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Non Footy Chat Thread II

S

Suitman

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Messages
55,991
Gary Gutful said:
Cracking day in Sydney today. Warm without sweating your ring off.
Click to expand...

I just posted this in a weather-related forum elsewhere......

"Amazingly dry airmass this one before the change.
Richmond currently 29.3 degrees, with minus 6.8 deg DP and humidity at 9%, giving an APP temp of 19.9 deg's.
In the shade, it does not feel hot at all.

Correct me if I'm wrong but I would think an app temp 10 deg's lower than the actual temp in the Sydney basin would be quite a rare occurrence."
 
Last edited:
Gary Gutful

Gary Gutful

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Messages
53,004
Suitman said:
Also, wherever you are in Sydney, I hope you've got a jumper with you.
It's going to feel decidedly colder this afternoon.
There was snow on the Snowy Mountains this morning.
Click to expand...
Thanks mate. Got a jumper in my bag.

On your other post, I’m no weather specialist but Cairns is regularly 5 degrees higher on the ‘feels like’ measure. Also rarely gets above 35, but as soon as it’s close to 30 it is brutal.
 
S

Suitman

Post Whore
Messages
55,991
Gary Gutful said:
Thanks mate. Got a jumper in my bag.

On your other post, I’m no weather specialist but Cairns is regularly 5 degrees higher on the ‘feels like’ measure. Also rarely gets above 35, but as soon as it’s close to 30 it is brutal.
Click to expand...
Indeed, and yes, I'm aware of the brutal dew point temps in Cairns.
Darwin is even worse.
When DP's get above about 18 - 20 C, it starts to become very uncomfortable and one thing I have noticed recently is that parts of Sydney are getting worse for this over the past few summers - getting up to Cairns levels of around 25 degrees DP at times.
The minus 6.8 at Richmond that I quoted earlier indicates a very dry air-mass. It's actually now minus 9.6 atm.
This will increase this arvo as the southerly takes hold, bringing in more humid air.
Syd AP for instance currently has a DP of 14.6. The southerly hasn't reached Richmond yet. We still have strong dry westerlies here.
The feels like temp at Sydney AP is currently 14.9 behind the colder change!!! Hence the suggestion of a jumper.
It should be here in Castle Hill in the next hour or so and I'm looking forward to that.
It's fighting against the westerly currently but will eventually break through.
 
Twizzle

Twizzle

Administrator
Staff member
Messages
153,355
Suitman said:
Indeed, and yes, I'm aware of the brutal dew point temps in Cairns.
Darwin is even worse.
When DP's get above about 18 - 20 C, it starts to become very uncomfortable and one thing I have noticed recently is that parts of Sydney are getting worse for this over the past few summers - getting up to Cairns levels of around 25 degrees DP at times.
The minus 6.8 at Richmond that I quoted earlier indicates a very dry air-mass. It's actually now minus 9.6 atm.
This will increase this arvo as the southerly takes hold, bringing in more humid air.
Syd AP for instance currently has a DP of 14.6. The southerly hasn't reached Richmond yet. We still have strong dry westerlies here.
The feels like temp at Sydney AP is currently 14.9 behind the colder change!!! Hence the suggestion of a jumper.
It should be here in Castle Hill in the next hour or so and I'm looking forward to that.
It's fighting against the westerly currently but will eventually break through.
Click to expand...

I've never heard anyone describe the air conditions as a negative dew point temperature. We generally refer to it as the wet bulb temperature and the correlation of wet and dry bulb determines the relative humidity.

The dew point temperature is the temperature at which moisture will condense on a surface which is also determined by the RH.

Where are you getting this terminology from ?
 
S

Suitman

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Messages
55,991
Twizzle said:
I've never heard anyone describe the air conditions as a negative dew point temperature. We generally refer to it as the wet bulb temperature and the correlation of wet and dry bulb determines the relative humidity.

The dew point temperature is the temperature at which moisture will condense on a surface which is also determined by the RH.

Where are you getting this terminology from ?
Click to expand...

How about we try the BoM and their official figures.


