1. San Antonio Flood of 1-3 July, 2002
Meghan Conway
ATM509
Dec. 9, 2016

2. Motivation
Determine the effects the unique geographic features in south-central Texas had on enhancing precipitation processes and flooding (i.e. rivers, orography, etc.).
Previous studies have shown San Antonio area is especially flood prone [Baker (1975), Hirschboeck (1987)].
This was a historic flood that hit the 100-year recurrence interval for 6-hour and 24-hour precipitation on all three days.
This event killed 12 people and caused around $1-billion in damage.
Talk about how rains occurred from July 1-6 with predecessor rain event happening the last week of June.
Consistent heavy rain signals for three days that have be concentrated on.

3. Information Slide Case study: Methodology:
Historical flood of 1-3 July, 2002 in the greater San Antonio area.
Predecessor rain event last week of June (saturated grounds).
Methodology:
Determine whether maximum rainfall and steep topography coincide.
Analyze wind direction and its orientation to the slope through NCEPS’s NARR data.
Study mesoscale/synoptic forcing's and their relation to the orographic regions using SPC archived data.
Talk about how rains occurred from July 1-6 with predecessor rain event happening the last week of June

4. Anomalously high values of PW advected from the Gulf by surface winds.
Continued upper level divergence throughout time period.
Also mention that PWAT values were above 75th percentile, and there was continued influx of that moisture throughout the period by surf winds
Also mention HYSPLT trajectory
Talk about the blocking high pressure in southeastern US (not shown)

5. Consistent southeasterly surface winds were observed throughout the period.
Moisture convergence/orographic ascent along Balcones Escarpment.
Mention winds were perpendicular to the steeper slopes of Balcones Escarpment

6. Conclusions Predecessor rain event, saturating grounds
Synoptic forcing
Blocking high in SE led to continued upper level divergence
Continued influx of moisture
Anomalously high precipitable water
Two sources of vertical motion at surface
Converging surface winds/WAA and upslope flow along Balcones Escarpment
Lift

7. References
Baker, V. R., 1975: Flood hazards along the Balcones Escarpment in Central Texas--alternative approaches to their recognition, mapping, and management. The University of Texas at Austin, Bureau of Economic Geology Geological Circular 75-5, 22 p.
Hirschboeck, K. K., 1987: Catastrophic flooding and atmospheric circulation anomalies. Catastrophic Flooding, L. Mayer and D. Nash, Eds., Binghamton Symposia in Geomorphology: International Series, No. 18, Elsevier, 23–56.
Kalnay, E. and Coauthors, 1996: The NCEP/NCAR Reanalysis 40-year Project. Bull. Amer. Meteor. Soc., 77,
Slade, R.M. and J. Patton, 2002: Major and Catastrophic Storms and Floods in Texas. U.S. Geological Survey. 11/15/2016. [Available online at:
Stevenson, S. and R. Schumacher, 2014: A 10-Year Survey of Extreme Rainfall Events in the Central and Eastern United States Using Gridded Multisensor Precipitation Analyses. Mon. Wea. Rev., 142, 3147–3162, doi: /MWR-D
Storm Prediction Center, 2009: Surface and Upper Air Archived Maps. NOAA/NWS. 11/15/2016. [Available online at:
Rolph, G.D. (2016). Real-time Environmental Applications and Display System (READY) Website ( NOAA Air Resources Laboratory, College Park, MD.
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