Aviation API

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25 Rain and Cloud Charts

Rain and Cloud forecast charts are produced from global weather model data produced by each of three global model issuing centres:

ecmwf - European Centre for Medium-Range Weather Forecasts,
ncep - National Centers for Environmental Prediction or
ukmo - United Kingdom Met Office.

The charts forecast out 84 hours from the analysis time (hour 0) of the model run and so there are 85 in total. If charts for a given analysis time are in the process of being generated then you may not receive a full list of 85 charts.

Rain Forecast charts

These charts graphically display the areas where rain is expected and the amount of rain forecast to fall around NZ at surface level. They also display wind speed and direction via wind barbs.

Cloud Forecast charts

These charts graphically display the approximate height of cloud (low or mid level) and the extent of the cloud (represented in oktas) around NZ. They also display wind speed and directions via wind barbs.

Extent of Cloud

0 octas - NIL

1-2 octas - FEW

3-4 octas - SCT

5-7 octas - BKN

8 octas – OVC

Height of Cloud

Low cloud – covers the range SFC-6,5000ft

Mid cloud – covers the range 6,500-18,000ft

Which model data to use

Each day MetService forecasters select a ‘model of the day’, which is the model that best represents the current weather situation. Therefore, when using these charts, the selected model of the days' data should be requested. The model of the day can be determined by calling the following API endpoint:

GET api.metservice.com/products/forecast/type/modeloftheday

The output will be similar to the following:

{
  "nzModelSelection" : {
    "coverage" : "Specifically for NZ conditions covering the next 3 days.",
    "model" : "UKMO"
  }
}

For the NCEP centre the above call will return GFS. 'ncep' must be used in the calls outlined below.

25.1 Latest Rain charts for a Region and Model

Request the latest rain forecast analysis charts for the specified region produced from the specified global model. At this time the only region accepted is nz (New Zealand).

25.1.1 API Call:

GET /aviation/chart/rain/{region}/{model}/latest

25.1.2 Path Parameters:

Path Parameter	Example	Description
region	nz	A supported region code. The only supported region current is 'nz'. This parameter is Mandatory.
model	ncep	A supported identifier for the selected model. Valid values: 'ecmwf' - European Centre for Medium-Range Weather Forecasts, 'ncep' - National Centers for Environmental Prediction or 'ukmo' - United Kingdom Met Office. The model code must be lowercase. This parameter is Mandatory.

25.1.3 Example:

This example would return the latest rain charts for the NZ region produced from 'ncep' global model data.

GET /aviation/chart/rain/nz/ncep/latest

25.1.4 API Response:

{
    "version": "1.0",
    "issue-time": "2025-08-31T20:15:27Z",
    "path": "/aviation/api/aviation/chart/rain/nz/ncep/latest",
    "response": [
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/rain/nz/NCEP/nz8kmN-NCEP_25083112_rain1_000.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "met:domain": "aviation",
            "met:model-name": "NCEP",
            "av:chart-type": "rain",
            "met:prognosis-period": "000",
            "met:valid-at": "2025-08-31T12:00:00Z",
            "met:region": "nz"
        },
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/rain/nz/NCEP/nz8kmN-NCEP_25083112_rain1_001.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "met:domain": "aviation",
            "met:model-name": "NCEP",
            "av:chart-type": "rain",
            "met:prognosis-period": "001",
            "met:valid-at": "2025-08-31T13:00:00Z",
            "met:region": "nz"
        },

        .....example response truncated for illustration purposes

        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/rain/nz/NCEP/nz8kmN-NCEP_25083112_rain1_083.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "met:domain": "aviation",
            "met:model-name": "NCEP",
            "av:chart-type": "rain",
            "met:prognosis-period": "083",
            "met:valid-at": "2025-09-03T23:00:00Z",
            "met:region": "nz"
        },
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/rain/nz/NCEP/nz8kmN-NCEP_25083112_rain1_084.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "met:domain": "aviation",
            "met:model-name": "NCEP",
            "av:chart-type": "rain",
            "met:prognosis-period": "084",
            "met:valid-at": "2025-09-04T00:00:00Z",
            "met:region": "nz"
        }
    ]
}

25.2 Latest Cloud charts for a Level, Region and Model

Request the latest cloud forecast analysis charts for the specified level and region produced from the specified global model. At this time the only region accepted is nz (New Zealand).

12.2.1 API Call:

GET /aviation/chart/cloud/{level}/{region}/{model}/latest

12.2.2 Path Parameters:

Path Parameter	Example	Description
level	mid	A supported identifier for the selected altitude, either ‘low’ or ‘mid’. This parameter is Mandatory.
region	nz	A supported region code. The region code must be lowercase. The only supported region current is 'nz'. This parameter is Mandatory.
model	ecmwf	A supported identifier for the selected model. Valid values: 'ecmwf' - European Centre for Medium-Range Weather Forecasts, 'ncep' - National Centers for Environmental Prediction or 'ukmo' - United Kingdom Met Office. The model code must be lowercase. This parameter is Mandatory.

12.2.3 Example:

This example would return the latest low level cloud charts for the NZ region produced from 'ecmwf' global model data.

GET /aviation/chart/cloud/low/nz/ecmwf/latest

12.2.4 API Response:

{
    "version": "1.0",
    "issue-time": "2025-08-31T20:24:48Z",
    "path": "/aviation/api/aviation/chart/cloud/low/nz/ecmwf/latest",
    "response": [
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/cloud/low/nz/ECMWF/nz8kmN-ECMWF_25083112_lcld_000.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "av:chart-level": "low",
            "met:domain": "aviation",
            "met:model-name": "ECMWF",
            "av:chart-type": "cloud",
            "met:prognosis-period": "000",
            "met:valid-at": "2025-08-31T12:00:00Z",
            "met:region": "nz"
        },
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/cloud/low/nz/ECMWF/nz8kmN-ECMWF_25083112_lcld_001.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "av:chart-level": "low",
            "met:domain": "aviation",
            "met:model-name": "ECMWF",
            "av:chart-type": "cloud",
            "met:prognosis-period": "001",
            "met:valid-at": "2025-08-31T13:00:00Z",
            "met:region": "nz"
        },

        .....example response truncated for illustration purposes

        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/cloud/low/nz/ECMWF/nz8kmN-ECMWF_25083112_lcld_083.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "av:chart-level": "low",
            "met:domain": "aviation",
            "met:model-name": "ECMWF",
            "av:chart-type": "cloud",
            "met:prognosis-period": "083",
            "met:valid-at": "2025-09-03T23:00:00Z",
            "met:region": "nz"
        },
        {
            "met:data-resolution": "8km",
            "met:locator": "https://api.metservice.com/aviation/assets/chart/20250831/12/cloud/low/nz/ECMWF/nz8kmN-ECMWF_25083112_lcld_084.gif",
            "met:analysis-time": "2025-08-31T12:00:00Z",
            "met:product-name": "chart",
            "av:chart-level": "low",
            "met:domain": "aviation",
            "met:model-name": "ECMWF",
            "av:chart-type": "cloud",
            "met:prognosis-period": "084",
            "met:valid-at": "2025-09-04T00:00:00Z",
            "met:region": "nz"
        }
    ]
}