SYDNEY METROPOLITAN​

��
DirSpd
km/h		Gust
km/h		Spd
kts		Gust
kts		Dirkm/h
time		kts
time
Date/Time
EDT		Temp
°C		App
Temp
°C		Dew
Point
°C		Rel
Hum
%		Delta-T
°C		WindPress
MSL
hPa		Rain since
9am
mm		Low
Temp
°C
time		High
Temp
°C
time		Highest Wind Gust
Badgerys Creek23/08:10pm23.517.1-1.51911.1W222612141004.70.023.4
08:10pm		29.6
01:28pm		WNW67
11:17am		36
11:17am
Bankstown23/08:10pm20.316.910.7545.2ESE192410131005.20.020.2
08:10pm		29.4
03:02pm		W59
01:49pm		32
01:49pm
Camden23/08:10pm23.016.1-2.61811.1SW242813151004.90.023.0
08:10pm		28.4
01:53pm		WNW65
11:07am		35
11:07am
Campbelltown23/08:10pm22.318.5-1.12110.4SW91357-0.022.3
08:10pm		27.7
03:58pm		SW50
12:50pm		27
12:50pm
Canterbury23/08:10pm19.818.011.0574.8SE111568-0.019.7
07:56pm		28.2
12:18pm		W54
01:19pm		29
01:19pm
Fort Denison23/08:10pm-----SE91156----W61
01:26pm		33
01:26pm
Holsworthy23/08:10pm19.416.910.9584.7SE1517891005.20.019.4
08:10pm		28.5
03:52pm		WSW56
02:15pm		30
02:15pm
Holsworthy (Defence)23/08:10pm18.617.49.4554.9SE6734-0.018.6
08:10pm		28.5
03:22pm		WSW56
02:40pm		30
02:40pm
Horsley Park23/08:10pm19.517.79.4525.4ESE9955-0.019.5
08:10pm		28.7
03:08pm		NW52
11:35am		28
11:35am
Kurnell23/08:10pm-----SSE111367----NW67
11:52am		36
11:52am
Little Bay23/08:10pm-----S7945----S50
02:31pm		27
02:31pm
Lucas Heights (ANSTO)23/08:00pm18.515.69.8574.6ESE1520811-0.0-----
North Head23/08:10pm-----SSE151789----S54
01:54pm		29
01:54pm
Parramatta23/09:00am25.322.49.7378.6WSW15-8--0.0-----
Penrith23/08:10pm23.819.7-0.52011.0W111367-0.023.7
08:10pm		29.8
04:02pm		W59
12:44pm		32
12:44pm
Richmond23/08:10pm24.018.2-1.81811.4WSW192010111004.70.023.9
08:10pm		30.6
02:52pm		W61
11:29am		33
11:29am
Sydney Airport23/08:10pm20.117.510.8555.1SE15198101005.30.019.6
08:05pm		29.7
01:15pm		W61
12:24pm		33
12:24pm
Sydney - Observatory Hill23/08:10pm20.018.711.2574.9SE9-5-1005.30.020.0
08:10pm		29.1
01:58pm		---
Sydney Harbour23/08:10pm20.2----SE111568--20.2
08:10pm		27.3
11:51am		W70
11:52am		38
11:52am
Sydney Olympic Park23/08:10pm19.817.711.3584.7SE131779-0.019.8
08:10pm		29.9
03:27pm		WNW52
11:58am		28
11:58am

You could always see this page as well, also from the BoM.

Feeling hot and bothered? It’s not the humidity, it’s the dew point - Social Media Blog - Bureau of Meteorology

The Bureau of Meteorology's blog gives you the inside information on weather, climate, oceans, water and space weather.
media.bom.gov.au media.bom.gov.au

What’s the difference between dew point and humidity?​

They both measure moisture in the air, but dew point is related to the quantity of moisture, while relative humidity expresses how close the air is to saturation. Relative humidity is the amount of moisture as a percentage of the amount that air can hold – and warmer air can hold more moisture than cooler air. So, if the amount of moisture in the air stays the same but the temperature rises, the relative humidity falls. Conversely, if temperature falls, relative humidity rises.

Because of its direct relationship to fluctuating temperature, relative humidity doesn’t provide suitable guidance on how much moisture is available at a specific location. Dew point however, is relatively consistent – unless affected by weather systems, such as troughs and fronts. For this reason, meteorologists prefer to use dew point when analysing atmospheric moisture and inferring what the conditions may feel like – represented by the apparent (‘feels like’) temperature.
Click to expand...
 
Last edited:
Twizzle

Twizzle

Administrator
Staff member
Messages
153,355
Suitman said:
How about we try the BoM and their official figures.


