RELATIVE HUMIDITY...RH

[crikey]

I heard some news reports that that northern areas of Australia had had some bush fires( Darwin NT , Rockhampton etc 2011 and some mountains in Queensland)
I thought the lower latitudes toward the equator were always very tropical with high humidity even in winter.
I came across this chart for relative humidity AUGUST 2011
The northern cross-section of Australia the air is very dry at the moment( last month of winter) .
Example the northern tip of Queensland has only 5 to 10% humidity. It is not tropical up there at the moment.?
Is this a usual occurence.?
What synoptic patterns cause the dryness? After all all that warmth and warm oceans? Is it just caused by lack of wind flow. The synoptic pattern of wide isobars indicates little to no wind, so no moist air being delivered to land ?? ( Now that was just a wild guess)
http://www.bom.gov.au/australia/charts/ ... u&model=CG" onclick="window.open(this.href);return false;

[retiredweatherman]

Townsville humidity at 5.30 p.m. currently only 9%, numerous bushfires in the ranges from our west to southeast..

[crikey]

Good heavens retired weatherman..I don't think l have ever experienced 9% humidity..
Must make your skin dry..
Just had a look at the stats for today 10th sept 2011

Sept 10th.morning...7.30am..ssw wind 0 km/hr..29% RH

12pm lunchtime ..southerly wind 28km/hr..13%.RH

2.30pm..afternoon..southerly..26km/hr..9% RH

5pm tea time..southerly...9% RH Dew point -8.2deg C..LOL

Now get this!!!
One and a half hours later with a wind change
6.30pm.. TV time..E/NE..15km/hr..RH..50%

That is an increase of 41% Rh in 1 1/2hrs..

At 7.30pm Its dark now.. Northerly 0km/hr..RH is now 60%.

Just amazing Weatherman. Not familiar with weather up there but that is amazing!

Noticed the southerly flow with moderate wind linked to the dryness?
As the the wind changed from south .. to East.. and then.. north in the space of 2 1/2hrs from 5.00pm ..to 7.30pm
That's a complete 180degree turn. the RH then increased dramatically.

The southerly stream is making it all the way up to Townsville then!! WOW

The southerly has been dry in Vic too. Noticed my mouth was dry today even though we had lots of cloud. round about 42 RH with the S/westerly. Not comparable to your dryness

How does it get so dry in the day time up in Townsville. What causes the air to be so dry like today. Is it just those southerlies??

[retiredweatherman]

Had two preiods of lower humidity earlier on this year, both down to 7%.

No, we have no worries about dry skin. After a year of floods, cyclones, bushfires we are bred tough up here, so dry skin is nothing.

Townsville is surrounded by ranges from the NW to SW to E. The dry southerly airflow progressively loses its moisture after transgressing 2,500km of the dry inland. Just before this air reaches here it pushes over these ranges and loses yet more moisture, and Townsville experiences a mini Fohn Effect, hence the extreme dryness locally, often the driest in the State.

Late yesterday after still recording 9% at 5.30 p.m., the NE seabreeze finally crept in pushing the humidity of higher quickly, again a normal feature for here. Today, the southerly is weakening as the flow becomes more divergent and is pushing more S to SE. Although the humidity will drop again this morning, maybe below 20%, the weaker southerly flow will allow the NE seabreeze to push in earlier, about lunchtime.

This will increase the humidity tonight and will result in higher minimum temperatures here commencing tomorrow, following our almost record low minimum temperature for September this morning.

[crikey]

Thanks Rweatherman for the 'low down' on your topography and the effect on the weather.
I didn't know that.
I was just looking through the Rel' Humidity 7 day forecast from
http://www.bom.gov.au/australia/charts/ ... u&model=CG" onclick="window.open(this.href);return false;
The pattern this week really caught my attention
A few days this week; this thursday 15th to at least sunday 18th sept 2011,the Rh across Australia is just incredibly dry!, during the day.
And at the mainland boundary on the southern Australian coastline there is a very tight gradient of RH . For example near Adelaide on Friday nearly 10% humidity at 4pm and just a few hundred km south the Rh is 100%
This pattern continues to at least Sunday. ( day time pattern)
I don't really know the ramifications of this.
I was reading a little introductory stuff on Tornado development tonight. My interest was stirred as we had a really decent twirly out here today and noticed Alexia reported a wind event that could have been a tornadic event. Quite unusual for this time of year. Usually see dusty ones in summer. This one was invisible because the ground is not dusty atm
http://www.nssl.noaa.gov/edu/safety/tornadoguide.html" onclick="window.open(this.href);return false;
Maybe l am just a little paranoid but l considered the RH chart with this statement

"During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours."

As far as l understand ..that tight gradients of any weather variable usually spells trouble!

Anyway l have pencilled thursday to next Monday in as a good weather watch to learn something new. LOL

[crikey]

Lack of humidity shocks Sydney
A report from weatherzone news by
Brett Dutschke, Wednesday September 14, 2011 - 17:31 EST

Sydney has just recorded its lowest humidity in two years, giving residents their first
electric shocks of the season.

Westerly winds were so dry and strong this afternoon, the humidity dropped to just 13%,
well below the average of 51% for a September afternoon.

Humidity hasn't been this low in Sydney since spring 2009, when it dropped to 12% on a
35-degree October day.

Today wasn't nearly as warm as that October day, but it still got to a beach-worthy 27
degrees, seven above the September average.

The air became so dry today because of the strength of the winds. They blew at more than
40km/h, bringing dry air from the inland to the otherwise relatively humid coast.

Early spring is typically Sydney's driest time of the year, when skies are at their sunniest
and westerly winds at their strongest.

Last year spring wasn't so dry, mainly because of the La Nina that eastern Australia was
under the influence of. The lowest humidity recorded during last spring was 17%.

Sydneysiders can expect more shocks from static electricity in the coming days and weeks
due to persistent dry and gusty westerly winds.

© Weatherzone 2011

[retiredweatherman]

The latest dry change went through here this morning, with the current humidity only 7%, with dew point of minus 9.7C. Will stir up the fires again, as if there is anything left to burn..

[retiredweatherman]

Local humidity at 1100 now only 6%, temp 31.6C..

[retiredweatherman]

Official local humidity has bottomed out at 5%, the equal lowest I have seen in my 25 years here. Temp. is a very comfortable 33.6C. Sea breeze now in, so humidity now climbing rapidly...