Time to clear up some more weather myths out there. Today's theme will be (mostly) about lightning but we will kick off this edition with a snow myth. We are heading towards winter, after all!
Myth: It can get too cold for snow?
Truth: While this is not common, it can occur. The basis behind this fact is rooted in the properties of the atmosphere at certain temperatures. Consider: In order for clouds to form and precipitation (in our case, snow) to
occur, air on a large scale must rise through the atmosphere. Warm air is less dense thus more likely to rise through the atmosphere. Colder air is more dense so it has a tendency to sink throughout the atmosphere. Sinking air promotes high pressure which stabilizes the atmosphere making it less likely for precipitation to form. So if air gets too cold there just isn't enough precipitation in the air nor is there the dynamic properties to produce snow! We're talking COLD though, temperatures around -40 degrees Celsius.
Myth: Lightning doesn't strike twice in the same place
Truth: This is false. Lighting strikes the same place multiple times, all the time. Lightning rods were designed to do this very thing. They attract lightning strikes in order to keep bolts away from surrounding buildings and utility stations. Nothing occurs that prevents lightning from striking the same place twice.
Myth: The temperature of lightning is hotter than the surface of the Sun.
Truth: This, believe it or not, is true. In fact, air around a lightning bolt can heat up to a temperature of 54,000 degrees! Lightning results from a static build-up between the atmosphere and the rain/ice crystals in the storm. The release of this build-up occurs in the form of lightning. The bolt lights up the sky and heats up the air surrounding the storm. Heating the air to such high temperatures sends shock-waves through the air and the expansion results in thunder.
Myth: There can be lightning without thunder.
Truth: Yes, this is true, but only based on how far away you are from the lightning strike. Thunder reflects, bounces, and gets absorbed by the earth's environment. If you are a sufficient distance away from the strike, you may see the flash but the sound wave of thunder may be effectively scattered by the time it reaches you.
Myth: Rubber tires make your car a safe place in a thunderstorm.
Truth: There is a partial truth to this. Yes, rubber makes it safe-er to be in your car during a thunderstorm but it is actually the frame of your car that makes the car a safe place to be. The metal cage that surrounds your car will help absorb the lightning bolt should one strike your car.
Lightning is a powerful thing,
Thursday, December 6, 2012
Tuesday, November 6, 2012
Sandy Recap and Part II
The ugly aftermath of "Superstorm" Sandy continues in the Northeast. Hundreds of thousands still without power and even without a home. Unfortunately, those who are still having issues nearly a week after Sandy struck are going to have new problems to deal with. More on this in a minuet but first, here is a great graphic that puts Sandy into context.
I'm not the biggest fan of The Weather Channel...too mainstream weather for me. My biggest gripe is their forecasting ability for cities not named Atlanta, Boston, Chicago or New York. But I have nothing wrong with their research department. Looking into the past is something they do quite well! They published this graphic that compares Hurricane/Superstorm Sandy with Tropical Storm Irene (last year's most costly tropical system) and Hurricane Katrina from 2005. The numbers are impressive given that Sandy only topped out as a Category 1 storm and wasn't even tropical at landfall!
Just as in real estate: location, location, location really matters with weather, too. Sandy hit the most populated area of the United States, impacting millions of people and damaging massive amounts of infrastructure. The clean-up effort will take time and that effort will be hindered by a new storm; a Nor'easter is on the way!
A Nor'easter is a typical winter-time storm that forms along the Atlantic southern coast and speeds up along the coastline bringing wind, rain and snow to the Northeast. Nor'easter gets its name due to the direction of damaging winds, not where it strikes.
Here is our surface map that is valid this Wednesday afternoon. The red arrow indicates overall wind pattern (from the Northeast). The models are putting out wind speeds sustained around 20-40 miles per hour with gusts approaching hurricane-strength over open water and coastal areas. Heavy rains expected at the coasts and a dumping of wet snow (multiple feet) further inland. The blue line I highlighted indicates a rough rain-snow line. I say rough because several more factors play into it but in this situation you can expect snow to fall behind that line. Notice that same line extends all the way into the Portland area--but we will not be seeing any snow! This Nor'easter is not as strong as Sandy was but the impacts from it will be felt hard as clean-up efforts will likely take a hit and more flooding will be expected from the storm surge. It's been an ugly first half of fall for the Northeast.
I'm not the biggest fan of The Weather Channel...too mainstream weather for me. My biggest gripe is their forecasting ability for cities not named Atlanta, Boston, Chicago or New York. But I have nothing wrong with their research department. Looking into the past is something they do quite well! They published this graphic that compares Hurricane/Superstorm Sandy with Tropical Storm Irene (last year's most costly tropical system) and Hurricane Katrina from 2005. The numbers are impressive given that Sandy only topped out as a Category 1 storm and wasn't even tropical at landfall!
