Rod's Weather Headlines

CELESTIAL EVENT OF A LIFETIME

Rare transit of Venus viewing: June 5, 2012 from 3‐9 p.m. at OMSI

Portland, OR (May 29, 2012) The last to occur in our lifetime, a rare celestial event called a transit of Venus is set to transpire on Tuesday, June 5, 2012. The Oregon Museum of Science and Industry (OMSI) and the Rose City Astronomers Club will host a free transit of Venus viewing party in OMSI’s south parking lot for this exciting occurrence.  Filtered solar telescopes and indirect viewing methods will be available for safely observing the transit.  NASA TV and San Francisco’s Exploratorium will display the transit of Venus from viewing sites around the world. OMSI will show their broadcasts live in the museum’s auditorium.  The auditorium doors will open at 2:30 p.m. and admission to the televised transit is free (no reservations required). 

A transit of Venus is the observed passage of the planet Venus across the disk of the sun.  It occurs when Venus, orbiting the sun “on the inside track,” catches up to and passes the slower Earth.  To viewers, Venus will appear as a small dot in the foreground, making its passage (or “transit”) from left to right across the face of the sun. 

For Portland, the transit will commence at 3:05 p.m. when Venus appears to the east of the Sun.  The greatest transit movement will occur at 6:29 p.m. when Venus appears just off-center to the right of the northern area of the sun. The sun will set at 8:55 p.m. and the transit will end at 9:44 p.m. as Venus exits to the west of the sun.

It is important to use eye protection or indirect viewing techniques when observing this transit activity. Viewers should use only an approved solar filter which blocks dangerous ultraviolet and infrared radiation as well as visible light.  Special solar viewing glasses are available at the OMSI Science Store for $2 (www.omsi.edu/science-store).

Transits of Venus always occur in pairs that are spaced eight years apart.  Each pair of occurrences is then not repeated for more than a century. For example, the last transit of Venus took place on June 8, 2004, and of course the next one will be visible this June of 2012. The previous pair of transits occurred in December, 1874 and December, 1882. After 2012, the next transits of Venus will take place in December, 2117 and December, 2125.

Learn how to view the Venus transit with the experts by joining us for the event at OMSI! You can find more information by visiting www.omsi.edu/starparties or by calling 503.797.4000.

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The above is courtesy of Jim Todd, OMSI Planetarium Manager

Tuesday's forecast calls for likely showers.  We will hope for breaks in the cloud cover and a look at the show. 

As of noon today, May 31st, PDX has received 14.51" of rainfall since March 1st.  The total becomes the all-time wettest meteorological spring, ( March, April, May), at PDX since records began in 1940.  Normal precipitation through the period is 8.88 inches.  Basically, we have received nearly 2 extra months of rainfall since March 1st. Last year's wet spring dropped 14.30"of rain.  The old record is 14.50", back in 1997.  

Here is the break down of spring rain this year:  

March 7.89" - all time PDX record and 4.21" above normal 

April 3.25", .52" above normal

May so far 3.37", .90" above normal

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Here is a break down of wet days this spring and 2011:

March - May 2011 had  65 days with measurable rainfall.

March - May 2012 , 52 days with measurable rainfall.  

Here is the difference of the last two springs:  2011 had 8 heavy rain days of .50" or greater.  Zero days had an inch of water.   This spring has had 9 days, including 3 days with 1.00" of rain or greater!  Of course making the list was the 1.03" of rain from thunderstorms on May 26th.  

Outlooks continue to call for below normal rainfall June, July & August.  

Portland's dry May streak of 14 days with no trace of rain, missed the record for consecutive dry days by one!  The May PDX record is 15 straight days with no rain, back in 1995.  As you know, much of this coming week will see measurable rainfall.  A return to drier, more pleasant weather is expected next week and into the 1st of June. 

The updated outlook through the month of August:

1.  The northwest is in the bulls-eye of below normal rainfall for June and to a lesser degree, July & August.  Realize that a below normal rain forecast for summer, means we might not see much of anything!  July is a month that can see zero precipitation. 

2.  Temperatures are expected to be slightly below normal for June, which could be a sign of numerous cloudy mornings.  The temperature outlook for July & August shows no confidence, meaning an equal chance of below, normal or above.  

With dry weather expected this summer, I will be watching for any sign of possible record heat.  At this time, there is no reason to believe we will get crazy hot.  Stay tuned.

