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Severe weather and more

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What is the Supercell Composite Parameter?

Multiple variables are important to consider when it comes to supercell thunderstorm development. The Supercell Composite Parameter (SCP) was created to factor three important ingredients to determine how favorable an environment is to produce supercells. SCP focuses on instability, wind shear and helicity (potential for updraft rotation). SCP is a parameter that starts at zero and becomes higher as there is better overlap of parameters to favor the formation of supercells. For example, an SCP o

Quincy

Quincy

 

Weekend Severe Threat: Dec. 12-13

Another vigorous through is forecast to sweep through the south-central states over the next few days, bringing a threat of thunderstorms to the region. Although this threat looks substantially less impressive than the event in mid-November, there still exists the potential for at least a few severe thunderstorms, especially Saturday.   The setup for Saturday has had a lot of question marks and red flags from the start, but now that the event is approaching, things are coming into better focus

Quincy

Quincy

 

Violent U.S. Tornadoes: 1962-2011

Over a 50-year span from 1962 to 2011, the most violent (F/EF-4 and F/EF-5) tornadoes occurred over Oklahoma and Mississippi. The maximum grid-points reported 16 over that period, with two of those grid-points in central Oklahoma and one in central Mississippi. While a broad area from the Plains to the mid-South sees the most tornadoes overall across the United States, there are three sub-areas with the most violent tornadoes. Much of Oklahoma falls into that category, as it is widely considere

Quincy

Quincy

 

Updated: Severe WX Outlook, NE, Mid-Atl.: Friday, April 19th

A strong cold front approaches the Appalachians Friday afternoon and evening. Along that cold front, a squall line with thunderstorms is currently expected is develop. (Marginal threat) Middle Appalachians into Pennsylvania, northwestern New Jersey and interior New York: Daytime heating is expected to push temperatures into the low to mid-70's in the valley locations with mid to upper 60's in the higher elevations. Low and mid-level clouds will likely limit just how unstable the atmosphere c

Quincy

Quincy

 

Updated Snow Forecast: Feb. 8-9, 2013

I expect mostly snow for just about all of southern New England (pictured on this map). Although there may be a brief mixture along the I-95 corridor in Conn./RI, I expect crashing temperatures and heights to bring a wind-driven snow right down to the coast and into eastern Long Island. As far as snowfall totals go, I think that higher ratios will help push NW Conn. and W Mass. to 20"+. Further east, heavy precipitation will offset somewhat lower ratios for 20"+ from IJD to BOS. There is still

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Quincy

 

Upcoming Severe Threats: 5/1

The final few days of April finished on the quiet side in terms of severe and that continued into May 1st. With that said, a larger-scale pattern change is likely to be accompanied by multiple threats of severe weather in the coming days. Saturday 5/2: Not seeing anything major here. Although we should finally see some modest instability up into the central Plains, dew-points are only expected to rise into the upper 40s to lower 50s across the area with some weak forcing during the evening. One

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Quincy

 

U.S. Tornado Days Per Year

The United States has a greater frequency of tornadoes than most other counties. For many factors, the vast majority of tornadoes occur east of the Rocky Mountains across the continental U.S. Although the central and southern Plains region is widely considered to be "Tornado Alley," there are other areas that see just as many tornadoes, if not even more. The two graphics below are adaptations of NOAA/NWS SPC graphics found in their Tornado Environmental Browser. A broad area from the east slope

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Quincy

 

Tuesday Tornado Threat – Sunday PM Update

A tornado threat is still being closely monitored for Tuesday, as computer model forecasts and trends have been fairly consistent with the potential for severe weather on February 2nd for quite some time. There really are no major changes from the previous forecast, but there are still a few question marks that need to be resolved. Some new high resolution model guidance that came out Sunday night suggested that the threat may be leaning towards a higher impact event than a lower impact one.  

