Thursday, October 29, 2009

Halloween Forecast!

October 29, 2009
9:40 P.M.

People have been begging me to do a forecast for Halloween, so write a forecast I shall .The good news is that Halloween should be fairly dry! But there could be a couple showers roaming throughout the area.

Let's talk about the first event. Tomorrow is a very, very big day for my saxophone teacher, Steve Treseler. He is getting married! And, at this point, it looks like he will be under dry skies. After about 8 o'clock though, when the drunk toasts are over and everyone stumbles back into their vehicles oblivious to what they just said, the rain will start to fall. This rain is the same rain from the remains of tropical Neki, it will just be the cold front.

This system is pretty big area-wise. Last night and today, we got warm frontal precipitation and are now in the "warm sector" of the storm. That means freezing levels are at 10,000 feet or so. Once the cold front comes swinging through though (should be about 2 A.M. Saturday morning), temperatures will drop and the steady rain will cease. Here is a diagram of your typical mid-latitude storm system, and the warm sector is the dry area between the warm and cold fronts.

It's rare to have a completely dry Halloween in Seattle, and I don't think it will be any different this year. However, most of you should be dry. We will have a few showers around, especially in the mountains and north by Everett in a convergence zone, but these showers could pop up anywhere and put a damper (literally :P) on your Halloween night. All and all though, it looks like a pretty dry forecast.

The extended is just rediculously complicated as the models are about as inconsistent as I've ever seen them, but we could see a little bit of a dry period after Halloween.

Of course, you'll know what I'll be wishing for.


Tuesday, October 27, 2009

Flooding Thursday into Friday

October 27, 2009
3:07 P.M.

I hinted at flooding at the middle of this week in one of my posts last week. Then, that same storm transitioned from a minor windstorm to a major windstorm with heavy rain and flooding to practically nothing. Now, we are back with the idea of flooding, with some wind to boot. There are many reasons why the models have had such a difficult time with this moisture and the storm system they are forecasting it to produce, but the biggest reason is that it has residual moisture from Typhoon Neki in it. Models generally have a hard time dealing with tropical moisture. This model shows the precipitable water values in the atmosphere at the time (the total amount of water vapor in inches in a given column of the entire atmosphere).

Here, you can see the 24 hour precipitation amounts for 5 P.M. Thursday to 5 P.M. Friday. It looks like the Puget Sound basin will be rain-shadowed from Everett South (usually it is the other way around). The mountains, on the other hand, will see tremendous amounts of rain. I would not be surprised if isolated spots hosted storm totals as high as eight inches, locally even higher. We'll be dry tomorrow but the rain will come in late that night and continue into Thursday for the lowlands, while it looks to be a mainly mountain show from there on out.


Sunday, October 25, 2009

Even more inconsistencies

October 25, 2009
11:55 P.M.

Hello fellow weather enthusiasts. Today I am going to talk about the inconsistencies in the weather models regarding the Thursday storm (the same one that I talked about last week, showing a diagram of it way out in the Pacific, possibly leading to flooding over the Pacific Northwest). As you can see with the picture below (again this is exempt to people reading the facebook blog), models used to show an extremely powerful and vigourous low pressure system (around 950 millibars).

That's equivelent to an extremely strong category 3 hurricane. The models showed it stalling and weakening off our coast, but bring it 300 miles closer or so and we could of been talking about a major windstorm in our area.

Now, the models show it heading up into the Alaskan panhandle, a ~1200 mile difference in track. They also show it much weaker, around 985 millibars. (see pic above)

Bottom line: at this point we don't really know what is going to happen, although a weaker storm to the north seems most likely. Stay tuned!

Friday, October 23, 2009

oh boy

this is andrew making the weather happen for the future and let me tell you all, people are in for a surprise this weekend; hurricanes, snow storms and even a small koolaid tsunami will be hitting the beautiful NW this weekend!

...not really.

what you should be expecting is some potential sun on saturday (a good time to get out) and more than likely more of the great Seattle gray. have a chill weekend guys!

Thursday, October 22, 2009

A Quick Update

October 22, 2009
5:02 P.M.
I just wanted to let you guys know of a couple changes in the forecast. First of all, Friday looks wetter for some and drier for others. The front is expected to not stall as much over Vancouver Island, so we will get more rain while they will get less. However, due to the westerly flow of this storm system, the central Puget Sound area will be rain-shadowed (as opposed to places north like Sequim that usually get it more). The diagram below shows the 3 hour precipitation totals from 2-5 A.M. Notice the large hole in precipitation over Seattle.

