First Impression: Easier Call/Second Impression: Crapshoot
May 4th, 2009 at 12:16 pm by Don Paul under Weather Watch 4
Parts of this week look to be tough calls. The operational GFS and NAM keeps us mainly dry on Tuesday, but Short Range Ensemble Forecasts (SREF) which include multiple runs of models, each with slightly different initial conditions (because we can never be certain of initial conditions) have been all over the map with a short wave going by tomorrow. All in all, it appears to me that the bulk of moisture with Tuesday’s system will stay south and east of us. Since the ensemble are all over the place, and the operational models are not, I’m going to lean toward the operational models. (I may regret that choice!) Somewhat more unsettled conditions return later Thursday night and continue into the start of the weekend, with some limited convection possible.
Any Update on Saturdays weather yet? In the afternoon into the evening? Was thinking showers in the morning giving way to just clouds in the afternoon, maybe a few peeks at the sun? Let me know what you think Don.
Thanks,
Rich
At this point, it doesn’t look terribly wet. But if there are showers, they’re more likely in the afternoon. In any case, right now it doesn’t look like a washout. Probably upper 50s to low 60s.
Doesn’t look like I’ll have to be backing down from my earlier dry forecast for Tuesday.
Related to my afternoon post, I’m a LITTLE concerned that the last 2 runs of our super microcast spit out a few showers tomorrow during daytime heating, and the UKMET seems to try to put a little precip in here as well. Most of the ensemble members and operational runs of the GFS keep us dry, as does the NAM and the Canadian GEM.
Don,
I’d like to be able to use your forecasts, and listing the chance of precipitation as slight doesn’t tell me much. I’d prefer it if you listed the chance for rain on a percentage basis.
Sorry, William. I don’t use percentages because research in our industry shows they are poorly understood by the public. For example, many people hear 20% chance of rain and assume that means 20% coverage of the area with rain. On the other hand, if I’m thinking a greater than 60% probability, I generally remove the word “chance” from my wording.
Percentages can be more precise, but that’s assuming the audience understands their meaning, or that I have the time to explain the meaning. From a purely statistical and scientific vantage point, percentages are likely the way to go. From a communications standpoint to a busy public audience, I’m not convinced they are the way to go.
Sure like it when the chance of rain is ZERO% Don! Come on warm up! According to your 6:00, not this weekend…there will be a lot of bummed out mothers!
There is growing evidence Mom and the rest of us aren’t going to see much sun on a Cool Mother’s Day. A trough over the Great Lakes favors plenty of cloud cover, and a bit of drizzle or a few spotty lt shwrs can’t be ruled out. The best chance for some Sct Shwrs on Saturday continues to be in the PM, but there are no signs of a washout. Sunday looks a little chillier than Saturday.
Still nothing especially encouraging about this weekend, overall. Saturday’s best chances for a Few Shwrs will be in the PM, although the chillier airmass behind a storm system won’t be here yet. There should be a good deal of rainfree time. Some of those showers will linger into the early evening.
Mother’s Day looks even a little chiller and more unsettled than it did yesterday. In the cold backwash circulation behind a departing storm system, there will be plenty of clouds (though we may still see some limited sunshine). A few showers might become more likely in any convection fed by breaks in the overcast. Right now, I’m forecasting a Sunday high of around 54, with a fairly brisk breeze. Some significant warming looks more likely to arrive by midweek next week.
Hey Don, The NWS is calling for a high of around 70 with partly to mostly cloudy skies, with a chance of thunderstorms in the evening. Does that sound pretty accurate?
I don’t see us getting up to 70…
Neither do the NWS zone forecasts, which go for upper 60s. I’m going for mid 60s, as I did last night, with skies becoming Partly Sunny, and Mostly Sunny meto later in the afternoon, due to a lake shadow.
Lots of rainfree time on a mild breezy Friday, but a few shwrs & tshwrs may form along the edge of the lake breeze in the afternoon. Still looks like Sct Shwrs and a few poss tshwrs arriving Saturday PM, mainly later, into the early evening, with breezy and chillier conditions setting in overnight into Mother’s Day.
