'll increase the risk for downed tree limbs, power outages, and it'll make it more difficult to shovel.

It's important to remember one of the rules of winter weather forecasting: small changes in storm track have a big effect on the final result. This especially holds true for nor'easters. If the storm moves one or two dozen miles to the east or west of what forecasters expect, it would move the axis of heavy snow accordingly. That could mean that areas expecting minor (or no) accumulations wind up with a shovelable snow, while areas bracing for a big thump get less than expected. Keep checking forecasts this weekend so you're ready if things change in your area.


It's going to get pretty windy behind the system. Gusts of 40 MPH are possible well behind the system into the Carolinas, which could lead to sporadic power outages where trees, already stressed by the parade of storms this summer and fall, struggle to keep their grip in the wet soil.

Up north, gusty winds will follow the snow on Sunday. Wet snow is bad enough on tree limbs and power lines, but the added stress of gusty winds could cause some issues. The risk for power outages ticks up with heavier totals, so folks from Worcester, Massachusetts, north through interior Maine should be ready for at least a day or so without power, just in case.

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November 16, 2020

Hurricane Iota, Latest Category Five On Record, Making Landfall In Pummeled Nicaragua

This has been one heck of a hurricane season and "it can always get worse" seems to be the rule at the moment. It's the middle of November. We're on our unprecedented 30th named storm. And Hurricane Iota, now a category five hurricane with 160 MPH sustained winds, is on track to make landfall in almost the exact same spot in Nicaragua where category four Hurricane Eta made landfall two weeks ago. Come on.

Iota rapidly intensified into a scale-topping hurricane on Monday morning as it encountered near-ideal conditions in the western Caribbean. The region features a deep reservoir of warm waters, light winds aloft, and ample moisture, all the necessary ingredients for a storm to thrive. The only limitation on the storm is that water temperatures—even a steamy 84°F—will only allow storms to intensify so far.

The latest forecast from the National Hurricane Center puts the storm into the Nicaraguan coast at full intensity. The only thing that could weaken the storm right now is either a hiccup in its internal structure that causes it to temporarily weaken, or the beginning of an eyewall replacement cycle that has the same effect. Time is running out for that to happen, though, and the storm is so strong that the catastrophic effects are essentially baked in at this point.

The National Hurricane Center's 10:00 AM EST discussion succinctly sums up the threat:
This is a catastrophic situation unfolding for northeastern Nicaragua with an extreme storm surge of 15-20 ft forecast along with destructive winds and potentially 30 inches of rainfall, and it is exacerbated by the fact that it should make landfall in almost the exact same location that category 4 Hurricane Eta did about two weeks ago.
Hurricane Eta killed more than 100 people in Central America after multiple feet of heavy rain triggered flash flooding and mudslides. It's always difficult to outline the true worst case scenario for any one region when a hurricane makes landfall, but Central American countries preparing for a category five hurricane just two weeks after the devastating winds and flooding of a category four hurricane has to sit pretty high up on the list. 

Adding insult to injury, there's a chance that another storm will form in the western Caribbean later this week. Indications point to the potential system not being quite so strong, but even a gentle shower over areas hit by these two hurricanes would make a horrible situation worse.

An infrared satellite image of Hurricane Iota on November 16, 2020. | Source: NOAA

The tropical Atlantic usually starts shutting down by the middle of November. The end of hurricane season isn't a hard deadline—it's based on climatology that shows waning tropical activity in the Atlantic as the cool, dry, and hostile winds of autumn start to call the shots in the northern hemisphere. While that's what usually happens, that isn't the case this month.

In addition to warmer-than-normal waters in the western Caribbean, Hurricane Iota likely managed to strengthen as a result of La Niña in the Pacific and a ridge of high pressure over eastern North America. 

La Niña, a period of cooler-than-average waters in the eastern Pacific, subdues thunderstorms over the eastern Pacific that could send strong wind shear eastward over the Caribbean. The ridge of high pressure over eastern North America, the one responsible for the relatively warm and calm weather we're experiencing today, further calmed the atmosphere over the Caribbean, fostering an environment where Iota could build itself up as much as possible.

It's also difficult to ignore the influence of climate change in a situation like this. We can't "pin" any one storm on climate change, but when you see rapid intensification in one storm after another, year after year, it becomes a worrying trend that could signal that we've crossed a threshold when it comes to warmer ocean waters and more favorable atmospheric conditions for rapid intensification.

