Transcript What’s New at NCEP? An overview of the HPC Winter Weather

What’s New at NCEP? An Update on the
HPC Winter Weather Desk and Recent
Changes to the NCEP Model Suite
Michael J. Brennan
Science and Operations Officer
Hydrometeorological Prediction Center
9th Northeast Regional Operational Workshop
8 November 2007
Outline
• HPC Winter Weather Desk
– 2006–2007 Verification
– What’s new for 2007–2008
• NCEP Model Upgrades
– SREF
– NAEFS
– Hi-Res Window
• New Uncertainty Guidance
HPC Winter Weather Desk
Overview
•
Internal deterministic
24-h snow/sleet and freezing
rain accumulation graphics for
days 1–3
– PRISM-adjusted for
Intermountain West
•
Public products of 24-h
exceedance probabilities for:
– Snow/Sleet: 4,8,12 in.
– Freezing Rain: 0.25 in.
– Probabilities computed from
deterministic forecast and
model spread
•
Track forecasts for sfc. lows
associated w/ significant
winter weather
•
Heavy Snow and Ice
Discussion (QPFHSD)
HPC Winter Weather Desk
2006–2007 Verification – Snow/Sleet
HPC adjustments show largest
improvement over model
guidance for snow > 12”
D1
D2
D3
HPC Winter Weather Desk
2006–2007 Verification – Freezing Rain
HPC Adjustments show most
improvement for FZRA amounts
<0.10”
Day 3
D1
Day 2
D2
D3
HPC Winter Weather Desk
2006–2007 Verification
Snow-Liquid Ratio
15 Oct 2006 – 1 May 2007 GFS
Root Mean Square Errors
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
•Roebber method had
lowest RMSE for
computation with GFS
model
•10:1 ratio second lowest
RMSE at all lead times
Climatology
QPF*13
Caribou
Roebber
QPF*10
36
60
84
Forecast Hour (from 00Z or 12Z)
HPC Winter Weather Desk
2006–2007 Verification
Low Tracks (Associated with “significant winter
weather” only)
•HPC low track
forecast RMSE
ranges from 85
nm at F12 to 140
nm at F72
•HPC shows most
improvement over
GFS and NAM
after 36 h
•Best guidance at
most times is
GFS/NAM blend
•SREF Mean also
performs well
(best at F12 and
F72)
HPC Winter Weather Desk
New for 2007–2008
• Grid spacing of nonPRISM-adjusted
snow/ice grids decreased
from 40 km to 20 km
• QPF from Canadian
model now available in
winter weather
precipitation blender
• Addition of ECMWF
pending receipt of 6-h
QPF
• CoCoRAHS snow data
will be used in verification
HPC Winter Weather Desk
New for 2007–2008
• Based on 2006-2007 verification, HPC Snow-Liquid Ratio will be equal
blend of:
–
–
–
–
10:1 ratio
Roebber method computed from NAM
Roebber method computed from GFS
Climatological SLR
• Computed every 6-h through forecast period
• Maps on internal WWD webpage show resultant 6-h SLR values
NCEP Model Suite Changes
Hi-Res Window (HRW) Upgrade
•
•
Code upgraded to official public
version of WRF distributed by NCAR
WRF-NMM:
– Decreased horizontal grid spacing
from 5.2 km to 4.0 km
– Added local NCEP changes made to
NAM
•
WRF-ARW:
– Decrease horizontal grid spacing
from 5.8 km to 5.1 km
•
•
No CP scheme used
Generate new post-processed fields:
– Simulated GOES satellite fields
– Improved simulated radar reflectivity
•
•
Available through TOC and ftpprd
Limited fields available on NCEP
models website
12 km
Black dots
represent water
points in model
(Chesapeake Bay)
4 km
HRW “Large” Domains
Large Domain Schedule:
Alaska
East-Central CONUS
00/12Z: East-Central
CONUS
06Z: West-Central CONUS
18Z: Alaska
•1 hurricane run cancels
ARW runs on large and
small domains
•2 or 3 hurricane runs
cancel both ARW runs and
NMM run on large domain
•4 hurricane runs cancel all
runs
•Small domains:
West-Central CONUS
•Hawaii (00/12Z)
•Puerto Rico (06/18Z)
Short Range Ensemble
Forecast System (SREF) Upgrade
•
21 members
– 10 Eta
– 6 WRF
– 5 RSM
•
Bias corrected output for all
parameters except QPF
– Same BC methodology used for
GEFS/NAEFS
– Decay function weights last
50-60 days most heavily
•
4 new aviation forecast
parameters
–
–
–
–
•
•
•
SREF Mean BC 500-mb hght (magenta)
SREF Mean 500-mb hght (red)
Icing
Clear Air Turbulence
Low-Level Ceiling
Flight Restriction
Parallel evaluation: 2 Oct.
