Cracking the 7-Day

Six days away from wedding-palooza and we are getting more details on the forecast for Labor Day. Over the last few days, numerical data has flipped-flopped almost hourly with giving us showers or not. One thing that remained constant was temperature, which looks to be somewhere in the low to mid-70's. Tuesday morning's run gives us a high temperature of 76 degrees.

The general weather pattern for Monday evening (5 P.M.) shows a weak trough off the Oregon/California coast. A general westerly flow is evident here. That would promote average or slightly below average temperatures. Notice the wind barbs are generally flowing in a northwesterly pattern. That tells me some cooler, Canadian air is heading our direction in the upper atmosphere. Winds closer to the surface tell a slightly different story.

Our 850mb chart (5,000 feet) is giving us a northerly wind at 5 P.M. on Monday. This is good news because a northerly wind usually means dry air is moving over us. Air that has spent more time over land is drier and warmer than air coming off the ocean. We would normally avoid seeing morning fog with this type of setup, the same would be true if we had an easterly wind.

Below is MOS (model output statistics) and it is just another numerical forecast.

 KPDX   GFSX MOS GUIDANCE   8/28/2012  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 TUE  28| WED 29| THU 30| FRI 31| SAT 01| SUN 02| MON 03| TUE 04 CLIMO
 X/N  76| 55  72| 54  75| 54  71| 51  72| 52  76| 53  76| 55  78 53 78
 TMP  75| 57  71| 55  73| 55  70| 53  72| 54  75| 54  75| 56  77      
 DPT  49| 50  49| 51  48| 50  47| 47  45| 48  45| 48  47| 50  50      
 CLD  PC| PC  PC| CL  CL| CL  CL| CL  CL| CL  CL| CL  CL| CL  CL      
 WND   7|  7   6|  5   8|  8  10| 10   6|  6   7|  7   8|  7   8      
 P12   9| 17  10|  2   9| 12  11|  7  12|  6   7|  5   9|  8  12 18 17
 P24    |     20|     12|     12|     12|      7|      9|     12    25
 Q12   0|  0   0|  0   0|  0   0|  0   0|  0   0|  0    |             
 Q24    |      0|      0|      0|      0|      0|       |             
 T12   1|  0   6|999   0|  2   1|  1   1|  1   2|  2   4|  2   1      
 T24    |  1    |999    |  2    |  1    |  1    |  4    |  4          

Highlighted is the pertinent information. MOS gives us a temperature (TMP) of 75, which corresponds with what I was thinking as well. CLD stands for Cloud and CL is not "cloudy" but "clear". It's tough to tell what a calculator thinks is "clear" or "partly cloudy" but generally there would be a good amount of sunshine expected. The numerical output is producing a very similar forecast to mine. At least partly cloudy and temperatures in the mid-70's. The days leading up to Labor Day are giving us dry, bright weather, so hopefully the trend holds on one extra day! The forecast has been improving!

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!

July in the Rearview

Most across the Lower 48 are glad that July is done and clinging to hope that August does not offer up more of the same. July turned out to be the warmest month on record, ever! The contiguous U.S. averaged a monthly temperature of 77.6 degrees Fahrenheit and that became the warmest month since records began in 1895. Below is a map distributed by NOAA that puts the heat into context.

Well over 50% of the U.S. saw a July for the record books. Most of the Midwest and Mississippi River Valley saw a Top 10 warmest July. Virginia is the only state that hit it's warmest July ever, seven other states saw their second warmest July on record. The heat can be contributed to a persistent upper level heat ridge that locked into place. That is typical for the summer months, but it doesn't often last as long as it has this year. With record heat comes record drought. Over 60% of the Lower 48 are seeing extreme or exceptional drought conditions.

While the eastern 2/3rds of the country baked, the West Coast saw dealt with comfortable temperatures. That's no surprise considering Portland just hit our first 90+ degree day just last week! Notice that Oregon is under the "Above Normal" category. A lot of that was contributed to Central and Eastern Oregon heat. The Beaver State also saw the largest wildfire in the state since 1840! The Long Draw Fire in Southeast Oregon burned 560,000 acres!

More locally, the July forecast report is in! With a forecast for 18 days, my temperature accuracy finished at 77% while conditions came in at an 83% clip. We saw a few days of thunderstorms and several days of morning clouds followed by afternoon sun. That pattern is typical of summer when the landmass cools off quicker than nearby ocean. When the air coming off the Pacific Ocean moves over land, it cools and condenses into a cloud. Those clouds travel down the Columbia River as well as find the low-level gaps in the Coastal mountain range and seep into the metro area each morning. Once the strong summer sun heats the atmosphere, the air mixes down to the low levels, breaking up the clouds and giving us pleasant afternoons. The Cascade Mountains are enough to block the low-level clouds from moving into the central and eastern portion of the state. Those clouds, known as the "marine layer" can bust a forecast in a hurry! It is just another facet of Pacific Northwest forecasting!

August has begun and we are in the midst of a 3-week dry stretch! However, I'm looking ahead about a month to my big wedding day! September 3rd feels far away yet it will sneak right up. We have access to a long range model here at the station. By long range, I mean 10-50 days into the future! So here is a sneak peak at the September 3rd forecast:

Things look dry and that's all I can ask for! Of course we are 24 days away and you MUST take this model with a grain of salt. I'll be monitoring how the model changes and once the Big Day is within reach of short range models I'll be updating you on that as well!

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!