Oh, and just in case you're keeping track...

Hurricane Iota is the 30th named storm of the season. The previous high water marks were 28 storms in 2005, 20 storms in 1933, and 18 storms in 1995.

We exhausted the list of 21 names back in September. Iota is the ninth letter of the Greek alphabet.

Hurricane Iota is the latest category five hurricane on record in the Atlantic Ocean.

This is the sixth major hurricane this season. 

This is the fourth storm to reach at least category four intensity this season.

This is now the fifth season in a row we've seen at least one category five hurricane in the Atlantic.

This is the eleventh storm this year to undergo rapid intensification, having jumped from 105 MPH to 160 MPH in just 12 hours. (Rapid intensification occurs when a storm strengthens about 35 MPH in one 24-hour period.)

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November 12, 2020

Why Tropical Storm Eta Followed Such An Odd, Zig-Zaggy Path Toward Florida

It's not a surprise that a strange storm formed during a strange year. We've been watching Tropical Storm Eta for almost two weeks now. The storm's followed a zig-zagging path from the Caribbean to the Gulf of Mexico, a winding journey that brought devastating flooding to Central America and more than a foot of rain on southern Florida. Here's a quick rundown of why the storm followed such an odd path.

Eta is the 28th named storm of this hyperactive and historic Atlantic hurricane season. The storm, named after the seventh letter of the Greek alphabet, formed in the middle of the Caribbean Sea on October 31. This is exactly where you'd expect to see tropical development this late in the season. The Caribbean is really the only oasis left for tropical cyclones once you reach October and November.

Prevailing winds steered Eta west across the Caribbean Sea in the days following its formation. A ridge of high pressure over the western Atlantic intensified as the system approached Nicaragua, causing it to make a southward jog that steered it directly into the Nicaraguan coast.

The storm rapidly intensified as it approached landfall, growing into a powerful category four hurricane just about a hundred miles off the coast. Any tropical system in this region has the potential to generate catastrophic flash flooding and mudslides, but this storm's ferocity made a dangerous situation even worse. News reports indicate that more than a hundred people may have died in the region as a result of the storm's flooding.

Environmental winds beneath ridges of high pressure are usually pretty calm. The lack of steering currents forced Eta to putter over Central America for a couple of days, slowly weakening as it turned north over Honduras. After entering the western Caribbean two days after landfall, the system regenerated into a tropical storm and drifted north over Cuba as it approached Florida.

This is where the track got a little...creative.

A large ridge of high pressure over the eastern United States and western Atlantic effectively blocked Eta from continuing out into the Atlantic after it crossed over Cuba. This forced the storm to make a westward hook into Florida, making landfall at Lower Matecumbe Key on November 8.

As the ridge moved eastward, Eta slowed to a crawl over the southeastern Gulf of Mexico. The storm slowly drifted toward the tip of Cuba before an approaching trough forced Eta to start moving northeastward. The tropical storm briefly restrengthened into a hurricane as it moved parallel to the west coast of Florida—winds were strong enough in the Tampa area to generate coastal flooding from storm surge. 

Eta made its fourth landfall in Florida's Big Bend region on Thursday morning, and the system will accelerate out to sea and dissipate as it gets swept up by a cold front moving over the eastern United States.

This isn't the end of it. We're likely going to see our 30th named storm of the season form in the Caribbean by this weekend, possibly threatening the same stretch of Central America hit by Eta last week.

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November 9, 2020

Subtropical Storm Theta Makes 2020 Atlantic Hurricane Season The Most Active On Record

Of course it was going to come to this: Subtropical Storm Theta formed in the eastern Atlantic Ocean on Monday night, becoming the record 29th named storm of the 2020 Atlantic hurricane season. This is now the most active Atlantic hurricane season on record, beating the hyperactive 2005 hurricane season by one storm. Theta will slowly drift through the eastern Atlantic through the end of the week.

Theta formed far to the southwest of the Azores Islands from a cluster of thunderstorms along a frontal boundary. The cluster of storms became organized enough for the National Hurricane Center to declare the system a subtropical storm and begin issuing advisories.

