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Preliminary Conn. Snowfall Totals

The image is comprised of snowfall totals from various sources, some of which include the New England forum on here. Snowfall totals across Connecticut were pretty uniform around 3-4", although slightly lower amounts occurred along I-95 and there were a few isolated amounts around 5". I'll post a contoured color map within the next 12 to 18 hours.

Quincy

Quincy

 

Mid-Atlantic Snow forecast For January 17 (Initial)

Here comes the first notable snow event for the southern Mid-Atlantic this winter! A powerful upper-level vort. max will push through the region tomorrow, bringing strong dynamics with it that will help create a period of moderate to heavy snowfall. The snow will start in the morning hours in the higher elevations and will work east through the afternoon and evening. The I-95 corridor will probably start off as rain in the morning. Some sleet could accompany the transition in the late morning and early afternoon, with the changeover to snow occurring around mid-afternoon on I-95 between DC and Richmond. This could lead to large traffic headaches during the afternoon rush hour. Just in case some people might be thinking it, the current forecast is not favorable for thundersnow/thundersleet.

Ellinwood

Ellinwood

 

Holy bombogenesis (W Pac 1/15/2013)

Surprised I haven't seen any discussion about this bomb on the board. Check out the DT pressure map I attached below. You'll never see a better signature of a tropopause fold. And obviously all sorts of upper level support with massive divergence aloft. From Ryan Maue:

OKpowdah

OKpowdah

 

Snow Forecast: CT and Surrounding Areas

I see this event as a widespread 2-4 incher across most of interior SNE. The tough call comes along I-95 for BOS-PVD-GON, as often is the case. I do think most areas even along the South Shore get a thump of snow/sleet at the beginning. I'm not really all that confident on widespread 4"+ amounts, but I've outlined an area with a black dotted line that could see locally 5-6 inches. I also expect precipitation to quickly shut off in the morning (by 7 or 8 a.m. across much of Connecticut) and taper to drizzle near and SE of I-84 with pockets of "snizzle" or flurries/freezing drizzle across the higher terrain. Connecticut Forecast: On the shoreline...(< 2 inches) Although there may be a period of snow and sleet, temperatures near the ground will likely remain above freezing through most of the event. Combine this with with a changeover to plain rain and areas near the coast should see less than 2 inches of snow/sleet. Inland...(generally 2-4 inches) Most areas should see a period of moderate snow before a changeover to sleet. Precipitation may actually end as a period of drizzle late Wednesday morning, with pockets of freezing drizzle in the hills. Before the changeover, generally 2 to 4 inches of snow/sleet is expected. Highest elevations...(locally 4"+) Due to colder air in place, Litchfield County and northern Tolland County may stay near or below freezing throughout the entire event. The end result is NEAR 4 inches of snow with localized totals that could reach perhaps 5 or 6 inches.

Quincy

Quincy

 

Prolonged negative QBO

This latest easterly QBO period is on track to become the "strongest" episode on record. Below I have plotted the QBO along with an integrated QBO index which very simply sums the monthly QBO across each full easterly period. So far this current -QBO period has an integrated magnitude of -280.62 ... which falls just short of the 2001 -QBO period with a magnitude of -280.79. The mean is -191.6 and standard deviation is 48.6. Data so far for January 2013 suggests the monthly QBO should come in negative once again. It's possible the recent SSW has helped stunt the descent of the westerlies, and is prolonging the easterly QBO. This will put the -QBO period at 18 months long ... behind only 2001 which was 19 months.

OKpowdah

OKpowdah

 

Mid-Atlantic Snow forecast For January 15-16 (Only/Final)

Very tough call on the southern edges of the contours as sleet and freezing rain make an appearance as far south as northern MD (not including the mountains). Some locally higher totals of 4-8" are possible, and I put a 4-8" contour area in the spot where I think that is most likely to occur. Ratios should be above 10:1 at least at the start of the snowfall across northern PA before the warmer mid-level air tries to nose in.

