US #Icestorm developing …

There is a huge frontal system slowly grinding to a halt across the US, with a low pressure system forming at the tail end over Texas. Here is the current synoptic weather map …

Synoptic weather map as of 7am ET with IR Satellite image

… and MRMS radar composite as of around 9:30am Thursday.

The low is expected to scoot up along the front, and over the next two days there is an increasing chance of a major ice storm event in an arc from Texas to the Northeast. In the this animation, the orange areas are areas where ice accumulation is possible:

GFS Simulated Radar and Precipitation Type for next couple of days (Thu/Fri/Sat). Click to embiggen.

Ice is a lot bigger problem than snow. Ice is a lot denser than snow, and tends to stick to and accumulate on things like tree branches and power lines (not to mention making roads just about impassible). The extra weight means branches and even whole trees breaking, and power lines coming down. So expect scattered outages across a wide swath of the US this New Years. The DHS/FEMA site has some advice on how to prepare for winter storms. So as you celebrate the new year, be careful!

Severe weather approaching Coastal GA, SC

The Charleston WSFO has raised severe thunderstorm warnings for most of the area, and a tornado has been detected near Hampton SC. Here’s the radar at the moment (just before 6:30pm Christmas Eve) – the tornado is the bright white dot just north (up) from the black circle of no data over the radar station …

Make sure your weather radios are on, or your mobile phones have the emergency alerts active … could be a busy hour or so.

The Coming Storm

No, not that one. Or that one. I mean the literal one, this one, the first big winter storm of the season. Here is the situation as of this morning (map forecast for 8am ET Wednesday, the storm is the “L” off the Georgia Coast):

Winter storm forming over Southeastern US … GFS model of precipitation type and moisture transport.

Like hurricanes, winter storms have to have a mix of conditions come together to cause them to grow and evolve. The key to weather on the earth is the need to balance the warm, moist air from the tropics with the cold, dry air over the poles. This happens in a number of ways, but in the summer the most dramatic are of course hurricanes. In the winter, it’s nor’easters. A classic nor’easter starts out as a low pressure system just off the coast of the Southeast. It moves northeast along the coast, carrying with it the warm moist air of the Gulf of Mexico and Bahamas, pushing that air inland where it meets cold polar air. It is along that swath where the air masses collide that the potential problems for Humans comes in. The danger this morning lies Appalachians and western North Carolina where the precipitation may be in the form of freezing rain, as well as inland in Kentucky (on the map, the red/purple area). Here is what things should look like this evening around 7pm. Notice that the low is deeper (stronger), the blue moisture transport vectors are longer (stronger), and across the New York/Pennsylvania area snow will be falling. The zone of freezing rain will by then have shifted to western Virginia.

The situation tonight …

By tomorrow morning the Low should be more elongated and off the Massachusetts coast, still pumping moist, snow-laden are into the NorthEast. The storm should be off the Canadian Marine Provinces by Friday.

Thursday Night

In terms of impacts, again the big concern is the area where freezing rain and ice will be falling. For the Northeast, snow could be fairly deep in places – some forecasts are for up to 24″ – but it’s more likely to be disruptive rather than truly dangerous, and again conditions should clear out by this weekend. For the Deep South (GA/SC), this will be a rain event, even for North Georgia. As things continue to cool off with the approaching winter season, the risk for ice storms will move further south … but the impacts of this event will be in North Carolina and the NEUS. How should you prepare for winter storm season? Take a look at the FEMA/DHS Winter Storm page for tips …

So what’s the weather going to be on Thanksgiving?

This year people are more attuned to the weather – for good reason. Given COVID19, gatherings outdoors are far safer than inside, so the weather is a bigger factor than usual. I’m getting a lot more questions like “what’s the weather going to be like next St. Swizzen’s Day” – be it for a holiday, wedding, birthday gathering, protest march, golf game, or whatever. My usual reply is “I study disasters; if I can tell you then you probably don’t want to know” doesn’t make people happy 😛 Of course I’ve got the tools here to do pretty much any kind of forecast from “nowcasts” to climate, but how does the average person answer that question without annoying their favorite scientist/blogger? Which provider is best? As it turns out, that’s an easy question to answer. Your tax dollars have funded a really great organization, the US National Weather Service, and they have some nice on-line tools for planning your holiday. Virtually all the other providers – be it big companies, TV stations, whatever, are using NWS data and perhaps “adding value” (although in most cases I’d argue they are adding FUD, but that’s a different post). So lets walk through using the NWS web site to see what tools are available, and if you can hold that Thanksgiving gathering outside, or if everyone will have to stay home and use video …

The starting place is https://www.weather.gov. Here’s what the main page looks like. Any warnings will be color coded:

The map is clickable … click on the location you’re interested in; it doesn’t have to be perfect, you’ll get the chance to refine it. But for your home location, enter the place name you want in the box on the left. You can use a zip code or place name – for example, you can enter “Ardsley Park, Savannah, GA” and the system will give you matching names …

If you click “remember me” then whenever you go to weather.gov your local forecast will pop up on the left side. Clicking “Get detailed information” and you will jump to the point location forecast … here’s where you can really get into seeing what is going on:

The page itself is a nice overview, but if I’ve got family coming over at 4pm Thursday, with dinner at 6pm, and people will probably start to go home at 8pm. How likely is it that we can eat outside at the picnic table, or will I have to set up tables all over the house inside, or just cancel? Jackets, build a fire in the fire pit, or Savannah being Savannah will we need bug spray? If you scroll down and look under the map on the right there is a box called “additional resources” …

Click the graph and you get the hourly forecast data.

