METWSG/1-SN No. 8
22/10/07
METEOROLOGICAL WARNINGS STUDY GROUP (METWSG)
FIRST MEETING
Montréal, 20 to 22 November 2007
Agenda Item 7: Amendments to provisions related to wind shear warnings and alerts
7.3: Consider the need to provide information on low-level temperature inversion
either in a specific warning or in the supplementary information appended to
local reports and METAR/SPECI
NEED FOR THE PROVISION OF INFORMATION ON LOW-LEVEL TEMPERATURE
INVERSION
(Presented by the Secretary)
SUMMARY
This study note discusses the need to provide information on low-level temperature
inversion.
1.
INTRODUCTION
1.1
The group may wish to note that this task was originated by the European Air Navigation
Planning Group (EANPG), through Conclusion 47/32, calling for ICAO to consider amending Annex 3
— Meteorological Service for International Air Navigation to include the low level temperature inversion
information as a meteorological related safety hazard at aerodromes. This conclusion was subsequently
endorsed by the Air Navigation Commission (ANC) at its 172nd Session.
1.2
The group may also wish to note that when discussing this issue, the EANPG agreed that
low-level temperature inversion had a detrimental effect on aircraft performance during take-off and
landing and suggested that there could be two possibilities for reporting such phenomena: as a specific
warning (similar to wind shear); or as supplementary information appended to local reports and
METAR/SPECI.
1.3
In this regard, the group may wish to note that this issue has been regularly addressed
over the years by the ANC. In 1986 during the review of the replies received to a letter to selected States
and international organizations on the possibility of using data extracted from flight data recorder to
determine the frequency, occurrence and magnitude of deviations from the standard temperature lapse
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rate, the International Air Transport Association (IATA) called for the encouragement of better reporting
of marked temperature inversion. However, the ANC felt that there was not enough information to
propose provisions for inclusion in Annex 3. Furthermore, it was noted that there was still confusion
between inversions and deviations from the standard lapse rate. The group may wish to note that at that
time the ANC agreed that provisions in Annex 3 were not required and that guidance material on the
provision of information on significant deviations from the standard temperature lapse rate should be
included in the Manual of Aeronautical Meteorological Practice (Doc 8896).
1.4
Subsequently, in 1994 the issue was readdressed during the preliminary review of an
amendment proposal to Annex 3 regarding the provision of information on weather phenomena hazardous
to low-level flights. In this regard, in reply to a query from the International Federation of Air Line Pilots’
Associations (IFALPA), the ANC felt that there was no need including temperature inversions in
AIRMET/GAMET, since they were mostly a problem in terminal areas and that guidance material had
been included in Doc 8896.
1.5
Regarding the guidance issued, the group may wish to note that the Manual of
Aeronautical Meteorological Practice (Doc 8896) contains some guidance related to temperature
inversion. In particular, it relates temperature inversions to wind shear for which a requirement to issue
warnings already exists. Furthermore, an appendix entitled “An operational wind shear and inversion
warning system for Helsinki-Vantaa Airport” (Appendix 13 refers) which provides extensive guidance
providing an example on how to deal with this phenomenon. It should be noted that for temperature
inversions, there is an alarm limit; when the limit value is exceeded a warning message is issued and
reported in the automatic terminal information service (ATIS) broadcast. The warning message is also
shown on the airport terminal data network.
1.6
The group may wish to concur that the situation has not changed and that temperature
inversions need not to be subject to a stand-alone warning provided that warnings related to the
accompanying wind shear are issued. Furthermore, the group is invited to agree that specific, local
warning systems such as the one described in Doc 8896 is satisfactory to cover operational requirements
and that there is no need to draft SARPs at this stage. Therefore, the group may wish to agree to the
following action:
Action agreed 1/..
Provision of information on low-level
temperature inversion either in a
specific
warning
or
in
the
supplementary information appended
to local reports and METAR/SPECI
That the sub-task be deleted from the work program of the study
group.
2.
2.1
ACTION BY THE METWSG
The METWSG is invited to:
a) note the information in this paper; and
b) decide on the draft action proposed for the group’s consideration.
— END —