Ellinwood

Ellinwood

 

Snow Chances Monday Night and Tuesday

Sorry I have been MIA over the last couple of weeks ... I spent the holiday with fiancee in PA (btw, the 12/29 storm was fun!) and then caught some kind of crud/flu that I have been fighting since the first of the year. This upcoming "event" is actually the most I have looked at anything weather-wise since the new year. Anyways, there are some rumblings of a potential snow or mix event for the Monday night and Tuesday time frame. Precip is expected Monday Night and Tuesday with a secondary wave behind a cold front that will cross the region Sunday Night. The air mass ahead of the front is obviously not very supportive of wintry weather ... with highs progged to creep into the lower 70s in some spots. Even behind the front though, really cold air fails to make it into the Western VA/NOVA areas ... therefore I wouldn't get to excited about this "event". Low level thicknesses across most of western and northern VA would support frozen precipitation, however a warm layer above that (h8-h7) would support an IP/zr/rasn type of event. Marginal surface temps should help to mitigate any onset-zr threat. North of I-66 looks to be the best for enough cold air for snow, however decent precipitation may struggle to make it this far north. Overall, I would expect this event to be characteristic of Early November or early spring than mid January. GFS sounding near Leesburg, VA: GFS sounding around Harrisonburg, VA:

thunderman

thunderman

 

A Look Back at Dec. 29 for Connecticut

Map above is based on reports from various sources, including this board, the National Weather Service and data viewers from across the state sent in. Event Summary: Scattered snow showers reached portions of western Connecticut by late morning on the 29th. This snow was associated with weakening low pressure over Pennsylvania. The main storm began to develop east of Virginia during the afternoon. Steady precipitation overspread the state from southwest to northeast between about 1 and 3 p.m. Most areas saw snow, but some ice pellets and graupel were reported near and southeast of I-95. Coastal New London County even switched to rain for a time. Colder air moved in and a heavy band of snow set up over central and eastern Connecticut. Snowfall rates between 1 and 3 inches per hour hammered portions of New Haven, Middlesex and New London Counties. This area of heavy snow eventually moved northeast and also impacted Tolland and Windham Counties. This band was a bit more intense than some predictions, resulting in higher snowfall amounts than forecast. Extreme western Connecticut was too far west to be affected by this heavy snow. The heaviest snow fell between about 4 p.m. and 9 p.m. before the shield of precipitation began to break apart. After midnight, the only leftover precipitation was occasional snow showers. By then, the bulk of the accumulation was over. I still find the Feb. 7, 2003 analog to be quite good for this event, with respect to Connecticut. It's clear that with a warmer solution, southeastern Mass. could not have had such high snowfall amounts. Shift the axis about 75 miles SW and you get a VERY good match-up. This analog showed up as a strong match about 2-3 days before the event: The point was that interior eastern Conn. and NW R.I. was favored for the highest amounts. Forecasts for the storm were decent within 24 hours of the event, but before that, most were playing catch-up. What was expected to be a minor event turned into a moderate one with several snowfall totals in the 10-12 inch range, especially across eastern Connecticut. My own forecast (from 5 p.m. the night before the storm) was too high for areas SW of Conn. and was generous as well for eastern Mass. With that said, I could have also pushed the 6-10" zone back further west: The image below shows approximate snowfall totals from across the region: Heavy snow focused in on the eastern half of Connecticut and the radar image below shows moderate to heavy precipitation pounding southern portions of the state. At the same time, some observed 2 to 3 inches of snow per hour for a few hours.

Quincy

Quincy

 

Mid-Atlantic Snow forecast For December 28-29 (Initial)

Another quick-turnaround forecast as the next system looks to bring widespread 1-4" totals to the Mid-Atlantic, with higher totals in the central Appalachians. Marginal boundary layer temperatures and initial surface winds out of the southeast makes finding that 1" boundary a challenge yet again. Luckily, the upper-level temperatures are cooperating more this time around, so if your surface temperature is at or below freezing you'll almost certainly be getting some accumulation. Mixing areas will mostly be rain/snow, but some sleet is still possible. I'll be traveling tomorrow, so if/when I update it will be in the evening.

