1. 1 Storm Prediction Center Use of GPS IPW Data as an Input to Severe Weather Forecasting Steven Weiss steven.j.weiss@noaa.gov NOAA GPS/GNSS Workshop October 24, 2007 Boulder, CO

2. 2 Outline Brief Overview of Storm Prediction Center Severe Thunderstorm Forecasting –Importance of observational data for short-term hazardous weather prediction Relationship between moisture and deep convection –Sources of observational data in operational forecasting Sampling and resolution issues Use of GPS-IPW at Storm Prediction Center –Several case examples Conclusions

3. 3

4. 4 STORM PREDICTION CENTER MISSION STATEMENT The Storm Prediction Center (SPC) exists solely to protect life and property of the American people through the issuance of timely, accurate watch and forecast products dealing with tornadoes, wildfires and other hazardous mesoscale weather phenomena. MISSION STATEMENT Protect Life and Property The Storm Prediction Center (SPC) exists solely to Protect Life and Property of the American people through the issuance of timely, accurate watch and forecast products dealing with hazardous mesoscale weather phenomena.

5. 5 Hail, Wind, Tornadoes Excessive rainfall Fire weather Winter weather STORM PREDICTION CENTER HAZARDOUS PHENOMENA

6. 6 TOR / SVR TSTM WATCHES (~1000 / yr) – Valid for 6-8 hours WATCH STATUS REPORTS (~5000 / yr) – Valid 0-1 hour CONVECTIVE OUTLOOKS (~3200 / yr) – Day 1; Day 2; Day 3; Days 4-8 MESOSCALE DISCUSSIONS (~2000 / yr) – Valid for 1-3 hours – Severe Potential Preceding Watch Issuance – Analysis of Severe Weather in Active Watches – Heavy Rainfall – Hazardous Winter Weather FIRE WEATHER OUTLOOK (~1200 / yr) – Day 1; Day 2; Days 3-8 FORECASTS ISSUED IN DETERMINISTIC AND PROBABILISTIC FORMATS – Text and Graphical Products SPC Forecast Products 75% of all SPC products are valid for < 24h period - Observational data are critical for short-term forecasting

7. 7 Severe Weather Outlooks Two Outlook Types Categorical Slight Risk Moderate Risk High Risk Probabilistic Tornadoes Hail Convective Winds

8. 8 Example of High Risk Outlook Day Day 1 Outlook 7 April 2006 Categorical Risk Tornado Probability Hail Probability Wind Probability

9. 9 What Happened on 7 April 2006?

10. 10 Mesoscale Convective Discussions (MD) Goal is to issue pre-watch MDs 1 to 3 hours prior to a Severe Thunderstorm or Tornado watch issuance. - Define area(s) of concern - State expected watch type - Provide meteorological reasoning – most important Also issued ~ every 2 hours for each active watch to provide diagnostic/short-term forecast information (when WFOs are busy with warning activities)

11. 11 Example of Pre-Watch MD MESOSCALE DISCUSSION 2112 NWS STORM PREDICTION CENTER NORMAN OK 0159 PM CDT THU OCT 18 2007 AREAS AFFECTED...LOWER MI CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 181859Z - 182000Z A FEW STORMS COULD DEVELOP OVER THE NEXT COUPLE HOURS. ISOLATED TORNADOES AND HAIL WOULD BE LIKELY. VISIBLE IMAGERY SHOWS CLEARING HAS TAKEN PLACE OVER MUCH OF LOWER MI. HORIZONTAL ROLLS BENEATH CAPPING INVERSION HAVE CHANGED CHARACTER OVER WRN MI SUGGESTING CAPPING IS BEING REMOVED BY COOLING ALOFT AND SURFACE HEATING. ENHANCED CONVERGENCE ALONG LAKE BREEZE LOOKS TO BE A FOCUS FOR DEVELOPMENT OVER THE NEXT FEW HOURS...POSSIBLY EXTENDING AS FAR S AS NRN IN WHERE CU FIELD IS ALSO INCREASING AND DEWPOINTS ARE RISING. CONTINUED HEATING AS WELL AS COOLING ALOFT SHOULD ALLOW A FEW STORMS TO DEVELOP. SHEAR PROFILES ARE VERY STRONG AND ROTATING UPDRAFTS ARE LIKELY...ALONG WITH ISOLATED TORNADOES...JEWELL.. 10/18/2007 ATTN...WFO...DTX...APX...IWX...GRR...LOT...

