DECEMBER SNOW IN AUSTRALIA!!!!!!!!!!!!!!!!!.

Dear Santa,

THANK YOU FOR THE SNOW!!.  There it is, folks.  Snow in Alpine Australia.  In December.  Unreal.

 

.BT

More Outback La Niña...

A couple of pretty amazing images from the Outback sky; I'll let them speak for themselves.

Synoptic Meteorology GR4713 FINAL

Here's some review stuff for the Synoptic Meteorology GR4713 final...

FINAL STUDY GUIDE #3
Some things to notice about this image...
The location of the Tropopause, the red line.
The location of the upper-level jet streaks, the blue lines. Notice how you are looking through the entrance regions of the jet streaks here.
The stability of the Stratosphere compared with that of the Troposphere.
Notice also how the jet streaks are all located in the mid- to upper-Troposphere. You can see how the 3 Tropopause folds occur to the left of the jet streak entrances, which is consistant with what we know about upper-level jet streak circulations in the entrance regions, with convergence and sinking air to the left (left rear quadrant), pulling down the Stratospheric air, and divergence and rising air to the right (right rear quadrant), forcing up the Tropospheric air.


*This image from Lecture 8 notes.

FINAL STUDY GUIDE #4
Please note this is an upper-level jet streak.
As air enters the jet streak, PGF becomes dominant, pulling it to the left, causing convergence in the left rear quadrant and divergence in the right rear quadrant. Once the air exits the jet streak, Coriolis becomes dominant, pulling the air to the right, causing convergence in the right front quadrant and divergence in the left front quadrant.


Please also note the Transverse Circulations of the entrance and exit regions. In the entrance, sinking air to the left and rising air to the right causes counterclockwise motion (as you are looking through the jet streak horizontally). This is the formation of the Low Level Jet, or LLJ. This is called a Direct Transverse Circulation because this particular circulation forces warm air to rise and cold air to sink. This also acts to weaken or destroy any thermal gradient in place. In the exit, rising air to the left and sinking air to the right causes clockwise motion (again, looking through the jet streak horizontally). This LLJ circulation is called an Indirect Transverse Circulation, because it forces cold air to rise and warm air to sink. This acts to create or enhance any existing thermal gradient.


Lastly, it should be noted that these Transverse Circulations and the way they create thermal gradients ahead of the jet streak and destroy thermal gradients behind it is what causes the movement of the jet streak itself, not wind advection.


Lastly, in straight-line flow, vorticity is created only by shear. Cyclonic shear to the left of the jet streak causes a vort. max. to form to the left; anticyclonic shear to the right causes a vort. min. to form to the right. PVA occurs ahead of the vort. max. because it is advecting FROM the area of maximum vorticity, and NVA occurs behind it because you are advecting TO the area of maximum vorticity, so it can only advect negatively onto the vort. max. NVA occurs ahead of the vort. min. because you are advecting FROM the area of minimum vorticity, and PVA occurs behind the vort. min. because you are advecting TO the area of minimum vorticity, and it can only be increased by any advections to it.


*I created this image.

FINAL STUDY GUIDE #4
This image is again a 300mb jet streak. The difference here is that it is cyclonically curved(NH). Cyclonic shear and cyclonic curvature combine to form a strong vort. max to the left, and anticyclonic curvature roughly negate one another, leaving you with no substantial area of vorticity, and subsequently no substantial vorticity advections to the right. There are also no substantial VV's on the right side.  Because of the strong Vort. Max. on the left side, strong PVA occurs ahead of the vort. max. and strong NVA occurs behind it.


*I created this image.

FINAL STUDY GUIDE #4
This image is a 300mb jet streak, once again. This jet streak is anticyclonically curved(NH). Anticyclonic shear and cyclonic curvature negate one another on the left, leaving you with no substantial area of vorticity, and subsequently no substantial vorticity advections to the right. There are also no substantial VV's on the left side.  Anticyclonic shear and anticyclonic curvature combine to form a strong vort. min. on the right side. Because of this, strong NVA occurs ahead of the vort. min. and strong PVA occurs behind it.


*I created this image.

