Warm & Humid

August 15, 2013

As promised, the humidity bumped up somewhat dramatically the past 24 hours.  Dewpoints went from the 40s yesterday to 60s today.  Dewpoint is the measure of the amount of moisture in the air.  Technically it’s the temperature at which fog would form if an airmass is cooled at a constant pressure.  As air cools it can hold less moisture, so at some point some has to condense out into fog droplets (or condensation on your cold drink).  Anyway, more moisture means your body can’t cool itself as well, thus the “sticky or sweaty” feel.

MarkCold_PortlandRecordLow

Last night we tied for the warmest temp of the summer at PDX (66), I see Vancouver was only 67 for a record and that tied the warmest of the summer too.  Our 66 was not since 3 record lows were 66-68 during a heat wave in mid August 2008.  Of course these numbers are dependent on the temperature not dropping lower before midnight since records are kept by calendar day.

We sure haven’t see the rain earlier anticipated though.  Starting with last night’s 00z models they turned much drier.  At least they caught the drier forecast 12 hours ahead of time, but I wish we could have seen that 1″ of rain in the Coast Range today.

Tomorrow should be warmer with less cloud cover and showers only developing over and east of the Cascades.  Weak and flat upper-level ridging develops over us Sunday through the middle of next week, then maybe troughing again beyond that.  Here are the two ensemble charts from the ECMWF and GFS.  First the 12z ECMWF, note the above average temps the first half of next week and then cooler towards the following weekend:

tseries_850t_000-360_Portland

then the 12z GFS chart, closer to average through the whole run.  Note the operational is cooler than the ensembles for next weekend:

tseries_850t_000-384_Portland

Here are the ECMWF weekly maps from last night’s run.  Interesting to note the strong ridging offshore in early September.  Otherwise no real negative or positive anomalies.

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

Last night I showed this graphic…

Mark_SummerWrapEarly

A sort of checkup on our summer weather so far.  For the record, Wayne Garcia gave it an A+ and Amy Troy an A-.  Or maybe the other way around.  Either way they are quite pleased with our summer so far.  The stats above are for PDX only.  Notice we had no chilly late spring/early summer weather.  Remember the run of 70s and even a few 80s in early May?  Then a big soaking of course.  So far we are above average on 80+ days, but do to the lack of extreme heat, we are only slightly above average with respect to temperatures.  As mentioned on an earlier post, we haven’t seen much heat, just 6 days at/above 90.  That’s normal for May-July.  And so far August appears that it COULD go down for below average 90 degree days.  We’ll see.  This doesn’t apply to all of Oregon.  I see that extreme SE Oregon saw its hottest July ever!

july

Chief Meteorologist Mark Nelsen