.... Whilst looking at this product he-

http://ows.public.sembach.af.mil/ind...ection=SFCAnal

I got to thinking, not for the first time, why some meteorologists use
the convention ' humidity-temperature ' and others the reverse, when
labelling air masses.

For example, on this chart, what I would call 'Tropical maritime' air
west of Iberia is labelled 'mT' (maritime Tropical), and over Britain
we have 'mod mP' (or modified maritime Polar), whereas I would label
it as mod Pm (etc.)

I'm not sure there is a 'right' or 'wrong' way of doing this [ except
to acknowledge Tor Bergeron's work - see below ], and looking back at
some books I have, it doesn't seem to matter which era you are in, or
which side of the Atlantic you are (which latter was my initial
thought).

Here is a list of the books which use the convention that I was taught
(School geography & Met O College), that is Tm, Pm, Pc etc.

.... [UK] Meteorological Glossary: Meteorological Office: 1939
.... [US] Through the Overcast: Jordanoff: 1939
.... [UK] Meteorology for Aviators: Sutcliffe/Meteorological Office:
1939
.... [US] Introduction to Meteorology: Petterssen: 1941 and 1958
editions
.... [UK] Observer's Book of Weather: Lester: 1955
.... [UK] Essentials of Meteorology: McIntosh & Thom: 1983
.... [UK] Handbook of Aviation Meteorology: Meteorological Office: 1994
edition

And here those using the reverse (e.g. cT, mP etc.)

.... [UK] Admiralty Weather Manual: Admiralty: 1938
.... [UK] Meteorological Glossary: McIntosh / Meteorological Office:
1972 edition
.... [UK] Climate of the British Isles: Chandler & Gregory: 1976
.... [UK] Meteorology for Mariners: Meteorological Office: 1978 edition

( Interesting to note that McIntosh switched his allegiance between
the 'Met Glossary' date of 1971 & the 'Essentials' date of 1983. )

I believe that Bergeron himself (who developed the basis of this
classification) considered the thermal properties first, then the
moisture characteristics - so it's interesting to speculate why over
time it has turned this way? I note that the vast majority of US
weather web sites as well as Wikipedia use the 'second' convention.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

As most of your stuff Martin is way above my amateur head,it did get me
thinking as to what is 'humid' ?,As i wallow in this glorious heawave(in the
southeast that is) my enjoyment is somewhat tempered by the Met Office
warning us of the very high humidity factor.
At present in my back garden the temp is 26C and the RH 55%,which with the
easterly breeze feels very comfortable ,so excuse my ignorance but how the
comfort levels determined viz a viz temperature combined with humidity ?.
I'd hate to enjoy myself whilst so many people seem to be struggling with
the dreadful heat and having to remove their anoraks.

RonB


"Martin Rowley" wrote in message
om...
... Whilst looking at this product he-

http://ows.public.sembach.af.mil/ind...ection=SFCAnal

I got to thinking, not for the first time, why some meteorologists use the
convention ' humidity-temperature ' and others the reverse, when labelling
air masses.

For example, on this chart, what I would call 'Tropical maritime' air west
of Iberia is labelled 'mT' (maritime Tropical), and over Britain we have
'mod mP' (or modified maritime Polar), whereas I would label it as mod Pm
(etc.)

I'm not sure there is a 'right' or 'wrong' way of doing this [ except to
acknowledge Tor Bergeron's work - see below ], and looking back at some
books I have, it doesn't seem to matter which era you are in, or which
side of the Atlantic you are (which latter was my initial thought).

Here is a list of the books which use the convention that I was taught
(School geography & Met O College), that is Tm, Pm, Pc etc.

... [UK] Meteorological Glossary: Meteorological Office: 1939
... [US] Through the Overcast: Jordanoff: 1939
... [UK] Meteorology for Aviators: Sutcliffe/Meteorological Office: 1939
... [US] Introduction to Meteorology: Petterssen: 1941 and 1958 editions
... [UK] Observer's Book of Weather: Lester: 1955
... [UK] Essentials of Meteorology: McIntosh & Thom: 1983
... [UK] Handbook of Aviation Meteorology: Meteorological Office: 1994
edition

And here those using the reverse (e.g. cT, mP etc.)

... [UK] Admiralty Weather Manual: Admiralty: 1938
... [UK] Meteorological Glossary: McIntosh / Meteorological Office: 1972
edition
... [UK] Climate of the British Isles: Chandler & Gregory: 1976
... [UK] Meteorology for Mariners: Meteorological Office: 1978 edition

( Interesting to note that McIntosh switched his allegiance between the
'Met Glossary' date of 1971 & the 'Essentials' date of 1983. )

I believe that Bergeron himself (who developed the basis of this
classification) considered the thermal properties first, then the moisture
characteristics - so it's interesting to speculate why over time it has
turned this way? I note that the vast majority of US weather web sites as
well as Wikipedia use the 'second' convention.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

"ronaldbutton" wrote in message
...
snip
At present in my back garden the temp is 26C and the RH 55%,which
with the easterly breeze feels very comfortable ,so excuse my
ignorance but how the comfort levels determined viz a viz
temperature combined with humidity ?.
I'd hate to enjoy myself whilst so many people seem to be struggling
with the dreadful heat and having to remove their anoraks.