A subtropical storm is a low-pressure system that exhibits both tropical and extratropical characteristics—it's a hybrid storm that looks and acts like a tropical cyclone, but it's not completely warm throughout and it derives some of its energy from upper-level winds.

The National Hurricane Center's current forecast shows Theta transitioning into a tropical storm as the thunderstorms near the core of the storm take over as the system's energy source. Theta will pose no threat to the United States, but it could bring hazardous conditions to Madeira this weekend or early next week.

Theta is the 29th named storm of this historic hurricane season. The previous record was 28 storms set back in 2005. The 2020 hurricane season beat 2005's record by starting early—Tropical Storm Arthur formed on May 16—and by racking up the storm count through several stretches of rapid-fire storm development.

Theta is the eighth letter of the Greek alphabet. The next letters in the Greek alphabet are Iota, Kappa, and Lambda. There's a decent chance we see at least one more storm this year. Hurricane season runs through November 30, and the final storm of the 2005 hurricane season developed on December 30.

[Satellite Image: NOAA]

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November 6, 2020

Tropical Storm Watches Up For South Florida As Eta Strengthens And Lingers

It's been...quite the news week...but something that shouldn't get lost in the chaos is that the atmosphere is still minting storms like they're state quarters. Eta, the 28th named storm of this historic hurricane season, is still plunking along in the western Caribbean Sea. Forecasters expect Eta to regain tropical storm strength as it heads toward Cuba and Florida through early next week.

Hurricane Eta made landfall in Nicaragua on Tuesday with maximum winds of 140 MPH. The system slowly wound down as it lingered over Nicaragua and Honduras these last couple of days, producing intense winds and several feet of rain over a region that's exceptionally vulnerable to flash flooding and mudslides.

The storm's core, while degraded, made it back over the Caribbean largely intact, giving the system a leg-up on reorganizing and strengthening as it moves over warm waters and encounters a favorable environment. Tropical storm conditions are likely across the Cayman Islands and much of Cuba over the next couple of days as Eta heads north.

Forecasters expect Eta's rain and wind to reach southern Florida by Sunday and linger for a couple of days as the tropical storm hesitates a bit. A ridge of high pressure to the north and east of Florida will prevent Eta from moving out to sea—without a clear exit, the storm is forced to meander into the Gulf of Mexico. What happens after that, though, is something we'll have to wait and watch.


If the current forecast pans out, Eta will arrive in southern Florida with sustained winds around 60 MPH with higher gusts. That's a pretty stiff sustained wind—they issue severe thunderstorm warnings for gusts that strong. It's enough to bring down trees and knock out power. Folks in southern Florida don't need to be told to prepare for power outages and whatnot, but it never hurts to take a look around to make sure you've got enough food and batteries to get through a day or two in the dark.


The rainfall here is a two-part story. We've got rainfall from Eta and rainfall influenced by Eta.

The greatest rainfall totals are likely across the southern tip of Florida as Eta passes through the area. Some communities could see up to half a foot of rain where the most persistent bands set up. Rainfall amounts are contingent upon the structure of the storm and its speed when it gets there. If it's better organized and meanders for a day or two as predicted, that leads to better odds of greater rainfall totals than if it's disorganized or moves faster than expected.

The rain farther north—from the Carolinas through the Northeast—is influenced by Eta. This is rainfall enhanced by the tropical moisture pushed north into the region. Several inches of rain are possible through the middle of next week. Heavy rain might cause some localized flooding issues—watch out for drains clogged with fallen leaves—but it'll likely just lead to a couple of dreary, rainy days.

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November 2, 2020

Hurricane Eta Rapidly Intensifies Into A High-End Category Four As It Approaches Nicaragua

Hurricane Eta rapidly intensified into a powerful category four hurricane in the western Caribbean Sea on Monday, packing maximum winds of 150 MPH as of Monday evening's advisory from the National Hurricane Center. This was...not anticipated until the strengthening trend had already begun, and now Eta is the strongest storm of the 2020 Atlantic hurricane season.

Satellite intensity estimates place Hurricane Eta in the upper echelon of storms. These automated intensity estimates use cloud patterns and temperatures (on the cloud tops and within the eye) to estimate the strength of a storm. It has a warm eye, a symmetrical and well-insulated core—an "angry wind bagel" as I used to tongue-in-cheekedly call it in a past blogging life—and the all-knowing algorithms consider it about as visually perfect as a hurricane can get.

