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High-Resolution Gridded MOS (HRMOS) QPF Guidance: Part I – Description of Products. Jess Charba Fred Samplatsky Meteorological Development Laboratory OST / NWS / NOAA. Motivation for HRMOS QPF Model.

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high resolution gridded mos hrmos qpf guidance part i description of products

High-Resolution Gridded MOS (HRMOS) QPF Guidance: Part I – Description of Products

Jess Charba

Fred Samplatsky

Meteorological Development Laboratory

OST / NWS / NOAA

motivation for hrmos qpf model
Motivation for HRMOS QPF Model

Predictive skill of model- and human-produced QPFs lags skill of other atmospheric variables and weather elements

Recent availability of fine grid radar-based precipitation data offers potential for improved MOS-based gridded QPF guidance

Improved guidance should exhibit improved spatial and intensity resolution

hrmos qpf model basics
HRMOS QPF Model Basics

Produces GFS-based MOS QPF guidance on a 2.5-km grid (4 km presently) for CONUS

New QPF products contain better spatial and intensity resolution than other numerical and statistical model QPF guidance

New QPF products exhibit equal or higher skill than comparable products

HRMOS model issues conventional and new QPF products

hrmos qpf products
HRMOS QPF Products

6- & 12-h QPFs to 192 hours on 2.5 km grid over CONUS

Produced (experimentally) twice per day by 0530 and 1730 Z

QPF products

- Probabilities for precip thresholds

- Categorical precip amount

- Continuous precip amount (web scores at http://www.weather.gov/mdl/hrqpf/verif.php)

- Prob-weighted precip amount

probability prob qpf
Probability (Prob) QPF

Probs for eight 6-h precip thresholds which range from ≥ 0.01” to ≥ 2.00”

For 12-h period probs issued only for 0.01” (POP)

Probs decrease with increasing threshold and projection

Probs are basic …other three QPF products are derived from them

http://www.weather.gov/mdl/hrqpf/gridded.phpand example prob maps

slide6

≥ 0.01 in.

≥ 0.25 in.

84-h Prob (%) for 18-00 z 18 Apr 2009

(Note scale chgs in these maps)

≥ 1.00 in.

≥ 2.00 in.

categorical precip cat qpf
Categorical Precip (Cat) QPF

Derived from probs along with pre-determined threshold probs

- Prob thresholds vary by precip threshold, geography, and projection

- Where prob thresholds are met for multiple precip thresholds, precip category selection algorithm applied to obtain Cat QPF

Cat QPF has bias of ~ 1.2 (perfect bias = 1.0) for all precip thresholds and projections

http://www.weather.gov/mdl/hrqpf/gridded.php and example maps of Cat QPF and Probs

slide8

Spatial pattern uniqueness for Cat QPF due to localized prob thresholds

Cat QPF (in.)

Prob (%) ≥ 0.25 in.

84-h Cat & Prob QPFs for 18-00 z 18 Apr 2009

Prob (%) ≥ 1.00 in.

Prob (%) ≥ 2.00 in.

continuous cont qpf
Continuous (Cont) QPF

Derived from Cat QPF by “interpolating” between (bounded) categories and “extrapolating” above top category

- use multi-variate algebraic formulae

- variables are probs, prob thresholds, categorical precip bounds, max prob and upper bound for ≥ 2.00 in. category

Max Cont QPF for 6-h period is 4.75 in. (7.0 in. for 12-h period)

http://www.weather.gov/mdl/hrqpf/gridded.php and example maps of Cont and Cat QPF

slide10

Note:

- spatial pattern similarity of Cont QPF to Cat QPF

- extrapolation above top category

Cont QPF (in.)

84-h QPFs

for 18-00 z

18 Apr 2009

Cat QPF (in.)

prob weighted prob wt d qpf
Prob Weighted (ProbWt’d) QPF

Computed from probs for bounded precip intervals (computed) and conditional means for precip intervals (pre-determined)

Contains non-zero values where precip (of any intensity) is a threat

Has tendency to spread low values over broad areas

High values are generally much lower than for Cont QPF

http://www.weather.gov/mdl/hrqpf/gridded.php and example maps of ProbWt’d, Prob, & Cont QPF

slide12

Prob Wt’d QPF shows:

- spatial pattern similarity to Prob QPF

- spatial pattern and magnitude contrasts to Cont QPF

- lower peak values than Cont QPF and Obs

Prob Wt’d QPF (in.)

Prob (%) ≥ 0.25 in.

84-h QPFs & Obs for 18-00 z 18 Apr 2009

Cont QPF (in.)

Obs (in.)

hrmos qpf strengths
HRMOS QPF Strengths

High spatial resolution in locations with local precip forcing, based on

- hi-res precip climatology

- hi-res topography

Example

slide14

Note precip amt scale chg

Prob (%) ≥ 0.50 in.

Prob Wt’d QPF (in.)

Cont QPF (in.)

Obs (in.)

84-h QPFs & Obs for 18-00 z 05 Jan 2008

hrmos qpf strengths cont
HRMOS QPF Strengths (Cont)

High precip intensity resolution (for extra-tropical and tropical systems) due to

- high precip thresholds

- geographical regionalization of model

- “smart” extrapolation of Cat QPF above top threshold

Example

slide16

Extra-tropical

18-h QPF & Obs

for 00-06 z

19 Mar 2008

Cont QPF (in.)

Obs (in.)

Extra-tropical &Tropical

72-h QPF & Obs

for 06-12 z

13 Sep 2008

HUR. IKE

hrmos qpf strengths cont17
HRMOS QPF Strengths (Cont)

Prob and ProbWt’d QPFs show high consistency across forecast projections and cycles

hrmos qpf weaknesses
HRMOS QPF Weaknesses

Probs drop off rapidly with increasing precip thresholds

Cat and Cont QPFs tend to

- fluctuate excessively across consecutive projections for a given cycle

- fluctuate excessively across consecutive cycles for a given valid period

- example / fix for problem in progress

All QPF products tend to over-forecast heavy precip events in the northern US and under-forecast in the southern US

All QPF products tend to under-forecast development of intense convection along southern flank of cold fronts

Examples of over/under-prediction

slide19

84-h QPF for 18-00 z 18 Apr 2009

Over-fcst in KS, NE

Under-fcst E TX

Cont QPF (in.)

Obs (in.)

42-h QPF for 12-18 z 28 Mar 2009

Over-fcst in E TN

Under-fcst S AL, GA

Cont QPF (in.)

Obs (in.)

targeted users of hrmos guidance
Targeted Users of HRMOS Guidance

NCEP/HPC

WFOs

RFCs

External customers/partners

real time hrmos qpf availability
Real-time HRMOS QPF Availability

Downloadable Grib2 files at http://www.weather.gov/mdl/hrqpf/

Graphical charts (including comparative QPF products) at same website

Operational ingest into AWIPS is work in progress

implementation plan
Implementation Plan

Replace and supplement GMOS QPF guidance over CONUS

Operational deployment FY 2010

user feedback
User Feedback

Feedback alternatives at http://www.weather.gov/mdl/hrqpf/

- “Comments and Suggestions” link

- “Contact Us” link

- “Join the Mailing List” link

Your constructive comments are welcome and appreciated