Aviation weather thread

Carnacalla wrote: »

Also to note Cork at the moment:
EICK 091930Z = Cork Airport, 09th Sept, 19:30 hours
30007KT= Wind 300 degrees 7 knots
0500= Visibility 500m
R17/1000U= RVR (Runway visual range) Runway 17 1000m up
R35/1100U= RVR (Runway visual range) Runway 35 1100m up
FG VV002= Fog, vertical visibility 200m
03/03= Temp 3c, Dewpoint 3c
Q0976= Air pressure 976hpa (Hector Pascals)
BECMG 3000 BKN003= Trend: Becoming vis 3000m, clouds broken at 300ft.

In terms of RVR and D, U and C:
D indicates downward trend.
U upward trend.
N no change.

This may change for example throughout the passage of a warm front.
From a piloting perspective, the wind speed and the dew point split will aid in discussion for approach planning.

The time of issue will also help decision making. The above example is at 1930Z (7.30pm), the dew point split is unlikely to increase heading into the night time, generally speaking in our climate at least.
However if it was in the morning, the dew point split is likely going to increase as the air temperature increases towards its diurnal maximum. This will result in the fog lifting and wind speed increasing, generally speaking.

Fog is unlikely to cause any delays where you have tightly spaced isobars. On the other hand, an area under the influence of a high pressure with the associated slack pressure gradient may experience issues in the early morning, or all day depending on humidity and dew point split.



From an Irish aviation point of view, Ireland is particularly complex compared to other areas of Europe.
The prevailing winds in Ireland generally come from a south westerly to westerly direction. This wind comes in from the Atlantic. Many of the weather systems that develop in the Atlantic happen to be low pressure systems.

Low pressure systems (also known as depressions) are areas where the pressure is relatively lower than the surrounding area. This results in the air movement on the earths surface moving toward the centre of the depression. As it reaches the centre from all directions it then rises upward toward the sky(imagine a funnel) where it will then move outward from the centre, the opposite of what happens on the surface. It converges at the surfaces and diverges at the top.

As the air mass moves across the surface it will pick up moisture until it becomes saturated, in other words, it cannot carry any more moisture. As the air mass rises, it becomes cooler as it moves away from the surface. Once the temperature (the actual temperature of the air) and the dew point (the temperature which causes the moisture laden air to freeze, which can vary depending on atmospheric conditions) are the same, this results in cloud formation.

You then have this moisture laden air which is steadily moving toward Ireland. Land mass is often warmer than the sea, particularly during the summer. As this moisture laden air mass moves toward Ireland the warm convection currents over land cause the moisture laden air mass to rise further into the atmosphere where it becomes colder and colder. The water droplets help in suspension condense (turn from gas to a liquid form) and become heavier until such time as they can no longer be held in suspension, and then fall as rain.

Thats a very simple view of why ireland receives so much rainfall and weather systems. The weather we experience mostly originates in the Atlantic and our prevailing wind means that Ireland and indeed France, the UK and Iceland often bear the worst as we are the first land mass in its path.
Of course there are other considerations such as stationary high pressures over mainland europe and greenland which can keep these depressions away from us and then you have to consider the different types of fronts which can form as part of these pressure systems, each bringing their own unique characteristics which are often observable from the ground.

Weather is a complex subject and getting a grasp of the basics can be difficult, it certainly was for me, but if you have more than a passing interest it can be rewarding. For the most part and in my own opinion, any local forecast more than 48/72 hours should not be relied upon except in the exceptional circumstances of a blocking high for example.

I have to laugh when I hear of the Donegal postman et al, predicting specific weather three months in advance. Pure codswallop and guess work.

Gaoth Laidir wrote: »

EFHK 03-09 –SN
ESSA 00-05 2000M SN
ENGM 00-00 –SN
EPWA 00-08 –SNRA
EGPH 02-08 300m FG FZFG
EGLL 00-10 tempo 300’
London area 16-22 +SHRA 20G30kts
Paris area 00-06 600m BCFG tempo 200m
LOWW 00-09 400M FZFG
LSZH 00-00 tempo -SN
LIML 03-08 400M FZFG
LDZA 00-12 300m FG 200’

As I said to Carnacalla, the above means nothing to your average poster on here. You need to provide translations so everyone can learn from it, not just licensed individuals ( on their high horse:D)

+1 for this thread.

I like aviation and meteorology, and this thread being a hybrid of the two is something I'd find interesting. There are a number of threads in this forum which I'd have shag all interest in, but hey it's not my place to dictate anything to those with an interest in these threads, nor stand in their way!

Live and let live as they say!

Pat Dunne wrote: »

I would be interested in acquiring more of an insight to Aviation Meteorology. Perhaps you could you provide a translation, for us who are a less learned

Based on what I know, (Which is still fairly little), the four letter codes like EGLL=London Heathrow are airport codes, ICAO codes, (SN= Snow, -SN= Light Snow +Snow= heavy snow) FG=Fog, FZFG=Freezing Fog,

OP well done i think this is a great idea for a thread, for example if anyone was planning on flying in Europe over the next few days they would have an idea of the weather where they are heading too and this may help with plans and indeed issues with connections etc.

Seeing as this thread is going to persist, for the time being at least, it may be prudent to edit the first post and include an explanation including what charts signify, an explanation of what an ATIS is as well as what TAF and METAR's are and the frequency of their issuing. Likewise with explaining sig weather charts and the symbols you may encounter on these.

An EASA abbreviation decoder will greatly help peoples understanding.

The jeppesen intro section gives good nuggets of information but is probably a bit too in depth for most. Older versions of this are available online for free.

In my own experience most people don't understand what is to be expected with warm fronts, cold fronts, occlusions, isobars, trough lines, jet streams and pressure systems amongst everything else other than they appear as lines on the RTE weather amongst all the rain.

I would agree that if this is going to become a copy and paste of METARs with little or know explanation, it is a pointless exercise.

EDIT: As most weather discussion increases around significant weather an explanation of what a SIGMET is and how to break it down would also be beneficial.

Wouldn't mind an ole +TSSNGR tbh.

My favourite is CAVOK!

This is from a handy Ipad APP called Wx Charts from ProgAero. The chart is from FL240-630, so when they use XXX in these charts it signifies that the level of weather/icing/turbulence is below the chart bottom limit of FL240. It doesn't mean that it's below FL100.

The official blurb is this... Heights are indicated on SWH and SWM charts in flight levels (FL), top over base. When XXX is used, tops or bases are outside the layer of the atmosphere to which the chart applies.

Aeroweather is great, but have you dug into the meanings of codes like TEMPO?

Gaoth Laidir wrote: »

At the moment, almost 8000 (49%) of the total delay minutes throughout the Eurocontrol network are due to weather (probably fog).

Can't assume that, ever! Usually Europe widespread fog is something we hear well about, and there's very little fog around in Europe in actual fact. Most of Poland has low vis (Mostly workable), and NCL in the UK has, but that's caused 1 diversion.