A Very Dry April with Extraordinary High Pollen Levels: But Change is Coming
April in our region has not only included "dry storms" of desiccated air and lots of sun. Not surprisingly this month has been extraordinarily dry in terms of precipitation, with Seattle only receiving .01 inch this month.
Some folks are already asking me about drought---but as we will see below, such worries are premature.
Let's start with the percentage of normal precipitation for the past two weeks, which is a study in contrasts. Portions of the Northwest have received less than 25% of normal, while southern California have been crazy wet, with a large area being hit by 800% of normal. You read that right.
Los Angeles and San Diego have been like Seattle in January. Obvious this is good for delaying the wildfire season in a large portion of the Golden State.
Although April has been dry in the Northwest (because the weather systems have been going into California), our long-term precipitation is generally fine. For example, below is plot of the accumulated precipitation at Seattle over the water year starting October 1 (purple is observed, cyan is normal). Almost exactly normal right now. That is why our plants look green and happy--the subsurface moisture is ok.
But relief is on the way....eventually.
The latest European Center (EC) model runs are insistent that rain will return in the second half of April.
The high resolution EC forecast (see below, from the wonderful weatherbell site) shows substantial rains during the last week of the month (green bars are rain)--about 1.1 inch in total. Temperatures will fall as well, mainly back into the upper 50s, which is normal.
A more regional view, looking at the average of the EC ensemble (running the forecasts many times, each a little different) for the total accumulated precipitation through May 2, shows a return to the normal pattern, with several inches (2-4) over the western side of the Northwest and drier conditions over California. So enjoy the beautiful weather today, by the end of the month cloudier, cooler, and wetter conditions will return. And thus suffering from tree pollen allergies can expect relief.
Some folks are already asking me about drought---but as we will see below, such worries are premature.
Let's start with the percentage of normal precipitation for the past two weeks, which is a study in contrasts. Portions of the Northwest have received less than 25% of normal, while southern California have been crazy wet, with a large area being hit by 800% of normal. You read that right.
Los Angeles and San Diego have been like Seattle in January. Obvious this is good for delaying the wildfire season in a large portion of the Golden State.
Although April has been dry in the Northwest (because the weather systems have been going into California), our long-term precipitation is generally fine. For example, below is plot of the accumulated precipitation at Seattle over the water year starting October 1 (purple is observed, cyan is normal). Almost exactly normal right now. That is why our plants look green and happy--the subsurface moisture is ok.
This dry spell was timed perfectly with the release of tree pollen in our region to provide a tree-pollen storm during the past two weeks (precipitation reduces pollen concentrations in the air). Take a look at the values from pollen.com for Seattle, shown below. Yikes. It has been very high for the past week or two. Miserable for those afflicted with allergies.
The latest European Center (EC) model runs are insistent that rain will return in the second half of April.
The high resolution EC forecast (see below, from the wonderful weatherbell site) shows substantial rains during the last week of the month (green bars are rain)--about 1.1 inch in total. Temperatures will fall as well, mainly back into the upper 50s, which is normal.
A more regional view, looking at the average of the EC ensemble (running the forecasts many times, each a little different) for the total accumulated precipitation through May 2, shows a return to the normal pattern, with several inches (2-4) over the western side of the Northwest and drier conditions over California. So enjoy the beautiful weather today, by the end of the month cloudier, cooler, and wetter conditions will return. And thus suffering from tree pollen allergies can expect relief.
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