La Message Board Archives

Some rain tonight?

Posted by Bret B on June 20, 2014, 5:11 pm

An unusual flow of moisture and clouds is beginning to stream over us from the Pacific this afternoon:

It's not directly associated with any particular storm or invest (even though there is a 20% Invest #95E WAY down to our SSW:

I don't see any big thunderstorms approaching right now, but this definitely increases our chances for rain tonight. It's been a little less hot ever since that nice afternoon rainstorm on Wednesday. Before that cool-down I was seeing the afternoon Heat Index hitting 118F at my place. Yesterday and today the HI has barely been over 100F. BRRRR....

Keep it coming!

Re: Some rain tonight?

Posted by Kathy B on June 21, 2014, 4:39 am, in reply to "Some rain tonight?"

What kind of an instrument do you use to measure the heat index? I just add ten degrees to what my thermometer says and call it good. Thanks.

Re: Some rain tonight? and heat index 101

Posted by Bret B on June 21, 2014, 8:48 am, in reply to "Re: Some rain tonight?"

Well, that rain last night was only 0.02", but there's still a chance of more today. The NHC Eastern Pacific tropical discussion ( mentions a surface trough attached to that Invest 95E far to our SSW, and an upper-level ridge in the same area. These two features are adding to the instability (i.e. thunderstorms) in the flow from the Pacific onto the western Mexican coastline.

Kathy, I don't have an instrument that displays heat index directly (although you can buy them.) I use the NOAA NWS heat index online calculator ( Just enter the current temperature (F or C) and the current relative humidity, or temp and dew point, and click Calculate. I also have printed out their heat index table for rough estimates without going online (link is on the calculator page.) In my example from the previous post, my backyard temp was 96F along with a RH of 62%. The calculator gives a heat index of 118F. Pretty steamy! I think the highest HI I've ever noted here was around 125F. And of course it's about the same inside the house. It's no wonder Donna and I are so lazy this time of year...

Heat index nerds can follow the "How do we calculate heat index" link at the top of the online calculator page. They use a fairly complex algorithm. And the Wikipedia article has even more long complex formulas to choose from: (I had to propose a correction to fix an error in one of these formulas last year, so as always take Wikipedia articles with a grain of salt. Anyone can edit them!)

Re: Some rain tonight? and heat index 101

Posted by Daniel Hallas on June 21, 2014, 9:29 am, in reply to "Re: Some rain tonight? and heat index 101"

Total Pro report. Thanks Bret.

0.74" in 22 minutes

Posted by ElkeG on June 21, 2014, 6:05 pm, in reply to "Some rain tonight?"

Started raining @ 5:15 PM in Melaque (rain gauge clock is an hour off)

Check out the rain rate, it came down pretty hard for a while...


Re: 0.74" in 22 minutes

Posted by Bret B on June 21, 2014, 6:47 pm, in reply to "0.74" in 22 minutes"

Wow, Elke, you guys in Melaque always seem to get more rain than La Manz does. And those rain rates are incredible: almost 10" per hour! Am I reading that right? I don't think I've ever seen a rainfall rate that high, even for a few minutes! That highly technical meteorological comment along the bottom of your display just sums it up, doesn't it?

I got 0.56" in an hour or so, along with some good thunder including one strike within a block of me. And there's plenty more moisture out in the Pacific still streaming toward Mexico...

Re: 0.74" in 22 minutes

Posted by ElkeG on June 22, 2014, 10:24 am, in reply to "Re: 0.74" in 22 minutes"

Yes, you read that right Bret - almost 10" per hour, but it only lasted for a short while. Current reading says we got about 1.62" total up until now.

Continuing rain and Invest 95E

Posted by Bret B on June 23, 2014, 10:45 am, in reply to "Re: 0.74" in 22 minutes"

Here in La Manz I recorded 0.74" on Sat (midnight to midnight), 0.76" on Sun, and 0.30" so far today, for a total of 1.80" from this persistent Pacific flow of moisture. It's been nice non-damaging rain. Great for the plants, and boy has it cooled us down the last few days. Me gusta!

Invest 95E is now a couple hundred miles to our west, and has a 30% chance of becoming a depression or greater in the next 48 hours. It shouldn't directly affect us, but it is associated with this flow of moisture that has been bringing us the rain.

This morning Invest 95E has generated a large area of thunderstorms out in the Pacific between Puerto Vallarta and the tip of Baja:

The Mexican weather agency has issued a rain alert for the middle swath of Mexico including Colima, Jalisco, Nayarit:

I personally don't see us getting any really heavy rains, at least not today. Still a chance for light or moderate rains though.