Don,
I know what a lake shadow does, (I think) but I don’t know why or the science behind it. I think it has some of the same characteristics as LES. Care to explain?
Thanks!
That is absolutely amazing! Thank goodness for Lake Erie! Our wedding is at 3:30, with pictures from 4:30 to 5:30. Sounds like perfect weather!
The lake shadow is induced when the air over the chilly lake waters is cooler than the general airmass. A SW flow in that case is stable, because there is no upward motion for clouds to form.
Richard,
Not to disappoint you, but if your wedding is Saturday afternoon, I wouldn’t count on perfect weather–I have no idea how you came to that conclusion based on what I’ve posted or aired.
with skies becoming Partly Sunny, and Mostly Sunny metro later in the afternoon, due to a lake shadow.
That’s how…
A strong short wave will be approaching WNY during the afternoon. Its dynamics can easily overwhelm any stabilizing effect from the lake. I hope your guesswork works out–it could, but at this point, I doubt it.
By the way, Richard, I suggest you read the Area Forecast Discussion from the Buffalo NWS on Saturday’s scenario. That’s in case you don’t accept my reasoning. It’s up to you whether to be prepared or not–that’s your call.
We’ll have to keep an eye on those late afternoon/early evening convective cells in WNY. There’ll be a strong jet max aloft, which can induce additional lift. Along with cold advection, some of those winds might stand a chance of mixing down to the surface, along with some hail. It does not look like a prime setup for severe convection right now, but it does bear monitoring at our end.
The Climate Prediction Ctr today issued its final La Nina advisory. By statistical analysis, we are now in ENSO-neutral conditions. The majority of the models used at the CPC project these conditions through the remainder of the year.
ENSO-neutral conditions can, along with other factors, allow tropical cyclones to develop in the Atlantic basis with less disruptive wind shear (that’s what El Nino produces).
Also, should ENSO-neutral conditions persist into the cold weather season later in the year, there has been some statistical correlation between those conditions and greater variability in our regional winter weather. It’s simply too soon to know whether these conditions will still be with us in November and December. This past winter’s la nina developed quite quickly and rather unexpectedly, even when we had a shorter lead time to predict such a phenomenon. However, we can be confident ENSO-neutral conditions will persist for the summer. This does not have much significance during warm weather months for WNY weather.
Vicious derecho crossing from Missouri into srn Ill at 12:25 today.
Very interesting, hope it’s ok to post a link.
http://www.intellicast.com/National/Radar/Summary.aspx?location=USAR0336
Finally, some interesting convective activity around YYZ; just in from taking a few neat shots; hopefully things will pick up a bit later today.
Talk about stealing my “Thunder”! I didn’t get a chance to get to the website earlier but found out about the same time you did, or so it seems!
Wow – up to 50 MPH wind gusts forecasted for Saturday! I guess I’ll batten down the deck furniture. Can’t spell windy without WNY.
Who is forecasting 50 mph gusts? While it will become very windy late in the day into the evening, and while there is a limited risk of strong thunderstorms which could produce such gusts, I don’t know your source of “forecasting.” That would be premature, and it’s not from the NWS or me.
By the way, my latest forecast, updated at 12:30, is on 844-4444. It does call for possible gusts in the late afternoon/evening period of more than 40mph, exclusive of any isolated stronger gusts which might develop with afternoon tstorms.
Hey Don. Will the Lake Shadow be in effect tomorrow? Looks like it already is today looking at the radar.
Dark clouds and pretty good rumbles of thunder south of Holland currently
My source is wivb.com as of 1-3pm.
“Good Thursday from Meteorologist Mike Cejka:
Mostly to Partly Sunny, with an isolated shower/thundershower possible this afternoon well north and southeast of the metro. Scattered showers and a few thunderstorms are likely Saturday. Strong winds could mix down to the ground in some of the storms Saturday afternoon and winds will continue to remain very gusty behind a cold front Saturday Evening. Temperatures take a big dip for Mother’s Day along with a brisk breeze, with readings in the low-middle 50’s. Morning clouds may result in a few morning showers. It still looks as though there may be a little more sun during the afternoon. Temperatures begin to moderate more noticeably on Tue-Wed next week.
