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The February 2024 VLab Forum will occur this Wednesday, the 28th,
at 3:00 PM – 4:00 PM (Eastern Time). The talk features a
presentation by Austin Coleman titled "Making the Most out of
Operational Ensembles with Clustering and Sensitivity
Analysis". We hope you can attend.
To participate in the forum, please register
for the webinar.
Abstract:
Ensemble clustering is an efficient ensemble post-processing
approach that distills an ensemble forecast into its prevalent
forecast scenarios by grouping similar ensemble members together.
This clustering approach has progressed quickly through the R2O
pipeline since its original implementation as a NOAA-CSTAR
collaboration for forecasting nor’easters. Initially adopted more
operationally CONUS-wide (and over Alaska) at the Weather Prediction
Center (WPC), the clustering product went from 38 NWS Area Forecast
Discussion (AFD) mentions in 2019 to over 3,600 AFD mentions in
2021. It has since been implemented as a centerpiece for the
experimental ensemble visualization platform known as the Dynamic
Ensemble-based Scenarios for IDSS (DESI), where forecaster feedback
suggests much potential utility of DESI clusters as a scientific
forecasting tool as well as a helpful messaging tool for
contextualizing forecast uncertainty when communicating with various stakeholders.
This clustering approach uses Empirical Orthogonal Function (EOF)
analysis to identify the leading modes of uncertainty in forecast
500-hPa geopotential heights across the ensemble membership. The
Principal Components (PCs) associated with these EOFs can be used to
determine which forecast scenario each member represents relative to
the ensemble mean. From there, the leading two PCs are used as
inputs into a K-means clustering algorithm that groups together
members with similar forecast scenarios. This methodology results in
a much more useful ensemble visualization approach given that the
best cluster forecast tends to verify better than the best ensemble
mean forecast or best deterministic forecast (Lamberson et al. 2023).
While clustering allows a forecaster to effectively characterize
and communicate forecast uncertainty, it does not provide any
information about the initial sources of that forecast uncertainty.
In direct response to forecaster requests for this extra context, we
are also developing an ensemble sensitivity analysis (ESA) approach
as a complement to the clusters to diagnose how the atmosphere must
evolve early in the forecast to result in each different scenario.
This talk will go over the ensemble clustering and ESA approaches,
its current utility in an operational context, and future research
directions for these techniques.
Agenda:
You can find the agenda for the Forum at the following link:
Slides:
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