Allison
Weather Guru
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Not much to talk about right now, so here's a question that's been on my mind for awhile....
Why do some models run "early" and some run "late"? This seems to be an issue every year for when issuing advisories, so why not run all the models at or near the same time?
Allison
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Good question Allison, and since I'm on-line I'll start a response, but a better answer would probably come from others on the site (such as scottsvb or Jason Kelley - hint, hint) that use the model outputs far more than I get a chance to on a day-to-day basis. As an old weather programmer, I know that we did have 'target' times that we tried to meet for each model run, and I'm sure that is still the case at NOAA. Sometimes a run would be placed 'on hold' if an entire block of data had not yet been received from a particular sector of the globe or group of reporting stations - usually because of some communications problems - so the initial analysis would not be as accurate and therefore neither would the forecast charts. Another reason for a late start is the computer itself - the schedule will easily get behind if the system has been 'down' for a period of time. I'm sure that I've missed a few other good reasons that others can help with to give you a better answer.
Cheers,
ED
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LI Phil
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I also think that different models run a different amount of times per day, i.e.:
_AVN_
The AVN model is a 72 hour Forecast Model and is run every 6 hours
_NGM_
The NGM model is a 48 hour Forecast Model and is run every 6 hours
_ETA_
The ETA model is a 48 hour Forecast Model and is run twice a day
_RUC_
The RUC model is a 12 hour Forecast Model and is run five times a day
_MRF_
The MRF model is a 288 hour Forecast Model and is run once a day at 00Zulu
*EDIT*:
Sorry, that is the schedule for the models, the tropical and global models are different:
AVN/ECMWF/GDFL/NOGAPS/UKMET
These present operational model fields that are being used in a study examining their forecast ability for tropical cyclogenesis in the eastern Pacific and northern Atlantic Hurricane Basins.
TPC/NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONES
This site offers the National Hurricane Center's Tropical Forecast Models,Index of Tropical Forecast models/BAM,BAMM,A90E,LBAR,SHIP,GDFL.
I couldn't find immediate information on when the tropical models are run, but I would imagine it is similar to the models in that different models run at different times.
Unless all models began their cycles at 00Zulu (maybe they do?), then depending upon how often a model is run, they would be run at different times for a 24 hour period, the cycle would then repeat.
There's probably a much deeper explanation than that (HF, Steve, JK, Scottsvb, et. al), so maybe the mets and may-as-well-be-mets can help out.
Cheers & Peace,
LI Phil
Edited by LI Phil (Mon Jun 21 2004 05:34 PM)
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wxman007
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Loc: Tuscaloosa, AL
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Good question Allison....
The reason why is that they all run on the same computer, (or computers) and you can't really run them concurrently...so you have to arrange them so that forecasters in the field get the data they need as quickly as possible.
The base runs of the models are set up off of the rawinsondes (weather balloon) launches at 00Z and 12Z. That data is critical to the models, so they have to run at those times. Then the models are sorted by 2 criteria a) which one is needed most by forecasters and b) which ones run the fastest. The Eta is the primary US short range model, and is used by every forecaster in the country, so it goes first (after the RUC, which a fine-scale model that runs every hour and only out to 12 hrs...it doesn't take long). Then the old NGM (shaking my head), then the AVN/MRF.GFS suite. The and other hurricane models have to run after the because they use it for the basis of their forecast.
I hope this answers your question...at least a bit....they CAN'T run at the same time, so they have to be prioritized.
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Jason Kelley
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Allison
Weather Guru
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Loc: Laredo, Texas
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Thanks for the responses guys!
When I asked the question, I didn't realize that all the models ran off the same computer.... I figured that since some belonged to the UK and some to the Navy, etc., each different group was just trying to be difficult... 
Allison
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wxman007
Meteorologist
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Loc: Tuscaloosa, AL
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Well,
Some do run on other computers...the models (GFS, ETA, RUC, NGM, and Hurricane Models) all run together...the USAF run on a different one, as does the Navy and COAMPS, and the European models run overseas. There are various reasons that they come out at various times...reasons that are rather detailed and beyond the scope of this board. And also remember that while the US is very forthcoming about releasing data as soon as it is available, the rest of the world isn't, and will release things slowly, if at all.
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Jason Kelley
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