Category Archives: Commentary

SO WHAT’S WITH THIS COLD WEATHER?

People are asking me, what’s with this prolonged winter weather and cold?

One thing not talked about recently is the solar cycle.  We are about to enter a solar minimum.   The solar cycle is a regular, periodic change in sunspot number and the mimimum correlates with reduced total solar irradiance.

The solar cycle repeats ever 10-11 years.

The SORCE PROJECT has been measuring the total solar irradiance since 2003.

SORCE project total solar irradiance
SORCE Project Total Solar Irradiance

The previous solar minimum was in 2009.  The minimum has been shown to have a total solar irradiance that is reduced by about 0.5 -1 watt/m2.  Over the surface of the entire earth, that reduction adds up.

Maybe you’ll recall that the summers of 2009 and 2010 were usually cool?  I think the coming summers of 2018 and 2019 might be similarly cool.   (We’ll find out!)

So if it’s a cool summer, remember, it may be the sunspot cycle.

BTW, Here’s a link from my old blog in 2009 talking about the solar cycle.

Clarification 4-14-18: When I say cooler weather, it doesn’t mean we won’t have heat waves.  But it means that there will be fewer days in the 90s and average temperatures for the months of June July and August may be just below average.

SNOWSTORM POST-MORTEM

My previous post included the link for the official snow totals. I always like to evaluate my forecast to improve on future forecasts.

For the immediate PHL area, snowfall was between 7-11 inches and areas  somewhat further north and west, totals approached 15 inches.

With my call of 4-7 inches with an emphasis on “7 most likely”, my forecast fell short.  So what happened?

Official QPF measured at the airport yesterday was 1.06 water, somewhat higher than the 0.87 predicted by the NAM and higher than the GFS. But overall the models did well on QPF. (The actual snow total for just Wednesday was 6.7 inches at PHL airport, according to the NWS.)

My emphasis on solar insolation through clouds lead my forecast astray.  Had it been January, I would have predicted 8-10, which I mentioned in several posts.  So I learned yesterday that heavy snowfall rates trump solar effects, even in late March.

While the models did well on QPF, they did less well on wind. That was lucky for our region.  Temperatures were predicted well.

Mesoscale banding set up northwest of the city and snowfall was heavier in those areas.

I’m ready for Spring!

Final Two day snow totals

 

LITTLE KNOWN FACT ABOUT DAYLIGHT SAVING TIME & TV WEATHER FORECASTS

An interesting and little known thing happens with weather forecasts on the evening TV newscasts when Daylight Saving Time is in effect. (Eastern Time)

Hmm….you’re thinking, what could that possibly be?

So let me cut to the chase and then I’ll explain.

When you watch the 10PM or 11PM news/weather on TV and you’re on Eastern Daylight Saving Time, the latest major weather models (with the exception of the NAM)  are not available until after the broadcast is over!

Essentially, we’re all getting forecasts that are still based on radiosonde measurement and global model forecasts that were done earlier that day!  You’re not getting the latest at 11 to 11:30 PM simply because the major models (GFS, European, Canadian)  aren’t done being calculated by the supercomputers!

It doesn’t make a difference whether you’re watching Accuweather on Channel 6 or whatever they call it on Channels 3 and Channel 10.  It’s simply not available on Eastern Daylight Savings Time until after the broadcast.

This is a peculiarity resulting from Eastern Daylight Time, (not Central or Pacific Daylight Saving Time) combined with how long it takes for the models to be computed.

More specifically, the earliest GFS data is available between 11:32 and 11:39 EDT.   (Before we make the switch to Daylight Saving Time it’s available 10:32 and 10:39 EST. )

And that’s just the forecast for the first 24 hours!  The latest “Five Day Forecast” isn’t available for another hour or so later!!

Here’s some more info:  Most of the major models are run every 6 or 12 hours, starting with 00 UTC (previously called Greenwich Mean Time).

00 UTC = 7 PM Eastern Standard Time but it is 8 PM during Eastern Daylight Time. 

Since the major models take a minimum of 3.5 hours to chew through the numbers, even on the supercomputers, it’s not until after 11:30 EDT  when the first “24 hour products” of the major models first become available.

Even hourly short range models use the major models as starting points, so they’re affected too!

If you’re a weather nerd, here’s the site where you can see what time each of the model outputs are going to become available each day.  (It’s sort of the on-time train schedule for US weather computer models.)

So during the warmer months on the east coast, when you hear one forecast on the late news and then wake up to hearing another forecast, this is one reason why!

SNOW FOR PHILLY ON WEDNESDAY- HERE WE GO AGAIN

The models have been advertising another coastal snow storm development for Tuesday night into Wednesday.  Not all of the major models are totally on-board with this scenario, but it still appears more than likely.   The wind intensity of this storm will NOT be anything like this past Friday, although snowfall rates may look impressive during the day.

NAM Forecast Wednesday 1 PM

Incredibly, the current range is anywhere from 6-10 inches of snow for Philadelphia , based on the GFS (6″) and the NAM (10″).

Current timing- light snow develops during the evening Tuesday and increases in intensity after daybreak Wednesday, as the secondary coastal low develops and intensifies.

There’s still some thought that warm air might mix in, but right now the NAM and GFS critical temperatures all support snow.

I’ve given much thought about this past storm  I’m not going to get into the March sun angle, solar insolation and ground temperature effects, since it made giving an accurate accumulation forecast impossible.   I guess in March, it’s really about snowfall rate, not accumulation since accumulations mean much less in March— the snow can start melting as soon as it falls.

I’ll keep an eye on this one and will update tomorrow!

Sunday 10pm: The latest NAM data shows a significant snowstorm for Philadelphia on Wednesday.  QPF values are almost two inches water.  Critical temperatures show it falling as heavy wet snow.  Still too early to be sure, but this could be a major snowfall.

11pm:  Tonight’s GFS confirms a major snowstorm likely for PHL.  We’ll be waking up to heavy snow falling on Wednesday, snowfall increases for the rest of the day.  Current models suggest as much as 15 inches!  Too soon to hang our hat on this.