Rod's Weather Headlines

With no rain in the forecast Thursday, Sept. 30th, the 2009-2010 water year will end at PDX with 39.24" of total precipitation.  The amount is 2.17" above the 30-year average of 37.07 inches.  Finishing above normal is an amazing feat when you consider the wet season months of November - February were all below normal.  May, June and September proved to be the wet months of the year in terms of surplus amounts.  The water year ending is only the 3rd normal or above season since 1999 - 2000.  

In terms of climatology, I consider a "wet" water year to be 40.00" of precipitation or more.  The last "wet" year was 45.93" back in 1998-1999.  I am sure you recall the soaker of 58.68" from 1996-1997!  With the La Nina winter approaching, we are due for a "wet" water year like we have not seen since the 1990s.  Most winter forecasts call for heavy rains.  As I always say, we'll see.

Latest information on the La Nina pattern in the equatorial waters of the Pacific show the water is continuing to cool.  Current reports show water temperatures averaging 1.8 - 3.6 degrees F below normal.  Cooling is expected to continue into January.  This makes the forecast for a moderate to strong La Nina likely.  The expected jet stream flow pattern will place a jet core into southern Oregon, near the California border.  We will be in the north and cold quadrant of the flow and close to potential heavy rain bulls-eyes.  All data continues to suggest an active, wet winter.  This could be the first real "soaker" since the 1990s.  Also of concern will be the potential for high wind events, primarily at the coast.  I still do not believe there is any confidence in predicting valley snow.  

In the short term, forecast charts show warm and mostly dry days through the first ten days of October.  Please enjoy the pleasant days ahead.  We may need our strength for later!! 

The autumnal equinox is Wednesday evening, (9-22-2010), at 8:09 p.m.

Characteristics of the equinox include:  The sun directly over the equator, near equal hours of daylight and darkness and the sun rising due east & setting due west.  

Portland will have seven minutes more daylight than darkness as fall begins.  Here are the solar times for Thursday,  the first full day of fall:  sunrise:  6:59 / sunset:  7:06

This Saturday the 25th will have equal daylight and darkness.  Sunday the 26th will have three minutes more darkness than daylight.  sunrise:  7:03 / sunset:  7:00 pm

The outlook for October - December continues to call for above normal precipitation.

Happy Fall!

  September has set or tied a total of six records to date at PDX:

Sept. 7,  1.55" daily rain record

Sept. 7,  1.03" between 8:00 & 9:00 pm.  All-time Portland one-hour rain record

Sept. 9,   High of 65 ties the daily record for low-high temperature

Sept. 16,  Low of 61 record for high-low temperature

Sept. 17,  Low of 62 record for high-low temperature

Sept. 18,  .97" daily rain record

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Normal September rainfall at PDX is 1.65 inches.  To date, the airport has received 3.18".   The all-time September record at PDX is 4.30" back in 1986.  Heavy rain possible next Monday and could push the rain total close to the monthly record.  The all-time record for Portland, dating to 1871 is 5.52" back in 1927.

The rain outlook calls for above normal precipitation October, November and December. 

Below is a record summary from Saturday's heavy rainfall.  The research and article are  courtesy of Steve Pierce, with the local chapter of the American Meteorological Society:

"Record setting rainfall continues to wilt the rose city, as summer officially comes to an end in the next few days. For the second time in the past 10 days, Portland has set a daily rainfall record. Heavy showers rolled through the Portland area this evening setting yet another rainfall record. The Portland International Airport has set a new one day rainfall record for September 18th. As of 10pm the Portland airport has picked up 0.88" of precipitation for the calendar day. The old daily record for today was 0.82" set in 1998. PDX received 0.45" in just one hour tonight between 9pm and 10pm and 0.76" just this evening from 7-10pm. Portland has now received 2.93" of rainfall for the month of September, which is quickly rising up the charts as one of the wettest on record. As of 10pm, Portland currently sits in the #12 position for all-time wettest September's on record with almost half of the month yet to go. Portland only needs a few hundredths of an inch more of rainfall to quickly ascend into the top 10 and a little more than 1" of precipitation in order to overcome the all-time wettest September on record which was set in 1986 with 4.30" of rainfall. Additionally, Portland is now a full 2" above normal for the month of September. That is nearly 200% of normal. A normal September in Portland sees a little more than 1.50" of rain for the entire month, when averaged from 1940-2010. We have nearly doubled the average in just the first half of the month. After recording the coldest summer in 17 years, along with the wettest June on record, September is certainly leaving its own mark in the record books.

No Dead Zones Observed Or Expected As Part Of BP Deepwater Oil Spill

Report finds decreased, but stabilized levels of dissolved oxygen in gulf areas with subsurface oil.  

The National Oceanic and Atmospheric Administration (NOAA), the U.S. Environmental Protection Agency (EPA) and the Office of Science and Technology Policy (OSTP) released a report today that showed dissolved oxygen levels have dropped by about 20 percent from their long-term average in the Gulf of Mexico in areas where federal and independent scientists previously reported the presence of subsurface oil. Scientists from agencies involved in the report attribute the lower dissolved oxygen levels to microbes using oxygen to consume the oil from the BP Deepwater Horizon oil spill. 
 
