Advice/Guidance: November Touring / Winter IFR Weather

How could that be used? You can’t hover over the image, etc. and there is no colour reference shown.

I fly from Blackbushe to Egelsbach (not exactly southern Germany yet) approximately once a month and the main weather planning tool to get a good feel for the approximate weather development over the next 10 days I use Windy. Besides checking weather overall, I specifically look for:

- Temperature at FL50 to see whether it is going to be close to zero or below zero as that is the minimum IFR altitude I assume, primarily due to MVA in Germany (for southern Germany, depending on where you go, you probably need to assume FL60)
- Relative humidity at different flight levels. If humidity is below 80%, one can fairly confidently assume that there would be no major cloud layer at that flight level. This is important and I use it in combination with the temperature forecast. If the temperature is below zero and humidity is above 90%, I normally assume that I need to expect icing
- Relative humidity at ground level to understand whether there would be fog to be expected
- Checking temperatures and relative humidity at different flight levels is like looking at a Skew-T. Windy just introduced the functionality (web only), so will need to experiment with that

For the actual day in question, I use the cross-sections and DWD and METEO France LLSWC charts available from DWD Flugwetter (a paid service). Cross-sections are very useful. I look at ADWICE for icing forecasts as well but they tend to be overly conservative for light icing but not for medium and severe icing.

Interestingly, one gets a relatively good pre-planned dispatch rate (I own a non-TKS/FIKI plane), especially ensuring that one is also able to get back, which is important! Depending on the location of the jet stream, there are surprisingly many days with positive temperatures. And then there are many days with sub-zero temperatures at altitude but low humidity.

Please do note that I find weather models are not very good at predicting details on temperature and humidity beyond 3 days (try the four models on Windy and see how their forecasts differ!) but they give you a general sense for the development of the weather situation days in advance, especially looking for days/periods with positive temperatures at altitude.

Also, get an MVA chart for Germany (NOT published online but needs to be ordered in hardcopy) to know what the effective minimum IFR altitude in Germany is in case you can’t get on top of clouds to check what conditions at the minimum IFR altitude would be. Although Eurocontrol will accept flight plans at lower levels (which Autorouter will also happily generate), ATC will not allow you to fly them below the MVA. FL50 (or 5000ft depending on transition level) works well across Belgium and Germany unless you get to higher elevation areas in Southern Germany with class E airspace at 2,500 AGL.

If you could let us know where you plan to fly to, I can scan in the relevant part of the MVA chart.

I would caution re icing forecasts. They are IME worthless. Really worthless. Like the Autorouter gramet nowadays, they are great when they come out right, but basically you can’t forecast when one bit of IMC will make ice, or not. I mean, they can’t even forecast IMC itself reliably! Well, not beyond what is obvious from the MSLP chart, and (on the morning of the flight) the radar and IR images.

A number of times I’ve picked up several cm in minutes, which would bring a plane down if you had no Plan B, or de-icing.

I used to have access to ADWICE for a while, and it was of no real use.

The only sure way is to fly VMC on top, and have a Plan B (usually a descent to warm air) for when you collect too much. This is true summer or winter. At FL100 (typical Eurocontrol minimum IFR level) in the summer you will get ice in IMC in most of Europe.

TimR wrote:

This is interesting.. I always assumed the “Plan B” to be to descend to MSA. In other words, any flight is ok if the temperature is >0c at MSA. You make a good point that ATC will likely get rid of you higher than that. How do I get at the minimum vectoring altitudes? I know the MEA’s from the Jeppesen en-route charts but presume this is not always the same as MVA?

MVA is a concept operated by certain countries, i.e. those with a certain type of airspace structure (class E blanket) and a certain type of ATC policy. The most famous one is Germany, but it also applies to Austria and Switzerland.

In essence, you will have varying MVAs, which are often noticeably higher than the MSAs. So, in these countries, you can’t just check MSAs and say “go” if the freezing level is above that. Because ATC will NOT let you go below that. If you need to go below that due to ice, you need to either delcare an emergency (not a good idea) or cancel IFR (in which case you will not usually be able to go IFR again at a later stage.)

MVAs are usually similar to airway MEAs (so, these do give you an idea), but not equal.

I guess in the winter months you can get long periods of freezing levels around FL50? This may be fine when climbing through & up but sort of removes the safety escape route when you need it?

In winter (and even in spring) you almost ALWAYS have the freezing level at FL50 or below.
One treacherous is that when you are VMC, the freezing level is often as forecast. But as soon as you enter IMC, the temperature usually drops by 3-4 degrees. So, effectively, your freezing level is always about 2000 feet lower then “forecast”.

It is a shame that these are not published on a broader scale. Jepp does have them for major airports, such as Frankfurt, Stuttgart, or Zurich (called Radar Minimum Altitudes), but that doesn’t help any for airports outside those areas.

The safest way for a non de-iced plane, and what I have nearly always done, is

• ensuring the cloud cover at departure is fairly thin, so not much ice is picked up (and if it is, you come back and land)
• ensuring (using IR images etc) the enroute portion is done VMC on top
• ensuring the cloud cover at destination is fairly thin OR the air is warm enough high enough so ice can be shed on the way down

It does mean one cannot fly through fronts, unless the IR image shows it can most probably be crossed in IMC above it (quite often the case for fronts which have almost no pressure gradient across them).

Another strategy, for IMC enroute, is to climb to a level where icing is unlikely. I used to think that until this happened a couple of times at -15C, which basically means you cannot climb as high because alternate air reduces the ceiling by some 2000-3000ft.

boscomantico wrote:

MVA is a concept operated by certain countries, i.e. those with a certain type of airspace structure (class E blanket) and a certain type of ATC policy. The most famous one is Germany, but it also applies to Austria and Switzerland.

You must always have MVAs when ATC has a radar service. It’s not specific to these countries. What I guess is specific is that enroute controlled airspace extend to such a low level that MVAs are relevant. E.g. Sweden only has MVAs in TMAs as the lower limit of enroute controlled airspace is well above any obstacles (FL95 or FL125).