Will This Be the Hottest Summer on Record?

With 8 days left to go in meteorological summer (June to August) this summer is in a dead heat with 2013 for the hottest summer on record at the Salt Lake City International Airport with an average temperature of 80.8ºF.

Source: NOAA Regional Climate Centers

This summer had a pretty good lead through early August, thanks to all of the pain and suffering from late June through most of July, but we've given some of that lead back this month.  Granted, August hasn't seemed to bad, but it's still above average for temperature.  Everything is relative.

Forecasts call for a high-amplitude ridge to build in over the weekend and dominate our weather over the next several days.  This mean highs in the mid 90s beginning tomorrow and lows near 70 at the airport (give or take a few degrees).

The average temperature for the entire summer in 2013 was 80.8ºF, which is right where we are at so far this summer.  Basically, we need to close out the last 8 days of August with an average temperature above 80.8ºF to bust the record.  Much will probably depend on the minimum temperatures.  It's going to be close, but I rate the odds as better than not that we eke this one out.

Let's hope we do.  We suffered a lot this summer.  I want bragging rights.

Weak Monsoon Surge Today

A tip of the hat to the astronomers for getting yesterday's forecast right.  It was a great day for science.  Much thanks from the weather guessers.

And, speaking of the weather, keep your fingers crossed that we see some hydrometeors today.  We have a weak monsoon surge pushing in from the south, with moisture on the increase.  The NAM analysis and forecast loop below shows cloud cover and precipitable water values on the increase overnight and today for northern Utah.

The HRRR forecast for later today shows scattered showers and thunderstorms across northern Utah and Nevada.

The chaotic nature of atmospheric convection prevents us from precisely predicting the location and intensity of those showers, but let's hope they deliver.  A bit of rain later today and evening would be greatly welcomed.

Scenes from the Eclipse

Note: Post has been updated to correct location of site with 10ºF temperature fall.

Before.

Source: CIRA

 After.

Source: CIRA

Incoming solar radiation (Salt Lake area sites).

Source: Alex Jacques, MesoWest, University of Utah

Temperature (Salt Lake area sites).

Source: Alex Jacques, MesoWest, University of Utah

Temperature at Peters Sinks (notorious cold spot in Bear River Range) site in the Bear River Range.  Fall of about 10ºF, although it's unclear if we're at the bottom yet (probably close).

Source: Utah State University, MesoWest

Morning Eclipse Nowcast

Morning has broken and things are looking good along the path of totality over the western U.S.  It's early for a visible loop, but as can be seen below, a band of mid and upper-level clouds is slowly but surely exiting the totality path area of far western Wyoming and Idaho.  

Here's a look at the GOES-16 geocolor imagery from CIRA at 13:32 UTC (7:32 AM) and it looks pretty good too.  There are some thin patchy clouds over portions of the Idaho panhandle and western Montana moving southward that are just barely discernible in the imagery.   

Source: CIRA

You couldn't ask for a better forecast from the operational HRRR than the one below, valid about a half hour after totality.  No clouds predicted along the entire track from Wyoming to the Pacific Coast. 

Source: ESRL

That forecast might be a bit optimistic as there may be a few high clouds around over Idaho and the remnants of the cloud band evident that is over southern Idaho and western Wyoming this morning could linger near and along the totality track over central Wyoming, as indicated by the NAM forecast below.  

Nevertheless, conditions look quite good for the totality track from Jackson to the Willamette Valley with just the threat of some thin clouds spilling down from the north.  You can see these clouds, for example, in the Montana Snowbowl web cam image below.  

Good viewing to those of you along the path.

Addendum @ 8:25 AM MDT

Now that the sun is a little higher, visible satellite imagery shows quite a bit of smoke in the valleys of the central Idaho Mountains.

Based on web cams, I don't think this smoke will obscure the sun, although it may redden it.  Hopefully it won't spoil any views.  

Eclipse Forecast Update at T-1 Day

"Eclipse viewing is about synoptic possibilities, 

but succeeding or failing based on unresolved cloud processes" 

– Slight paraphrasing of quote about storm chasing from meteorologist Chuck Doswell

Model forecasts have trended in the "right" direction since our post on outlooks for the eclipse on Friday.  At that time, the models, such as the NAM below, alled for a short-wave trough to be over Idaho at eclipse time, with at least partial cloud cover over portions of Idaho and Wyoming.

As I write this, the latest (0600 UTC) NAM forecast calls for that short-wave trough to be both further east and weaker, with the Pacific coast ridge also shifted further east.  Much of Oregon is still in a prime spot for lack of cloud cover, but the situation, at least synoptically, is better for Idaho and the Jackson area than one would have anticipated from the forecasts on Friday.

