Andy Wehrle
EF5
....annnnnnnnd they're back to northeast blocking/cold high pressure over the Midwest ad infinitum. Gag. Let's HOPE they're wrong!
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The Foibles of Long-Range Models (and Why Many Chasers Use Them Anyway)
- Thread starter Bob Hartig
- Start date
Paul Knightley
EF5
ECMWF does not go beyond 240 hours, at least the deterministic model. As has been mentioned, one should not put much faith in deterministic models beyond about 7 days. The ensembles are the way to go, and even then you should look at trends over several runs, not specifics. It is always interesting to see where the deterministic run fits into the ensembles, and follow its trend within them.
Clustering of ensembles is another nice way to look at them. Often you'll find a splitting point where the ensemble members diverge into 2 or even 3 clusters.
A great example I can recall where ensembles were a good guide was back in May 2008. The week before I was heading out (I got out there on Monday, May 19th) I was looking at the various models. Both the ECMWF and GFS deterministic models showed a big 'death ridge', and forums were full of desperate posts of how the season was coming to an end, or going to be very slow. However, the ECMWF ensemble mean had been consistent over several runs of a western US trough developing later in the w/c 19th May. When the deterministic model began to trend that way, confidence quickly started to grow in a major outbreak of severe weather, even 7 days out. The GFS still had a ridge, but then slowly came into line. What transpired was the 22nd/23rd May Kansas tornadofest.
Clustering of ensembles is another nice way to look at them. Often you'll find a splitting point where the ensemble members diverge into 2 or even 3 clusters.
A great example I can recall where ensembles were a good guide was back in May 2008. The week before I was heading out (I got out there on Monday, May 19th) I was looking at the various models. Both the ECMWF and GFS deterministic models showed a big 'death ridge', and forums were full of desperate posts of how the season was coming to an end, or going to be very slow. However, the ECMWF ensemble mean had been consistent over several runs of a western US trough developing later in the w/c 19th May. When the deterministic model began to trend that way, confidence quickly started to grow in a major outbreak of severe weather, even 7 days out. The GFS still had a ridge, but then slowly came into line. What transpired was the 22nd/23rd May Kansas tornadofest.
David Wolfson
EF5
The post mortem on my post #11 is that significantly less upper energy (cold air) than forecast was able to make it into the mountain west. However I think the actual outcome is fairly characterized as the "first traditionally chaseable early-season system for Texas and Oklahoma" with slight SPC risks, though with low tornado potential.
ATTM the models 7 days+ seem to be promoting major troughing in the southern Rockies sufficient for the first major (SPC Moderate) multi-day traditionally chaseable early season system for Texas, Oklahoma, and Kansas. Let's see what happens....
ATTM the models 7 days+ seem to be promoting major troughing in the southern Rockies sufficient for the first major (SPC Moderate) multi-day traditionally chaseable early season system for Texas, Oklahoma, and Kansas. Let's see what happens....
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