A Nor'easter is a typical winter-time storm that forms along the Atlantic southern coast and speeds up along the coastline bringing wind, rain and snow to the Northeast. Nor'easter gets its name due to the direction of damaging winds, not where it strikes.
Friday, October 26, 2012
Thoughts on Sandy
Doomsday scenarios have been playing out for a large portion of the eastern seaboard. There have even been comparisons to the 1991 Perfect Storm that struck New England. Sandy isn't a reprise of that Nor'easter. Sandy is her own storm, like each storm is. All models indicate that Sandy will still be a hurricane when she makes landfall sometime early next week. There is no "Frankenstorm" situation; not even sure what that means. Sandy will be Sandy. Let's break down Sandy and her impacts.
Sandy has a few things going for her right now. Her current path will take her right along the coastline.
All models bring her right up the coast. She would parallel the coast if it wasn't for factor number 2, the approaching cold front.
This cold front will aid in bringing Sandy inland. The front will essentially scoop up Sandy and swing her inland.
There was suspicion as to what the storm will be like at landfall. Will it be a hurricane? Tropical storm? Nor'easter? The high pressure set up to the north of Sandy will help deepen the low pressure at the center of Sandy and the forecast reflects that strengthening. Look for Sandy to make landfall as a category one hurricane.
Now timing and location becomes the next challenge. Guidance is indicating a landfall sometime between Monday A.M. and Tuesday P.M. She may strike anywhere from Delaware to Long Island. The closer we get landfall, the better idea we will have. Either way, the entire east coast needs to take action NOW to avoid disaster LATER.
Potential impacts could cripple a large portion of the east coast as well. With the cold front sweeping through, significant snow accumulations could fall as cold air filters in behind the front. There is plenty of moisture with Sandy, so 6-8 inches of rain as Sandy skirts the Carolinas is not out of the question. Added water from the storm surge may cause devastating flooding for certain places. Storm surge is enhanced by storm winds.
This is a model's forecast for landfall and the impressive wind field associated with Sandy. This is from the European model which has been the most consistent in forecasting landfall. But what is impressive here is the winds. The closer the lines are together, the stronger the winds are. Look how far out the wind field extends! Tropical storm winds may be seen all the way out in Ohio! I like this situation to verify.
A lot is yet to play out. As a forecaster I am anticipating this storm. It could be historic but it will be a deadly one.
Sandy has a few things going for her right now. Her current path will take her right along the coastline.
All models bring her right up the coast. She would parallel the coast if it wasn't for factor number 2, the approaching cold front.
This cold front will aid in bringing Sandy inland. The front will essentially scoop up Sandy and swing her inland.
There was suspicion as to what the storm will be like at landfall. Will it be a hurricane? Tropical storm? Nor'easter? The high pressure set up to the north of Sandy will help deepen the low pressure at the center of Sandy and the forecast reflects that strengthening. Look for Sandy to make landfall as a category one hurricane.
Now timing and location becomes the next challenge. Guidance is indicating a landfall sometime between Monday A.M. and Tuesday P.M. She may strike anywhere from Delaware to Long Island. The closer we get landfall, the better idea we will have. Either way, the entire east coast needs to take action NOW to avoid disaster LATER.
Potential impacts could cripple a large portion of the east coast as well. With the cold front sweeping through, significant snow accumulations could fall as cold air filters in behind the front. There is plenty of moisture with Sandy, so 6-8 inches of rain as Sandy skirts the Carolinas is not out of the question. Added water from the storm surge may cause devastating flooding for certain places. Storm surge is enhanced by storm winds.
This is a model's forecast for landfall and the impressive wind field associated with Sandy. This is from the European model which has been the most consistent in forecasting landfall. But what is impressive here is the winds. The closer the lines are together, the stronger the winds are. Look how far out the wind field extends! Tropical storm winds may be seen all the way out in Ohio! I like this situation to verify.
A lot is yet to play out. As a forecaster I am anticipating this storm. It could be historic but it will be a deadly one.
Tuesday, August 28, 2012
Cracking the 7-Day
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.
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!
Friday, August 24, 2012
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:
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!
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!
Tuesday, August 21, 2012
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.
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!
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 % |
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.
Friday, August 10, 2012
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!
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:
Tuesday, August 7, 2012
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 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!
Wednesday, July 18, 2012
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.
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.
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.
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