These dissolved oxygen levels, measured within 60 miles of the wellhead, have stabilized and are not low enough to become “dead zones.” A dead zone is an area of very low dissolved oxygen that cannot support most life. Dead zones are commonly observed in the nearshore waters of the western and northern Gulf of Mexico in summer, but not normally in the deep water layer (3,300 – 4,300 feet) where the lowered oxygen areas in this study occurred. Dead zones, also known as hypoxic areas, are defined in marine waters as areas in which dissolved oxygen concentrations are below 2 mg/L (1.4 ml/L).

“All the scientists working in the Gulf have been carefully watching dissolved oxygen levels because excess carbon in the system might lead to a dead zone. While we saw a decrease in oxygen, we are not seeing a continued downward trend over time,” said Steve Murawski, Ph.D., NOAA’s Chief Scientist for Fisheries and the head of the Joint Analysis Group. “None of the dissolved oxygen readings have approached the levels associated with a dead zone and as the oil continues to diffuse and degrade, hypoxia becomes less of a threat.” 

Tuesday evening between 8:00 pm and 9:00 pm, 1.03" of rain was recorded.   The amount is the highest hourly rain total since PDX began keeping the statistic in 1953.  The spotter on duty, said most of the rain fell in twenty  minutes!  The previous record was .93" on May 24, 2008.  Total rainfall Tuesday at the airport was 1.55" of rain.  The amount is the 5th wettest September day at PDX and a new rain record for September 7th.  The old daily record was .26" in 1951.  Tuesday was also the wettest day in Portland since 2.49" of rain fell on Jan. 1st 2009.  Also, the rainfall puts the water year total at 37.45", which means we made it!  The average rainfall between Oct. 1st and Sept. 30th is 37.07 inches.  Portland's water year for 2009-2010 goes in the book as above normal!

To check area rainfall amounts, go to the Northwest forecast page and click on daily climate reports above the Northwest map.  More rain totals can be found by clicking on individual cities on the metro and Northwest currents maps.  

Below is a copy of an email response I wrote to a KGW viewer who asked my thoughts regarding this winter's La Nina season:

Here are my thoughts on a La Nina winter.  The only high confidence of the forecast is
that we will likely have an active winter.  Meaning, a consistent westerly flow pushing
numerous fronts inland.  The result will be normal to above rainy days.  Little confidence 
as to whether or not we will see a high number of strong storms.  I would say, the coast will 
likely have a handful of descent high wind events -much more so than last year.  Total precipitation
will likely be at least close to normal and may be above, although I believe it has been over 10 years and closer to 15 since we have had a true wet winter.  (Actually we are do for a wet winter!!)  Snowpack over 
the Cascades will be nice and hefty, assuming snow levels average near or below 4,000 feet.  I have seen
La Nina winters where the snow level was often above 5,000 feet.  As for the valley, the simply truth
is that our snowfall is too sporadic to have confidence in a forecast.  I will say, our larger snow events
are more typically during so called neutral winters.

To recap:  Wet winter in terms of the number of rainy days, a handful of high wind events at the coast
          and high hopes for a hefty Cascade snowpack.

Make sense??

Rod Hill

Meteorological summer is June, July, August.  Below is a summary, courtesy of Steve Pierce, local chapter vice-president, American Meteorological Society:

PORTLAND SUMMER COOLEST IN 17 YEARS!

"Portland just finished its last full month of summer 2010, and with it comes the distinction of being the coldest "meteorological" summer (June, July & August) in the past 17 years. The last time Portland experienced a summer this chilly was in 1993. This was the exact opposite of last summer, which was the warmest summer on record at the Portland International Airport (1941-2010). This was also the first summer since summer of 1976 (nearly 35 yrs) that all three summer months (June, July and August) recorded back-to-back below normal average monthly temperatures. In fact, Portland has now been below average for five back-to-back months, beginning in April and continuing through August. Either way you slice it, it was a chilly summer by Portland standards. Summer 2010 will also be known as the summer that featured large temperature swings from one extreme to the other, along with morning low clouds that persisted longer than normal." 

Other facts:  

* 10th coldest June on record at the Portland Airport.  

* Single wettest June ever recorded (1941-2010). More than four and a quarter inches of rain fell. 

Hurricane Earl will get lots of media attention in the coming days. The Category 4 storm is showing increased likelihood of moving close to the east coast of the United States.  Current projections take the storm center near the outer banks of the Carolina's Thursday night and Friday morning.  The track continues to parallel the U.S. coast line all the way north into New England.  Here at the 5 classes of hurricane strength defined by wind speed:

#1 74-95 mph sustained winds

#2  96-110 mph

#3  111-130 mph

#4  131-155 mph (EARL)

#5  >155 mph

You may follow the Hurricane Center Forecast Track at:   www.nhc.noaa.gov

The above link will take you to a map of the storms.  Click on each storm to see the forecast path.