Ellinwood

Ellinwood

 

12-27 Snowfall forecast for New England

For posterity's sake, here is my final call for snowfall totals for the New England area. Expect maximum accumulations in the Monadnocks region of southwest NH and in a swath from eastern NH through western and central Maine ... where up to 18" could fall.

OKpowdah

OKpowdah

 

Mid-Atlantic Snow forecast For December 26-27 (Only/Final)

Forecast confidence is low as most of the snow falls at the front end of the system before many areas switch over to mixed precipitation and/or rain. Very small changes in temperature at various levels of the atmosphere could lead to significantly different snowfall totals, especially east of the mountains. The northwestern parts of the forecast region could/should stay all snow throughout the event, which roughly matches up with the 8-12+ inch area along and west of the mountains. There will be some lingering snow in the central Appalachians at the end of the event as cold, northwesterly flow takes over.

Ellinwood

Ellinwood

 

Exploring Ensemble Sensitivity Analysis for Dec 27th Winter Storm

Using 00z NCEP (including 20 ensemble members), let's begin by defining the EOFs describing the greatest amount of variance in the ensemble forecasts: Alright what is this telling us? First of all, note the asymmetry in the mean/spread ... there is a maximum in the spread over E PA and NJ ... to the west-northwest of the mean low. EOF1 -- explains 46.6% of the variance -- describes the depth of the low for the cluster of solutions to the NW of the mean ... in general the average SLP across the domain of the low ... so a positive EOF1 is related to lower SLP. EOF2 -- explains 21.5% of the variance -- describes the west-east position of the low ... positive EOF2 is west of the mean, negative is east of the mean. EOF3 -- explains 18.2% of the variance -- describes the north-south position of the low, but also the amplitude of the system ... notice the maximum is colocated with the mean low ... a negative EOF3 is associated with a stronger low off the delmarva peninsula with higher pressures to the north and northwest. Perhaps as you can tell, a negative EOF3 pattern is actually quite similar to the SLP pattern we might look for in an East Coast winter storm threat. So although it explains less of the variance in the ensemble forecast, I'm personally most interested in this EOF. So now let's use this forecast diagnostic and find the correlation to a variable in the ensemble forecast, such as 500mb height. Here we can see that the greatest correlation (sensitivity of the EOF3 to the 500mb height) is associated with the trough moving through the Northeast and Quebec over the next 48 hours. Lower heights over the northwest Atlantic over the next two days correlates with a negative EOF3 ... and a SLP pattern characteristic of Northeast snowstorms. More later.

OKpowdah

OKpowdah

 

Mid-Atlantic Snow forecast For December 21-23 (Final)

No major changes to the forecast, though I did decide to go a bit more aggressive with the totals in some areas. The most notable changes were in northern PA and southwestern NY, with an 8-12" contour added as lake-effect off of Lake Erie helps drive up totals. The back edge of the main area of precipitation is expected to change over to snow, but how much of that actually accumulates ahead of the later snow is uncertain. Localized totals of >12" are possible within the 8-12" contours.

