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Hilltop avoiding non-isallobaric wind from heaven... UKMET/Euro try to save society as we know it

Typhoon Tip

By Typhoon Tip,
in New England

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Ginx snewx

Ginx snewx

Posted
Posted

Is there a piece of strapping involved? lol

Weenie question - how do models get their data? Is it just from ASOS stations and buoys and radiosondes? Do satellites get in on the action?

http://www.4cast4you.com/models/modelology-101a/

So what are numerical weather models and how do they work?

Numerical models attempt to simulate the state of the atmosphere at various times in the future. Models need to ingest data before they begin running. Where do they get their data from? Well, every day at synoptic times 12Z and 00Z worldwide, radiosonde balloons are released that collect weather observations up to 100,000 feet (30 kilometers). Radiosondes are units that measure various atmospheric parameters, such as air temperature, humidity, and pressure, which are transmitted to a fixed receiver on the ground. Models are initialized using observed data from the radiosondes, weather satellites, and surface weather observations.

The forecasts are computed using mathematical equations for the physics and fluid dynamics of the atmosphere. These equations are nonlinear and are impossible to solve exactly. As a result, numerical methods obtain approximate solutions.

Different models use different solution methods. Some global models (GFS,  ECMWF) use spectral methods for the horizontal dimensions and finite difference methods for the vertical dimension, while regional models and other global models usually use finite-difference methods in all three dimensions. Regional models (NAM) also can use finer grids to explicitly resolve smaller-scale meteorological phenomena, since they do not have to solve equations for the whole globe. The irregularly-spaced observations are processed by data assimilation and objective analysis methods, which perform quality control and obtain values at locations practical by the model’s mathematical algorithms (usually an evenly-spaced grid).

Primitive equations are initialized from the analysis data and rates of change are determined. The rates of change predict the state of the atmosphere a short time into the future. The equations are then applied to this new atmospheric state to find new rates of change, and these new rates of change predict the atmosphere at yet a further time into the future. This time stepping procedure is continually repeated until the solution reaches the desired forecast time. Forecast time maxima for global models may range from 10-16 days (GFS) whereas regional/mesoscale models forecast ranges from a few hours to 4 days (NAM).

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CoastalWx

CoastalWx

Posted
Posted

Is there a piece of strapping involved? lol

Weenie question - how do models get their data? Is it just from ASOS stations and buoys and radiosondes? Do satellites get in on the action?

Satelltie estimation on wind, temp, moisture, etc.....the estimates are actually pretty darn close to the real thing. All others are incorporated too.

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HoarfrostHubb

HoarfrostHubb

Posted
Posted

http://www.4cast4you...odelology-101a/

So what are numerical weather models and how do they work?

Numerical models attempt to simulate the state of the atmosphere at various times in the future. Models need to ingest data before they begin running. Where do they get their data from? Well, every day at synoptic times 12Z and 00Z worldwide, radiosonde balloons are released that collect weather observations up to 100,000 feet (30 kilometers). Radiosondes are units that measure various atmospheric parameters, such as air temperature, humidity, and pressure, which are transmitted to a fixed receiver on the ground. Models are initialized using observed data from the radiosondes, weather satellites, and surface weather observations.

The forecasts are computed using mathematical equations for the physics and fluid dynamics of the atmosphere. These equations are nonlinear and are impossible to solve exactly. As a result, numerical methods obtain approximate solutions.

Different models use different solution methods. Some global models (GFS, ECMWF) use spectral methods for the horizontal dimensions and finite difference methods for the vertical dimension, while regional models and other global models usually use finite-difference methods in all three dimensions. Regional models (NAM) also can use finer grids to explicitly resolve smaller-scale meteorological phenomena, since they do not have to solve equations for the whole globe. The irregularly-spaced observations are processed by data assimilation and objective analysis methods, which perform quality control and obtain values at locations practical by the model’s mathematical algorithms (usually an evenly-spaced grid).

Primitive equations are initialized from the analysis data and rates of change are determined. The rates of change predict the state of the atmosphere a short time into the future. The equations are then applied to this new atmospheric state to find new rates of change, and these new rates of change predict the atmosphere at yet a further time into the future. This time stepping procedure is continually repeated until the solution reaches the desired forecast time. Forecast time maxima for global models may range from 10-16 days (GFS) whereas regional/mesoscale models forecast ranges from a few hours to 4 days (NAM).

Thanks Steve,

I also watched a bit of a video on ECMWF. Does a good job explaining it in a authoratative English accent

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ORH_wxman

ORH_wxman

Posted
Posted

Unreal, how the heck do -3/-5 850 s screw us, holy sh it, highh SSTs?, lack of snow cover?

Lack of snow cover has hurt for sure...esp in these airmasses coming from the W or WSW...nothing keeping them from modifying. There is some truth that the cold and snow can start feeding back on itself and this is the opposite of that.

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Ginx snewx

Ginx snewx

Posted
Posted

Well before this event, it's been srly flow. Srly flow is a killer.

Lack of snow cover has hurt for sure...esp in these airmasses coming from the W or WSW...nothing keeping them from modifying. There is some truth that the cold and snow can start feeding back on itself and this is the opposite of that.

Thanks we are so lucky to have you two. Guess Tips denuding event is cancel.

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CoastalWx

CoastalWx

Posted
Posted

Thanks we are so lucky to have you two. Guess Tips denuding event is cancel.

What I meant by srly flow, is that the layer from 3000-5000ft up was plenty cold, but srly flow ruined the bottom 1500ft or so. When the flow went se and then south...well ahead of the low, and also with a crappy airmass..I think we knew we were in trouble. Will is right in that snowpack will start to hurt our temps if we continue without one. That will cause an airmass even from the west, to moderate.

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ORH_wxman

ORH_wxman

Posted
Posted

Would the berks at least be snow at 66?

Probably...it would be close even here as WBZ heights at 66h are about 925mb here...so if there was a good shot of lift coming through then we'd probably snow. Heck, the other night (Feb 17) we managed to snow with cruddy lift even...but either way I don't think there would much accumulation.

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weatherMA

weatherMA

Posted
Posted

Probably...it would be close even here as WBZ heights at 66h are about 925mb here...so if there was a good shot of lift coming through then we'd probably snow. Heck, the other night (Feb 17) we managed to snow with cruddy lift even...but either way I don't think there would much accumulation.

You did...we had rain with a few mangled splats on the windshield...although there could have been a period of legit mix but it was tough to tell with it being dark. And yeah it doesn't matter as surface temps even in the Berks at 66hr are like upper 30s...

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