SYDNEY METROPOLITAN​

��
Date/Time
EDT		Temp
°C		App
Temp
°C		Dew
Point
°C		Rel
Hum
%		Delta-T
°C		WindPress
MSL
hPa		Rain since
9am
mm		Low
Temp
°C
time		High
Temp
°C
time		Highest Wind Gust
DirSpd
km/h		Gust
km/h		Spd
kts		Gust
kts		Dirkm/h
time		kts
time
Badgerys Creek23/08:10pm23.517.1-1.51911.1W222612141004.70.023.4
08:10pm		29.6
01:28pm		WNW67
11:17am		36
11:17am
Bankstown23/08:10pm20.316.910.7545.2ESE192410131005.20.020.2
08:10pm		29.4
03:02pm		W59
01:49pm		32
01:49pm
Camden23/08:10pm23.016.1-2.61811.1SW242813151004.90.023.0
08:10pm		28.4
01:53pm		WNW65
11:07am		35
11:07am
Campbelltown23/08:10pm22.318.5-1.12110.4SW91357-0.022.3
08:10pm		27.7
03:58pm		SW50
12:50pm		27
12:50pm
Canterbury23/08:10pm19.818.011.0574.8SE111568-0.019.7
07:56pm		28.2
12:18pm		W54
01:19pm		29
01:19pm
Fort Denison23/08:10pm-----SE91156----W61
01:26pm		33
01:26pm
Holsworthy23/08:10pm19.416.910.9584.7SE1517891005.20.019.4
08:10pm		28.5
03:52pm		WSW56
02:15pm		30
02:15pm
Holsworthy (Defence)23/08:10pm18.617.49.4554.9SE6734-0.018.6
08:10pm		28.5
03:22pm		WSW56
02:40pm		30
02:40pm
Horsley Park23/08:10pm19.517.79.4525.4ESE9955-0.019.5
08:10pm		28.7
03:08pm		NW52
11:35am		28
11:35am
Kurnell23/08:10pm-----SSE111367----NW67
11:52am		36
11:52am
Little Bay23/08:10pm-----S7945----S50
02:31pm		27
02:31pm
Lucas Heights (ANSTO)23/08:00pm18.515.69.8574.6ESE1520811-0.0-----
North Head23/08:10pm-----SSE151789----S54
01:54pm		29
01:54pm
Parramatta23/09:00am25.322.49.7378.6WSW15-8--0.0-----
Penrith23/08:10pm23.819.7-0.52011.0W111367-0.023.7
08:10pm		29.8
04:02pm		W59
12:44pm		32
12:44pm
Richmond23/08:10pm24.018.2-1.81811.4WSW192010111004.70.023.9
08:10pm		30.6
02:52pm		W61
11:29am		33
11:29am
Sydney Airport23/08:10pm20.117.510.8555.1SE15198101005.30.019.6
08:05pm		29.7
01:15pm		W61
12:24pm		33
12:24pm
Sydney - Observatory Hill23/08:10pm20.018.711.2574.9SE9-5-1005.30.020.0
08:10pm		29.1
01:58pm		---
Sydney Harbour23/08:10pm20.2----SE111568--20.2
08:10pm		27.3
11:51am		W70
11:52am		38
11:52am
Sydney Olympic Park23/08:10pm19.817.711.3584.7SE131779-0.019.8
08:10pm		29.9
03:27pm		WNW52
11:58am		28
11:58am

You could always see this page as well, also from the BoM.

Feeling hot and bothered? It’s not the humidity, it’s the dew point - Social Media Blog - Bureau of Meteorology

The Bureau of Meteorology's blog gives you the inside information on weather, climate, oceans, water and space weather.
media.bom.gov.au media.bom.gov.au
Click to expand...

Interesting, I've never seen dew points that low, and I can't check them on my charts as we don't go that low when designing air conditioning or refrigeration systems for low-humidity rooms. I did a low-humidity room earlier this year for preparing and packing shake supplements.

Those conditions you provide are as they say, off the chart, and extrapolating doesn't work when the values are represented by a curve rather than a straight line on a graph.

They also do not answer the question of what is the difference between dew point and humidity, they only say it "is related to" while not defining it like I did. What is the point of having that title and not answering the question ? It's not difficult to explain but I guess they don't want to get too technical with the general public.

I don't study the weather like you do and I've never seen negative dew points when providing psychometric data on the air conditions. We occasionally design systems that are not near the coast or a capital city where the weather data is easily accessible, mostly through our software data bases. When we have to start from scratch we get our data from the nearest airport which has years of data available through the BOM but it's only ever supplied as wet and dry bulb temperatures from which we work the humidity out from there. DP temperatures have no impact on building heat gains, its more of a human comfort thingy.
 
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