.... well, I'm probably way out of date now on all this as I know that
a lot of work has been done in the Met Office with the DoH &
individual NHS trusts. However, the standard algorithm we used to use
to work out a 'temperature-humidity' index is as follows:-

THI = 0.4 (T + W) + 4.8 .... (for degC).

whe
THI 'Temperature/Humidity Index'
T = Dry bulb (screen) temperature
W = Wet bulb (screen) temperature

For THI 20, " increasing discomfort felt" [ for ' sedentary workers
indoors ' or outside in shade in light winds ]
THI = 24 .. half sample population will feel 'discomfort'.
THI 27 .. 'all' are likely to be distressed.

From your figures, I make your THI somewhere around 23.

As I say, things have no doubt moved on, but it should give a
reasonable guide.

The Met Office system here ...
http://www.metoffice.gov.uk/weather/...lth/index.html

appears only to be triggered by temperature, though given that night
minima are included (which in turn are governed by boundary-layer
humidity), you could argue that the humidity element is implicitly
covered. I believe though that in the US humidity is explicitly
modelled in heat-stress warnings.


Martin.

--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

Martin Rowley wrote:

"ronaldbutton" wrote in message
... snip
At present in my back garden the temp is 26C and the RH 55%,which with the
easterly breeze feels very comfortable ,so excuse my ignorance but how the
comfort levels determined viz a viz temperature combined with humidity ?.
I'd hate to enjoy myself whilst so many people seem to be struggling with
the dreadful heat and having to remove their anoraks.

... well, I'm probably way out of date now on all this as I know that a lot
of work has been done in the Met Office with the DoH & individual NHS trusts.
However, the standard algorithm we used to use to work out a
'temperature-humidity' index is as follows:-

THI = 0.4 (T + W) + 4.8 .... (for degC).

whe
THI 'Temperature/Humidity Index'
T = Dry bulb (screen) temperature
W = Wet bulb (screen) temperature

For THI 20, " increasing discomfort felt" [ for ' sedentary workers indoors
' or outside in shade in light winds ] THI = 24 .. half sample population
will feel 'discomfort'. THI 27 .. 'all' are likely to be distressed.

From your figures, I make your THI somewhere around 23.

As I say, things have no doubt moved on, but it should give a reasonable
guide.

The Met Office system here ...
http://www.metoffice.gov.uk/weather/...lth/index.html

appears only to be triggered by temperature, though given that night minima
are included (which in turn are governed by boundary-layer humidity), you
could argue that the humidity element is implicitly covered. I believe though
that in the US humidity is explicitly modelled in heat-stress warnings.


Martin.


The one that I've used for a long time is the so-called Humisery Index which is


Index = (((2Td) +T)/3)-12 (for deg C)

An index value of 0 is very comfortable for most people while an index of 10 is
extremely uncomfortable.

My 1500z obs gives an index of 7.9 which fits very well with how it feels.

I don't know where the Humisery Index came from. I was introduced to it by
Philip Eden many moons ago. I have half an idea that Philip actually devised
the index but I'm not sure. No doubt he will tell us.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.

"Norman" wrote:
Martin Rowley wrote:

... well, I'm probably way out of date now on all this as I know that a
lot
of work has been done in the Met Office with the DoH & individual NHS
trusts.
However, the standard algorithm we used to use to work out a
'temperature-humidity' index is as follows:-

THI = 0.4 (T + W) + 4.8 .... (for degC).

whe
THI 'Temperature/Humidity Index'
T = Dry bulb (screen) temperature
W = Wet bulb (screen) temperature

For THI 20, " increasing discomfort felt" [ for ' sedentary workers
indoors
' or outside in shade in light winds ] THI = 24 .. half sample population
will feel 'discomfort'. THI 27 .. 'all' are likely to be distressed.

From your figures, I make your THI somewhere around 23.


The one that I've used for a long time is the so-called Humisery Index
which is

Index = (((2Td) +T)/3)-12 (for deg C)

An index value of 0 is very comfortable for most people while an index of
10 is
extremely uncomfortable.

My 1500z obs gives an index of 7.9 which fits very well with how it feels.

I don't know where the Humisery Index came from. I was introduced to it by
Philip Eden many moons ago. I have half an idea that Philip actually
devised
the index but I'm not sure. No doubt he will tell us.

The story is as follows. When I first started on LBC radio in 1983, Arthur
Blackham (for readers who may not know he was my boss at Noble
Denton Weather Service at that time) persuaded me that I should
introduce a variety of novel concepts (some might unkindly call them
gimmicks; in truth they were rather more than that), including the first
regular UK outing for the Wind Chill Factor, as well as the Humisery
Index. Another, the temperature on the Noble Denton window-sill,
quickly vanished! I'm happy to admit I was reluctant, but you don't
go against your boss when you're six months into a new job.

We looked at various comfort indices in use at the time,
and discovered the term "Humisery" in a late-1970s paper in the
Bulletin of the American Met Soc, and we liked the term and
thought it was certain to catch on. (The fact that there is no
Wiki entry for it -- or even a mention -- suggests that it didn't!)

