2008-01-07

Rain 0.62" this storm; 5.96" this season

EDIT 29 Jan: updated second graph to current rainfall.
EDIT 25 Jan: Replaced the second graph with an updated, and more importantly, correct, version.

It looks like the storms have cleared the area with 1.05" 0.06" and 0.62" = 1.73" total for this series of storms in my backyard. That's a good amount for my neck of the woods.

Rainfall total for my backyard this season is 5.86". Median Los Angeles rainfall is slightly above 6" at this time of year.

The graph above illustrates, statistically, what typically goes on. The solid lines bound the monthly probability of rainfall at the 25%, 50%, and 75% level for light blue, medium blue and dark blue, respectively, when read against the left vertical axis: There is a 25% chance for rainfall to be at or below the light blue line in any given month, 50% to be at or below the medium blue line, and 75% to be at or below the dark blue line.

The dashed green lines represent the cumulative total rainfall in an analogous way: 25% chance to be at or below the light green line, 50% to be at or below the medium green line, and 75% chance to be at or below the dark green line.

Examples:
~Median rainfall (50% chance above or below) for our wet season is about 7.5".
~February is typically the wettest month, except in dry years. In dry years, January is typically the wettest month.
~There's wide variation in typical (50% chance) rainfall. For example, in February, half of the time rainfall is between 0.5 inches and almost 4.5 inches.

Below is rainfall measured in my backyard (90250) for the 2004-05, 2006-07, and the 2007-08 (year to date) seasons. I left off the 05-06 season because it was visually confusing, but it was also less interesting as it wasn't such an extreme as the 2004-05 (very wet) and 20o6-07 (driest year on record).



One of the predictions of global climate change is greater weather extremes. The human tendency is to immediately jump to the conclusion that we're seeing those effects in local rainfall observations (years 2004 and 2006, above). Jumping to that immediate conclusion based on this data alone would be hasty. I may take that task on in a more rigorous but still rudimentary way in a later post.