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! 

Portland and Thunderstorms

Often times when we forecast the chance for thunderstorms here in the Portland-metro area, we get e-mails from viewers who would like to know very specific details when it comes to when, where and why. In an attempt to provide you with a better understanding of how we get these thunderstorms (and how we get the weather we see in general), I will be writing a series of posts that break down these weather set-ups.

Summer-time thunderstorms are not uncommon for Portland. In the Willamette Valley, we average less than 10 thunderstorm days per year. Since 2012, we have averaged 5 thunderstorm days. The "stormiest" month of the year is actually July. July 3rd, 13th and 22nd are actually three of the stormiest days of the year over the last 13 years! So why during the summer do we see thunderstorms? There are a few ingredients.

In order to get summer thunderstorms in Portland, we need daytime heating. The hottest time of year for us is mid to late July when we have a daily average of 82 degrees. When the sun is out and heating the earth's surface, that causes air to bubble up from the ground and rise in the atmosphere. As the air bubble rises, it cools. As long as the air bubble is warmer than the air it is rising through, that bubble will continue to rise on its own. The typical temperature profile of the atmosphere is for temperatures to cool as you go higher. You can imagine that on a 80 or 90 (or occasional 100) degree day, the bubbling of air is going to rise quite high on its own. This gives the air instability.

Now that we have a rising bubble of air, we must add some moisture to the atmosphere or thunderstorms will not occur. How do we get moisture into the air? We often see a general southerly flow through the atmosphere on thunderstorm days. That southerly flow provides us with moisture from the more mild Pacific waters off the coast of California as compared to the waters off of the Oregon coast. The southerly flow helps push that moisture north into our area. So we have added moisture to our rising, unstable air bubble and now we can create a cloud that has potential to create lightning.

Our final step is a trigger needed to agitate the atmosphere and spark the thunderstorm. There are several different "triggers" that can help us out. One is a front, be it warm or cold. During the summer we don't see a lot of warm or cold fronts so this isn't a common summer-time trigger. Strong winds in the higher levels of the atmosphere can also aid thunderstorm development. The winds help evacuate those rising air bubbles at the top of the atmosphere and prevents air from sinking back down. A "vorticity maximum" can be a good summer-time trigger. A vorticity max is basically a kink in the overall flow of the atmosphere. Think of it as a mini-low pressure system. As this passes over head it would be the last little push that would give our rising bubble that last ingredient and a thunderstorm would develop!

Over the last few days, Portland has had the threat of some afternoon thunderstorms. Yet, we have not seen those develop over the metro area. Here's why:

This is our 500 millibar chart valid for Wednesday at 8 am and is a snapshot of the happenings half way up the atmosphere. The main feature is obvious, a closed low pressure system off the Oregon/California coast. Notice the wind barbs flowing around the low. This has been the weather setup for the last couple days. A generally southerly flow winding into the Portland area. With the summer-time heating, south flow and some good moisture (you may have noticed a "muggy" feeling the last few days) thunderstorms looked like a strong possibility. Our problem? We lacked a trigger! This upper low would have been the PERFECT trigger for us but due to its location being so far away from the metro area, that doesn't help! This setup did have some strong upper level winds but they were located over central and eastern Oregon thus helping fire off some severe storms in those parts.

Thursday's setup looks a bit more promising for storms here in Portland.

 To the left is a different view of the 500 mb chart we saw above. This shows the low moving back to the north around Thursday evening. The feature to look at however is the dark red dot just east of Portland. That is a vort max trigger. With the low closer to us, plus this vort max, I see a good setup for storms.

The next map shows rising and sinking motions at nearly 10,000 feet. There is a dark red dot right on top of Portland at the same time as our vort max. The red dot is telling us that we have rapidly rising air occurring at that time. This probably due to the forecast high of 83 degrees Thursday. Now we have two ingredients: rising air and a trigger. Just need that moisture.

Finally, our precipitation map is showing a very heavy cell just southeast of Portland at the same time as our rising air and trigger mechanism. The models are showing plenty of moisture as well but the models are not always right! However, as I see this on multiple forecast charts, I would definitely keep an eye to the sky tomorrow late afternoon and into the evening. 

