La Manzanilla.info Message Board Archives

Friday update: even heavier rain forecsat?

Posted by Bret B on March 13, 2015, 8:50 am, in reply to "Slight chance of rain in next 10 days?"
187.148.141.155

Summary:

Not much change in likelihood and timing of the online rain forecasts for this weekend (25-50% chance on Sat, then near-100% chance on Sun, Mon, Tue.) But it looks like the total accumulations are predicted to be heavier than yesterday's forecasts, and sliding more into Tuesday.

Details:

> W.U. now forecasts OVER 5 INCHES total accumulation for the whole 4-day period:
http://www.wunderground.com/q/locid:MXJO0760?MR=1


> CONAGUA predicts even more: SOMEWHERE in Jalisco gets 0-1" today, 3-6" Sat, 3-6" Sun, 2-3" Mon:
http://smn.cna.gob.mx/boletin/discusion/discusion.html
Here's their 4-day graphical forecast (yes, it's this tiny on their site also!) I circled our vicinity in red on the 1st map. You can see the "cut-off mid- and upper-level low pressure feature ("eighth winter storm") settling in to our northwest that is to blame for sweeping that thick band of moisture from the Pacific (blue arrows) over the western Mexico coastline:


But the computer models shown on the CONAGUA site don't really support this much rain in Jalisco. The WRF-SNM and GFS both show most of the rain staying to our south: http://smn.cna.gob.mx/index.php?option=com_content&view=article&id=16&Itemid=87

>The 7-day GFS model ( http://www.hpc.ncep.noaa.gov/mike/gfs/crb_p24i_loop_12.html ) also shows the heavier rains staying just to our south in Colima and Michoacán. Then on Tuesday it shows us getting a couple or three inches.

My opinion:

I think the various models don't support multi-inch rainfall for La Manzanilla, especially when we have seen in the past how these heavy Pacific moisture plumes tend to drop most of their rain just before crossing the coast, and then they resume heavy rains inland over the higher terrain. We seem to have a localized "coastal effect" that the models don't include very well.

So my forecast: high chance of rain later this weekend, but more like 1-2" total. But keep in mind it would only take a 50-100 mile shift northwards of the heavy rain band to greatly increase our accumulation (6-8-10 inches worst-case.)

Get your laundry hung and your roofs finished today to be safe!

Until tomorrow...
185



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