The Moon passes in front of the Sun on Sunday, May 20, bringing an annular eclipse to the border between Oregon and California and a partial eclipse to the rest of the Pacific Northwest.  OMSI and Rose City Astronomers Club will host an eclipse viewing party at the east parking lot of OMSI. The free event will begin at 4:30 p.m., feature live, dramatic interludes by Portland Taiko, a premiere local Japanese drumming ensemble, and end at 7:00 p.m. Filtered solar telescopes and special viewing glasses will be available for safely viewing the Sun.

This unique phenomenon occurs when the Moon is directly between the Earth and the Sun, but at a farther distance from the Earth than with a total solar eclipse.  As a result, the Moon appears too small to completely cover the Sun, and we observe the Sun as a ring (or “annulus”) surrounding the Moon.  At 6:24 p.m. PDT, viewers along the center line in southwestern Oregon will see the Moon block 87% of the Sun's diameter; this will last 4 minutes and 47 seconds.  A much broader region – from as far north as the Arctic Circle to the southern Pacific Ocean - will experience a partial solar eclipse. The path of annularity will be visible from China to the southwestern United States.  

For Portland, the eclipse gets underway at 5:04 p.m. when the Moon makes first contact with the Sun.  The maximum eclipse accords at 6:21 p.m. when the Moon covers 81 percent of the Sun's diameter at 25 degrees above the western horizon. The partial eclipse will end at 7:29 p.m. as the Moon exits.

Most important, do not view any of this eclipse without eye protection.  Even during the annular phase, the Sun shines brightly enough to damage your eyes if the eclipse is observed without a protective filter.  Use only an approved solar filter which blocks dangerous ultraviolet and infrared radiation as well as visible light.  The special solar viewing glasses are available at the OMSI Science Store for $1.99.

This will be the first annular eclipse visible in the United States since May 10, 1994. The last partial solar eclipse for Oregon was on June 10, 2002. After the May 20 eclipse, the next partial eclipse will be on October 23, 2014.  The next annular eclipse for the U.S. won't come until October 14, 2023.  Before then, observers will have the good fortune to enjoy an even more spectacular eclipse: a total eclipse visible from most of Oregon, on August 21, 2017.

Learn how to view the eclipse with the experts and be a part of the event at OMSI!  For more information or to check for possible weather-related cancellations, call the OMSI Star Parties Hotline, 503.797.4610 #3 then #5, or check the OMSI Star Parties web site: http://www.omsi.edu/starparties

Google Map: http://xjubier.free.fr/en/site_pages/solar_eclipses/ASE_2012_GoogleMapFull.html

WARNING: ANY TYPE OF SOLAR ECLIPSE IS NOT SAFE TO VIEW WITHOUT ADEQUATE EYE PROTECTION
Sunglasses DO NOT provide adequate eye protection: http://eclipse.gsfc.nasa.gov/SEhelp/safety.html

Jim Todd

OMSI Planetarium Manager

(Courtesy Mr. Jim Todd)

We may soon pay the price for our abrupt change into a mostly dry weather pattern.  Forecast outlooks call for our area to see below normal precipitation June, July and August.  Early spring rains have produced heavy brush and grasses across the Northwest, which are now beginning to dry.  Fire weather meteorologists at the Northwest Fire Coordination Center project the wildfire season to begin the final week of June.  Once started, wildfire season will likely continue through September.  The mentioned season is near normal but much longer than our last few years.  Last spring's record June rain delayed wildfire season until August.  Experts say there is a strong correlation between the length of the fire season and it's severity.  Last year's season was roughly 60 days.  This year's wildfire season will be more than 100 days.  Highest fire danger is reported to be southeastern Oregon, where the winter snow pack was far below normal. 

The number of wildfires is dictated largely by lightning strikes.  I am told 40% of Northwest wildfires are started by humans.  The 40% statistic has been flat over the past 20 years, which means we need to listen more closely to Smoky Bear.  I was surprised to learn that human behavior is as careless today as 20 years ago when it comes to triggering a blaze.

Rod Hill

May's full moon takes place at 8:35 p.m. PDT on Saturday, May 5. As temperatures warm and the ground thaws, flowers are abundant and in bloom by this time. Thus, May's moon is called the Flower Moon; but it can also be called the Corn-Planting or Milk Moon. When we look at the full moon on Saturday, it will be just 221,705 miles away making it the Moon's closest approach to Earth in 2012.

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 2012 May 5, the full moon will occur within a minute of reaching actual perigee position (perigee at 8:34 p.m. PDT, and the full Moon at 8:35 p.m. PDT), but the actual perigee this month will be just a bit farther than the one of last year. 