Aircraft recon flying into the storm Monday night found winds pushing the upper bounds of category four intensity. The official NHC forecast brings the system up to category five intensity before it makes landfall in Nicaragua on Tuesday.

What else can you say? It's times like this when descriptors and pointing out broken records kinda loses its punch. Eta is the record-tying 28th named storm of the season. Eta is now one of the strongest Atlantic hurricanes ever observed in November. Its sudden and rapid period of intensification puts it up there with...well, pretty much every other hurricane we've seen this season, but this storm pushes the upper bounds for the fastest intensification seen in the Atlantic.

Here's the storm's wind history, taken from the NHC's updates every three hours since Saturday night. (All times Eastern.)

1100 PM SAT:    40 MPH / 1005 MB
100 AM SUN:    40 MPH / 1005 MB
400 AM SUN:    40 MPH / 1005 MB
700 AM SUN:    40 MPH / 1005 MB
1000 AM SUN:  50 MPH / 1000 MB
100  PM SUN:    50 MPH / 1000 MB
400 PM SUN:     65 MPH / 992 MB
700 PM SUN:     70 MPH / 989 MB
1000 PM SUN:   70 MPH / 989 MB
100 AM MON:   70 MPH / 989 MB
400 AM MON:   75 MPH / 987 MB
700 AM MON:   90 MPH / 974 MB
1000 AM MON  110 MPH / 962 MB
100 PM MON  : 120 MPH / 957 MB
400 PM MON:   130 MPH / 948 MB
700 PM MON:   150 MPH / 934 MB
1000 PM MON: 150 MPH / 927 MB

Meteorologists expected Eta to rapidly intensify given the warm sea surface temperatures and low wind shear surrounding the storm. However, rapid intensification is still very difficult to accurately predict, and it wasn't clear that this storm was going to explode the way it did until the process was already underway.

This is a terrible development for folks in the path of the storm. 

Yesterday—yes, yesterday—the storm looked like it would creep up to hurricane status and become a major flood threat for Nicaragua, Honduras, and El Salvador. That's a pretty bad situation on its own. The region is poor, geographically primed for major flash flooding and mudslides, and also stricken by the same pandemic as the rest of the world. The potential for flooding alone could have produced a humanitarian catastrophe.

Now this is a different situation altogether. A major, potentially historic storm is knocking on the region's door. The winds of a high-end category four hurricane will devastate communities with destructive winds and a catastrophic storm surge that could easily inundate one-story buildings near the coastline. And that's on top of flash flooding and mudslides from several feet of heavy rain.

As I mentioned last night, landfall isn't the end of this system. We have to watch what it does by the end of the week. Eta could regenerate into a tropical storm in the western Caribbean. Don't let your guard down if you live along the U.S. coast. Hurricane season isn't over yet.

[Satellite imagery from NOAA. Top image is infrared and the bottom image is water vapor.]

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November 1, 2020

Tropical Storm Eta, Historic 28th Named Storm Of 2020, Threatens Central America This Week

Tropical Storm Eta could strengthen into a hurricane before making landfall in Central America later this week, bringing damaging winds and flooding rain to parts of Nicaragua, Honduras, and El Salvador. The storm's slow movement will lead to widespread flash flooding across a mountainous region that's exceptionally vulnerable to flash flooding and mudslides.

Models have signaled for a while that the Caribbean would be favorable for tropical development around the beginning of November. Just like Zeta last week and Delta before it, Eta formed right about where you'd expect to see tropical systems develop this time of year. The Caribbean is home to the warmest waters and the most favorable atmospheric conditions to support tropical development this late into the season.

Eta will slowly move west toward Central America over the next couple of days. Hurricane conditions are likely in eastern Nicaragua and eastern Honduras on Wednesday as Eta makes landfall. While the wind will damage weaker structures and the electrical grid, the big story from this storm is rain.

Any tropical cyclone making landfall in Central America is a scary prospect because of the region's heavily mountainous terrain.

The National Hurricane Center's latest forecast notes the potential for 15-25 inches of rain in parts of Nicaragua and Honduras, with upwards of three feet (really!) of rain possible in higher elevations. Tropical cyclones are terrible in mountainous regions because the moist winds of a hurricane roaring up the side of a mountain is the atmospheric equivalent of wringing out your washcloth in the shower.

