10 Day Weather Outlook

Now just 10 days away from the nuptials and we continue to get a better look at the September 3rd forecast. We continue to get data from only one model, the GFS model. The GFS offers a look much further into the future than it's main counterpart NAM. However, GFS sacrifices a higher resolution in favor of time. The NAM only goes out roughly 4 days into the future but has a much higher resolution so broken down in more detail. Once the two models overlap, it is a great way to compare biases. So we continue to look at the GFS data. Here is what we are looking at 10 days out!

Let's peak at the numerical data first:

FCST Hour	Valid Time	Max Temp	Min Temp	Td	10m Wind mph	850mb Wind mph	Total Precip(")	Conv. Precip(")	500-1000 THKNS	500mb Height	850mb Temp °C	500mb Temp °C	MSLP mb	Total Cloud Cover
192	Sat 09/01 06Z	61 °	58 °	58 °	N 18	N 7	0.00	0.00	563	578	12 °	-11 °	1016	0 %
204	Sat 09/01 18Z	60 °	56 °	57 °	N 13	NNE 13	0.00	0.00	562	577	12 °	-11 °	1017	5 %
216	Sun 09/02 06Z	61 °	57 °	55 °	N 18	NNE 13	0.00	0.00	563	577	13 °	-12 °	1016	35 %
228	Sun 09/02 18Z	60 °	56 °	46 °	N 11	N 11	0.01	0.00	561	576	12 °	-13 °	1016	46 %
240	Mon 09/03 06Z	61 °	56 °	34 °	NNW 13	N 7	0.02	0.00	561	575	12 °	-13 °	1016	74 %
252	Mon 09/03 18Z	59 °	56 °	32 °	NW 7	NNW 4	0.02	0.00	559	574	11 °	-14 °	1017	76 %
264	Tue 09/04 06Z	60 °	57 °	48 °	NNW 13	NNW 9	0.02	0.00	557	573	10 °	-15 °	1018	81 %

Highlighted are the times for September 3rd. Our mid-level air temperatures are right around 10 degrees Celsius. This should translate to a surface temperature in the mid-70s. The big change from the last post shows that we have a precipitation chance through the day, calling for 0.02". September 3rd actually averages 0.03", so rain isn't unusual. What you can't see is that with each model run (GFS runs 4 times per day), the precipitation forecast changes. The waffling of the runs tells me that the GFS is trying to pick up something on the maps, so lets take a look.

The 500mb map offers a pretty good hint as to why we are seeing some precipitation in the forecast. Notice the large bump over the middle part of the country. A nice ridge of high pressure dominates a good chunk of the U.S. and that causes a kink in the weather pattern on both coasts. This setup is known as the "Omega Block" named after the Greek letter Omega. Generally, fair conditions dominate over the central U.S. and both coasts would see some potentially unsettled weather. This would explain the cooler than average temperatures as well as the hint of precipitation that numerical data has been showing at times. Coincidentally and totally unrelated, a tropical storm/hurricane is the big feature on the east coast. 

So, the forecast 10 days out goes something like this: I'd expect partly to mostly cloudy conditions with a slight chance for a shower. If I saw this setup on September 2nd, I would not put a rain icon on the forecast, but it is definitely worth a mention. With 10 days to go and the flip-flopping of the model output, there are still no concrete details. Stay tuned, only three more days until September 3rd hits the seven-day forecast!

A First Look at the Big Day Forecast

I am in the middle of a 13-day work binge. Pretty sure that's the longest stretch of consecutive work days for me at the station. It will all be balanced out when I take 9 days off starting Wednesday of next week. For those who may not be aware, I am getting married on September 3rd. So the time off will all be related to that.

There have been a few people asking if I am nervous for the ceremony. I'm not really nervous (at least not yet) for the vows. Rather, I am more nervous about the weather cooperating as we are having an outdoor ceremony. As always, best to have a "Plan B" which we do. That involves cramming about 130 guests into an outdoor tent and doing the ceremony/reception all in one place. Luckily, climatology says that the likelihood of a "rainout" is very slim. The average temperature in Portland on September 3rd is 79 degrees. Our wedding will be in Oregon City which typically runs a degree or two warmer than Portland. The last 5 years have seen an average of about 82 degrees with nothing but sunshine.

It appears our hottest stretch of weather this year just wrapped up. It's going to be tough to see more triple digits the later into summer we get. We've entered a stretch of below-average temperatures with a lot more cloud cover now as we begin the second half of August. I'm wondering how long it will last and will it impact the wedding. Portland hasn't seen any measurable precipitation in 31 days but that's not even half of our longest stretch, which was 66 days set in 1967. The GFS model run is finally showing the first glimpse of what we might expect for September 3rd.

