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!

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 …

Zeta treks across the Southeast, stormy day in store; another one?

Zeta make landfall yesterday evening and passed right over New Orleans. Surprising just about everyone who wasn’t just guessing, it was almost a Category 3 storm as it make landfall in Timbalier Bay, with the peak winds across Grand Isle, Port Sulphur, and Gulfport. This was a bit lucky for New Orleans, as had it passed a bit further east it would have put more stress on the Levees, although in theory they should have been able to hold up to this class of storm. There is structure damage across the region, and a lot of power outages, with outages and trees/limbs/light damage now extending across southern Mississippi, Alabama, and now into central Georgia. Here’s the damage swath …

The situation today is really complex. Zeta is merging with a strong frontal system that has been pushing into the southeast, bringing some nice fall weather behind it – but it has to push Zeta out of the way first. The storm is riding up the front and will be offshore by tomorrow – a very fast mover. Here is the latest (6am) synoptic weather map with water vapor image:

Synoptic Weather Map: pretty complex mess today!

The main thing to get from the above is that Zeta and the front are interacting, with the front accelerating Zeta and pushing it offshore, and the tropical moisture giving the front an energy boost (contrasting air masses – hot/cold, wet/dry – produce stormy weather). Here’s the current radar – you can clearly see that “tail” streaming south of Zeta that is headed towards the coast …

Radar this morning – hard to find Zeta in all this mess!

For the coastal GA/SC area, most of the severe weather potential (in the form of isolated tornadoes) is inland of I-95. We’ll have blustery winds and rain showers as that “tail blows through today. So keep your weather radios handy just in case.

In other tropical news, NHC is watching the same area where Zeta formed, and currently has it as a 40% chance of something forming early next week, but the models have been trying to spin stuff there for some time. For now, nothing to worry about.

not really very Tropical Storm Nestor (AL162019) SaturdayUpdate

As NHC notes in their forecast discussion this morning, Nestor really isn’t very tropical.  As I’ve been saying all along, structurally it’s more like a nor’easter.  While it is raining heavily across Florida this morning, there is very little convection or thunderstorm activity, mostly off the Atlantic shore over the Gulf Stream.  There do seem to be a lot of storm tracks with rotation in them.  Here is the 7:22am composite radar, long with a neat product from the “Multi-Radar Multi-Sensor” or MRMS system, low level rotation tracks …  those “streaks” in the map or the right are storm tracks where there is rotation, or potential tornadic activity.  That is probably the biggest threat from not-really-tropical Storm Nestor.Same map with the watch boundaries … as always, click to embiggen and see detail!

Expect tornado watches to expand north into Georgia and probably South Carolina later today, so keep your weather radio handy.  Finally, here is the forecast rain and surface pressure from the High Resolution Rapid Refresh model for 5pm this afternoon …

So again, bottom line, rain, gusty (but not dangerously high) winds, potential for tornadoes.  Try not to travel if you don’t have to, but if you are going to a football game or something take extra time, and bring a raincoat (the umbrella will just blow away 😛 ).

 

Typhoon Soulik and Japan

Typhoon Soulik is headed for Japan, with landfall early next week.  Here are two satellite images, one from last night and one from this morning.  The night-time shot is neat, the storm is being lit up by the waxing first quarter moon …

Night View of Soulik approaching Japan
12 hours later

The storm may still be fairly strong when it hits Kyushu in a few days.  It will be the second strong storm to hit Japan (third overall), but worse is all of the rain and flooding that has impacted the Islands this year.  Record rains, followed by record heat, have killed hundreds (over 300 at a minimum) and sent 22,000 to the hospital with heat related symptoms.  It’s been a tough year in Japan …