Rod's Weather Headlines

We lucked out and got to see little bit of the "Supermoon" last evening.  The peak viewing will be tonight when the full moon rises at 9:16 p.m.  But, as you likely know, solid cloud cover is expected to cover the show.  Here is all you would ever want to know about what appears to be the largest moon of the year, courtesty of Jim Todd, OMSI Director of Space Science Education:

June's full moon takes place at 4:32 a.m. PDT on Sunday, June 23  It is called the Strawberry Moon; but it can also be called the Rose Moon or Honey Moon. When we look at the full moon on Sunday, it will be just 221, 824 miles away making it the Moon's closest approach to Earth in 2013.
 
Full moons vary in size because of the elliptical (oval) shape of the Moon's orbit. Perigee, or the Moon's closest approach Moon to Earth is about 31,068 miles closer to Earth than the its apogee or farthest distance. The Moon's distance at perigee changes by 3% over a period of 18.6 years, but in general while at perigee, a full moon would appear about 14% bigger and 30% brighter than a corresponding full moon at apogee, but it's not really all that much more dramatic than a regular full moon.
 
In March 2011, the full moon was less than one hour away from perigee, a near-perfect coincidence that happens about every 18.6 years.  On May 2012, the full moon was a minute of reaching actual perigee position.  The point of the moon’s full phase at 4:32 am PDT in June 2013, and perigee at 4:09 am PDT, fall within an hour of each other.  On August 2014, the full moon and perigee will be just 3 miles closer to Earth.
 
Before 2011, the comparable biggest/closest full Moon was March of 1993, and presumably the next comparably large full Moon will be 18.6 years from then sometime in late 2029.
 
Many are calling this full moon the "Supermoon," blaming it for dramatic land and ocean tides which trigger earthquakes. The tides are greatest during full and new moons, when the sun and moon are aligned either on the same or opposite sides of the Earth.  A very small correlation exists between full or new moons and seismic activity, because the stronger tidal forces caused by the alignment of the sun and moon puts added stress on tectonic plates. However, seismologists have found no evidence connecting lunar perigees to heightened seismic activity. Instead, the Earth constantly stores up energy and releases it any time the built-up energy becomes too great.

The National Weather Service confirms an EF1 tornado Thursday afternoon at 4:33 in McMinnville.  Winds were estimated to be 86-110 mph.  The tornado is further classified as a cold core funnel.  The twister was produced by the cold upper level low responsible for today's heavy showers and small hail.  I spoke with the Weather Service to confirm that no warning was issued.  Doppler radar briefly showed rotation during one scan and then nothing.  In other words, radar operators only saw a quick bleep, which would rarely if ever alert a meteorologist to issue a warning solely based on radar data.  

Today's severe weather is a reminder that due to the weak and isolated nature of Northwest tornadoes, warnings are very rare.  The good news is that cold core tornadoes in our region are typically the weakest two categories of the EF tornado scale. 

There were several reports of funnel clouds today, meaning the funnel stayed high and did not touch down.  One funnel observed at 1:13 pm south of Corvallis lasted for 3 minutes.  A second funnel cloud was spotted from the Hillsboro airport at 5:05 pm.  Today's funnel clouds are a good lesson that when our weather is unstable with heavy showers due to a cold upper level low, tornadoes and micro strong wind events can develop and we should all keep an eye to the sky. 

Another chance tonight at 9:41 to see the International Space Station!  Look for an object similar to an airplane in the sky, but higher and moving quickly.  Look to the west,southwest at 52 degrees and track the flight to the east.  The station will be visible for 7 minutes.  The brightness will be a magnitude -3, which equals the brightness of Venus.  The flyover will take place Thursday evening at 9:41 pm.    

The Space Station orbits earth at 240 miles high and moves at 17,500 mph!  The international station is roughly the size of a football field.  The brightness we can see is made possible by sunlight shining on the station's metallic modules and enormous solar panels.

I have seen the station from my backyard several times.  Skies will be clear tonight for the 9:41 viewing.  If you look up to the southwest, you should see the bright object moving east.  You will know it when you see it.  Enjoy the view!

An update to this article:  PDX will finish May tied for 3rd all-time on the wet list with 4.75 inches of rain. 

Steady rainfall expected tonight will likely push PDX into the top 5 list of wettest Mays at the airport!  Monday's record rainfall of .88 inches puts the monthly total at 4.23 inches.  Forecast charts show likely rain tonight, totaling .25 - .50 inches through the day Wednesday.  The additional rainfall would move PDX into at least 5th place on the wet list and maybe as high as number 3!  Here is the list of wettest Mays at PDX:

1.  1998 - 5.55 inches

2.  1996 - 4.88

3.   2010 & 2013 - 4.75

4.   1945 - 4.57

5.   1993 - 4.36

As you can see, we only need .13 inches to tie 1993 for 5th place.  Normal May rainfall at PDX is 2.47 inches.  Most of this months rain has fallen since May 16th.  May is the first above normal precipitation month since December when PDX was better than 2.00 inches above normal with 7.56 inches of rainfall.

Other Monday rain totals:  Astoria .93 inches, Tillamook 1.14, Kelso .38, Vancouver .73, Troutdale 1.28, Hillsboro .47, McMinnville .45, Salem .51, Hood River .32

Several of Monday's rain totals were records for the date, including PDX and Vancouver. 

Wow, what a difference a week makes!  May 15th ended with PDX total rainfall for the month reaching .20 inches.  We were still talking about the driest May in recent memory and parts of the metro were continuing to see the driest 5 month start to a year in recorded history. 

