UK and European low-level sig wx charts (F215 and F415)

Map area

The map area shows a snapshot of the fronts and areas of weather at a specific validity time (VT) shown at the top right of the chart.

The 'top' of the chart is 10,000 ft.

F215 worked example

In response to questions arising from the F215 format, further guidance on this product is now available in the form of a worked example.

F215 worked example (PDF, 225 kB)

Weather

The text boxes on the right show the weather for each area of the map and have been designed to follow the TAF code appearing in the same order; visibility and weather followed by cloud. The METAR weather codes are also used in this section to refer to specific forecast weather types (e.g. TS, +RA, FG, etc.)

Sub areas

On occasions there will be a need to include sub areas within a larger area of weather. A sub area to an area C would, for example, be named area C1.

A sub area will include single element changes from the main area. Changes will be detailed either within brackets or as a separate line of text. Minor changes of one element of either weather or the extent, coverage or period of the change may be shown in brackets. More-general changes will be included as a separate line of text. Some examples are provided below.

Cloud

Cloud amount is: FEW, SCT, BKN or OVC, followed by the cloud type (e.g. ST, CU, CB, SC, AC). An additional two symbols may then appear to indicate whether MOD/SEV ICE or TURB is expected in this cloud. A key to the symbols is included in the lower left corner of the chart.

Cloud heights then appear in hundreds of feet in the form 020/050 (in this case the cloud base is 2,000 ft and the top 5,000 ft AMSL). If a cloud top is expected to extend above 10,000 ft then XXX will appear. For example, BKN/OVC STSC 008/060 indicates 5-8 oktas of stratus and stratocumulus base 800 ft top 6,000 ft AMSL with moderate turbulence and moderate icing expected within.

Key

MOD ICE		Moderate icing
SEV ICE		Severe icing
MOD TURB		Moderate turbulence
SEV TURB		Severe turbulence

Mountain wave

Wherever necessary, mountain wave forecasts will appear in the 'visibility and weather' box as MTW followed by a vertical speed VSP and height(s) above mean sea level, e.g. 'MTW MAX VSP 700 FPM AT 080'. Mountain wave maximum vertical speed 700 ft per minute at 8,000 ft with moderate/severe turbulence expected.

Definitions

The definitions used in the F215 relating to the extent of weather are adopted in the UK by the Aviation Met. Authority in the CAA, and used by the Met Office. These are:

WIDESPREAD
Implies conditions affecting many places, which will be difficult to avoid (greater than 50% of area affected) (used for non-convective and convective types).

FREQUENT
Used if within a particular area there is little separation between phenomena, and the spatial coverage is greater than 50% of the area forecast to be affected by that phenomenon (used for convective types only). These features will be difficult to avoid.

OCCASIONAL
Used if an area consists of well separated features which are forecast to affect an area with a maximum spatial coverage of between 25% and 50% of the area concerned. These features can be avoided by users.

ISOLATED
Used if an area consists of individual features which are forecast to affect an area with a maximum spatial coverage of between less than 25% of the area concerned. these features can be easily avoided.

Abbreviations used in aviation forecasts and warnings

Issue/validity times

Chart times cover a nine-hour period. The table below summarises the times for the charts.

Issue/validity times

Chart	Issue time	Valid for flights between	Validity time *	Outlook to	Prognosis
UK low-level sig weather (F215)	0330	0800 and 1700	1200	0000	1800
	0930	1400 and 2300	1800	0600	0000
	1530	2000 and 0500	0000	1200	0600
	2130	0200 and 1100	0600	1800	1200
European low-level sig weather (F415)	0330	0800 and 1700	1200	n/a	n/a
	0930	1400 and 2300	1800	n/a	n/a
	1530	2000 and 0500	0000	n/a	n/a
	2130	0100 and 1100	0600	n/a	n/a

* Validity time is the time at which the position of the fronts and areas of weather are valid.

All times are in UTC (denoted by 'Z' or 'Zulu' on the new briefing charts).

Prognosis

The prognosis chart (forecast for six hours on) is shown below the main F215 chart on the Met Office website. This prognosis chart shows only the expected positions of the principal synoptic features and mean sea-level isobars at the end of the period. Weather zones are not given on the prognosis chart.

UK and European spot winds charts (F214 and F414)

Chart	Issue time	Valid for flights between	Validity time*	Outlook to
UK spot winds (F214)	0000	0300 and 0900	0600	n/a
	0600	0900 and 1500	1200	n/a
	1200	1500 and 2100	1800	n/a
	1800	2100 and 0300	0000	n/a
European spot winds (F414)	0000	0300 and 0900	0600	n/a
	0600	0900 and 1500	1200	n/a
	1200	1500 and 2100	1800	n/a
	1800	2100 and 0300	0000	n/a

Amendment of charts

Only the current chart will be amended, therefore a chart will be subject to amendment as soon as it has been issued.

Example for F215 and F415

If we consider three chart issues of F215/F415, the 0200-1100 chart issued at 2100, the 0800-1700 chart issued at 0300 and the 1400-2300 issued at 0900. If the actual weather were to change from the forecast weather at say, 1000 with un-forecast thunderstorms which are now forecast to last all day, the 0800-1700 chart would be amended instantly since this is the current chart. The previous chart valid 0200-1100 would not be amended since it is no longer current (even though its period is unfinished). If forecasters believe that the thunderstorms will also affect the period 1400-2300, then this chart would also be amended.

Users are advised to use the latest chart wherever possible since this should include the most up-to-date information and amendments as necessary.

Amendment criteria

1. Surface visibility

	Original forecast	Revised opinion
Visibility (general visibility)	8 km or more	< 8 km
	5,000 m to 8 km	< 5,000 m or > 8 km
	3,700 m to 5,000 m	< 3,700 m or > 5,000 m
	2,500 m to 3,700 m	< 2,500 m or > 3,700 m
	1,600 m to 2,500 m	< 1,600 m or > 2,500 m
	800 m to 1,600 m	< 800 m or > 1,600 m
	0 m to 800 m	> 800 m

2. Weather phenomena

TS, SQ, GR,SA, RASN, SN, FZFG, FZRA, FZDZ

Original forecast	Revised opinion
Not included	Now expected
Included	Not now expected

3. Cloud amount

Original forecast	Revised opinion
All forecasts of cloud amount	Changes in the general forecast lowest cloud base below 1,500 feet from 4 oktas or less to more than 4 oktas, or more than 4 oktas to 4 oktas or less

4. Cloud height

	Original forecast	Revised opinion
General cloud base, AMSL (amounts of SCT or more)	2,500 ft or more	< 2,500 ft
	1,500 ft to 2,500 ft	< 1,500 ft or > 2,500 ft
	700 ft to 1,500 ft	< 700 ft or > 1500 ft
	500 ft to 700 ft	< 500 ft or > 700 ft
	300 ft to 500 ft	< 300 ft or > 500 ft
	200 ft to 300 ft	< 200 ft or > 300 ft
	SFC. to 200 ft	> 200 ft

5. Turbulence

Original forecast	Revised opinion
Nil	Moderate or severe
Light	Severe
Moderate	Nil
Severe	Nil or slight

6. Zero degree Celsius isotherm

Original forecast	Revised opinion
Below 5,000 ft	Changes of 1,000 ft or more
Above 5,000 ft	Changes or +25% or 2,000 ft, whichever is smaller

7. Airframe icing

Original forecast	Revised opinion
Nil	Moderate or severe
Light	Severe
Moderate	Nil
Severe	Nil or light

8. Area boundaries, significant fronts

Original forecast	Revised opinion
Not included	Now expected
Included	Not now expected or 60 n mile different from forecast