First Warning: Much needed rain may finally be on the way


AUSTIN (KXAN) — With barely half an inch of rainfall in Austin this month and drought conditions worsening, our luck may be about to change.

We’re seeing more consistent signals pointing toward more rain opportunities during the final third of May.

The importance of May & June rain

May is typically our wettest month of the year, by far, with an average of more than 5″ of rain in Austin. Our wettest period of the year usually cuts off by mid-June as we head into a hot summer. July-August is usually just hot and dry with tropical systems being our best shot for rainfall along with a few isolated thunderstorms.

If we head into those hotter summer months with very dry soil, we have the possibility of dozens of triple digit days while exacerbating the drought. Alternatively, heading into summer with normal rainfall and wet soils would help to keep temperatures down during the summer and improve the drought and our lake levels.

That’s why getting plenty of rain as we wrap up May and begin June is very important.

What are the long term models suggesting?

Several of our long term computer model ensembles paint a promising, but not drought-busting, outlook for the final third of the month beginning around next weekend (May 21-22).

Here is the European and American ensemble rainfall spread. Pay close attention to the “Mean” line.

European Computer Model Precipitation Spread (Weatherbell)
GFS (American) Computer Model Precipitation Spread (Weatherbell)
GFS (American) Computer Model Precipitation Spread (Weatherbell)

What do those graphs mean?

Let me first explain what an “ensemble” is:

Various iterations of the same computer model are run with slightly different initial conditions and those different runs of the model are known as ensembles. The ensemble mean is the average output of those various iterations of the same model. In this instance, the ensemble mean looks at the average rainfall predicted by the end of the month.

Both computer model ensemble means suggest around 1-1.5″ of additional rain in Austin by the end of the month. Remember, we need about 4.5″ of rain by the end of May just to have a normal month, so this rain may not be a drought fixer, but it is a sign of some much needed wet weather in our future.

Certainly we may end up with more than that or less rain than that as the downpours that we typically get in May can have wide ranging totals, but at least the signs are pointing wetter than we’ve been in weeks.

What is the Climate Prediction Center forecasting?

NOAA and the CPC are on board with a wetter outlook! Both the 6 to 10 day rainfall outlook and the 8 to 14 day rainfall outlook have odds favoring wetter than normal weather. Remember, in this wet month of May, even “normal” rainfall would be good news for us.

6-10 Day Rainfall Outlook (CPC)
6-10 Day Rainfall Outlook (CPC)
8-14 Day Rainfall Outlook (CPC)
8-14 Day Rainfall Outlook (CPC)

When will rainfall confidence rise?

We’ll know more as we get closer, simple as that. We still have a hot and dry week to get through before we can start getting too excited about the prospect of rainfall. Long term outlooks are not gospel and wetter trends can sometimes reverse.

Stay with the KXAN First Warning Weather team as we continue to track the heat and the prospect for some needed rain.



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