You can change the date to see up to a week in the future; in this case let’s set the start point at 12am (midnight) on Thursday. Click submit and you get:

So for Ardsley Park area in Savannah, the temperature should be 70 degrees, light wind, 31% Cloud Cover. The precip chance is 18% – but if you look at the graph, it never gets above 20%, and drops to only 8% by 7pm, so chances are this is not a sharp rain producing weather system. Now that you’ve tagged this as your “remember me” location any time you to to weather.gov on that device it will have your forecast on the main page – and you can easily get the very detailed details!

But what if you are travelling? Just click on the national map … it will take you to the forecast for that point. In this case, as noted on the first map I directly clicked on Andrews NC, then got the “additional details” to see the timing and intensity of any rain:

Looks like rain overnight Wednesday (80% chance at midnight!) and perhaps Thanksgiving morning, but will clear out and be nice overnight, with rain maybe coming back Friday night (back up to 30% chance) .

When planning an event, obviously the closer in time the better the forecast. By the time we’re within three days they are pretty good; 3 to 5 days are fair, over five days takes some interpretation. I’ll try to do some more posts on that in the future, but hopefully this will get you started …

You Got The Fire Down Below …

The fires out west are epic – you can actually see the flames from the GOES satellite in geosynchronous orbit, 22,236 miles up … here is the color view:

Click to embiggen and animate …

Here is a static view zoomed in a bit:

Yes, those red patches are actually fire!

These fires, and their impacts, are a wicked combination of short term weather patterns, human development and “management” practices, the natural order of things (fires are a normal way nature cleans out the brush; some plants and animals that depend on them actually need periodic fires to survive), and probably a bit of climate change thrown in. Either way, it’s spectacular (in a bad way if you live out there).

So what’s a derecho? (and a tropical update)

It’s fascinating to see how some terms that are used in specialist setting make their way in and out of journalistic usage. It seems that Derecho is one of those that I’ve seen more of in the last few years. The term has been around since the late 1800’s, about the same time this painting by John Curry was made …

“The Line Storm,” by John Steuart Curry, 1897-1946, a painting possibly inspired by the approach of a derecho-producing storm in Curry’s home state of Kansas. (Oil and tempera on panel, 1934; Collection of Sidney Howard, New York; Lithograph in Smithsonian American Art Museum, Washington, D.C.)

A derecho is a straight-line wind system associated with a mesoscale convective system (in other words, high winds associated with a group of stable, fast moving thunderstorms). They can cause winds over 100mph and damage over a wide area. Here’s a nice overview from the Storm Prediction Center (SPC).

Yesterday a derecho moved over the US midwest causing a lot of damage (NY Times Article). Here’s an animation of the low-level radars from the region …

Midwest RADAR composite, Monday Afternoon, 10 August 2020

This system has caused 10’s of millions in damage across the region. This was a strong and extensive MCS/Derecho, but derecho’s aren’t uncommon. A system like this happens somewhere in the midwest every 4 years or so.

In the tropics, still watching AL95. NHC has it as a 70 percent chance of spinning up, which seems more likely this morning. However, in a few days it will be moving into unfavorable conditions, so even if it does, its long term risks are still low right now. Typhono Jangmi has hit South Korea, causing mudslides and flooding, and killing at least 30. This year has been extremely wet across parts of Asia, and while there have been no severe typhoons thus far, the rain and flooding has caused extensive damage. Sadly, aside from a few brief articles noting the risk to the Three Gorges Dam, I haven’t seen lot of coverage of this in the US media.

ZOMG! There will be actual weather next week!

So there’s already talk of a winter storm sweeping through the nation next weekend (14th or so of December), possibly even the dreaded words “ice storm” that cause Atlantians (the ones in Georgia, not the ones Way Down Beyond The Ocean) to panic and start smashing in to each other on the perimeter and clogging up spaghetti junction with the carcasses of perfectly drive-able automobiles, even if said ice isn’t even going to hit Atlanta.   This is all part of the trend towards sensationalizing marginally bad weather, something discussed in this Washington Post (shudder) article.   While the screed starts of ok, the next to last paragraph is totally wrong.  This has a real economic and physical cost in human stress and needlessly disrupted businesses.  It’s all part of modern American society, which keeps people constantly on edge for marketing purposes.