12. 12 SPC Convective Watch Goals WATCHES ATTEMPT TO CAPTURE:WATCHES ATTEMPT TO CAPTURE: –ALL SIGNIFICANT SEVERE EVENTS: 2” or larger hail2” or larger hail 65+ kt wind gusts65+ kt wind gusts EF2+ TornadoesEF2+ Tornadoes –MULTIPLE SEVERE EVENTS FROM ORGANIZED CONVECTION SupercellsSupercells Squall linesSquall lines Mesoscale Convective Systems (MCSs)Mesoscale Convective Systems (MCSs) –ISSUE 1-2 HRS BEFORE ONSET OF SEVERE Allows WFOs, Emergency Managers, Media, etc. time to implement hazardous weather contingency plansAllows WFOs, Emergency Managers, Media, etc. time to implement hazardous weather contingency plans –Deploy storm spotters –Increase staffing –Contact critical customers (e.g., hospitals, utility companies)

13. 13 URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 44 NWS STORM PREDICTION CENTER NORMAN OK 730 AM CST THU MAR 1 2007 THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF MUCH OF ALABAMA PARTS OF EASTERN ARKANSAS WESTERN FLORIDA PANHANDLE SOUTHEASTERN LOUISIANA MISSISSIPPI WESTERN AND MIDDLE TENNESSEE COASTAL WATERS EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 730 AM UNTIL 600 PM CST....THIS IS A PARTICULARLY DANGEROUS SITUATION... DESTRUCTIVE TORNADOES...LARGE HAIL TO 2.5 INCHES IN DIAMETER... THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS. THE TORNADO WATCH AREA Example of SPC Tornado Watch

14. 14 Watch Hazard Probabilities Tornado (2+ reports):High (>95%) EF2+ Tornado: High (70%) Wind (10+ reports): High (80%) 75 mph Wind:High (70%) Hail (10+ reports): High (70%) 2”+ Hail:Mod (60%) Hail & Wind (6+ reports):High (>95%) Watch Counties -- Watch Probabilities Note: The Aviation Watch (SAW) parallelogram product is an approximation to the watch area. The actual watch is depicted by the shaded county areas.

15. 15 Severe Thunderstorm Forecasting

16. 16 Modified Forecast Funnel SPC focuses on relationship between synoptic - mesoscale environment and subsequent thunderstorm development and evolution Must maintain awareness of mesoscale - synoptic scale interactions Severe weather events occur on scales smaller than standard observational data (and traditional model output) The real atmosphere is more important than a model atmosphere How well do we sample environment?

17. 17 Physical Processes for Deep Convection Ingredients for deep moist convection: 1)Moisture2) Instability 3) Lift This sounds straightforward, but…

18. 18 Physical Processes for Deep Convection Moisture Typically focus on PBL moisture (dew point or mixing ratio) But moisture sources above PBL can be associated with elevated convection Instability Temperature lapse rates and moisture are key contributors (juxtaposition of steeper lapse rates above moist layer) Sufficient CAPE within hydrometeor mixed phase region CAPE twice as sensitive to lifted parcel moisture than to parcel temperature

19. 19 Physical Processes for Deep Convection Moisture A major limitation in convective forecasting is the lack of high resolution 4D water vapor data Observing system does not sufficiently resolve details needed to properly “initialize” forecasters, researchers, and NWP models NWP models reflect strengths / weaknesses of each model as well as observational limitations (physics and IC uncertainty) Lack of necessary detail in mapping water vapor has been identified by USWRP as major obstacle to improved QPF and severe weather forecasting New sources of accurate and reliable observational data are critical to improve assessment of environment and convective forecasting

20. 20 Some Observational Sources for Atmospheric Water Vapor Data

21. 21 Common Operational Observing Systems All observing systems have strengths and limitations –Radiosondes High vertical resolution, low time and horizontal resolution –Surface METAR High horizontal and time resolution, no vertical information –Wind profilers and NEXRAD VAD winds High vertical and time resolution, moderate horizontal res. No thermodynamic data –Satellite retrievals (winds and thermodynamic) Variable horizontal and time resolution, low vertical resolution Sounder impacted by clouds; microwave best over oceans –ACARS/TAMDAR aircraft data Variable time/space resolution; limited water vapor data

