Report on Rainfall Fluctuations For S. Cal Custom Homes Conducted by M. Blazek On Behalf of S. Cal. Custom Homes March 29, 2004 MeteoTech Corp. Consulting Engineering and Meteorology

Problem Statement S. Cal. Custom Homes seeks to reduce delays associated with construction in the hilly terrain within the San Gabriel Mountains –Are recent news reports correct regarding the PDO (and El Nino) and expected rainfall? –What is the state of the science? –What are the consultants views of the report and recommendations regarding timetable?

Recent Media Claims (2003) Claims in Recent Reports: –In S. California, the seasonal rainfall correlates with Pacific Decadal Oscillation (PDO) and has shown significant reduction in seasonal rainfall. –PDO can be used to predict rainfall in S. California. –El Nino and Southern Oscillation Index (SOI) have limited predictive implications in area.

Procedure Data Validation and Review Using the CDC Climate Division Website, PDO, SOI and Nino 3 were correlated to seasonal rainfall and S. California. PDO and Data from LA Civic Center seasonal rainfall were correlated. Statistical tests were run to evaluate the significance of the correlations and the percent of the variance that is explained.

Seasonal Rainfall 25-Year Running Mean Seasonal Rainfall

South Coast = 0.5

South Coast = -0.5

South Coast =.2

Analysis of Statistical Significance Statistical TestPDO/S. Ca. Rainfall SOI/S. Ca. Rainfall Nino3/S. Ca. Rainfall Coefficient of Correlation SignificantNoYes Percent of Variance Explained6.2530

Analysis of Statistical Significance Statistical TestPDO/LA Civic Center Rainfall Coefficient of Correlation0.27 SignificantYes, at 5 percent level Percent of Variance Explained 7 percent

Summary of Findings of Statistical Significance Even for the LA Civic Center, PDO cannot be used to predict because it explains little of the variance. –These results are far less than 50 % explanation described in recent published reports. –So even if the PDO is trending negative, it cannot predict, with any certainty, drier seasons. The SOI and the Nino 3, while significant, can only explain 30 percent of the variance. –The SOI and Nino 3 results do not support the recent published results of 40 percent explanation of variation.

Summary of Findings Recent media accounts regarding of use of PDO for long-term rainfall predictions cannot be replicated. In LA Civic Center, the 25 year running average of seasonal rainfall appears to be nearly constant.

Recommendations Client should NOT expect lower rainfall quantities for the five year period in The San Gabriel Mountains. Recommendation to revise design and include storm water management program.