Long Term forecasting ( May 7-13 chase days)

[Greg Flint]

Given my location (near Boston MA) I had to commit to a block of time where I basically am flying to TX and drive wherever the target area may be. OBVIOUSLY the closer to this timeframe the more accurate SPC will be with its forecast, but what resources can I use to check predictions beyond 7-8 days out?

http://weather.rap.ucar.edu/model/index.php?model=gfs

The above link prodives surface/aloft data extending out to 8 days. Are there plots people use for 14 days out? Should I simply ignore any predictions that go further out than 8 days? I'm not looknig for pinpiont accuracy here, because I realize things change, but I'm just trying to understand what too look for on forecast for that far out if they even exist.

I'm making a serious effort to study and learn as much as possible before I go out, and have been using several DVDs as guides (none of which star helen hunt I have to be honest though, reading so many negative posts on this site about other storm chasers behavior has got be pretty bummed about the community in general. I am doing this purely out of a long lived interest in weather/mother nature. I've been thinking about doing this long before any movie or TV shows came out glamorizing the hobby. Anyway - I'll be there on May 7 whether the forecast becomes more clear the day of or the week before I leave. Thanks for reading.

 

[Andy Wehrle]

At http://www.twisterdata.com/ you can view the GFS output to 384 hours.

As this week has demonstrated though, even when there is good run-to-run consistency and agreement between models 5-6 days out, that doesn't mean the event will pan out as depicted. That can go both ways ("sleeper" days that didn't look that impressive early on can produce significant outbreaks, as well as exciting-looking setups not panning out).

 

[Greg Flint]

At http://www.twisterdata.com/ you can view the GFS output to 384 hours.

As this week has demonstrated though, even when there is good run-to-run consistency and agreement between models 5-6 days out, that doesn't mean the event will pan out as depicted. That can go both ways ("sleeper" days that didn't look that impressive early on can produce significant outbreaks, as well as exciting-looking setups not panning out).

Thank you Andy, I'll check that out. I'd be curious to know historical accuracy - again only for curiousity sake as I realize it would not provide a learning opportunity.

Good point about this week, which isn't unusual to see I guess. So I guess I'll simply take it all with a grain of salt and hope the best.

 

[Marcus Diaz]

Since there's no real way to nail a forecast more than a couple of days out, you'll have to do what I do. Basically just pick a timeframe that the climatology says is the best time. For that, this chart made by Patrick Marsh is a good start. It appears like the last week of May and first half of June really stay consistently active. Just thinking of the past few years, I know that the last week in May is usually active with a couple of good setups. So my vacation this year is May 23-June 1.

 

[Dan Robinson]

In addition to the GFS, I also use the NCEP ensembles spaghetti plots at:

http://www.cpc.ncep.noaa.gov/products/predictions/threats/briefs/hgtP1.html

The ECMWF (European) model goes out to 10 days. It's is generally more reliable than the GFS at 7-10 days:

http://www.ecmwf.int/products/forecasts/d/charts/medium/deterministic/msl_uv850_z500

 

[Mark Blue]

There are several resources available but I'll just point out a couple. The Climate Prediction Center (CPC) issues 6-10, 8-14, and longer range outlooks here: CPC. The Weather Prediction Center (WPC - formerly known as HPC) issues great surface analysis maps for current and future time frames, a 3-7 day outlook, as well as other products. The WPC is an awesome resource for the shorter forecast periods.

I hope these help you with your chase plans.

 

[John Wetter]

We're also doing some work using the CFS to try and spot severe trends in the 4-6 week ballpark... http://cfs.hopwrf.info

 

[JamesCaruso]

Greg,

Take it from me as a fellow long-distance "chase vacationer" (I live in the Philadelphia area): if your days are set anyway, then don't stress out about the long-range forecast. You are going to be on an emotional roller coaster and drive yourself crazy, and there is nothing you can do about it anyway if your days are set in stone.

After years in a similar situation as you, I now have a little more flexibility. I can only spare two weeks to chase, but I can usually reserve a three week window and keep some flexibility during that timeframe. For example, this year my window is 5/19 to 6/6. If the week of 5/19 looks good, I will head out and stay two weeks from that point, returning 6/1. But if it does not look good, then I will delay my trip. But no matter what, I will head out by 5/23, because I have to be back on 6/6 so if I want a full two weeks I can't go out any later than 5/23.