Ellinwood

Ellinwood

 

Eastern U.S. Winter Storm Threat Dec 27th

Let's begin with the state of winter right now. Where is it? Recent reports say Russia has found it (http://rt.com/news/r...emperature-379/). In other news, the planetary reconfiguration that is occurring right now. Major ridging burgeoning from the Aleutians to the Bering Strait and right up over the North Pole by Saturday. The effect? Well at 22/00z that's 125kts at the DT crossing the NP toward the western hemisphere. Clear at this stage the magnitude of nonlinear processes leading to anticyclonic breaking of the ridge over the NP toward Greenland this weekend. Quite a signal for developing negative AO and negative NAO regime. At the same time, we have this blizzard ongoing over the Plains associated with an impressive trough, continuing to amplify tomorrow (around -2.5 to -3SD anomaly at 500mb). The trough breaks over the Northeast into Quebec this weekend, amplifying downstream ridging from the northern Atlantic into the Davis Strait. By Christmas Eve, this ridge is starting to bridge with the NP ridge. By Christmas Day, we're actually on our way to achieving a quasi-stable anticyclone from the Hudson Bay to Baffin Island ... i.e. a west-based negative NAO. This pattern is clearly characterized by a tumble in both the AO and NAO domains as seen on the forecast maps I'm presenting here. Notice also in the above map the disturbance (lowered DT / PV anomaly) over the Davis Strait. Tracking it back in time reveals that it originates over eastern Russia currently and is brought around the Pacific ridge as it is bursting poleward. From the Davis Strait, this disturbance continues westward (south of the anticyclone) into eastern Quebec and Newfoundland and Labrador by the 27th. In the end this disturbance in fact plays a crucial role in the 50N/50W slot, with its miriad relationships in Northeast snowstorms. So I see you perked up at the mention of the word "snowstorm." Yes, I suppose I should get to the actual storm itself. The storm of interest originates as a shortwave from the GOA vortex. The shortwave is ejected into the Pacific Northwest on the 24th. At this time, attention turns back to the North Pacific where a strong shortwave is plowing under the recently broken-off ridging from the Aleutians to the NP. The shortwave continues eastward, amplifies and breaks just off the west coast. This results in the Pacific jet briefly splitting as ridging amplifies downstream over the western U.S. ...can also note a relate spike in the PNA at this time ... so certainly convergence of teleconnections supporting this event. Coinciding with this PNA spike, the shortwave associated with our storm amplifies into the southern Plains by late on the 25th-26th. The general progression of events that I outlined above is supported in the model guidance. But some minor discrepancies leads to large disagreements in the end result for the eastern third of the nation. Some of these disagreements I think can be related to the span of time between the ejection of the shortwave and the PNA spike ... the greater separation there is between these two events, the further east the shortwave will amplify. ...Can be thought of simply as timing of the group energy catching up to the shortwave. By the evening of the 26th, we're watching the development of beautiful dual-jet structure, with excellent upper level mass evacuation over an intensifying low. The ECMWF has tended to want to cut this low inland ... actually track it along the spine of the Appalachians, meanwhile attempting but failing to produce a secondary low along the coastal baroclinic zone. The GFS and CMC both achieve this secondary development with the coastal low taking over. Below I've included some maps from the 20/12z run of the GFS that presents the features I discussed above. It's worth noting on the DT theta map signs of convection wrapping into the system from the central Atlantic --> Meteorology ... helps amplify downstream ridging and the overall system. Modelology... can introduce potential convective feedback errors in the model forecast. Some things to think about for the coming week.

OKpowdah

OKpowdah

 

Mid-Atlantic Snow forecast For December 21-23 (Initial)

Since my forecast maps cover parts or all of several different sub-forums in the eastern US, I've decided to just post my snowfall forecasts on this blog to get more exposure without having to spam all of the different sub-forums with my forecast. For those of you who don't know, my main focus with snow forecasting is centered around the Mid-Atlantic. The geographical location does not regularly change from storm to storm, and neither do my snowfall contours. You can interpolate snowfall totals within the contours (for example, the outer edge of the 2-4" contour is for 2", and in most cases the center of the 2-4" contour is closer to 3-4"). I usually try to issue an initial map and one updated (final) map, though sometimes I like to throw in an a second update. Other times, I might only issue one forecast near the start of the event. No updates are issued once the snow starts to accumulate within the forecast region (except in rare cases when the accumulation starts just before I get home from work). ----- Most if not all of the snow with this disturbance will accumulate well behind the cold front, with lake-effect snow bringing some respectable totals to western PA and WV. Most of the snow will fall Friday morning through Saturday afternoon. Low-level temperatures will limit accumulations across central and eastern PA. South and east of the 1" line could see snow in the air Friday, with little to no accumulation expected.