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Quincy

 

Tornado Threat for Tuesday, Feb. 2nd

The threat for severe thunderstorms, including tornadoes, continues for Tuesday. The area of focus is the lower Mississippi Valley into portions of the Tennessee Valley and lower Ohio Valley. Nothing significant has changed from the computer models, suggesting that a severe weather event is still probable Tuesday into Tuesday night with at least a few tornadoes possible. There are still details to nail down, but at least a few key ingredients are in place for tornadoes across the region.   Thi

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Quincy

 

Tornado Outbreak Expected Tuesday, Feb. 2

A tornado outbreak appears likely on Tuesday into Tuesday night across portions of Alabama, Mississippi and Tennessee. Over a broad area from the lower Mississippi Valley to the Tennessee and lower Ohio valleys, scattered severe thunderstorms are expected to develop Tuesday afternoon, continuing into Tuesday evening. The threat will shift east overnight, gradually lessening, especially after midnight. The setup looks favorable for several tornadoes, including at least one or two strong tornadoes

Quincy

Quincy

 

Supercells in Massachusetts Aug. 4

A series of supercell thunderstorms moved through central and eastern Massachusetts this afternoon. Some of the storms prompted tornado warnings and there were multiple significant severe weather reports as a result. Some of the thunderstorms originated as far west as eastern New York and later reached peak intensity as they moved into portions of central and southern New England. Even the coastal community of Boston was hit with some regionally impressive severe weather. The prelude to these a

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Quincy

 

Snowfall Forecast: Nov. 26-27, PHL-BOS

An early season storm is expected to bring a heavy, wet snow to the interior hills of the upper mid-Atlantic region and New England on Wednesday into very early Thanksgiving morning. While the big cities from Philadelphia to New York and Boston can expect some snow, the greatest amounts will be to their north and west. Low pressure will develop along the Carolina coast this morning and ride up the East Coast. With the low passing close to, if not over Cape Cod, no strong high pressure center in

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Quincy

 

Snowfall Forecast: March 6-8, 2013

Just a very brief discussion: Low pressure slowly moves east of the mid-Atlantic coast Wednesday night into Thursday. A relatively broad storm with possible multiple low centers spin around and pinwheel periods of snow (some rain mixing in at the coastal plain) through the region from Wednesday into Friday. This looks to be an elevation-dependent event, but heavy amounts or precipitation across eastern Mass., eastern Conn. and much of R.I. will help offset some of the "snow losses." In those a

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Quincy

 

Snowfall Forecast: January 25-26, 2013

This isn't really a big event, but due to the amount of discussion it's had, I felt a map was warranted. Low pressure moving through the Great Lakes brings an usual push of generally light snow towards the Appalachians. A new area of low pressure is forecast to form east of the mid-Atlantic region, enhancing snowfall amounts ever so slightly around the coastal plain. This map does not show it, but light snow should extend southward into Virginia. I believe that most areas will see an inch or l

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Quincy

 

Snowfall Forecast: February 8-9, 2013

I just want to quickly share my latest thoughts for Connecticut and surrounding areas. There's little doubt that a strong storm with plenty of precipitation will impact the tri-state area and southern New England Friday into early Saturday, but there are still a few details to discuss. Concern #1: Mixing along the shoreline. An initially "warm" boundary layer may cause mixed precipitation to fall near the Connecticut shoreline and coastal Rhode Island for several hours. With that said, as lo

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Quincy

 

Snowfall Forecast: February 26-27, 2013

Outside of the hilly terrain across the interior, this snow event does not look like a big deal. I expect 3-6"+ across the east slopes of the Berkshires and much of Worcester County. Connecticut only sees a brief period of rain, with generally 1-3" across the northern hills. The boundary layer temperatures are simply too marginal for much to change, especially with dew-points in the upper 20's as of early Tuesday evening. Downstream observations don't indicate that cold air damming across New E

Quincy

Quincy

 