In my case, I am only looking at a 5-7 day forecast to see if "week one" of my window looks OK. The synoptic pattern is pretty reliable on the models during that timeframe. I just look at 500mb flow and surface dew points for this purpose. I am not looking for a perfect pattern, I am just making sure a death ridge isn't forecast, or a flow regime that is shunting moisture too far east. But even if it looks okay but not great, I head out. You see, I know I will be out there during "week two" of my window, so I need to basically decide whether to trade "week one" for "week three." No matter what I do, "week three" of my window is a complete unknown (can't trust the models that far out), so I don't want to risk trading a decent "week one" for the complete unknown of "week three," which could be better but could also be a lot worse.

If you have any flexibility, even if you just have a week to chase, you could set up a two week or 10 day window and do a similar thing.

If not, just head out for better or for worse, see what you can see, find alternative diversions if there is no severe weather, and just try to live in the moment with a positive attitude and a mind open to serendipitous experiences!

 

[Greg Flint]

Greg,

Take it from me as a fellow long-distance "chase vacationer" (I live in the Philadelphia area): if your days are set anyway, then don't stress out about the long-range forecast. You are going to be on an emotional roller coaster and drive yourself crazy, and there is nothing you can do about it anyway if your days are set in stone.

After years in a similar situation as you, I now have a little more flexibility. I can only spare two weeks to chase, but I can usually reserve a three week window and keep some flexibility during that timeframe. For example, this year my window is 5/19 to 6/6. If the week of 5/19 looks good, I will head out and stay two weeks from that point, returning 6/1. But if it does not look good, then I will delay my trip. But no matter what, I will head out by 5/23, because I have to be back on 6/6 so if I want a full two weeks I can't go out any later than 5/23.

In my case, I am only looking at a 5-7 day forecast to see if "week one" of my window looks OK. The synoptic pattern is pretty reliable on the models during that timeframe. I just look at 500mb flow and surface dew points for this purpose. I am not looking for a perfect pattern, I am just making sure a death ridge isn't forecast, or a flow regime that is shunting moisture too far east. But even if it looks okay but not great, I head out. You see, I know I will be out there during "week two" of my window, so I need to basically decide whether to trade "week one" for "week three." No matter what I do, "week three" of my window is a complete unknown (can't trust the models that far out), so I don't want to risk trading a decent "week one" for the complete unknown of "week three," which could be better but could also be a lot worse.

If you have any flexibility, even if you just have a week to chase, you could set up a two week or 10 day window and do a similar thing.

If not, just head out for better or for worse, see what you can see, find alternative diversions if there is no severe weather, and just try to live in the moment with a positive attitude and a mind open to serendipitous experiences!

James - I like your advice. My flight back is May 13th, but you can bet if the apocolypse is forecasted for May 14th-15th -16th I am simply going to have to tell my boss "something suddenly came up" and just stick around for a couple extra days.

The 7-8 day forecast from the SPC looks like SOMETHING might be brewing. I'm easily chasing a slight risk and maybe even if there is a chance, I'll be there. Flying into Austin and if ZERO is forecasted I have the Red Sox in town versus Rangers. I will keep busy no matter what, but I'm thinking next year I'll try to delay trip towards end of May.

THanks everyone for their ideas. As the days get closer, I am climbing the walls with excitement.

 

[JamesCaruso]

James - I like your advice. My flight back is May 13th, but you can bet if the apocolypse is forecasted for May 14th-15th -16th I am simply going to have to tell my boss "something suddenly came up" and just stick around for a couple extra days.

The 7-8 day forecast from the SPC looks like SOMETHING might be brewing. I'm easily chasing a slight risk and maybe even if there is a chance, I'll be there. Flying into Austin and if ZERO is forecasted I have the Red Sox in town versus Rangers. I will keep busy no matter what, but I'm thinking next year I'll try to delay trip towards end of May.

THanks everyone for their ideas. As the days get closer, I am climbing the walls with excitement.

Greg - That's the spirit! A bad day of chasing (or hanging out in a place like Austin or catching a ball game in the heartland) is better than a good day at the office!

I will take a similar approach and extend a couple days at the end of my two weeks IF there is a MAJOR event forecast. That's why I am inclined to get out there earlier rather than later within my window, because I know I could at least theoretically extend if I have too...

Good luck!

Jim




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