FRIDAY; Mostly to Partly Sunny and Mild with an Isolated Shower/Thundershower, mainly well north and SE of the metro, but mostly rainfree. High: 67-71. Lt. S/SW 10-16. Clouds increase overnight with just a chance of a shower.
SATURDAY; Scattered Showers and Thunderstorms are Likely. Some Storms could become Strong. Becoming Very Windy by late. Gusts to 45-50 mph are possible. High; 65-70.”
Tomorrow is a very different story, Richard. Strong short wave approaching, jetstream dynamics. Bndry lyr winds don’t go SWly until late in the day anyway, primarily behind cold front.
Good luck in any case–sorry nature couldn’t have been more wedding-friendly.
“Possible” is not the equivalent of “forecasted” windy–and it’s not really much different than my earlier mention of gusts of 40+.
Bloggers; if you’re going to quote or paraphase a forecast here, please source it.
To be fair, I shouldn’t pretend surprise at strong wind projections, since I hit on the possibility of strong gusts and hail with some tstorms last night on the air and, at 11, projected Very Windy conditions behind the front in the evening.
I just like to see forecasts sourced on this blog, since there are a couple of sources I take much less seriously than others. The NWS fcst carries much more weight than that from a certain private fcst group or cable channel local fcst.
OK, let me rephrase. All I’m saying is that with forecasts warning of the possibility of maybe up to: 40+ mph gusts (D. Paul, see above) 40-50 mph gusts (M. Cejka, 1-4pm, wivb.com), and 50 mph gusts (NWS Buffalo, 3:46pm) for late Saturday, I think it is sensible to secure one’s deck furniture tonight or tomorrow morning. Perhaps others would agree. My apologies to those offended by my unclear, un-annotated post(s).
You (still) can’t spell windy without WNY.
Windy–couldn’t agree more with your last post.
One sliver of a bright spot for the Richard Wedding. The heaviest, most persistent precipitation from this strong storm system will be crossing from central MI into Ontario, so our activity will be more Scattered. There will be something of a dry slot (not a lake shadow, but a classic dry slot associated with maturing cyclones) following the cold frontal passage. At that time, we’ll temporarily dry out, but we’ll also see widespread SW to W winds increase to 25-40 with stronger gusts all across the region (by late afternoon).
Lightning and thunder over north Toronto at 7:40pm; I thought I was hearing things but there IS one red pixel on the King radar map for 7:30pm!
Don, recently in school we took the NYS 8th Grade Science test and there was one wx related question with a low in the Iowa-Illinois-Missouri region and the question was “What direction will the storm likely move?”. I first thought “That’s a crappy question, a lot of factors will dictate the direction the storm moves” so then I decided I’d just put the common “Weather Channel” person answer of east to ENE. Today I found out that one of the science teachers in our school said the answer was North to NE. How could we have known? What if the storm dropped out of Canada and was moving southward? What if it went just due east? What if it was stationary and slowly dissipated? What if a was an ‘oddball’ and moved a little bit west? Of course it could move north, but wouldn’t it be more likely to move east to ENE until it got off the coast, or even south and then up the coast or Apps? The question was silly IMO because it could move so many ways. The common person would likely say east, wouldn’t they? Am I missing something here?
If I’m not, I am furious… On Monday I’ll be allowed to ask my science teacher and another science teacher because make-ups finished today…
From the context you’ve given me, the answer would seem to be indeterminate. If you knew there are a strong blocking ridge to the east of the low, you could make a case for its moving N or NNE. Without a high amplitude blocky type of pattern, the most favored answer would NOT be to the N or NE in that part of the country, but more likely E or NE. It might be a different story for a deepening cyclone developing near Cape Hatteras, but that’s not the example you’ve provided.
It was too simple a wx map. It had fronts and what could have been a weak high to the east (I think it was at something like 1012-1020 mb at the very edge of the map), but well off the central eastern seaboard based on the pressures provided. They did not show much at all of the Atlantic, the Pacific, Greenland Canada, and Alaska, so you couldn’t use the ridges/troughs over there. There wasn’t enough, at least for me. I’ll try to find a similar question on one of the past tests.