This week's upper level low has dropped 2.43 inches of rain over the past three days.  The total is just shy of 2.47 inches, which is considered normal for the entire month of May.  PDX began today with 2.94 inches of total May rainfall.  The much needed moisture has returned our grass to the expected deep green color this time of the year.  Widespread moisture this week and more than a foot of Cascade snowfall will also help delay the start of wildfire season. 

As a forecaster, it is frustrating to realize the lack of skill, modern meteorology still has in foreseeing a sudden change in weather pattern.  Forecast outlooks did correctly call for below normal spring rainfall but did not offer a clue to this week's heavy rain and change to wet, cooler weather pattern now expected through the first 10 days of June.  To be clear, this past week's weather was correctly projected on the 7day forecast, but the fact that we would shift into a long stretch of cooler, wet weather was not picked up.

The only way to describe our dry spring weather so far is "surprising!" Going back to March 1st, today will become the 38th dry day with no more than a trace of rain.  Compare the number to recent years.

Dry days March - April (a trace or less at PDX): 

2012 - 21 days

2011 - 14 days

2010 - 17 days

2009 - 22 days

Forecast outlooks continue to show below normal rainfall through July.  Current forecast charts show no chance of rainfall for Portland through Friday of next week.  With projections of an early and possibly bad wildfire season, you have to wonder just how dry we could be?  The driest May of record at PDX had .10 inches of total rainfall back in 1992.  The driest June only recorded .03 inches in 1951 and July has had no measurable rainfall more than once.

This past week, I visited the National Weather Service and spoke with several meteorologist about our record dry start to the year.  Everyone agreed there were no known indicators to predict how dry we have been since January 1st or if we will approach records for lack of rainfall in the coming months.  There is concern that we are about to enter the driest climate portion of the year, meaning normal rainfall is typically low and below normal rainfall can be next to nothing until next October.  The temperature forecast looking forward to summer is uncertain but does not show any strong indication of warmer than normal numbers.

A number of grass fires this past week may be a signal of an early fire season to come.  As of April 27th, total rainfall at PDX since January 1st is 8.33 inches.  The total is only 57 percent of what is considered normal.  When compared to a year ago when more than 20 inches of rain had fallen, this spring measures to be even drier.  In fact, so far this spring has been our first non-soaker since the spring of 2009. 

The latest outlook from the National Weather Service calls for well below normal rainfall this May and below normal precipitation through the months of June and July.  The temperature forecast has little confidence but likely favors near normal conditions. The water year surplus that we quickly built last fall will likely become a deficit this coming week with another stretch of sunny, warm days in the forecast.

The wet spring months of the past few years led to a late start to the fire season.  Experts say a key ingredient to a calm fire year is to have a short season.  It is feared that our dry spring and continued dry forecast could make this coming season one of the longest in recent years.  Of course fire season is always greatly dependent on human behavior and the number of lightning strikes.  One we have the power to control and one we do not. 

Peak viewing of the Lyrid Meteor Shower occurs this weekend and the weather is expected to deliver partly cloudy to clear skies!   Astronomers predict peak viewing April 21 and 22nd.  The shower is the result of the earth entering a stream of debris from ancient Comet Thatcher.  A typical viewing with good weather conditions will average 5 to 20 meteors per hour.  Some years can produce outbursts reaching 100 meteors per hour. 

The tail left by Comet Thatcher contains flakes of comet dust, no bigger than grains of sand.  The comet dust strikes Earth's atmosphere at speeds of 110,000 mph and disintegrate as steaks of light.  Best viewing is to look straight up and slightly to the east.  Meteors can be seen in all directions. 

Wednesday morning's chance of near freezing temperatures in the metro may be for much of the area, the end of freezing temperatures until next fall.  I will remind those of you that live in out-lying areas, such as Battle Ground or Hillsboro, the average final freeze for your area is roughly May 1st.  The average final spring freeze for the Portland city center is closer to April 1st.

The current batch of cold air overhead will exit Wednesday.  As much warmer air builds this weekend and much of next week, it appears the threat of freezing temperatures for the majority of the metro area will end.  The green light will be illuminated this weekend for the planting of annuals and other tender vegetation.

If PDX stays above freezing this week & the remainder of spring, the period of freezing temperatures will hold at a short 71 days.  PDX did not freeze last fall, in fact the first freeze occurred on Dec. 29th.  As of right now, the final early spring freeze was back on March 9th.  The average growing season for Portland is 223 days.  The above dates would give the past 12 months a growing, meaning frost-free period of 294 days.  

A low pressure center pushed inland near and north of the Portland metro area Saturday night and early Sunday morning.  The center of low pressure  produced gusty winds between 40 and 52 mph across the inland metro valley.  Strongest winds occurred between 4:00 a.m. and 6:30 this morning.  Oregon City reported the highest gust of 52 mph at 6:15 at an elevation of 50 feet.

Here is a list of peak wind gusts: 

Happy Valley 45 mph

Estacada 44 mph

Molalla 44 mph

Salem  41 mph

Troutdale 44 mph

Portland (PDX) 41 mph

Tualatin  41 mph

The strong winds produced power outages and scattered tree damage.  Clackamas county seemed to be the worst hit.  Peak wind gust near the coast was 61 mph at Lincoln City.  High Coast Range elevations reported 70 mph wind gusts.  Mt. Hood at 7,000 feet, above Timberline Lodge reported an 89 mph gust at 6:00 a.m.

High winds were in the forecast, including the Sunday morning timing.  Calmer weather is expected to start the new week.