According to the NASA JPL Solar Systems Dynamics (Horizons) computer, the "super-Moon" of 2011 March 19 was a tiny bit bigger than the "super-Moon" of 2012 May 5/6:

2012-May-06 angular diameter: 2008" (= 0.5577 degree)

2011-Mar-19 angular diameter: 2010" (= 0.5583 degree)

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 above is courtesy of Jim Todd

OMSI Planetarium Manager

Through 27 days of April, our weather is showing signs of getting back to normal after the wettest March at PDX in the record book!  At just over 3.00" of rainfall, this month is above the April normal of 2.73", but closer to normal than record territory.  Temperatures this month have been warmer than average 12 days, cooler than average 12 days and normal 3 days when taking the 24 hour mean temperature.  The winter La Nina cycle has ended.  The outlook calling for much improved weather starting this month has come true!

Forecast outlooks from the National Weather Service call for May to be cooler and drier than normal.  The 3-month outlook May, June & July calls for temperatures likely near normal and drier than average rainfall.  If true, our spring weather and early summer will be the most pleasant in recent memory.    

Here are the normal rainfall amounts for the next three months:

May  2.47"  

June 1.70"

July   .65"

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Remember, we do not live in Arizona.  A few wet spring days, followed by a few dry days is weather to celebrate.  

Average number of days with at least .01" of rainfall:

May  13 days

June   9

July    4

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Let's all look forward to nice weather in the weeks ahead;  not cold, not hot and not wet - at least by our standards.

A new moon tonight with clear skies will make for perfect viewing of the meteor shower.  Experts say 10-20 meteors an hour could be seen.  The earth is passing through a stream of debris from ancient Comet Thatcher.  Tonight, April 21st will be the peak viewing!  The shower can be seen in all directions.

NASA Science News for April 18, 2012

Astronomers and astronauts are joining forces for an unusual astrophotography experiment during the peak of the Lyrid meteor shower on April 21st.

ISS Flight Engineer Don Pettit will be operating the camera on the space station.  "Even though his equipment was designed for tasks other than meteor observing, Don is a skilled astrophotographer, and we have every confidence that he will maximize the chances of capturing a Lyrid from 400 km above Earth's surface."

As the Space Station passes over North America multiple times on the night of April 21st, a network of all-sky cameras--some operated by amateur astronomers and others by NASA--will be recording the shower.  In Bishop, California, a group of high school and middle school students will launch a helium balloon to the stratosphere.  The payload floating some 40 km above Earth’s surface will carry an experimental low-cost meteor camera and recorder developed by the Meteoroid Environment Office.

FULL STORY: http://science.nasa.gov/science-news/science-at-nasa/2012/18apr_lyrids/

Oregon astronaut Don Pettit will take part.

The above is courtesy of Mr. Jim Todd, OMSI Planetarium Manager

As you know, I am doing all I can to find reasons to forecast near normal rainfall April through June.  Forecast charts continue to show near normal rainfall through the first 20 days of this month.  (A huge change from March!)  

I find it interesting that the record March of 1957 was followed by dry weather all the way into summer.  Take a look at monthly rainfall:

March 1957:  7.52"  (at the time was a new PDX rainfall record)

April:              1.84"   (very dry)

May:               1.97"  (still below normal)

June:                .73"   (about 1/2 of normal)

July:                 .19"   (very dry)

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The above likely means very little, but the dry months following a record March should give us a little promise!  The winter of 1956-1957 was La Nina episode, weaker than the current La Nina that is rapidly ending.  The spring months of 1957 were going into an El Nino event.  Our current transition is leading us into a "neutral" pattern.

Here is hoping for more pleasant weather than not over the coming months. 

Final March 2012 PDX precipitation was 7.89".  This total becomes the all-time March record for PDX.  (Records began in 1941.)  The old record was 7.52" back in 1957.  The all-time record for all Portland locations, dating back to 1871 is 12.76", which fell in the year 1873.  I have received several reports of more than 10.00" of rain this month from the Canby, Oregon City and Damascus areas.  This month has seen 22 days with measurable rainfall.  Last March of 2011 holds the record of consecutive wet March days at 23 & March days with rainfall at 28 days.  The 2011 rainfall of 6.43" stands in 6th place all-time for PDX.  Normal March rainfall is 3.68 inches.

Forecast charts are hinting at closer to normal rainfall for the months of April, May and June with below normal temperatures.  I reported on KGW last week, that beginning in April, we would see close to normal precipitation.  If our weather turns out to be "normal" in April, it would seem very, very dry!  The April average is 2.73".  Lets pray for normal.

Rod Hill