Portland Area Forecasts

We have reached the "Dog Days of Summer" here in the Northwest. We seem locked into a nice summer weather pattern, more on this in a moment. First, let's recap June which will go down as one of the wettest in Portland history. My June challenge was to compare the four Portland stations morning weather forecasts. First, a disclaimer: I am not trying to belittle any other stations nor their meteorologists. This experiment was done just out of pure curiosity and results will not be used in any promotions.

With the quality of forecasters we have in this city as well as the quality of forecast information and data, the results are not all the surprising to me. There is not much variation from station to station. Starting with Channel 2: The A.M. weather forecast had a 83% rate and was off the exact temperature by an average of 2.5 degrees. Channel 6 saw a 77% accuracy rate and was off the exact temp by a 2.4 degree average. Channel 8 also recorded a 77% accuracy level and was off the daily high by an average of 2.1 degrees. Finally, our channel saw a 94% accuracy rate, off the exact high temperature by an average of 1.9 degrees. The difference between the channels, .06 degrees, makes literally zero difference. But the fact that each station was off by almost 2 full degrees goes to show you how sensitive the atmosphere is. One little shift in wind patterns or change in moisture content can alter a high temperature. So all in all, not too bad Portland.

Portland's July has been of to a nice start. Through the first week, we've only recorded .03 inches of precipitation which is right at average. Our average temperature has been 77 degrees, just one off the average. But the reason I think the Dog Day are upon us, four straight 80-degree days. Ironically, the stretch of 80 degree days began on....July 5th, the unofficial start to summer in Portland! Our average high temperature will only continue to climb as there is no end in sight to the warm weather! Take a look at this morning's seven day forecast.


Since we have reached the halfway point of 2012, I'm taking a quick recap of the first half of the year to see where my overall accuracy sits. My temperature accuracy stands at 83% and conditions are slightly higher at 91%, that includes a 94% conditions report in June. Passing grades, if I do say so myself. No one's perfect, right?

Spring 2012 in Pictures

Time for one of my favorite posts. We get tons of photos sent into the station from viewers across the state. The number one most sent in photo? Double rainbows. ALL THE TIME! People love a rainbow, people freak over two! Of course, double rainbow viewer photos spark all sorts of quotes. "Full on double rainbow" "What does it mean?" can all be heard throughout the newsroom! There won't be any rainbows in my pictures today, but still some awesome stuff from the spring season!

The first photo was sent to us by Chris Jense. Here, we are looking at an awesome convective process. The cumulonimbus cloud, commonly referred to as a cauliflower cloud, is built by a process of warm and cool air. The sun heats the earths surface and causes the air to warm and rise. The rising warm air is cooled by the atmosphere above and eventually it becomes a large cloud like the one above. At some point, the cloud can no longer hold the moisture. The result is a short, intense downpour that we see above. This specific cloud is still building. You can tell by the sharp edges of the top of the clouds against the blue sky in the middle of the photo. Notice the bands of rain pouring down over the Jack In The Box. That's some heavy rain and most likely some small hail mixed in as well.

Linda Sullivan got a sunset snapshot of a passing thunderstorm. Again, we see the cauliflower-style clouds that extend well up into the atmosphere. The higher these cloud tops bubble up, the stronger the "updraft" is from the surface. The updraft is that column of warm rising air from the surface into a cooler environment above. The stronger the updraft, the faster the air is rising. This style of cloud is typically associated with active weather. We had a few weeks of afternoon thunderstorms around the Portland-metro area towards the end of spring.

Another convective picture, this time sent in from a viewer along I-5. Love the contrasts in this picture. The lighter clouds against the blue sky on the right side shifts to the dark rain clouds and the rain shaft on the left side. That dark area is actually rain falling from the clouds. Again, we are looking at convective rainfall here. The rain falls when the updraft can no longer sustain the rain. The weight of the rainfall overtakes the updraft and the result is the rain core you see above!