The various THI indices available then were designed for places
like Florida, or the US Gulf Coast, or Bahrain, or Singapore, so
they were not really appropriate for typical 1980s summers in
London, so it fell to me to design it. I didn't want yet another
equivalent temperature (I was already coming to the conclusion
that a windchill temperature was potentially confusing and soon
dropped it -- just as the MO were picking it up! -- in favour of
a qualitative rather than a quantitative approach. By 1985 I was
already talking of, say, a temperature of minus 5 with a large
additional chill factor, and I think this is far, far better than
throwing two different temperatures into a weather forecast).
So I came up with the idea of an index. The index had to be
simple, and what's simpler than a scale of zero to ten? So
that's what it was, and I simply used a version of the basic
THI formula that actually fitted that scale. The very rare
occasions when the index climbed above 10 were classed as
a 10, which everybody understood meant "absolutely
drippingly horrid".

The heyday of the Humisery Index on LBC was in the late-80s
and early-90s when a company selling standalone air-conditioning
units used it in their advertising campaign.

Thanks Arthur!

Philip

On Jul 1, 12:02*pm, "Philip Eden" philipATweatherHYPHENukDOTcom
wrote:
"Norman" wrote:
Martin Rowley wrote:
... well, I'm probably way out of date now on all this as I know that a
lot
of work has been done in the Met Office with the DoH & individual NHS
trusts.
However, the standard algorithm we used to use to work out a
'temperature-humidity' index is as follows:-

THI = 0.4 (T + W) + 4.8 .... (for degC).

whe
THI 'Temperature/Humidity Index'
T = Dry bulb (screen) temperature
W = Wet bulb (screen) temperature

For THI 20, " increasing discomfort felt" [ for ' sedentary workers
indoors
' or outside in shade in light winds ] THI = 24 .. half sample population
will feel 'discomfort'. *THI 27 .. 'all' are likely to be distressed.

From your figures, I make your THI somewhere around 23.

The one that I've used for a long time is the so-called Humisery Index
which is

* * * * * * * * * * *Index *= *(((2Td) +T)/3)-12 *(for deg C)

An index value of 0 is very comfortable for most people while an index of
10 is
extremely uncomfortable.

My 1500z obs gives an index of 7.9 which fits very well with how it feels.

I don't know where the Humisery Index came from. I was introduced to it by
Philip Eden many moons ago. I have half an idea that Philip actually
devised
the index but I'm not sure. No doubt he will tell us.

The story is as follows. When I first started on LBC radio in 1983, Arthur
Blackham (for readers who may not know he was my boss at Noble
Denton Weather Service at that time) persuaded me that I should
introduce a variety of *novel concepts (some might unkindly call them
gimmicks; in truth they were rather more than that), including the first
regular UK outing for the Wind Chill Factor, as well as the Humisery
Index. Another, the temperature on the Noble Denton window-sill,
quickly vanished! *I'm happy to admit I was reluctant, but you don't
go against your boss when you're six months into a new job.

We looked at various comfort indices in use at the time,
and discovered the term "Humisery" in a late-1970s paper in the
Bulletin of the American Met Soc, and we liked the term and
thought it was certain to catch on. (The fact that there is no
Wiki entry for it -- or even a mention -- suggests that it didn't!)

The various THI indices available then were designed for places
like Florida, or the US Gulf Coast, or Bahrain, or Singapore, so
they were not really appropriate for typical 1980s summers in
London, so it fell to me to design it. I didn't want yet another
equivalent temperature (I was already coming to the conclusion
that a windchill temperature was potentially confusing and soon
dropped it -- just as the MO were picking it up! -- in favour of
a qualitative rather than a quantitative approach. By 1985 I was
already talking of, say, a temperature of minus 5 with a large
additional chill factor, and I think this is far, far better than
throwing two different temperatures into a weather forecast).
So I came up with the idea of an index. The index had to be
simple, and what's simpler than a scale of zero to ten? So
that's what it was, and I simply used a version of the basic
THI formula that actually fitted that scale. The very rare
occasions when the index climbed above 10 were classed as
a 10, which everybody understood meant "absolutely
drippingly horrid".

The heyday of the Humisery Index on LBC was in the late-80s
and early-90s when a company selling standalone air-conditioning
units used it in their advertising campaign.

Thanks Arthur!

Philip- Hide quoted text -

- Show quoted text -

I wonder if you had thought of using the wet-bulb temperature
as a humidity/comfort index. Over the range of temperatures and
dewpoints relevant to comfort in the UK it amounts to the same thing
as Humisery+12 to within less than one unit except for very low
dewpoints. After all, a sweaty body can be regarded as a sort of wet
bulb and will respond similarly.
The figures I have used to show this are for an aspirated psychrometer
so the sweaty one had better keep moving.
Of course, dewpoints are more readily available than wet-bulb
temperatures but this has the advantage of being an actual temperature
without the misleading connotations of windchill equivalents which I
agree are far better described qualitatively.
You could sell summer T-shirts emblazoned with the words "WET BULB".

Tudor Hughes, Warlingham, Surrey.