There's some nervous hesitation about what happens after Eta makes landfall. The most likely scenario, the one depicted by the NHC's forecast, is that Eta will slowly degenerate over land as the rough terrain takes its toll on the storm's structure.

There's a chance that either 1) the storm reemerges into the Caribbean later in the week, or 2) a different storm forms in the same area. It's a little too far off to say anything for sure, but it's something to file in the back of your mind so it doesn't come as a galloping shock in our post-election daze. 

Speaking of the potential for one more storm...

Some (More) Record-Keeping

Eta is the 28th named storm of the 2020 Atlantic hurricane season, tying the all-time record of 28 storms seen back in 2005.

Matching 2005's record is a remarkable feat for a remarkable year. It's tremendously difficult for the Atlantic basin to produce this many storms in one season. The previous all-time high was 20 storms back in 1933. Even hurricane seasons held in infamous regard like 1995 and the 2010-2012 stretch were only able to produce 19 storms each.

While 2005 stands alone for the sheer strength of the storms that formed that year—Dennis, Emily, Katrina, Rita, Wilma— this year saw its 28th storm nearly two full months before that historic season. The 28th named storm formed on December 30, 2005, so there's a decent chance this year could break the record before it's over.

The next three names on the list are the Greek letters Theta, Iota, and Kappa.

This is also the first time we've ever used the seventh Greek letter—Eta—to name a storm in the Atlantic.

The "missing" storm from the 2005 season was an unnamed subtropical storm that forecasters didn't catch until they conducted their routine post-season analysis the following spring. If forecasters had caught the unnamed storm contemporaneously, it would've been called "Subtropical Storm Tammy" and every subsequent storm that formed after October 4, 2005, would've been pushed back one letter, making the final storm Eta instead of Zeta.

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October 27, 2020

Hurricane Zeta Will Bring Strong Wind, Heavy Rain To Northern Gulf Coast On Wednesday

Tropical Storm Zeta will restrengthen into a hurricane before making landfall in eastern Louisiana on Wednesday. The storm made its first landfall as a hurricane near Cancun on Monday. Forecasters expect Zeta to restrengthen as it accelerates toward the northern Gulf Coast over the next day. Strong winds, a dangerous storm surge, flash flooding from heavy rain, and tornadoes are possible as the storm races inland.

The tropical storm had a tremendous pinwheel appearance on satellite imagery this evening. The system's outer bands and upper-level outflow covered most of the Gulf of Mexico. It's one of the most stunning satellite images we've gotten from a storm in a while.

A closer look at the core of the system shows a tropical storm that's on the cusp of strengthening. Favorable conditions over the southern Gulf of Mexico, combined with sufficiently warm sea surface temperatures, should allow the storm to regain hurricane strength as it picks up speed and moves toward eastern Louisiana.

There's a chance that the storm could ramp up rather quickly tonight, especially if that eyewall can wrap around and close itself off. Given the expected increase in its forward speed, it'll be difficult for the storm to shed much of the strength it manages to build up as it nears landfall.

Eastern Louisiana has been in the cone of uncertainty quite a few times this year. Laura and Delta went west. Marco weakened. Sally went east. But those were different storms in different situations. Zeta looks like it's on a direct approach to eastern Louisiana, with hurricane conditions likely in and around New Orleans at the height of the storm. Don't let your guard down because all the other storms missed you. This one probably won't miss.

Once the storm makes landfall, Zeta will get swept up by a cold front as the system races over the southeast. The system could actually start to restrengthen a bit as it moves inland toward the Mid-Atlantic as a result of extratropical transition. The system will start gathering some of its energy from the jet stream on Thursday, which could lead to an increased threat for damaging winds for folks well inland from the point of landfall. 


The greatest potential for wind damage will occur at and around the point of landfall. Hurricane force winds can easily blow down trees and power lines. Folks who experience the strongest winds should prepare for power outages that last at least a couple of days.

Even though the storm will weaken to a tropical storm as it moves inland, don't think that you're in the clear when it comes to strong winds. Tropical storm watches extend into northern Georgia in anticipation of a thump of strong winds as Zeta and its remnants race through the area. Somewhat similar to what we saw with Isaias a couple of months ago, the storm will begin feeding some of its energy from the jet stream like an extratropical cyclone. This will allow Zeta to produce strong winds over a wide area even when it's hundreds of miles inland.

