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Information about IHOP NWP

Published on February 28, 2008

Author: Terenzio

Source: authorstream.com

Real-time Storm-scale Forecast Support for IHOP 2002 at CAPS :  Real-time Storm-scale Forecast Support for IHOP 2002 at CAPS Ming Xue1,2, Keith Brewster1, Dan Weber1 Kevin Thomas1, Fanyou Kong1, Eric Kemp1 mxue@ou.edu Center for Analysis and Prediction of Storms (CAPS)1 School of Meteorology2 University of Oklahoma IHOP_2002 (International H2O Project 2002):  IHOP_2002 (International H2O Project 2002) A field experiment that occurred over the Central Great Plain between 5/13 – 6/25/2002 Science Objectives and Components Quantitative Precipitation Forecast (QPF) Convection Initiation (CI) Boundary Layer (ABL) Processes Water Vapor Instrumentation and Data Assimilation Research IHOP_2002 Operations Domain and Instrumentation Sites:  IHOP_2002 Operations Domain and Instrumentation Sites IHOP Related Research at CAPS:  IHOP Related Research at CAPS CAPS is supported through an NSF grant to Contribute to the IHOP field experiment and Perform research using data collected Emphases of our work include Optimal Assimilation of and the Qualitative assessment of the impact of Water vapor and other high-resolution observations on storm-scale QPF. Goals of CAPS Realtime Foreacst:  Goals of CAPS Realtime Foreacst To provide additional high-res NWP support for the real time operations of IHOP To obtain an initial assessment of numerical model performance To identify specific data sets and cases for extensive retropective studies CAPS Real Time Forecast Domain:  CAPS Real Time Forecast Domain 273×195 183×163 213×131 CAPS Real Time Forecast Timeline:  CAPS Real Time Forecast Timeline Model Configuration:  Model Configuration ARPS 5.0 of CAPS was used with following options: Nonhydrostatic dynamics with vertically-stretched terrain-following grid Domain 20 km deep with 53 levels. First level 10m AGL. 4th-order advection, simple positive definite scheme for water and TKE. 3 ice-phase microphysics (Lin-Tao) New Kain-Fritsch cumulus parameterization on 27 and 9 km grids NCSA Long and Short Wave Radiative Transfer scheme 1.5-order TKE-based subgrid scale turbulence closure and PBL Parameterization 2-layer soil and vegetation model Data and Initial Conditions:  Data and Initial Conditions Initial conditions produced by ARPS Data Analysis System (ADAS) with cloud / diabatic initialization Eta forecast for BC of CONUS grid and first guess for IC analysis Rawinsonde and wind profiler data: Used on CONUS and SPmeso grids MDCRS (aircraft observations): All grids. METAR (surface observations): All grids. Oklahoma, Western TX and ARM Mesonets: All grids Satellite: IR cloud-top temperature used in cloud analysis. CRAFT Level-II and NIDS WSR-88D data: Reflectivity used in cloud analysis on SPmeso and SPstorm grids, and radial velocity used to adjust the wind fields. Cloud Analysis in the Initial Conditions:  Cloud Analysis in the Initial Conditions Windband Level-II data from 12 radars (via CRAFT) and Level-III (NIDS) data from 12 others in the CGP were used in a cloud analysis procedure that analyzes qv, T and microphysical variables The cloud analysis also used visible and infrared channel data from GOES-8 satellite and surface observations of clouds Example of Initial Condition on 3km Grid:  Example of Initial Condition on 3km Grid Computational Issues:  Computational Issues The data ingest, preprocessing, analysis and boundary condition preparation as well as post-processing were done on local workstations. The three morning forecasts were made on a PSC HP/Compaq Alpha-based clusters using 240 processors. The 00 UTC SPstorm forecast was run on NCSA’s Intel Itanium-based Linux cluster, also using 240 processors. Perl-based ARPScntl system used to control everything Both NCSA and PSC systems were very new at the time. Considerable system-wide tuning was still necessary to achieve good throughput. A factor of 2 overall speedup was achieved during the period. Data I/O was the biggest bottleneck. Local data processing was another. Dissemination of Forecast Products:  Dissemination of Forecast Products Graphical products, including fields and sounding animations, were generated and posted on the web as the hourly model outputs became available. A workstation dedicated to displaying forecast products was placed at the IHOP operation center. A CAPS scientist was on duty daily to evaluate and assist in the interpretation of the forecast products. A web-based evaluation form was used to provide an archive of forecast evaluations and other related information. The forecast products are available at http://ihop.caps.ou.edu, and we will keep the products online to facilitate retrospective studies. CAPS IHOP Forecast Page http://ihop.caps.ou.edu:  CAPS IHOP Forecast Page http://ihop.caps.ou.edu Example: Animation of Page Precipitation Rate at 1 hour intervals:  Example: Animation of Page Precipitation Rate at 1 hour intervals Example Cases:  Example Cases May 12, 2002:  May 12, 2002 NCEP Hourly Precip ARPS 9 km Forecast – Precip rate 12 Hour forecast valid at 00 UTC May 17, 2002:  May 17, 2002 NCEP Hourly Precip ARPS 9 km Forecast – Comp. Ref. Initial Condition at 12 UTC June 15, 2002:  June 15, 2002 NCEP Hourly Precip ARPS 3 km Forecast – Comp. Ref. 11 hour forecast valid at 02 UTC May 17 ARPS fcst Eval:  May 17 ARPS fcst Eval submit_by: jbrotzge@ou.edu Date: May 17 General_Comments_on_Weather: Friday, May 17th, was characterized by an early morning (prior to 12Z) bow echo across much of the region, followed by building high pressure across the southern and Great Plains. Low to mid-level clouds remained over much of the IHOP region, with gradual clearing from N/NW to S/SE. High level clouds remained over the OK/TX panhandles and western OK. Light, northerly winds dominated across much of the area. IHOP_Field_Operation: A "down" day - no field operations. Forecast_Evaluations: Numerous delays and model configurations. Despite the delays, the 12Z SPMESO, CONUS 12hr and 36hr forecasts were available for 00Z, May 18th, for