Use Case: multi-model ensemble forecasting to reduce or mitigate impacts of potential landfalling hurricane

(Loosely based on the TIGGE project of WMO THORPEX [http://www.wmo.int/pages/prog/arep/wwrp/new/thorpex_new.html] - THORPEX aims to improve the accuracy of 1-day to 2-week high-impact weather forecasts for benefit of society, the economy and the environment)

12 numerical weather prediction centers around the world are collaborating to improve the prediction of high-impact weather events at up to a 14-day horizon by creating a global ensemble with 14-day duration. Routine (& operational) forecasts from the contributing centers are collected in near real-time. The data is shared under a license for non-commercial exploitation.

Each of the forecasts from the contributing centers may be provided on their original (native) horizontal & vertical resolution.

Parameters are collected at 6-hour intervals (up to 14 days) ...

Surface parameters:
-- mean sea-level pressure
-- surface pressure
-- 10 m winds (U + V components)
-- 2 m temperature
-- 2 m dew point
-- 2 m max temperature (over 6-hour interval)
-- 2 m min temperature (over 6-hour interval)
-- total precipitation (liquid + frozen) (over 6-hour interval)
-- snow fall (over 6-hour interval)
-- snow depth
-- total cloud cover
-- total column water
-- surface latent heat flux
-- surface sensible heat flux
-- surface solar radiation
-- surface thermal radiation
-- sunshine duration (over 6-hour interval)
-- convective available potential energy
-- orography
-- land-sea mask

Upper-air parameters (@ 1000 hPa, 925 hPa, 850 hPa, 700 hPa, 600 hPa, 500 hPa, 300 hPa, 250 hPa and 200 hPa):
-- temperature
-- geopotential
-- wind speed (U + V components)
-- specific humidity

The 'data collection and processing centre' DCPC that collects the ensemble contributions undertakes combination, comparison & statistical analyses of the global multi-model ensemble. Bias correction due to systematic errors are applied using statistical correction derived from verification (comparison of forecast against observations).

As a response to day-to-day changes in uncertainty predicted by the global multi-model ensemble, extra observations could be targeted on sensitive areas with a potential high-impact on society, the economy or the environment. Alternatively, targeted mesoscale models (or limited area models - LAMs) can be initialized to better resolve the predicted weather within the identify region.

In this particular scenario a tropical storm has been identified that appears to have potential to cause significant human, economic & environmental impact.

An assessment of the available sensor platforms indicated that there are no re-deployable observation assets available. However, a re-locatable high-resolution ensemble 'crisis-area model' (CAM) is configured for the area covering the anticipated severe weather event. The operational schedule is set for the CAM to execute four-times daily.

Over the next few days the tropical storm continues to be monitored. The forecast indicates that it will develop in to a hurricane with significant chance of landfall. Close communications are maintained with governmental and legally mandated organizations (LMO) with responsibility for public safety. International relief organizations are also advised of the situation.

Once the probability of the hurricane landfall in a specific location reaches the appropriate threshold [[can this be defined?]] clear warning advisories are sent the government and LMOs in the impacted region, who decide to take action and mobilize their emergency response plans.

Whilst significant loss of life is avoided, the weather event leaves tens of thousands, perhaps even hundreds of thousands, of people homeless without food, power of clean water. Tremendous damage has occurred to the physical infrastructure within the region, leaving large proportions of the region inaccessible.

A relief operation is rapidly organized.

Whilst much diminished, the legacy of the weather system that brought the hurricane continues to disrupt the relief effort which requires aerial transport to reach many of the impacts regions. The CAM continues to be executed four-times daily, now supplemented with additional observations from the many temporary airstrips throughout the region that are being used by the relief effort.

Forecasters provide standard aviation operational meteorology services (OPMET) including TAF, METAR and low-level aviation charts to support the air operations.

Additionally, forecasters provide high-resolution data products and mission-oriented commentary to the relief planners who are able to use this information when overlain with high-resolution satellite imagery, asset locations and geo-located damage reports (etc.) to plan their activities with reduced sensitivity to the remaining adverse weather. To provide this service, the forecasters employ decision-support algorithms within their forecaster workstations that provide 'first-guess' indications of areas where local conditions meet requirements for air-drop missions, including probablistic assessment of risk. The forecasters are then able to modify the 'first-guess' fields at their discretion, finally publishing simple geo- and time-located polygons with associated commentary that can be ingested into simple visualization systems like Google Earth. These polygonal weather advisory features are often referred to as 'sensible weather objects' as they convert complex physical weather phenomena into a simple product with relevance to the consumer.