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Richmond Metro/Hampton Roads Discussion


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October 25, 2018

this Thursday night

911 PM EDT

 

--  Big, COLD RAIN EVENT coming for Richmond Friday & Friday night, 10/26 --

--  Deepening surface low glides up the East coast, driving an over-running rain event --

 

Let's have a look at the forecasting QPF model amounts for this next rain-maker coming through Richmond on Friday, October 26, through Friday night, and early Saturday morning.  It does look like a goodly amount of rainfall.  Here's what forecasting numbers show:

 

***  Centered on Richmond, VA, for Friday & Friday night, 10/26 *** :

Nam -->>  1.50" of rainfall 

Gfs -->>  1.33" of rain

C-Gem -->> 1.29" of rain

ECMWF -->>  0.81" of rain, later onset time, Friday afternoon; later finishing time, Saturday afternoon.

WRF -->>  1.25" to 1.50" of rainfall; start 10 AM continue rest of day & night, Friday PM & night.  Heavier rain in Richmond between 3 PM and 9 PM Friday PM and night, but light rain continues overnight; Heaviest South of Richmond.

UKM -->>  Not avail. 12Z, Thurs.

NavGem -->>  1.32" of rain

 

This gives an average total rainfall amoungst 6 models above to be 1.27" of rainfall for Richmond, starting late Friday morning, continuing Friday afternoon, evening, & through late overnight Friday night, 10-26.  As cited earlier, few forecasting models continue rainfall in to early Saturday morning, before tapering, but the residual, left-over rain Saturday morning should be light. 

 

Precipitable Water values escalate from 0.84" 11 AM Friday upwards to 1.47" late Friday night at 11 PM, with the highest surge of moisture entering our Richmond area during the evening & 1st half of Friday night.  This is when I expect rainfall to be heaviest is Friday evening hours in to Friday night, coincident with rising Precip Water values and an increasing LLJ at 850 mb, growing from Southerly at 25 kts, 5 PM Friday up to a peak of 40-45 kts, from the Southeast at height of 5K ft, 11 PM that night.  So, I'd suspect this timing to correlate to heaviest rainfall.

 

Come look with me at Mos data, and you'll see that we remain entrenched in the COLD sector airmass Friday afternoon & night, with temperatures running mid 40's to low 50's at the time the elevated LLJ from the South-Southeast arrives.  LLJ = Low-level jet maximum for Friday night.  

 

Surface Level --  The surface low starts near the Southeast Georgia, South Carolina border at 5 PM Friday, North of Savannah, scooting Northeast to near Myrtle Beach by 8 PM, Friday, (29.60").  Then by 2 AM Saturday morning, surface low deepens further to 29.50", still headed Northeastward, located over Northeastern North Carolina, just a jog South of Elizabeth City, NC.  3 hours later, by 5 AM Saturday morning, the surface low takes a left-ward turn Northbound reaching near Virginia Beach, Virginia, 5 AM Saturday morning, at 29.45".  The surface low continues its track up the Delmarva peninsula the rest of Saturday morning. 


I tried to insert JPG simple picture illustrations of PW mappings, LLJ mapping, surface low position, and Skew-T sounding profile, but this forum board seems to be 20 yrs. old and can't accommodate these simple static illustrations, even when they're under the file limit size.  Too bad!   

 

-- cyclogenesis

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November 2, 2018
this Pre-Dawn, Friday morning
127 AM EDT

***Another Good-sized Rain Event Is Coming for Richmond, VA late this afternoon, this evening, & tonight on Friday night, 11/2***


*** Next Cold Front to reach Richmond, late Friday night/pre-dawn Saturday, between 12 Midnight & 2 AM ***


A developing low pressure area will be in position over Southern Virginia late this afternoon, between Roanoke and Richmond, about 5 PM. This low pressure will be gliding Northeastward to near Fredericksburg, VA by 8 PM along a slow-moving cold front that will extend South-Southwest from the low at that time. Expect the cold front to lay across Western Virginia about 5 PM late this afternoon, advancing Eastward and bisecting Central Virginia by 11 PM tonight, finally reaching Richmond, 1-3 hours thereafter, dropping temperatures in to the mid 50’s by Saturday morning, after reaching a daytime high on Friday in the mid 70’s.

Timing of this rain event, for Richmond, VA, appears to be coming in the late afternoon hours, through this evening, & all of tonight up until early Saturday morning, before ending shortly after sunrise Saturday.

Timing of the most robust, heaviest rainfall looks to come between 3 PM to 9 PM, for Richmond, and any isolated one or two occurrences of a severe storm look most likely between 4 PM and 8 PM. I’m not that thrilled about the severe weather threat, on account of the limited CAPE that is advertised by the HD-HR models at only 400-500 J/kg, at optimum late this afternoon. More on this a bit later in this writing.

