metar slp reading?

[Paul kgyy]

Some metars report a Sea Level Pressure: who uses the "slp"
information, and why?

[TheSmokingGnu]

Paul kgyy wrote:
> Some metars report a Sea Level Pressure: who uses the "slp"
> information, and why?
>

Seaplanes/amphibians, aircraft with millibar altimeters, analysis of
current pressure gradients vs. "standard" (?)

TheSmokingGnu

[quietguy]

SLP reports are the way meteorologists compensate for elevation
differences among the reporting stations; when SLP rather than station
pressure is plotted on a synoptic map the high and low pressure
centers can be accurately tracked even as they cross mountain ranges.

[Dallas]

On Mon, 05 Nov 2007 14:12:03 -0800, quietguy wrote:

> SLP reports are the way meteorologists compensate for elevation
> differences among the reporting stations;

Maybe I'm missing something... Aren't all pressures reported in METARs
corrected to sea level?

--
Dallas

[quietguy]

On Nov 5, 5:32 pm, Dallas > wrote:
> Maybe I'm missing something... Aren't all pressures reported in METARs
> corrected to sea level?

In aviation weather observations, yes; in the data coming over the
wire to weather forecast offices and data processing centers, station
pressures are also reported by WMO-designated synoptic reporting
stations. Even though station pressures aren't disseminated to
aviators the SLP is marked so there'll be no confusion over what sort
of pressure it is.

[Dallas]

On Mon, 05 Nov 2007 16:32:59 -0800, quietguy wrote:

> the SLP is marked so there'll be no confusion over what sort
> of pressure it is.

It's nice they endeavor not to confuse us.

For instance they code 998.2 hectopascals to SLP982 so they don't confuse
anyone.

:-)

--
Dallas

[The Visitor[_2_]]

Well put!

quietguy wrote:
> SLP reports are the way meteorologists compensate for elevation
> differences among the reporting stations; when SLP rather than station
> pressure is plotted on a synoptic map the high and low pressure
> centers can be accurately tracked even as they cross mountain ranges.
>

[Andrey Serbinenko]

Metar's "altimeter" pressure is a value such that if you set your
altimeter to it on the ground, it will show your elevation above MSL.
Altimeter's mechanism assumes standard atmosphere where pressure changes
with altitude linearly: it doesn't take into account possibly non-standard
temperature. SLP, on the other hand, does similar reduction of station's
barometric pressure to MSL, but adjusts it for non-standard station
temperature.

Andrey


Paul kgyy > wrote:
> Some metars report a Sea Level Pressure: who uses the "slp"
> information, and why?
>

[[email protected]]

thanks for the good discussion.