22. 22 GPS Integrated Precip. Water (IPW) GPS IPW sampling characteristics –High time resolution., mod. horizontal. res., low vertical res. GPS IPW data have unique attributes that enhance ability of SPC forecasters to monitor moisture distribution and transport –All weather sensing (not affected by clouds and precipitation) –CONUS domain –Accurate (observational uncertainty 1-2 mm) –Continuous operating capability Lack of vertical moisture profiles compensated by knowledge that majority of water vapor is located in lowest 2-3 km AGL –Changes in GPS IPW largely reflect changes in low level moisture field

23. 23 GPS Integrated Precip. Water (IPW) Schematic of vertical distribution of water vapor and temperature Water vapor mixing ratio decreases rapidly with height in the atmosphere ~50% of IPW in the lowest 1.5 km ~75% of IPW in lowest 3 km Less than 6% of IPW above 5 km Source: Water Vapor in Climate System Special Report, AGU (1995)

24. 24 GPS IPW at the Storm Prediction Center

25. 25 GPS IPW at the Storm Prediction Center SPC forecasters directly access GPS IPW data three ways –Hourly station plots in N-AWIPS workstation displays –GSD web page (http://gpsmet.fsl.noaa.gov/jsp/index.jsp) –Six-hourly internet graphics from CIRA - CSU web page (http://amsu.cira.colostate.edu/gpstpw/) GPS IPW data also are part of EMC data assimilation for the RUC and NAM models –RUC model analyses and forecasts improved by GPS IPW data –At SPC, RUC analyses and 1-hr forecasts combined with hourly surface data to create SPC 3D Mesoscale Analyses (http://www.spc.noaa.gov/exper/mesoanalysis/) –SPC Mesoscale Analyses used heavily by SPC and NWS field forecasters during high impact weather events

26. 26 GPS IPW in SPC N-AWIPS Workstations Data received via link from NCEP/HPC

27. 27 Case Example – 19 Sept 2007 SPC Day 1 Convective Outlook Issued 13 UTC

28. 28 N-AWIPS Display 13 UTC 19 Sept 2007 GPS IPW Plot and Analysis

29. 29 N-AWIPS Display 13 UTC 19 Sept 2007 GPS IPW Plot and Analysis

30. 30 N-AWIPS Display 14 UTC 19 Sept 2007 GPS IPW Plot and Analysis

31. 31 N-AWIPS Display 15 UTC 19 Sept 2007 GPS IPW Plot and Analysis

32. 32 N-AWIPS Display 16 UTC 19 Sept 2007 GPS IPW Plot and Analysis

33. 33 N-AWIPS Display 17 UTC 19 Sept 2007 GPS IPW Plot and Analysis

34. 34 N-AWIPS Display 18 UTC 19 Sept 2007 GPS IPW Plot and Analysis

35. 35 N-AWIPS Display 19 UTC 19 Sept 2007 GPS IPW Plot and Analysis

36. 36 N-AWIPS Display 20 UTC 19 Sept 2007 GPS IPW Plot and Analysis

37. 37 N-AWIPS Display 21 UTC 19 Sept 2007 GPS IPW Plot and Analysis

38. 38 N-AWIPS Display 22 UTC 19 Sept 2007 GPS IPW Plot and Analysis

39. 39 Grenada CO GPS IPW Trends 00 UTC 16 Sept-06 UTC 20 Sept 16-00z

40. 40 Blended GPS TPW on CIRA - CSU Web Page (http://amsu.cira.colostate.edu/gpstpw/) GPS over Land and AMSU-SSM/I over Oceans Output at 6-hr intervals during past 72 hrs Animated Loops and Anomaly Charts (Case Example: Courtesy Sheldon Kusselson (NESDIS/SAB)

41. 41 CIRA - CSU Blended TPW AMSU and SSM/I Over Oceans Only Now Include GPS over CONUS Addition of GPS IPW provides MUCH better support for CONUS forecasters

42. 42 Tornado Outbreak 28 March 2007 Oklahoma Panhandle Silverton, TX SPC Severe Reports (preliminary) red - tornado green - hail blue - wind

43. 43 Blended TPW 18 UTC 28 Mar 2007 Blended TPW Blended TPW Anomaly

44. 44 Blended TPW 00 UTC 29 Mar 2007 Note increase in anomaly magnitudes and moist/dry gradient Blended TPW Blended TPW Anomaly MOIST DRY ABOVE BELOW

