A Tie for the Driest Summer in Seattle History, While Texas Floods

Quite a precipitation contrast is occurring across the U.S.  

The Northwest is enjoying one of the driest summers on record, with Seattle destined to tie the all-time record low precipitation for July and August.

In contrast, an extraordinary precipitation event is about to occur in Texas, with Hurricane Harvey heading towards the Gulf Coast, bringing 15-25 inches in places over the next few days.

First, the situation here.   Since the rain event in mid-June, Seattle has had nearly no rain, with only .02 inches falling in July and August so far.

The plot of observed and normal precipitation at Sea-Tac Airport for the past 12 weeks shows the story (see below).  The observed rainfall (purple line) has been essentially flat-lined since mid-June.    Even with the heavy rain in June, we are now about 1.5 inches behind normal--not so much since the summers are so dry here.

The record low July-August precipitation was .02 inches in 1914 and .03 inches in 1967.  The latest model runs suggest no rain for the rest of the month.  Thus, it appears nearly certain that folks are now experiencing the driest summer (July-August) in over 100 years.

If one looks at the percentage of average precipitation for the last 60 days (below)...it looks really scary, with some locations getting less than 5% of normal in WA, OR, MT, ID, and CA.

Looking at the actual departure from normal in inches, the scare goes away--most of region is only down 1-2 inches, which is easily made up by slightly wetter month during fall and winter.

Fortunately, with a good snow pack last winter and lots of winter/spring rain, our water supplies are in good shape.

But if you REALLY want something scary, check out what is about to happen in Texas--perhaps the most damaging U.S. hurricane landfall in over a decade could happen later tomorrow....Hurricane Harvey.

Here is the latest precipitation forecast by the National Weather Service Weather Prediction Center.  Wow...over 20 inches in places.

Want to see an amazing contrast?    Here is the precipitation forecast from the NWS GFS model for the next 144 hr (6 days).  Over 25 inches in parts of Texas, with loads of folks getting more than 15  inches.  But nothing over most of Washington.  Next time a Texan jokes to you about the wet weather in Seattle, send them this image.

An interesting aspect of this storm is that the best NWS weather models don't agree on what will happen tomorrow and the next few days.

Here are some of the latest forecasts.  The left panel shows the tracks (purple is HWRF, the just replaced hurrican model and the green is HMON, the new NWS hurricane model).  Some other models are also shown like the Navy COAMPS (orange), and the operational GFS (blue line).   They all start the same, but some go left, some go right, and the some just hang around coastal Texas (which is very dangerous regarding flooding).

The lower right panel shows central pressure. HMON goes for 910 hPa, which is very low and would bring in a CAT 4 or 5 storm.  Catastrophic.  In contrast, HWRF is 940 hPa, 30 hPa weaker--perhaps a CAT 3 event.

Anyway, this is an extraordinarily serious hurricane that will bring a major storm surge along the coast, flooding, and wind damage.  No one should be on or near the Texas coast tomorrow.   The latest infrared satellite image is enough to put chills down the back of any coastal resident.  This will be a major test of the Trump administrator and his FEMA director--lets hope they are up to it.

Meteorological Effects of the Eclipse...and More

I returned home last night viewing the total eclipse (I was position within the Ochoco National Forest of eastern Oregon).

I was really moved by the experience...the period of rapid darkening before totality is strange and unsettling, and totality is other wordly, with a huge corona that pictures don't do justice.

The darkening of the eclipse was very obvious in visible satellite imagery....here are two shot at 10:15 AM, one (left) for eclipse day (August 21st) and the other from the day before

I had my trusty digital thermometer with me and I was impressed by eclipse-related temperature decline from 72 to 59F (13F) between 9:30 and 10:30 AM (totality started roughly at 10:20 AM and was a little less than 2 minutes long at the centerline).

Other places in eastern Oregon had declines even larger (14-15F).  For example,  John Day, Oregon declined 14.9F (see graph below)

Keep in mind that the cooling effect of the sun is even greater than these number, because under normal sun, the air temperatures would have continued to warm from the strengthening morning sun.  So think about a cooling impact of 15-20F...that is impressive!