FINAL STUDY GUIDE #4
This image is an 850mb jet streak. Please, PLEASE PLEASE PLEEEEEEEEASE be aware that a lower-level jet streak causes very different results in terms of VV's (vertical velocities). The convergence still occurs in the left rear and right front quadrants, and divergence still occurs in the right rear and left front quadrants. However, in the lower levels, convergence causes air to rise and divergence causes air to sink. Due to this, sinking air happens in the right rear and left front quadrants, and rising air happens in the left rear and right front quadrants.


*I created this image.


.BT

Geographic Temperature Variability, etc...

Okay, so let's get stuck right into it, then.  I love the weather, sky watching, forecasting (more like learning to right now...).  What I love ten times as much, though, is Geography.  Talking about it, teaching it, learning it.  I absolutely love looking at weather from a Geographic perspective.  Here is an example.  Here we will compare high temperatures forecast for Tuesday at 2 different times of the day.  There are several Geographic items I would like to address here.  First image is for 0500, the second is for 1700, 12 hours later.

0500 Local

1700 Local

First off, I would like to set the stage here.  Some things we should know are what, where, when.  We are looking at the Australian Continent.  It is located at the crossroads of the S Indian and S Pacific Oceans, which puts it in the S Hemisphere.  Typically temperatures get colder the further S you go, or we shall simply say henceforth "poleward", and vice versa for warm temperatures and N, or "equatorward".  When, well this is taken for 7 December, which means that down here we are right smack in the middle of Summer.  Also we shouldn't expect characteristic climatic conditions due to the La Niña sector of the ENSO (El Niño Southern Oscillation).  El Niño is characterized by predominately high surface pressure over Indonesia,  Malaysia, Polynesia, Australia, and the S Indian Ocean, and low surface pressure over N and S America, as well as a decrease in the trade winds, allowing 'backed up' warm water to flow E towards the Americas.  La Niña is the opposite.  The reasons for all of this are still unknown, though the object of stern scientific scrutiny.

Notice in the second image, forecast high temperatures for 1700 Local, the spatial distribution of the temperatures.  Notice all around Australia how zonal the temperature distribution is, almost parallel with latitude.  Have a look at where the hottest temperatures are ocurring; bulls-eyed almost dead center over mainland Australia.  This is due to the fact that land has a much lower specific heat than does water.  Water has one of the highest specific heats on earth, at roughly 1.81.  This means that land heats and cools much quicker than water does.  Out here in the Australian Outback, temperatures can easily break 35C, while plumetting to below 10C at night.  To change the temperature of a body of water with the surface area of Australia even 1C would take a catastrophic amount of energy; several times the power of a nuclear bomb.  It simply does not happen.  This oceanic or maritime effect acts to moderate temperature, as well as fuel storm systems with moisture in the summer months and moisture and relative heat in the winter months.

Compare this continentality effect of Australia with that of New Zealand.  Primarily two islands, New Zealand is moderated year-round by maritime influence.  Notice N of Australia, in the Tropics, the island of New Guinea (the Geographic island; the island itself is 2 countries, parts of Malaysia and Papua New Guinea).  People often times make the mistake of thinking that the hottest temperatures on earth are found along the Equator.  This isn't true.  Intense solar radiation from the sun strikes the Tropics (between roughly 23.5ͦN/S latitudes) and the hot air is forced to rise.  Once it rises, it diverges poleward in both directions.  At roughly 30N/S latitudes the air sinks, and diverges along the surface both poleward as well as equatorward.  This circulation between 30N/Equator and 30S/Equator is called the Hadley Cell, in both hemispheres.  This sinking air at roughly 30N/S latitudes causes the formation of deserts along these latitudes.  If you don't believe me, have a look at the image below.

The Equator runs through Northern S America, Central Africa (the green bit), and Malaysia, the group of islands N of Australia.  Notice the proximity of the desert areas to the Equator, roughly the same distance N and S of it.  The green is, in fact, vegetation, and this is due to the nature of the Tropics.  All that hot air rising causes condensation, clouds, and precipitation.  This causes a "belt" of clouds that pretty well encircles the earth almost any time of the year, which is called the ITCZ (Intertropical Convergence Zone).  This belt shifts N and S depending on the time of year.  Which is something else to note, is seasons.

