COVID is Collapsing in Washington State: Just as Predicted!

Three weeks ago, there were fears that COVID was increasing again and Governor Inslee was thinking of backtracking on reopening the State.  

Local papers were carrying stories warning that herd immunity was impossible.

But a careful analysis of the numbers, as provided in my blog of May 1st, showed the opposite:  that Washington COVID cases were about to plummet.

And that is exactly what has happened.   

Consider a plot of Washington COVID cases from March 1st to May 16th below, showing both daily cases and a 7-day average (data from the WA Department of Health website).

The daily cases (and 7-day average) peaked in late April and then declined rapidly by roughly 40% through mid-May.  Note there is a weekly cycle of collection, with some days with better collection than others.

Washington State COVID is collapsing.  And it makes perfect sense.

If you read my earlier blog, the analysis started by trying to get a measure of the percentage of residents (of each state) that possessed antibodies to COVID,  This was done by adding the percentage vaccinated to the percent that was immune because of contracting COVID.  

You simply can't look at vaccinations alone, as some have done.  And to estimate the percentage with COVID immunity, I multiplied the number of reported cases by three, since there are many cases that are not reported or are asymptomatic.   There is strong support in the scientific literature for this multiplier, with several papers/reports based on serology data.

Then I compared this measure of the population's antibody rate to the change of COVID for the previous two weeks (last half of April) for all 50 states.

 I was stunned with the result.  Once my measure of COVID immunity got to roughly 70%, the number of cases collapsed.   A transition to herd immunity was occurring.

Oregon's cases dropped like Washington's:  Exactly as Expected

At the end of April, Washington State and Oregon were national outliers with rising cases, while the rest of the country had declining new cases of  COVID.  Why?  My index explained it all. WA and OR were LOW outliers in my index, mainly because our states had not had as many COVID occurrences.   Thus,  WA and OR were fertile grounds for COVID spread. 

But we were getting close to the 70% level and within days we would cross the magic number as vaccinations continued apace and plenty of folks (mainly young people) were getting COVID.

And it happened just like clockwork.

Our state crossed the threshold of approximately 70% total of my immunity index in early May and the state COVID case rate rapidly declined.  

And it won't be going up....both because increasing numbers are getting the vaccine (and, yes, some are catching COVID).  Plus, the warming weather is highly favorable, with people spending more time IN THE COMPLETELY SAFE outdoor air and opening their windows.  Plus, increased sunshine is a potent killer of COVID.  Only a radically different viral variant could change the story....and there is no hint of that at this point.

But what is happening now you ask?  

And is every country in Washington State showing declines?   The answer is no and that demonstrates the power of my approach.

Consider the ten most populated counties in Washington State.  Here are their corresponding immunity indices.  There are BIG differences. King and Yakima counties have the highest indices (about .7--70%), mainly because both had a lot of COVID cases.  But Whatcom and Clark counties are low--around .55.

So what happened in these counties the past months?  First, the counties with high values (over .7)

King County has been in decline all month.

And Yakima has been falling for longer because many COVID cases got them to .7 early.

Contrast their experience with Whatcom County, where the immunity index is low.  Rising well into May.  Same with Clark County.

I have looked at all counties in the State and the signal is clear:  once the immunity index gets to approximately .70, the case rate declines.

I could show you more, but the message is clear, an immunity index based upon BOTH past infection and vaccinations appears to be highly useful in explaining past COVID cases and provides a way to see into the future.    

Several epidemiologists contacted me after my first blog, and they supported my analysis.  And if any have any concerns with the above, let me know.   If there are flaws, I want to know them.

This is a good example of the scientific method:  creating a hypothesis based on data and then making a prediction based on the hypothesis (that COVID herd immunity accelerates when the immunity index gets to roughly .7).   If the prediction fails, one goes back to the drawing board. This time the hypothesis appears to be supported by new data.

My question:  why isn't the Washington State Department of Health doing such an analysis?

The Daily Cycle of Coastal Low Clouds and Flowing Fog

 During the middle to late spring, the northeastern Pacific fills will low clouds, as illustrated by the visible satellite image from two days ago (shown below).

And during fair-weather periods, as we have experienced during the past week, there is a daily rhythm of clouds along the coastal zone east of the Cascade crest, with clouds pushing in overnight and burning back during the day.    

Consider what has happened during the past day.

Last night at 5 PM, there were lots of low clouds along the coast and a tendril of stratus/fog extending into the Strait of Juan de Fuca

But overnight, the low clouds surged inland, as shown by the image at 7 AM.  Coastal river valleys filled with clouds and stratus and fog pushed eastward into the Strait of Juan de Fuca, the Chehalis Gap (south of the Olympics), and along the Columbia River Valley.

Central Puget Sound was fog free this morning as were the western slopes of the Cascades.

By noon, the low clouds had pulled back to the coast

And there was further retreat by 2 PM.

This cycle of nighttime influx and daytime retreat has been going on for days.  

You, of course, are asking why.

One reason is that the pressure difference between the coast and inland varies over the day.

The general pressure pattern over the region for the past week has been high pressure offshore and lower pressure inland (see sea level map for 5 AM on Friday).  The lines on the map are isobars of constant pressure, and you can see the high pressure offshore and lower pressure east of the Cascade crest.  This pressure pattern (high pressure offshore, low pressure inland) tends to produce northwesterly winds along the coast, with a weak onshore component of the low-level winds.

This pressure pattern tends to push the offshore stratus/fog inland across western Washington.   But the pressure pattern is modulated over time, with warming inland tending to cause the pressure to fall, which produces a stronger onshore pressure difference (higher pressure offshore, lower pressure inland).  This increases the onshore (westerly) winds at low levels, which help to bring in low clouds.

Want proof?    Here is a plot of the difference in pressure between Hoquiam on the coast and Seattle.  Positive values mean Hoquiam has higher pressure.  The daily heating caused the onshore pressure difference to increase during the afternoon and early evening to about 1.9 hPa (hPa is a unit of pressure) around 10 PM.  This helped push the stratus in.    Nighttime cooling over land caused the difference to decrease rapidly overnight. Then heating today resulted in the onshore pressure difference (or gradient) increasing during the day, which will cause the stratus to push in again tonight.

The wind effects are not the only mechanisms for the diurnal (daily) changes in low clouds. 

 Heating during the day causes vertical mixing that helps destroy low clouds from its edges. 

 Keep in mind that the low clouds are quite shallow, something that is evident from the view of the low clouds from the Seattle panocam this morning around 9 AM.     Note that the tongue of the stratus barely made the entrance to Elliott Bay.

A few days ago, the tongue of morning status got a bit further south and crested over portions of West Seattle.  Here is an extraordinary video taken by Michael Snyder of what happened.  Quite beautiful.  It looks like water pushing a boulder.