If you're anywhere near the forecast path of the storm—whether you're on the Gulf or in central North Carolina—take stock of your supplies and make sure you've got enough food, water, batteries, and other items necessary to make it through a power outage.

Also, try to avoid rooms where large trees or tree limbs loom overhead outside. Trees falling into structures are responsible for lots of injuries during storms like this.

Storm Surge

Source: NHC

A life-threatening storm surge could occur along the coast when Zeta makes landfall. The latest forecast from the National Hurricane Center calls for a potential maximum storm surge of 5 to 8 feet above ground level near and to the right of the point of landfall. Based on the current forecast, this maximum surge is possible along the coast in Southern Mississippi and Dauphin Island, Alabama. A storm surge could extend as far east as Florida's Big Bend. 

Folks who live at the coast don't really need to be told this, but storm surge is nothing to mess around with. The water can rise quickly and cut off means of escape before folks who stayed behind realize that they should've evacuated. If you're told to evacuate, it's wise to heed the word. Once the storm is raging, you're on your own until it's over.


Heavy rain will track along Zeta's path inland. The Weather Prediction Center expects up to 5 inches of rain in southern Mississippi. The threat for flooding rains will follow the path of the storm all the way through the Mid-Atlantic, where several inches of rain are possible by the end of the week.

This much rain in such a short period of time will lead to flash flooding issues in vulnerable areas.

Flash flooding is the leading cause of fatalities during landfalling tropical cyclones in the United States. It only takes a few inches of moving water to lift up a vehicle and carry it downstream. It's impossible to judge the depth of the water over a roadway until it's too late, and sometimes the road isn't even there anymore underneath the floodwaters.

If you have to go out during the storm, make sure you know several ways to get around so you an avoid flooded areas.

It's worth noting that not all of the rainfall on this map is from Zeta. Much of the rain west of the Mississippi River is from the storm system producing a major ice storm in Oklahoma and Texas, while the bulk of the rain over the Mid-Atlantic and Northeast is from Zeta merging with that storm system by the end of the week.


As always, there's a threat for tornadoes as the hurricane makes landfall. The greatest threat lies to the right of the storm's forward motion, which puts the greatest tornado risk in parts of Mississippi, Alabama, and Florida on Wednesday evening.

Tropical tornadoes occur quickly with reduced lead time. Even though these tornadoes tend to be weaker than we'd see in a springtime outbreak, even the smallest, weakest tornado is a life-threatening hazard if you're in its path. Make sure you've got a way to receive tornado warnings the moment they're issued by activating the Wireless Emergency Alerts feature on your smartphone.

[Satellite Images: NOAA]

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October 25, 2020

Yet Another Tropical Storm Could Hit The Gulf Coast This Week

Tropical Storm Zeta could make landfall on the northern Gulf Coast by the middle of this week, becoming the unprecedented 11th named storm to make landfall in the United States in a single hurricane season. The storm could be at or near hurricane strength by the time it makes landfall, further damaging a region that's seen more than its share of storms this season.

Zeta formed from a vigorous tropical wave in the western Caribbean. Models did a good job sniffing out the general pattern that was conducive to this tropical storm's development. This is exactly where you'd expect to see tropical development in October and November—the waters here are still warm and the atmosphere is able to bounce back from cold fronts pushing off North America.

Source: NOAA
The latest advisory from the National Hurricane Center shows Zeta gradually gathering strength as it approaches the Yucatan Peninsula. Forecasters expect the system to reach hurricane strength before it makes landfall near Cancun on Monday evening. Once the storm crosses the Yucatan, it should emerge into the Gulf of Mexico and steadily make its way toward the northern Gulf Coast.

Don't focus too much on exactly where the forecast shows the center of the storm making landfall. While the precise track of the storm will determine who sees the worst conditions, the effects of wind, heavy rain, and storm surge can extend far away from the center of the storm. Based on the current forecast, Zeta could make landfall in Louisiana, Mississippi, or Alabama during the day on Wednesday. 

The NHC's forecast discussion on Sunday afternoon notes "significant uncertainty" in the storm's intensity forecast as it approaches U.S. landfall this week.

