World Meteorological Organization Symposium on Nowcasting - WMO

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and flexibility expanded during its life cycle.With the procurement of the next generation high
performance computing system the convective scale capability is expanded to provide
coverage of the whole UK with forecast lengths of at least 24 hrs. 4 times per day. This
configuration is to be implemented in June 2009 and eventually will replace the current high
resolution, 4 Km gridlength, operational and the 1.5 Km On-demand models. The new system
will be nested in the regional, 12 Km gridlength, NAE model using a stretched grid from 4 Km
to 1.5 Km to avoid numerical problems arising from a high nesting ratio and to keep the
transition area, where the convective showers spin up from parametrised convection at the
boundaries to resolved convection, away from the region of interest at an affordable
computational cost. Initial conditions will be provided by a continuous Data Assimilation 3D-
VAR system with either three hours or hourly update cycle.This presentation covers the
description of both systems, results during pre-operational tests and production, and plans for
future development.
3.9
Overview of the Rapid Update Cycle and Rapid Refresh
Stephen S. Weygandt [1], T. G. Smirnova [1,2], M. Hu [1,2], J. M. Brown [1], D. Devenyi [1,2],
S. G. Benjamin [1], W. R. Moninger [1], S. E. Peckham [1,2], G. A. Grell [1,2], K. J. Brundage
[1,3], B. D. Jamison [1,4], C. W. Harrrop [1,2], J. B. Olson [1,5]
[1] NOAA Earth System Research Lab/Global Systems Division [2] Cooperative Institute for
Research in the Environmental Sciences [3] Cooperative Institute for Research in the
Atmosphere [4] System Research Group [5] National Research Council
The Rapid Update Cycle has served as the "situational awareness" and very short-range
numerical weather prediction forecast model at the USA National Oceanic and Atmospheric
Administration's National Centers for Environmental Prediction since 1994. Forecasts of 9- or
12h duration are initialized every hour from a 1-h assimilation cycle using a 3dVAR analysis
using the previous 1-h forecast as the background. The domain covers the 48 contiguous
states of the USA (excluding Alaska and Hawaii). The 3dVAR analysis is tailored to use of insitu
observations from aircraft and from surface station networks, but also includes a variety
of frequently-available remotely sensed observations such as profilers, weather radars and
GPS zenith wet delay. Because of its rapid updating and its emphasis on careful and
thorough use of asynoptic data, the RUC has become the primary source of weather
guidance for aviation operations, and is also used extensively by forecasters in the USA
responsible for prediction of short-fused, high-impact weather events. A unique feature of the
hourly assimilation cycle is a hydrometeor assimilation based on satellite and radar, followed
by diabatic initialization of the model initial state through use of a digital filter to provide a
measure of dynamical balance between the diabatic heating field and the divergent
component of the horizontal wind. This procedure, to be described in a separate talk by
Benjamin et al., greatly improves the prediction of precipitating systems during the first few
hours of the forecast and greatly mitigating the non-physical adjustment process often seen
during the first few hours of NWP forecasts. The Rapid Update Cycle is due to be replaced in
NCEP operations by a new system, but with similar functionality as the RUC, in 2010. This
new system is called the Rapid Refresh. It will operate on a much larger domain, covering
nearly all of North America including Alaska. Further, the present RUC 3dVAR analysis will
channels, ~82 separate indicators that assess cumulus clouds can be formed, 67 derived
from the eight infrared channels. Although past research describes how some of the channel,
channel differences, and time-trends of channel differences may be used to monitor aspects
of growing convective clouds, this work adds to our understanding as various new uses of
MSG data are found. Through correlation and principal component analysis, between 15 and
21 infrared interest fields are shown to contain unique information for nowcasting CI at 3 km
scales. Data from the 2007 Convective Orographically Induced Precipitation Study (COPS)
experiment will be exploited for this effort, with 122 selected CI events analyzed.Other
aspects of this talk will focus on how SATCAST CI nowcasts are used within real-time
systems that forecast aircraft routing, and arrivals and departures at major U.S. airports.
Through research involving the Corridor Integrated Weather Systems (CIWS) we are
fortunate to be able to test these improvements within a methodology to nowcast CI. Work
already completed shows that GOES information from moving convection has value above
that previously used within this system. This presentation will report on our progress and
most recent findings. Other transition activities in the NOAA Algorithm Working Group, within
Central America, and for EUMETSAT, will be discussed.
8.8
Implementation of the EUMETSAT RDT Algorithm for New York City
Brian Vant-Hull [1], Shayesteh Mahani [1], Arnold Gruber [1], Reza Khanibilvardi [1], Robert
Rabin [2], Robert Kuligowski [3], Mamoudou Ba [4], Stephen Smith [4]
[1] NOAA-CREST, City College of New York, [2] National Severe Storm Laboratory, USA, [3]
NOAA-NESDIS, Hydrology, USA, [4] <strong>Meteorological</strong> Development Laboratory, NWS, USA
The EUMETSAT Rapidly Developing Thunderstorm (RDT) algorithm detects and tracks
thunderstorms. Storm shape and life history is used to identify storms using a single IR
window channel. In cooperation with the Meteo-France developers of the algorithm, NOAA-
CREST at the City College of New York has modified RDT to work with GOES data and has
implemented it using a direct satellite receiver station.Validation is done via the Vaisala
National Lightning Detection Network. Tests show that the False Alarm Ratio (FAR) is
generally below 10%, but the Probability of Detection (POD) ranges from 40% for warm cloud
tops to nearly 100% for cold cloud tops. The horizontal extent of the storm has a much
smaller effect on POD and FAR. Increasing the image frequency allows detection of smaller
cells.A comparison of RDT to the SatCast algorithm is underway. While RDT uses a single
IR channel to detect cloud tower structures and growth, SatCast uses multiple channel
thresholds to detect the presence of cold or cooling cloud pixels relative to the water vapor
layer. This particular comparison is of interest because the FAA has requested
implementation of the SatCast algorithm in the New York area. The main concern is
detection of convective cells before radar would indicate precipitation. Lightning data will be
used as validation, using RDTs capability to backdate a trajectorys status depending on later
indications of convection. Preliminary results of this cross validation study will be presented.
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