45. 45 Example of Current Watch MD MESOSCALE DISCUSSION 2095 NWS STORM PREDICTION CENTER NORMAN OK 0236 PM CDT WED OCT 17 2007 AREAS AFFECTED...ERN TX...LA...SRN AR CONCERNING...TORNADO WATCH 710... VALID 171936Z - 172130Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 710 CONTINUES. THE THREAT FOR TORNADOES CONTINUES WITHIN WW 710. LOW LEVEL WARM/MOIST ADVECTION CONTINUES WITH GPS WATER VAPOR SENSORS CURRENTLY INDICATING 2.00-2.32 INCHES FROM LA INTO SRN AR. MEANWHILE...SATELLITE IMAGERY INDICATES LOW LEVEL VORTICITY CENTER MOVING NWD ALONG THE SABINE RIVER...ON CYCLONIC SIDE OF 700 MB JETLET OVER THE LOWER MS VALLEY. THIS FEATURE IS HELPING TO FOCUS CONVECTION AND WILL CONTINUE NWD INTO AR. SHEAR PROFILES ARE ALREADY FAVORABLE FOR ROTATING UPDRAFTS AND TORNADOES...ALTHOUGH RELATIVELY WARM PROFILES AND WEAK LAPSE RATES HAVE ACTED TO SLOW DEVELOPMENT. SHEAR PROFILES WILL LIKELY INCREASE WITH TIME AS UPPER TROUGH CONTINUES TO DEVELOP NEWD. THIS WILL MAINTAIN OR INCREASE TORNADO THREAT FARTHER N INTO AR...AND POSSIBLY SERN MO...WHERE AN ADDITIONAL WW MAY BE REQUIRED LATER TODAY INTO THIS EVENING...JEWELL.. 10/17/2007 ATTN...WFO...JAN...LIX...LZK...LCH...SHV...HGX...FWD...

46. 46 Example of Heavy Rain MD MESOSCALE DISCUSSION 1949 NWS STORM PREDICTION CENTER NORMAN OK 0114 AM CDT SAT SEP 08 2007 AREAS AFFECTED...PORTIONS NRN/WRN OK...E-CENTRAL/NERN PANHANDLE OF TX. CONCERNING...HEAVY RAINFALL VALID 080614Z - 080915Z BAND OF TSTMS HAS BEEN INCREASING IN COVERAGE FOR A COUPLE HOURS...FROM CHEROKEE-GARFIELD-ROGER MILLS COUNTIES OK INTO GRAY COUNTY TX. THIS ACTIVITY SHOULD PERSIST WITH MINOR FLUCTUATIONS IN ITS MESOSCALE GEOMETRY...PERHAPS INCLUDING SLGT NET SWD DRIFT... THROUGH 9Z. RAIN RATES 1-2 INCHES/HOUR WILL BE COMMON... LOCALLY AROUND 2.5 INCHES/HOUR IN HEAVIEST CORES. WITH LITTLE MOVEMENT EXPECTED FOR ASSOCIATED MAIN ZONE OF LOW LEVEL LIFT...PERSISTENT HEAVY RAIN EVENT WITH TRAINING/MERGING OF CELLS WILL ENHANCE HEAVY RAIN HAZARD. ………………………….. RUC FCST SOUNDINGS AND GPS DATA INDICATE PW COMMONLY AROUND 2 INCHES ACROSS THIS CORRIDOR...AND AS MUCH AS 2.3 INCHES INVOF TUL...WITH 500-1500 J/KG MUCAPE IN SUPPORT OF TSTM POTENTIAL...EDWARDS.. 09/08/2007 ATTN...WFO...TSA...OUN...AMA...

47. 47 Conclusions SPC forecasters depend heavily on high quality observational data that provide increased temporal or spatial measurements of atmospheric structure to support our severe storm forecast mission –4D evolution of water vapor is critical for thunderstorm prediction GPS-IPW provides reliable, timely, and accurate measurements of integrated water vapor over land –Most IPW resides below 3 km (proxy for low-level moisture) –Availability of GPS IPW enhances forecaster situational awareness Particularly important during dynamic, rapidly changing situations GPS IPW improves RUC model analyses/forecasts –RUC is a key input to SPC Mesoscale Analysis fields