Some initial, exploratory plots of PRISM precipitation relationships between winter and summer seasons across 4 watersheds in the SW US.

For context, annual average precipitation and watershed boundaries using PRISM data (1895-2020)

This map shows the grid-based Pearson r correlation between winter (JFM) and subsequent summer (JAS). These would be the local correlations and don’t account for remote influences. Correlations are negative across much of our study watershed (and significant) and max out close to -0.3.

These interactive scatterplot plots depict winter (JFM) vs summer (JAS) precipitation relationships (areal watershed averages for each season). The red line is the linear regression fit line and the blue lines are the quantile regression fit lines for the 10th, 50th and 90th percentiles. Overall, that weak negative relationship is present across all the watersheds and across the different quantiles. There is a bit of difference with the 10th and 90th quantile relationships…like in the Gila, there is much less of a relationship with dry monsoon seasons and preceding winter precipitation. A bit stronger on the wet monsoon side, with more very wet monsoon seasons associated with dry winters.

This table shows counts of JAS precipitation categories (in terciles of dry/normal/wet) in relation to preceding winter precipitation rankings (terciles as well). Shows slight shifts in counts associated with weak inverse relationship.

HUC JFM Dry Normal Wet
Salt Dry 12 12 18
Salt Normal 14 13 14
Salt Wet 16 16 11
Little Colorado Dry 10 16 16
Little Colorado Normal 19 10 12
Little Colorado Wet 13 15 15
Rio Grande-Elephant Butte Dry 13 16 13
Rio Grande-Elephant Butte Normal 13 11 17
Rio Grande-Elephant Butte Wet 16 14 13
Upper Gila Dry 13 11 18
Upper Gila Normal 14 15 12
Upper Gila Wet 15 15 13

Interactive time series of seasonal precip by watershed.

Things to try…