Satellite imate of the ITCZ.

Typical proximity of the ITCZ which characterizes Tropical seasons, distinguising them between Wet and Dry.

A season is, by definition, a division of the year marked by changes in weather (temp., pressure, precip., etc.), daily hours of sunlight and ecology.  The Tropics do not know the traditional seasons so many of us are used to, Spring, Summer, Autumn, & Winter.  Rather Wet & Dry seasons, depending on the location of the ITCZ.  In the middle latitudes you find the greatest weather variations, and so you find Spring, Summer, Autumn, and Winter.  Other places have different seasonal classifications; for example, India has six distinct seasons.  Many areas around the Tibetan Plateau experence a monsoon season.  Then in the Polar regions the seasons are limited to simply Polar Day and Polar Night.

The first image from James Stewart's Calculus Early Transcendentals 5th edition, and is one of my favorites.  This graph plots hours of daily sunlight (Y-axis, dependent variable) as a function of time of the year (X-axis, independent variable).  Don't be too scared by the math, it's really simple, this one.  Notice the variability, that's what I'm really going for here.  Notice how close to uniform 20N is throughout the year.  To do this, follow the line for 20N from left to right.  The more "up and down" motion in the line, the more variability through the year of daily hours of sunlight.  Now compare this to 40N.  Now to 60N.  This is why higher latitudes (~60N/S -> 90N/S) experience seasons by Polar Day and Polar Night, because of the high degree of variability of daily hours of sunlight.  The middle latitudes are between the two, and moderate relative to the Tropics and Poles.

Back to New Guinea.  You notice that the forecast high temperatures are not as extreme as are those of Australia.  You can even see something opposite happening with regards to interior temperatures on New Guinea island.  The further inland you go, the lower the temperatures get.  Any idea why this might be?.  If you said it is because of mountainous regions, you would be correct.  This effect is called "orography", and it impacts both temperature as well as precipitation (or lack thereof).  You see this down in New Zealand as well along the Southern Alps especially.

Notice now the first image.  This is forecast temperatures for 0500 Local time.  Notice how zonal the temperature distribution continues to be, again except for Australia.  This is, again, due to the continental effect.  Notice Australia as well as New Zealand.  Many people make the assumption that this cooling is Antarctic air "creeping up" N, but hardly.  This is due to radiational cooling, which means that Australia will often times be cloudless on its interior, which means it radiates away most of the heat it gained during the day.  Not all of it, though; like a bank balance during the summer it is gaining more than it loses, thus heating up.  In New Zealand, the way the ocean keeps it from getting too hot, in the same way it keeps it from getting too cold.  During the day the land (outside of the mountainous regions) will tend to get hotter than the ocean, but at night it is opposite; the ocean you will often find is warmer than the land.  That's why during the day the ocean feels cool after standing on hot sand, but at night the ocean will feel warm after walking on the relatively cool sand.

There will be much more in the near future, this was just a bit of a primer, as well as setting the tone of this blog.  I hope you enjoy reading what I have to say and I always welcome feedback.

.BT

Australia's La Niña continues...

So this is my first posting on my new Meteorology blog; oh boy, have we had a wild one here in the Australian Outback.  Working at Nockatunga Station, circa 53km WSW of Noccundra, SW QLD, Australia, conducting 3D seismic operations.  We have had system after system come through in the last 3 months, last week dropping 20mm of rain in 20 minutes.  We had 35mm 5 days ago from the system below.

00Z 26 Nov.  A relatively weak surface low, slightly upstream the upper-level trough with a slight positive tilt.  We would expect this surface low to follow the thickness lines towards the SE.

22.5 hours later we can see the surface low has done just that now located in the Tasman Sea off of the Victorian Coast, disrupting our marine crew in place there, as well as rapidly intensified.  This system dropped over 100mm of rain across Victoria, into NSW, and areas in N QLD, coupled with tropical systems, experienced 200mm+, filling dams to capacity from Cairns down to Melbourne.

.BT