It's late in the season and there's only so much fuel for a tropical cyclone to tap into as it moves out of the Caribbean. Recent cold fronts and residual cool water churned up by Hurricane Delta a few weeks ago leave Zeta entering a Gulf of Mexico that isn't favorable for the explosive intensification we saw several times during the heat of the summer. 

Once Tropical Storm Zeta moves inland, the system's remnants will bring heavy rain (and the potential for tornadoes) to the southeast and Mid-Atlantic before a cold front swoops down and brings cooler, drier conditions for the weekend.

Zeta is the sixth letter of the Greek alphabet. This is the 27th named storm of the 2020 Atlantic hurricane season. We're one storm away from tying the all-time record of 28 storms that developed during the 2005 hurricane season.

There's still the potential that we could see additional storms after Zeta. The next name on the list is Eta, followed by Theta and Iota.

The letter Zeta is as deep into the Greek alphabet as we got in 2005. The "missing" 28th storm was an unnamed subtropical storm that developed on October 4, 2005. Forecasters missed that system at the time, catching it after the fact during the post-season analysis and adding it to the year's total.

If the NHC had caught and issued advisories on the unnamed storm contemporaneously, every storm that formed after Hurricane Stan would've been pushed back one letter, and we would've reached the letter Eta. (Hurricane Wilma was that close to being Hurricane Alpha!)

If Zeta makes landfall as predicted, it'll be the 11th named storm to hit the United States this year. Previously, the most named storms to make landfall in the United States was 9 storms during the 1916 hurricane season. Hurricane Sally tied as the 9th storm, and Hurricane Delta broke the record as the 10th.

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October 9, 2020

Hurricane Delta On Track To Make Landfall In Already-Damaged Southwestern Louisiana

Hurricane Delta restrengthened into a major hurricane on Thursday as it steadily made its way toward the Louisiana coast. The hurricane will make landfall Friday afternoon in southwestern Louisiana, very close to where Hurricane Laura hit back in August. Destructive winds, a life-threatening storm surge, and flooding rains are likely along Delta's path into Louisiana. The effects of this hurricane will be exacerbated by lingering damage and structures weakened by the previous hurricane.

This has been a tenacious storm since the day it formed. Delta managed to strengthen into a powerful and tiny category four hurricane before crashing into Cancun on Wednesday morning. The storm weakened over land, but warm water and favorable environmental conditions over the southern Gulf of Mexico helped Delta recombobulate and begin to strengthen again. The hurricane even developed a clear eye for a little while on Wednesday evening.

Source: National Hurricane Center

The 10:00 PM CDT advisory from the National Hurricane Center bumped Delta's winds up to 120 MPH, making it a major hurricane again. The storm's winds will likely tick down a bit as it approaches landfall in southwestern Louisiana on Friday afternoon, but this is a powerful storm that'll do quite a bit of damage to an area still trying to recover from Hurricane Laura.

Communities around the point of landfall will experience the strongest winds and the greatest storm surge, but make no mistake—this is a large hurricane and it'll have wide-reaching impacts in the region.

As expected, Hurricane Delta's wind field is larger than it was Wednesday. The storm's growth will expose a larger region to damaging winds and a life-threatening storm surge that could measure as high as 11 feet above ground level near the point of landfall. The National Hurricane Center's latest advisory measured Delta's tropical storm force windfield at about 320 miles wide, with hurricane force winds stretching 80 miles across the eye.

Widespread power outages—numbering in the hundreds of thousands—are likely across Louisiana as Delta makes landfall and pushes inland. Trees weakened by Hurricane Laura will struggle to withstand Hurricane Delta, endangering homes that sit beneath large trees and tree limbs.

Source: Weather Prediction Center

Flash flooding is also a major threat along Delta's path inland. Communities from southern Louisiana to southern Arkansas could see more than five inches of rain through Saturday. This much rain falling this quickly will lead to flash flooding in vulnerable areas.

Even though I'm confident that you already know this if you're reading my blog (thank you, by the way!), it feels like a requirement to stick this in here, so here goes..

The leading cause of death during landfalling tropical cyclones in the U.S. is flash flooding from excessive rain. It only takes a small amount of water to lift up a vehicle and carry it downstream. It's impossible to tell how deep the water is before it's too late, and sometimes the floodwater can obscure that the road itself is washed away. It's not worth it. Find another route or stay put if you can.

[Satellite Image: NOAA]

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