So what’s the facts in this case?  In short, there will be weather next weekend.  Some of it will be rain.  As it is want to do this time of year, as you move northeastward, at some point that rain will change over to a “wintery mix” of ice and snow, changing over to only snow along the back side of the system as you get further north.   Here’s the current forecast precipitation types from the latest GFS model run Thursday (120 hours) which is about as far in advance as I’m willing to post a picture of …  green/yellow is rain, purple blue is a mix (the dangerous part), white is snow.

When we get closer, if it looks like anything unusual is happening will post more.  As usual with forecasts, don’t believe everything you see from 7-10 day forecasts!  I don’t get too excited until 5 days, since we really don’t have a lot of skill forecasting the exact mix more than 3 days in advance, just the “big picture”.  But that’s fine: you really only need a day or so to prepare for a winter storm.  FEMA took some time off from covering up UFO crashes and building internment camps to post some advice on the subject which is worth reviewing.  So be ready for wintery weather this season, as you should be for other events, and as always don’t panic unless you just need the cardio.  And if you live in Atlanta, by the ghosts of Rhett and Scarlet please learn how to drive …

California Fires (28 October 2019); over $25Billion in property within one mile

It’s another bad fire season in California.  Wait, you may ask, isn’t it fire season year round in Cali?  It turns out no!  There are two distinct fire seasons, with two different forcing factors.  The Santa Anna wind driven fire season runs from October through April (winter/spring).  The high winds can drive fires into a frenzy – such as is happening this weekend, where winds in California have been gusting into tropical storm levels.  The second fire season, during the driest and hottest months of the summer, runs from June to September.  So … May is nice sometimes.

Here is a satellite view of the Kincade fire as the sun comes up this morning (from GOES 17) … click to animate if you dare (it is big):

Labeled view … click to embiggen:

In all seriousness this is a bad situation.  The Kincade fire, north of San Francisco, has over $10 Billion in property within a mile of the fires.  The Getty fire near LA has another $15 Billion at risk; statewide the total is over $25 Billion of property at immediate risk, being within one mile of an active fire.

 

The Not-A-Tropical-Storm in the Gulf (AL162019), Friday mid-day update

Structurally TTITG isn’t a tropical storm yet, although with 50 knot winds (60mph) if it had a closed circulation it would be a healthy one.  Sort of looks like one too …

… and it will cause tropical-storm like damage across the Big Bend area of Florida and south Georgia.  Potential economic impacts jumped a bit with the higher winds speeds, up to nearly a Billion dollars, most of it indirect like canceled travel plans (grumble).

Here is the estimated impact swath based on the new (11am) forecast by NHC:

Bottom line hasn’t changed much: heavy rains, gusty winds, scattered power outages, just a wet messy day tonight and Saturday across North and Central Florida, extending in to Georgia and South Carolina Saturday.  For GA/SC, a bit more drift to the right (east) will keep the worst of it offshore, so those worried about Football in Athens and Columbia might get off a bit easier.  In short, inconvenient, hazardous to travel or be outside in the darker red areas, or south or east of the pink line on the above map, but not really dangerous except right on the Florida shoreline from maybe Clearwater around to the Pensacola area.

NOAA’s Atlantic Hurricane Season Update

Last week the US National Oceanic and Atmospheric Administration (NOAA) released an updated seasonal forecast, and due to the waning El Nino has increased their forecast for the number of storms expected this year, now saying there is an increased chance for an “above average” season.  What does that mean to you, the huddled masses cowering in fear along the shoreline, waiting for your inevitable doom?

Exactly nothing (assuming you have a hurricane plan already, which you should no matter what the seasonal forecast says).

First, even if you knew *exactly* how many storms were going to form in a year, it tells you nothing about how bad the season will be.  There have been above average years in raw numbers with no hurricane landfalls.  1992 was a below average year – well, except for Hurricane Andrew.  So unless you know where they are going to go, even one hurricane can ruin your day, and 20 can be no big deal if they are all fish storms.

Second, the numbers used to compute the averages are becoming more and more suspect.  This year’s “hurricane” Barry more than likely would not have been classified as a hurricane in past years for a number of reasons (before anyone yelps, no, this isn’t part of the Vast Global Warming Conspiracy(tm), it’s because of better observation systems that can see small patches of possible hurricane force winds, and different classification criteria).

I really don’t like the hype around seasonal forecasts and their updates.  Dr. Mark Johnson of UCF and I used to do them (including something NOAA doesn’t do, landfall probabilities), but the media circus and subsequent fear mongering were just a bit too much.  We still generate them, and they have decent enough skill, but they aren’t really “actionable” except for narrow applications.  About the only thing they are good from a public safety standpoint is “awareness,” but there are other ways of doing that than shoveling out the statistical stables …

So if you haven’t put together a plan yet, slap yourself and go to visit the FEMA web site and get some checklists to think about, consult your local EMA for risk maps for your risk of flooding (which is by far the major threat to life; the golden rule is shelter from wind, evacuate from water), and put together a plan.  Then don’t worry about it.