forecast evaluation. The 12hr SPMESO forecast valid for 00Z performed "okay", with precipitation in the general vicinity of the cold front. Precip amounts were not correct, but most forecast precip was near the domain boundaries. Perhaps more importantly, while only a small amount of precip was observed in CO (and nowhere else in the west), ARPS produced "blobs" of rainfall throughout the Rockies from WY to NM. Perhaps a KF problem? ARPS sfc temperatures across the IHOP region were significantly warmer (5-10F) and drier (Tds 5-10F) than observations. Perhaps a problem with the current sfc physics? The CONUS 12hr and 36hr forecasts (both valid at May 18, 00Z) both captured the strong, eastward moving cold front fairly well. The 36hr run was much too fast in its eastward progress of the system, especially over the Ohio Valley region. On the other hand, the run was much too slow in its southward progress through TX. The 12hr forecast improved the speed of the system across both regions The rainfall and frontal speed was now well progged over TX. However, the frontal speed across LA and KY was now too slow in its eastward progression. Overall, ARPS performed much better than the RUC, comparable to ETA. May 17 IHOP Weather Summary:  May 17 IHOP Weather Summary Date(UTC): 2002/05/17 21:17 Author: ed szoke Submitted at(UTC): 2002/05/17 23:50 Revised at(UTC): 2002/05/17 23:53 REVIEW OF PREVIOUS FORECAST NOTE: THIS REPORT IS FOR 16 MAY (was submitted on 17 May) GENERAL OVERVIEW A very interesting weather situation over the area involving 1) an unseasonably cold airmass heading south with the frontal boundary of this air mass at 12z entering northeastern CO and northern KS. 2) Strong lower level s to ssw flow importing increasing moisture northward acrosss the IHOP domain. 3) Zonal flow aloft but an embedded s/w trough apparently helping to develop a surface low in the vicinity of SPole around 12z, with a "cold front" trailing sw from this low. This feature swept across the SPole in the early morning hours (near sunrise) and was the focus of a potential bore study. 4) A separate surge of cooler air from the MCS that formed over KS during the night and this more e-w boundary could be seen dipping south across the OK/KS border 12-16z in the OK mesonet data (see image 1). 5) A not-very-well-defined dryline that trailed south from the surface low near SPole and was generally along the TX/OK border, aligned about N-S, and occasionally showing as a wind shift to WSW in the westernmost OK mesonet data. 6) Initial convection was already underway not only in eastern KS with the overnight MCS remnants, but scattered into eastern OK (see image 2). This is the setup for the day during the 12-16z period. A CI mission was planned, note that facilities were not all ready for other mission types yet (as a nighttime MCC/MCS was forecast, for example). DISCUSSION Evolution of the weather. The forecast discussions from the SPC group should be examined as they did a good job on the overall developments on this day. There are details that were quite interesting and some still difficult to understand. It turned out to be a difficult mission for the CI folks to work because the dryline never really pushed eastward, and in fact ended up working westward somewhat, but was only somewhat defined well back in the TX Panhandle. So there was no real triple point to be worked. What happened was the "lead" cold front (the one trailing south from SPole around 12z) became more N-S oriented as it stalled near the OK/TX border, and they worked this as it drifted westward during the afternoon. Another interesting thing that developed was a sw-ne thin line of convection extending from the sw corner of OK to the ne corner, that seemed to evolve from a line of hi and mid level cloudiness that was present in the morning to early afternoon (see image 3). At 18z this began to show up on the radar as weak echoes, then by 19z the part east of OKC had good echoes, which expanded sw along this feature with time. What was this? No surface feature that I could find to go with this. Could it have been connected to some subtropical streamer of moisture? The main show was the convection that developed in the upslope over eastern CO during the afternoon, as the main surge of colder air moved south (and west into CO). By 22z substantial echoes were found from extreme se CO to the western OK Panhandle, and these increased in size and coverage next few hours (a severe tstm watch issued I believe by ~00z). This activity organized and came east with the nern CO stuff into a substantial mass of echoes, with the strong echoes at the southern end of the activity, mainly TX and OK Panhandles, between 00z-03z. Stuff tried to go during this period near OUN, but it was quite capped (see image 4). However by 03z a solid line of echoes developed separately ahead of this system moving from the Panhandle, developing e-w along the surge of colder air ("real" cold front). These developed and merged with the Panhandle activity to form a large linear complex across OK east to across southern MO by 06-07z/17 May. The part from central OK westward then took on a beautiful bow structure which expanded southeastward from 07z to when it exited OK after 12z, with a huge trailing stratiform region. After 12z activity became a large squall line, now extending from nern TX to TN. SUMMARY Very interesting day, complex structure with ill-defined dryline early on. Then curious thin line of convection in the afternoon evolving seemingly from a linear mid to hi level cloud band. Finished with a MCS (MCC?), with part of it in evolving in a classic bow echo structure across the se quarter of OK. Future Work (where real fun starts):  Future Work (where real fun starts) Multi-scale QPF Verification under way Simulation Studies of Selected Cases IC and BC Sensitivity Studies using the Forecast Model and its Adjoint Continuous Data Assimilation Studies (including radar and GPS data) using 3DVAR and later 4DVAR Study of Data Impact Studies of Physical Processes using Model Data Sets

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