What about here in Seattle?   At the top of the atmospheric sciences building on the UW campus, temperatures dropped about 4F (see below).  But there are some subtleties you might find interesting.

This plot of weather conditions at the UW on August 21st  includes the solar radiation (lower panel).    A big chunk was taken out by the eclipse (time is in UTC, so 18Z is 11 AM).  Temperatures were suppressed for a few hours, with a decline of about 4F from what occurred before and perhaps 5-6F from what would have occurred.   Wind speed dropped a bit during the eclipse and was less variable (top panel).

Why?   Because the weakening of solar heating at the surface lessened the vertical mixing of thermals in the lower atmosphere.  Less mixing means less downward movement of stronger winds aloft and reduced variability.  Wind direction shifted noticeably with the eclipse, shifting from northerly to southwesterly.

As another way to get at the eclipse temperature effects, here are the differences between model forecasts and observed temperatures at Redmond, Oregon--just inside of totality. (UW research scientist Jeff Baars did this analysis).  The UW WRF model does not have the eclipse radiative effects, so the difference between forecast and observed gives you an idea of eclipse impacts.  11 AM (right after the eclipse) is shown.  In the days before the eclipse, the model was too cold by roughly 2 F, but is was too warm by roughly 7F right after totality, implying a large cooling impact of the eclipse.

The NWS ran a model (HRRR) with and without the radiation corrections and plotted the difference in temperature at 11 AM.  It suggested cooling of 4-6F over much of the region, with some locations getting to 8-12F.

In other parts of the country, the reduced heating greatly attenuated the development of cumulus clouds, which are also driven by solar heating at the surface.

Here are two GOES-16 visible satellite images, one at 1722 UTC (1222  PM EDT), before the eclipse, and the other at 1947 UTC (2:47 PM) EDT, after the eclipse.  The small cumulus are nearly gone after the eclipse cools the lower atmosphere.

I should note that the models and forecasts were quite good, providing good guidance for eclipse lovers.
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And  now for an editorial.  I have sometime complained about the media hyping and exaggerating stories, which has gotten me into loads of trouble with a few local outlets, such as the Seattle Times and the Stranger.    Well, I can't help but mentioned that the media, in concert with some local government folks, profoundly exaggerated the difficulties of traveling to the eclipse in Oregon.  And relatively easy steps were not taken to facilitate travel. 

Last week, there was story after story about travel Armageddon.  That travel would be impossible, total gridlock, gas and supplies unavailable, no places to stay, and crazy prices for rooms or parking.  They talked about wildfires started by folks parking on the sides of roads and overwhelmed cell phone networks.

 Some samples below:

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The reality was very different.

There was very little traffic in Oregon over the weekend (even in the early morning hours on the same day).    Lots of gas and no lines.   Stores and restaurants were stocked...and not very busy.

The crazy stories in the media caused panic among some Oregon residents, who lined up to get gas last Wednesday.  This was NOT the visitors.  Gas supplies were promptly restored the next day.

The media hype resulted in hotel/models/rentals jacking up prices and even canceling reservations of those who "paid too little" by making reservations a long time ago.  We are talking major greed here and our local governments did not protect us from it.  Some farmers were selling parking spaces for hundreds of dollars a day.

Turns out the high prices discouraged folks from making reservations and there was a lot of rooms available the night before!  I checked myself....big discounts available with room prices dropping from $1200 to $149 at some places in Bend and Redmond, Oregon.

There was  bad traffic in Oregon immediately after totality, but the State could have greatly lessened the traffic by using police to open up some intersections.  Stop signs in remote rural towns resulted in long waits for no reason.  And Washington DOT did rock blasting in the Snoqualmie Pass, closing it down from 7-8 PM as the surge of traffic was trying to get through.

In short, the media did the people of the Northwest a major disservice in scaring folks away from one of the most amazing, moving events of the natural world. They did so with little real information, echoing increasingly problematic warnings among themselves.

Local governments did not protect travelers from cancellations, and did little to deal with traffic problems when folks wanted to go home.  Will the media do a story about this?