Implementation: 11 Dec.
Bias-corrected SREF output will
eventually replace current output
in AWIPS
Magnitude of bias correction for 87-h
500-mb height forecast
Short Range Ensemble
Forecast System (SREF) Upgrade
• Next SREF upgrade – tentatively scheduled for the 3rd
quarter of FY08
– Upgrade the WRF members to the latest version
– Increase the resolution of all members to as close as 32 km as
possible given computational resources
– Eta members already running at 32 km
SREF Probability of 24-h
QPF > 2” with TS Noel
Experimental HPC/SPC SREF-based
Winter Weather Impact Graphics
Real Time Mesoscale Analysis (RTMA)
• 5 km NDFD resolution hourly
analysis of T, Td, wind, sfc. pres.
• First Guess: downscaled RUC
(NAM) as first guess for CONUS
(AK, Hi, PR)
• Uses ‘all’ sfc obs within +/- 12 min
of analysis time
• Data assimilated with 2-D version
of NCEP’s Gridpoint Statistical
Interpolation (GSI) analysis
scheme
• Available on NDFD page
http://www.weather.gov/forecasts/
graphical/sectors/
• Used for NAEFS downscaling
2-m T
10-m WND
North American Ensemble Forecast
System (NAEFS) Upgrade
• Combined NCEP and CMC
ensemble system
– 40 members, available twice daily
(for now)
• Bias corrected output using
same methodology as SREF
• Output includes
– Ensemble Mean, Spread, Mode
– 10th, 50th (median), and 90th
percentile probabilities
– Anomalies compared to
NCEP/NCAR reanalysis
• Downscaled output to 5-km
NDFD grid using RTMA
– 2-m T, 10-m wnd, sfc. pres.
• Parallel evaluation: 25 Oct.
• Operational implementation:
4 Dec.
NAEFS Ensemble Mean MSLP and Spread
90-h forecast of Noel from 00 UTC 31 Oct
NAEFS
Downscaling
NAEFS Ensemble
NAEFS Ensemble
Mean Bias
Mean
Corrected
Bias Corrected
& Downscaled
2-m Temperature
2-m Temperature
(F) (1°)(F) (5km)
NAEFS
Uncertainty Information
Mean
90th percentile
10th percentile
Median (50th percentile)
HPC Alaska Desk
• Working with EMC to provide additional
uncertainty information medium range
guidance for Alaska WFOs
10
Mode
90
– HPC deterministic forecast  mode
– 10th and 90th percentile probabilities
computed from downscaled NAEFS and
adjusted with HPC forecast for Min/Max T &
wind speed
• Remaining issues
– How to downscale for max/min T occurring at widely varying
times?
– Quality of RTMA over Alaska (for downscaling and verification)
– Potentially very large spreads for temperature, wind speed – is
10/90 best range?
– Desk will begin issuing experimental products in December
– Opportunity to try new things – if successful may be transitioned to
CONUS medium range
Looking Ahead...
NOAA Center for Weather and Climate
Prediction (NCWCP)
College Park, Maryland
268,762 ft2 building will be new home for NCEP,
NOAA’s Satellite and Information Service, and
Air Resources Laboratory
Scheduled to be complete early 2009
Construction Progress as of
23 October
Questions/Comments?
[email protected]