  

Here is the 18z (11 A.M.) snapshot on the 3rd. This is the 500mb chart, giving us an idea where systems are and might be headed. The wind barbs show a strong "on-shore" flow, air will be coming off the ocean, thus giving us a cooler air mass.A westerly flow in late summer typically means that we start off cloudy as the marine air surges inland. This is all behind a system that comes onshore a day or two before the wedding that may produce some rain. Models that predict cloud cover do not go out this far, so using the map above I would say that we are looking at a somewhat cloudy start to the 3rd. Does that mean it will rain?

Above is the graphical precipitation output from the GFS model for the 3rd. It leaves us high and dry around 12 noon on Monday. Numerical numbers also back the maps.

FCST Hour	Valid Time	Max Temp	Min Temp	Td	10m Wind mph	850mb Wind mph	Total Precip(")	Conv. Precip(")	500-1000 THKNS	500mb Height	850mb Temp °C	500mb Temp °C	MSLP mb	Total Cloud Cover
192	Wed 08/29 06Z	61 °	58 °	58 °	NNW 4	SW 4	0.00	0.00	564	578	13 °	-12 °	1016	0 %
204	Wed 08/29 18Z	59 °	56 °	57 °	SSW 11	SSW 16	0.00	0.00	555	566	8 °	-16 °	1013	3 %
216	Thu 08/30 06Z	60 °	57 °	56 °	SSW 13	SW 20	0.01	0.00	552	564	6 °	-19 °	1014	10 %
228	Thu 08/30 18Z	58 °	57 °	42 °	W 7	W 11	0.06	0.04	551	566	5 °	-17 °	1018	44 %
240	Fri 08/31 06Z	58 °	57 °	33 °	NW 7	NW 9	0.01	0.01	553	571	5 °	-15 °	1022	15 %
252	Fri 08/31 18Z	59 °	57 °	34 °	N 7	N 11	0.01	0.00	555	576	7 °	-13 °	1024	69 %
264	Sat 09/01 06Z	59 °	56 °	47 °	N 18	NNE 9	0.00	0.00	559	579	9 °	-13 °	1023	15 %
276	Sat 09/01 18Z	58 °	55 °	54 °	N 18	NNE 11	0.00	0.00	560	578	11 °	-13 °	1021	2 %
288	Sun 09/02 06Z	60 °	56 °	57 °	NNW 20	N 7	0.00	0.00	561	577	12 °	-13 °	1019	0 %
300	Sun 09/02 18Z	59 °	55 °	56 °	N 16	NW 11	0.00	0.00	558	575	9 °	-14 °	1021	12 %
312	Mon 09/03 06Z	59 °	55 °	54 °	N 16	NNW 11	0.00	0.00	557	575	8 °	-15 °	1021	12 %
324	Mon 09/03 18Z	57 °	55 °	45 °	N 11	N 11	0.00	0.00	557	575	8 °	-13 °	1022	25 %
336	Tue 09/04 06Z	59 °	55 °	39 °	N 20	N 11	0.00	0.00	559	576	10 °	-13 °	1019	26 %
348	Tue 09/04 18Z	58 °	55 °	39 °	N 18	N 11	0.00	0.00	558	574	9 °	-14 °	1019	2 %
360	Wed 09/05 06Z	59 °	55 °	51 °	NNW 20	N 9	0.00	0.00	558	574	10 °	-14 °	1019	2 %
372	Wed 09/05 18Z	58 °	55 °	55 °	NNW 16	NNW 11	0.00	0.00	556	574	9 °	-15 °	1021	5 %
384	Thu 09/06 06Z	59 °	55 °	56 °	N 16	N 11	0.00	0.00	559	576	10 °	-14 °	1020	8 %

I have highlighted the precipitation (yellow) and mid-level air temperature (red) columns above. This model showing zero rain. That's good. It is also showing an 850mb air temperature of 8 degrees Celsius. We use the temperature at 850mb (that's about 5,000 ft) to help translate a surface temperature. On average, 850mb temperature of 8 degrees Celsius translates to a surface temperature of about 71 degrees Fahrenheit at the surface. That is a bit cool considering the average high for that day is some where around 79 degrees F. You may notice the temperature output for that day is 57 degrees F! This model is notoriously bad at temperature forecasting but has strengths in other areas.


These charts give us a good idea of what ALL model runs are doing with temperatures. Each model runs several different parameters and these charts compile all the 850mb temperature outputs and compares them against average (green line). The red line is the average of ALL those runs, and the blue line is the operational (published) model run.
 The first model is the ECMWF (European model). The red arrow indicates the 3rd. Not surprised to see such a wide variety of temperatures this many days out. However, the average of all the models looks to be pretty close to climatological average. One model goes as high as 22 degrees C, which would translate to 85-90 degrees F at the surface! The Euro also goes as low as 4 degrees C which would mean

 Let's look at the GFS, my personal favorite model. September 3rd is indicated by the black arrow this time. GFS is thinking that things will be a bit cooler, indicated by all model averages (red line). Still plenty of variation and even more time to go for things to change. But this chart kind of supports what we saw on the numerical output with cooler than average temperatures on the 3rd.