Nevertheless, things should "even out" precipitation-wise later in the evening as a Puget Sound convergence zone will settle down over Seattle, while all the other places will be clearing up. It's as if we just cut and pasted our rain a couple hours ahead.

We are still looking at a storm Sunday and then some mountain showers with chillier temps afterward. The models, as previously stated, have been inconsistent, but after a brief break early next week we could see another storm Thursday the 29th.


Wednesday, October 21, 2009

Inconsistency in the Models

October 21, 2009

4:08 P.M.

Yesterday, it looked like the models were behaving fairly consistently. They all showed a (very) strong jet stream over the area and got the systems for the most part, although they were a little wobbly on some of the details. Now, looking at the models, lots of things have changed. The storm on Sunday, which first looked perhaps major but probably minor, was practically a no-show yesterday and even this morning. But the afternoon 18 UTC GFS shows it as a wet and strong low pressure system that may carry a little wind (but not too bad).

Friday we will see a low pressure front that will stall to some degree over the northern Cascades and southern Vancouver Island.

This picture (sorry facebook users, check the blogspot!) shows the total precipitation in the past 24 hours ending at 5 P.M. Friday. As you can see, the heaviest amounts are centered north of us. Still, we should get a decent shot of rain with this system. Sunday, we may be rain shadowed, but everywhere else will see rain nontheless. After that, we will be under the influence of a cool northwesterly flow, and all the passes (including Snoqualmie) should see snow. I'm not going to attempt to forecast what's going on after that. The models are all over the place.

Thank you!


Tuesday, October 20, 2009


October 21, 2009
3:38 P.M.

Looking at the weather models this afternoon, I noticed that we could see our first flooding event of the season next week if the situation shown by the models comes true. Let's take a look at the furthest time frame the extended WRF-GFS model from the UW goes out.
This model frame shows post-frontal showers over the mountains (notice the broken appearance of the precipitation over our area and how the mountains orographically enhance it). It also shows a very moist and juicy warm front out over the Pacific, and although this model doesn't got out far enough in time to show it hitting us, the global models say that it will, bringing heavy rain, wind, and mild temperatures. I hope that happens; that would be exciting.
Regarding the system I talked about yesterday, the model today shows that it will be very weak but also shows an extremely powerful (almost 200 knot!) jet stream powering it, so I don't really know what is going on there. We'll see.
Thanks for checking out the new blog!

Monday, October 19, 2009

A Consistent Pattern

October 19, 2009
10:44 P.M.

We are in a pattern of consistency as far as storms go. Several storms are lined up in the Pacific, and although we won't bear the brunt of them, we will see the tail effects of most. Here is the schedule as far as storms go:
1st storm: Wednesday morning into Wednesday afternooon

2nd storm: Friday evening

3rd storm (strongest): Sunday
All these storms will be fairly weak for our area because most of the energy is being directed north into the Alaskan panhandle. The Sunday storm will be the strongest for our area as more of its energy is directed directly at us. I'm looking forward to Monday though. There is a possibility of a strong storm system as a strong jet resides straight over the area. It isn't looking like much right now, but it warrants some attention


Saturday, October 17, 2009

October 17, 2009
9:06 P.M.

Hello everybody. I'm actually switching from facebook groups to blogger because I can post pictures on blogger. Still, I'll have them up on facebook, but I'll let everybody know that I am on blogger now as well via a message.

Both of these pictures are from Cliff Mass' blog... I don't want to get busted for plagiarizing...

This picture is a picture of the radar at around 4 P.M. After the main front came through today, we were under the influence of an unstable atmosphere with VERY heavy showers. I even heard some thunder. Where you see the red, rain is extremely heavy, with amounts of .4 inches occurring in 15 minutes! In contrast, we average .2 inches of rain in an entire day in the last week of November, statistically the stormiest and rainiest week of the year.
The picture above is a radar-estimated diagram of the total precipitation from the Rainwatch system, a new system/map thingy Cliff Mass is developing for Seattle Public Utilities. As you can see, the highest precipitation amounts are over the north coast and Vancouver Island, but Seattle and points north still got quite heavy rain, over an inch in most spots. Keep in mind this is radar-estimated, so the further you go from where the radar is located (I think it is Camano Island) the less accurate the results are. Also, there is blockage from the Olympics and some parts of the Cascades.
The next week looks pretty wet as we will be under the influence of a zonal flow, meaning the jet stream will be oriented more or less west to east across the Pacific, giving us systems on a fairly regular basis every 48 hours. The timing is uncertain, but we should see either rain or showers and sunbreaks every day with highs around 60.