Funnel clouds are not unusual for Oregon. Tornadoes are. A funnel cloud is just a rotating cloud in the air. It can't cause any harm unless it touches the ground, then it becomes a tornado. It can be difficult to identify a funnel cloud from a still photo. It needs to be visually confirmed or else it may appear to be a low-hanging cloud. This definitely has the look and structure of a funnel cloud, however. No tornadoes have been confirmed in Oregon for the 2012 spring.

A well-timed shot was sent to us from Estacada. That looks like an impressive bolt. Notice how it goes from cloud-to-ground. These type of strikes are the only ones that produce thunder. A cloud-to-cloud lightning bolt can put a nice charge into clouds, but no thunder is heard from it.

This winter weather wasn't limited to the winter season in Portland. This is a great shot from outside the station in the middle of spring! Portland saw near 5 inches of snow over the spring, making up for the usually dry first half of winter we had.

This tranquil photo was sent in by Barbra Lane from Parkdale, Oregon. An amazing, peaceful photo after a heavy dose of snow fell near Mt. Hood.The Cascades got plenty of snow this past winter and first half of spring. That should make for a great water recreation summer.

 This photo wasn't sent in to the station and isn't even from Oregon. This photo was taken in McCalla, Alabama. I am really hoping that this is the actual photo and not photo-shopped in any form. If this is a true photo, WOW! It looks like the lightning is striking the street! The clap of the thunder was probably ear-piercing. Very powerful!

 

Finally, a little bit of astronomy. The west coast was treated to a solar eclipse on May 20th. A solar eclipse occurs when the moon travels between the earth and the sun and blocks the sun from view on earths surface. Above is the western satellite view that caught the dark spot on the earths surface. The next eclipse will be a partial eclipse on October 23rd, 2014.

Spring offers up some of the best weather and thus, weather photo ops. I'll be monitoring the summer photos and will be sure to share any interesting pictures!

May Report....and More!

A lot to cover in this post. It has been a while since I've last posted, probably because this past month has been a busy one. Let's start with my May report card!

Remember that this month's challenge was to accurately forecast the LOW temperature for Portland. Low temperatures can be a challenge given cloud cover and nocturnal radiation or how the day's heat escapes the atmosphere. Anyways...on to the results! May was one of the best months so far. Both high temperatures and conditions were at a 94% mark! Each category had one miss out of 18 forecasting days. The May challenge of low temperature came in at 88%. A confession, I don't often pay too much attention to the low temperatures each day. I do not forecast low temperatures out any further than the next day. There is more emphasis on the daily high temperature than the low. That's why people watch, right? June will be the half-way point of the year and I am going to bring on a big challenge. I will aim to have Portland's most accurate morning forecast. Using the normal criteria, I will chart each station's morning forecast (high temperatures only) and at the end of the month, we will see who's on top! At the end, you can choose who you trust for your morning forecasts!

May wrapped up "meteorological" Spring. It's how us weather geeks break down March-April-May. The graphic below sums up what has been a soggy three months!

March contributed a majority of the Spring rainfall, setting a record of 7.89"! April received 3.25" and we just finished up May with 3.37". The interesting thing about May is that we tied an all-time May record with 15 straight dry days! Despite just over two weeks of dry weather, we still finished ABOVE average for May rainfall! If we didn't have that dry stretch, we may have cracked the top 5 wettest May's but we will just have to settle for above-average. But this was a different "Spring" than a year ago. Spring 2012 was a warmer spring than 2011. Last year, Portland's first 80 degree day was June 4th. This year, we only had to wait until April 22nd to get to 80 degrees and we've hit it a couple more times since then; 5 times to be exact. Weekends have been rather nice over the last two months as well. Between April and May, Portland had four completely dry weekends! But is was the last Saturday in May that gave Portland one of its wettest hours. On the 26th, 1.03" of rain fell in 60 minuets! That 1.03" grand total ties Portland's wettest hour and set a daily rainfall record for May 26th. Ahhhh, Spring!

Coming next week, I'll have Portland's Spring in pictures. Some awesome photos that you won't want to miss!

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?