However, considering 70% of the people had no clue what they were looking at or what “That big L” was…
Some thinly scattered elevated convection has developed to our west, SW and in a few spots in WNY (since cells have actually intensified over chilly L Erie, it’s safe to assume these cells are elevated above the boundary layer, with elevated instability in a layer aloft. Were they surface based, they would not strengthen over those waters–not that they’re very strong. This elevated layer can be found in the evening sounding).
So, the evening forecast has to be revised to include some isolated showers & tshwrs, which were not showing until much later tonight in earlier model runs.
Carbondale Ill had a gust to 106 and Paducah KY went to 100mph with that derecho, from straightline winds. There were also several tornadoes, but most of the wide swatch of damage came from the straightline winds. System started in ern KS and is into VA at this hour.
No wind advisory issued as of yet, but I still expect strong winds following the cold front in mid-afternoon, exclusive of any possible strong gusts with prefrontal convection.
Not looking too good as of now, but I hope Richard can maybe catch a break from mother nature for the wedding.
Heavy rain and small hail (largest I could see was about 6mm diameter), lots of lightning around 9am. Weather network has reports of “toonie” sized hail in the west end of Toronto (I’m a bit sceptical but I guess anything’s possible!). Btw, it was very interesting to watch the storm as it approached Toronto and see the new cell form over the lake when it appeared everything would miss us.
http://www.weatheroffice.gc.ca/radar/index_e.html?id=wkr
To see a 3 hour cycle, click on ‘customize you map’, set 3 hr and hit close.
Sorry, should have also said (after closing), hit the ‘play’ button to the upper left of the display. Also should note absolutely no wind at all with the cell that passed over my area (north Toronto).
I suspect Richard is a little preoccupied to visit the blog on his wedding day. But he may luck out, to a certain extent. The prefrontal convection should be east of us by the time of his ceremony, and there should be a dry slot-of-sorts behind the front before synoptically driven cold advection showers move in late. The timing is tight, and anything outdoors at his ceremony is going to be buffeted by the strong winds (and falling temperatures). But I suppose all that beats having tstorms overhead at that time
I hate Buffalo!!!
Thanks for the update Don! Needed to, we have 2 options for pictures, if we can catch a break between 4:45-6, with no rain it would be amazing, the wind might hamper things, but as long as we can stay dry, it would be awesome! Thanks so much! Come on Dry Slot =)
In the interim, a Severe Tstorm WATCH has just been issued for all WNY until 7pm. The primary threat would be damaging straightline winds, with a lesser threat of hail.
However, I expect the 8 WNY counties to be cleared from the Watch well before 7pm, owing to the analyzed position of the cold front to our west, prefrontal pressure falls, satellite and radar imagery.
In addition to the Severe T-Storm WATCH posted until 7pm for all of WNY, a
WIND ADVISORY is issued from 4pm today through 2am Sunday. Strong Southwesterly winds will continue to strengthen this afternoon into tonight. Sustained winds will generally average between 25-40mph with gusts as high as 55mph+. Winds of this magnitude may produce some minor property damage. Be sure to secure all loose objects such as garbage cans and any lawn furniture that you may have already put out this season. Motorists, especially high profile vehicles, be sure to use extra caution while traveling on elevated road spans. Winds will gradually subside late tonight and tomorrow as the storm quickly pushes toward the Canadian Maritimes. Stay tuned for the latest tonight on News 4…
72 dbz cells over the Adirondacks near Tupper Lake,NY
http://radblast-mi.wunderground.com/cgi-bin/radar/WUNIDS_map?station=TYX&brand=wui&num=6&delay=15&type=N0R&frame=0&scale=0.125&noclutter=0&t=1241895772&lat=0&lon=0&label=you&showstorms=0&map.x=400&map.y=240¢erx=-256¢ery=576&transx=-656&transy=336&showlabels=1&severe=0&rainsnow=0&lightning=1&smooth=1