Ellinwood

Ellinwood

 

Blogs for non-mets

Some non-mets have asked for blogs recently and we're aware there are plenty of members here who are just as informative as a degreed meteorologist. Therefore, we'll allow access to blogs for non-mets by request and allowed on a case-by-case basis. We're stilling figuring exactly how to go about doing this but you can still reserve your place once we get a plan in place. Just PM one of the admins. Thanks.

Wow

Wow

 

Low stratus/fog Keeping Temps Down For Some

Low status/fog has been hanging out all day across some portions of MD, Extreme Northwest VA, and Eastern PA. The result has been a near 20 degree temperature gradient across west-central VA and southeast PA! Some current temps as of 4PM across the area: KSHD 67 (High unofficially 69) KOKV 55 (High unofficially 61) KIAD 60 (High unofficially 62)

thunderman

thunderman

 

Introduction

I just want to take a few minutes outline the areas that I will be posting about and to introduce myself as I do not post much in general and rarely really post outside of the Mid Atlantic forum. I have been a member since the Eastern era of the board and have been tracking the weather as an enthusiast since the early 2000's. I moved to Southeastern PA to go school at Millersville in August 2008 and graduated from there with a B.S. in Meteorology in 2011. I enjoy forecasting in general and especially mesoscale forecasting. I try to get out and do some local chases, though lately I haven't gotten out as much as I would like too. I hope to keep this blog updated at least weekly with a focus on general forecasting. Obviously during slow times you may not here much out of me. On the other hand, during severe weather days I may use this blog to voice my opinions on the very short term as the event evolves and update several times a day. My "area of interest" (or whatever you want to call it) will generally be the Shenandoah Valley of Virginia and the more western suburbs of DC. I may post outside of this area occasionally if there is something overly interesting happening and things are dull here. As a computer/technology, don't be surprised to see the occasional technology oriented post either!

thunderman

thunderman

 

Welcome to our new Blog System!

Welcome mets to the new Blog System offered by American Weather. I hope this new feature will help your thoughts stand out from the crowd with the use of your own personal space. Spread your word! As you become acclimated to the new system, if you have any questions just shoot me a PM.

Wow

Wow

 

The catalyst for a pattern change

A significant cyclogenesis event in the North Pacific will be the primary catalyst of a pattern change over the next few days. Let's take a look at the evolution over the Pacific into western North America. Notice our N Pac storm gets dual jet support and really goes to town over the Aleutians. Wait isn't that where a massive ridge was last week? ... or for that matter the last three months. Well that's one thing that changes. The ridging once over the Aleutians and Bering Straight retrogrades west, while the N Pac storm breaks cyclonically northward. It's really a beautiful event. Minor flat ridging over the eastern Pacific gets pumped up into the Gulf of Alaska, with an intensifying polar jet streak pushing north into the Yukon. What happens after that? Fantastic classic anticyclonic wave breaking into British Columbia! The result is a 170kt+ northerly jet diving into the Pacific Northwest. So you know the trough and all that energy bottled up over Alaska and the Gulf? Well a lot of that comes pouring southeast on the wings of this jet into the northern Rockies So that's the atmosphere's plans for Saturday.

OKpowdah

OKpowdah

 

Welcome to our new site!

Welcome to our new content-managed, community-driven web site, powered by our online community of professional meteorlogists and weather enthusiasts alike. The creation of a true front page will help to showcase many of the well-written articles, blog entries, and forum posts which may have otherwise been buried deep in a long forum thread. This new design will really show how resourceful our growing online community can be.

Wow

Wow

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