Snowfall Forecast: Blizzard of 2015

A major snow storm is projected to bring blizzard conditions to much of New England Monday night through Tuesday. When all is said and done, many areas in and around the Boston area can expect two feet of snow with locally higher amounts. Despite the European model staying the course with greater snowfall amounts for areas around New York and New Jersey, it appears that most other data favors sharply decreasing snowfall amounts west of southern New England. As low pressure rapidly intensifies a

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Quincy

 

Snow/Ice Forecast for CT & Vicinity

I expect light snow to reach the NY/CT and NY/MA border around 9 a.m. or so and then overspread the area from west to east. The heaviest precipitation amounts impact northern Connecticut into central and western Massachusetts. Quick warming at 850mb should push most areas over to sleet and freezing rain. The cold layer aloft up to about 925mb looks deep enough where the inland hills may get a thump of sleet, while the interior coastal plain could see several hours of freezing rain. By late aft

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Quincy

 

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 ta

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Quincy

 

Significant MCS/Severe Threat: June 19

A severe thunderstorm threat is expected to develop late this afternoon into the evening hours across portions of the northern Plains. The setup includes an area of surface low pressure ejecting from Wyoming toward the Nebraska/South Dakota border late today. At the same time or shortly thereafter, an embedded upper level shortwave swing through the Dakotas. The combination of kinematic support and strong instability will likely result in several severe thunderstorms with all severe weather haza

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Quincy

 

Severe WX Outlook, Northeast: Wednesday, May 29th

As a warm front lifts into the Northeastern United States on Wednesday, a warmer, more humid air-mass floods into the Northeast. Some thunderstorm development is forecast and some of those storms may be capable of reaching severe limits, particularly across portions of New York and west-central New England. Low threat (Conditions are somewhat favorable for severe thunderstorms) Interior New England, New York, northwestern New Jersey and norther Pennsylvania: As a warm front clears, an increas

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Quincy

 

Severe WX Outlook, NE, Mid-Atl.: Wednesday, April 24th

A cold front is forecast to move from west to east across the East Coast on Wednesday. The result could mean scattered thunderstorms along the front, along with a few severe thunderstorms. (Marginal threat) Middle Appalachians into DE, PA, inland NJ and interior NY. A similar setup to this past Friday is expected on Wednesday, with a cold front moving across the area during the afternoon and evening hours. The only difference here is that the cold front is not as strong as that scenario (last

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Quincy

 

Severe WX Outlook, NE, Mid-Atl.: Saturday, May 11th

As a cold front moves towards the East Coast on Saturday, some thunderstorm development is possible during the afternoon and early evening hours. Low threat (Conditions are somewhat favorable for severe thunderstorms) Mid-Atlantic region (east of Appalachians), lower Hudson Valley and SW New England. Conditions will destabilize in a warm, somewhat moist air-mass before an approaching cold front swings from west to east through the area. The biggest question mark is how much daytime heating wi

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Quincy

 

Severe WX Outlook, NE, Mid-Atl.: Friday, April 19th

A strong low pressure system is forecast to move up into the Great Lakes by Thursday and eventually into southeastern Canada late Friday into Saturday. A potent cold front associated with this storm will move towards the Appalachians by the second half of Friday. (For Wednesday and Thursday, severe thunderstorm activity is probable for the Mississippi Valley and portions of the western Ohio River Valley. I see a marginal setup for severe storms from Central N.Y. into the middle Appalachians. Ev

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Quincy

 

Severe WX Outlook, Mid-Atl.: Wednesday, May 15th

As a warm front lifts into the Northeastern United States on Wednesday, some thunderstorm development is forecast and some of those storms may be capable of reaching severe limits. Low threat (Conditions are somewhat favorable for severe thunderstorms) Central Pennsylvania and portions of Maryland: A warm front is expected to lift into the Northeast on Wednesday. The focus is across the warm sector where some strong wind shear combines with surface/low-level instability to enhance the severe

Quincy

Quincy