Mind you, we are still some 320+ hours away from the wedding and weather is ALWAYS changing. But if I had to make a forecast guess for the 3rd right now, I'm saying things will be in the mid to upper 70's with partly cloudy conditions by the afternoon. I'll be here to update the forecast as I see things change! Only 13 days away now!

Portland Trends

One of the reasons I find weather fascinating is the trends and percentages it yields. Some records are amazing. Take, for instance, Portland's all-time high temperature of 107 degrees which has only been reached once on 7/30/1965. Compare that to Oklahoma City's record all-time high of 113 degrees, most recently reached on 8/3/2012. You would tend to think that either Portland's record high would be cooler or that Oklahoma City's would be hotter. But that's weather!

Portland just notched it's 3rd consecutive day of 90+ degree weather on Monday. . Those three days have been our only at or above 90 degrees in 2012! Here is a funny stat: Portland topped out at 100 degrees (8/4) before it topped out at 90 degrees (8/5-6)! That 100+ degree day actually reached 102 degrees and that was the first time we hit 100+ since 2009.
The Rose City typically sees the 90's a lot earlier in the season. That day usually falls on June 16th. So we are a little late this year, but we were even later last year when it took us until August 20th to hit 90 degrees. Our first temperatures in the 80's is a completely different story for 2012. On average, Portland's first day of 80+ degrees falls on May 10th. 2012 saw it's first 80 degree day on May 7th! Pretty much right on cue. Funny how the two vary so much.

Currently, Portland is in the midst of our longest dry stretch of the year at 17 days and counting. The dry weather began on July 21st. Getting long stretches of dry weather in the middle of summer is not unusual for us. But what is interesting here is the previous dry streak of 2012 occurred in the middle of May and lasted for 15 days! In the middle of MAY! From May 5th to the 19th, Portland never received any measurable precipitation. On average for those 15 days, Portland gets 1.16" of rain! That is nearly half of the 2.47" that May averages. In our current stretch, we only average .26" of rain and most of that is received via thunderstorms.

The majority of the country is looking at drought on a Dust Bowl-era scale. 22 states are reporting extreme drought conditions and a handful of states are in the exceptional drought range. In fact, over 50% of the contiguous 48 are looking at drought conditions. The Pacific Northwest is one of the very few areas that has escaped any drought conditions. Given some of the complaints about conditions being too cool (or now, too hot), we should all consider ourselves lucky that we don't have to deal with week-long stretches of triple digits! 

Recapping and Looking Ahead

We're a third of the way through 2012 and I'd have to say that April was the best month so far! The main story from April was the amazing run of weekend weather that we had which included some record-breaking temperatures. On April 23rd, Portland hit 82 degrees! That broke the old record of 79. The very next day, our temperature was 64, resulting in an 18 degree difference between Monday and Tuesday! Pretty crazy to see temperatures in the 80's in April, let alone to see such a drastic two-day temperature change. The April weather pattern not only brought heat but some active weather as well. A few days late in the month had some thunderstorms hit the metro area and a few severe thunderstorms rocked parts of the southern Willamette Valley.

My challenge for April was to work on precipitation forecasting. As you will see, the results show that I still need some work. April breaks down like this (forecasts for 17 days): 88% conditions accuracy, 70% temperature accuracy and only 52% precipitation forecast accuracy.

Out of the 17 days worked, only one day were all three categories missed. I had called for some showers and sun-breaks on that day and wound up with a mostly cloudy and very wet day (nearly half an inch fell). There are so many precipitation models out there, it is tough to know which one to use under specific weather patterns. Different models tend to handle different patterns better than others, so the more experience the better. The takeaway message is that my forecast is down and April is a tough month to predict due to the potency of the spring atmosphere.

Looking ahead to May, my new challenge will be to tackle each daily LOW temperature. Speaking of May, lots of information is being released ahead of the approaching summer season. First is the push of Severe Weather Awareness by the National Weather Service. Spring and Summer is our most active weather seasons, where we average 2-3 tornadoes a year! Washington also averages the same amount of twisters and Idaho just a few more at 3-4. Easily overlooked, the Pacific Northwest once lead the nation in tornado deaths in 1972! Six were killed amongst hundreds injured on April 5th when a F3 tornado ripped through Vancouver. We are not immune to severe weather here!

CPC Summer Outlook

Many might ask if the brief run of 80-degree weather we had in April translates into a warmer summer? Portland reached 80 or better on back-to-back days in late April. We only average one day at 80 or above during the fourth month and the most its ever happened was 5 times in 2004! We set 3 temperature records in April during 2004 and then went on to set ZERO temperature records the following month. So whats in store for the summer? The Climate Prediction Center released this map showing temperature anomalies for the June-July-August period. 

Two things jump out at me after looking at this map. The first one is quite obvious. Well above-average temperatures are being predicted for the southwest this summer. This very well may be a record-breaking summer in parts of the desert SW. The second thing that I notice is that none of the continental US is predicted to be BELOW average temperatures. Might this be an indication of global climate change?