If we look at time-height sections, however, there remains one concern to give me a little heartburn, and that is a sliver of upper-level moisture coming through around the time of the eclipse, as evident in both the Sun Valley and Jackson time-height sections.  Note, in particular, the area of higher relative humidity air in both sections [note that time increases to the left and that the eclipse occurs just prior (to the right) of 18Z Mon].

Because of that sliver, one can't rule out the possibility of some high clouds being around.  The odds are low, but non-zero, an perhaps higher in Jackson than the central Idaho mountains.

There's also some smoke around, as evident in satellite imagery from 13:55 UTC this morning. 

Source: CIRA

The webcam from Stanley looks pretty good this morning, however, so perhaps it is not dense enough to be a concern.  

By and large, the synoptic odds for eclipse viewing look good.  The primary issue now is whether or not unresolved cloud processes throw a low probability monkey wrench over your location at the time of the eclipse.    

Forecast Outlooks and Products for Eclipse Planning

As I write this, we are now about 3 days from the 2017 Eclipse and the ultimate test of transportation and communications infrastructure in rural areas of Idaho and Wyoming, where the vast majority of Utahns and University of Utah students hope to view the eclipse (Question: Will anybody attend class on the first day of the semester, which is also Monday?).

The large-scale forecast for Monday seems to be stabilizing, but I still consider highly specific cloud forecasts to be difficult given the weak large-scale forcing.  A high-amplitude ridge parked over our area would be a godsend for forecasters, but that's not what we're looking at for Monday.

Instead, the GFS calls for a weak upper-level shortwave trough to sweep across Idaho and Wyoming from 1200–1800 UTC (0600–1200 MDT), and be accompanied by some mid- and high-level clouds.  A short-wave ridge further west builds along the Pacific Northwest coast.

Eclipse time is approximately 1721 UTC (1121 MDT) in Redmond, OR, 1730 UTC (1130 MDT) in Stanley, ID, 1736 UTC (1136 MDT in Jackson, WY, and 1741 UTC (1141 MDT) in Riverton WY.  That's just before the bottom image above, which given the GFS forecast would yield the lowest cloud cover odds and fractions during the eclipse over eastern Oregon and increasing cloud cover odds and fractions as one moves eastward to western Wyoming.  

The NAM agrees with the basic synopsis being advertised by the GFS, but note that the shortwave trough orientation is more from SW to NE (positively tilted in meteorological vernacular, and that the structure and characteristics of the clouds varies when one examines the gory details.  

That variation in the structure and characteristics of the clouds represents the dilemma for forecasts along the path of totality over Idaho and Wyoming.  This is a weak shortwave trough, so a routine "public" forecast would be pretty straightforward.  Probably mostly sunny given the fact that some mid and high level clouds aren't going to be a big deal.  

However, exactly where and when clouds will be at the time of eclipse is difficult to ascertain.  Will one have a clear view of the sun in Jackson, but have an untimely patch in Driggs?  Impossible to say.  In part, this reflects the unpredictability of such cloud cover at such long lead times, but also the fact that present day forecast models do not explicitly resolve cloud processes, adding to the forecast uncertainty.  Timing will also matter.  For example, if you just happen to be underneath a local area of clouds at the time of eclipse, that's a bummer.  

Based on current forecasts, the greatest likelihood of clear skies over the interior mountain west eclipse path is eastern Oregon.  The potential for some mid or high clouds exists as one moves eastward, especially over eastern Idaho and Wyoming.  The timing, location, and extensiveness of that cloud cover remains uncertain.  

For your planning purposes, here are a few products for your consideration:

1. NWS Digital Forecasts. You'll need to use the drop-down menu to request "Sky Cover (%)" and select the appropriate time.  12 PM is the closest available.  One disadvantage of these forecasts is that they are "deterministic" and don't show the full range of possibilities.  Numbers represent percent of cloud cover.  

Source: NWS

2. Experimental High Resolution Rapid Refresh (HRRRX). HRRRX is an experimental version of the HRRR that is being developed and tested by the NOAA Earth Systems Research Laboratory for future operational implementation.  Forecasts are available out to varying lead times (probably dependent on computer time availability), including cloud products.  At 3-km grid spacing, this is the model to go to for short-range cloud-cover guidance.  In addition, they have added sun-obscuration mods to account for reductions in solar radiation during the eclipse (details here).  I've been told that a more "crash proof" web access to the HRRRX is available here.

Keep in mind that even at short time scales, errors in cloud cover are to be expected.  Use the HRRRX (and other model forecasts) as guidance, but not absolute truth.

3. GOES-16 Imagery.  I'm a huge fan of these high-frequency, geocolor loops from CIRA.  Use for "eclipse chasing" the morning of the event and fine tuning during the event, if traffic permits.

Hopefully, the forecast verifies with minimal clouds and not an unfortunate veil of thick cirrus.  Good luck!