QPF rainfall totals centered on Richmond are much more diverse than my last writing to you. 
The global models are in far better agreement than the new age, HD-HR models, as shown below:

Rainfall storm total centered on Richmond:

►NAM -- >> 0.69”
►GFS -- >> 0.63”
►C-Gem from 12Z Fri -- >> 0.23”
►UKMET from 12Z Fri -- >> 0.54”
►WRF -- >> 1.50” to 2.50”
►H-Rap, 00Z version -- >> 4.18”, but 2” West Richmond; up to 4” East Richmond

On the subject of severe weather, a close look at the higher definition, new-age models does indicate pockets of 400-500 J/kg of CAPE. This amount is too marginal to expect anything more than an isolated occurrence here and there of a severe storm. This evening’s threat looks to be from an isolated high wind gust or two.

Both modeling simulations show a PEAK wind gust between 30-40 mph to be commonplace most areas, but it’s interesting to note that both the high-def. models show a distinct striping bullseye of heaviest rainfall coming very near or atop the Richmond area. That’s why those higher rainfall totals are indicated from the last 2 models shown above.

Additionally, it has been suggested by 1 of them, that a broken squall line may indeed materialize and right as the main, heaviest rain band is developing over, and passing East of Richmond, say between 4 PM and 8 PM this evening. 


850 mb wind fields, at an altitude of 5,000 ft, ramp up from 30 kts at 2 PM to 40 kts at 5 PM and to 55 kts, from SW, at 8 PM this evening over Richmond. While these wind speeds are plenty ample enough, for a severe weather risk, this potential won’t be realized because of the very throttled-back CAPE amounts discussed above. Also 500 mb mid-tropospheric wind fields, near 18,000 ft, are also plenty high enough, running between 65-80 kts, from SW.


A look at upper divergence values by GFS at 2 PM to 8 PM today show only moderate levels at 3 units, and a brushing of a strong 6 units farther to our East.


While helicity comes upwards to 325-350 m2/s2, 0-6 km shear of 60 kts, and SWEAT index also climbs to 343 at 8 PM tonight, this will be curtailed by the dull-looking instability, characterized by LI’s of only -1°C, moist-adiabatic sounding profiles, and associated weak lapse rates.  To get strong tornadoes, there needs to be strong instability present, which will be unavailable.

For if it wasn’t for this shortcoming on weak instability and small Cape, the strength of the wind fields at all levels aloft are quite impressive & rock solid. All *measureable* rain comes to an end by 8 AM Saturday, followed by a much cooler high of only 63° on Saturday.
 

-- cyclogenesis

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Weather Update, Richmond, VA, 315 PM EDT -- Rain onset appears to be starting a few hours later and ending several hours later, timed between 6 PM and 2 AM tonight. 
Additionally...
Because of the later onset of rainA ribbon sleeve of a bit higher Cape, between 500-1000J/kg looks to slip in to our Eastern counties, East of Richmond around 7 PM to 10 PM tonight, which can correlate to a better prospect for an isolated few severe storms, mainly East & Southeast of Richmond spreading to Williamsburg, Jamestown, Newport News.

Indications show that a thin squall line should develop very near the vicinity of Richmond in about 5 hours from now, in the vicinity of 8 PM. Indeed, the past 3-hourly iterations of updated guidance DO show pockets of wind gusts of 40-45 kts appearing on 2 of the past 3 iterations passing Southwest & South of Richmond around 7 PM to 10 PM tonight, in some developing convection down South 1 of the 3 iterations showed a small area gusting to 50 kts down South of Richmond early tonight with a thin broken band. The 2nd model is more mute on the subject only indicating largely 30-40 kt wind gusts. Hourly predictive lightning looks toned-down with this event.

Timing will place the better severe threat from 7 PM to about 11 PM. Rain amounts look lesser for Richmond, as heavier rain is poised to move about 2 hours Northwest-North of Richmond, in to the DC area. Nonetheless, I do expect that it's conceivable a few severe storm warnings may be needed primarily EAST of a Dinwiddie to Richmond to Fredericksburg line, for early tonight between 7 PM to 11 PM.

-- cyclogenesis

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2 hours ago, cyclogenesis said:

An MCD was released by SPC at 655 PM EDT touching on a 40% chance for watch issuance in this area, later tonight.  At 815 PM a line of heavy showers is solidifying between Nottoway counties and Mecklenburg counties.

The line is moving through Wburg now, just heavy rain. There's been no lightning or thunder. 

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On 11/2/2018 at 11:19 PM, RIC Airport said:

The line is moving through Wburg now, just heavy rain. There's been no lightning or thunder. 

I had an eye on it, late last night on radar, as it made final approach to Williamsburg, and y'all got more out of it than we did in Richmond.  Looks like the gauge there registered 1/2" of rain at the Jamestown/Williamsburg airport.  Richmond only received 0.14", with 0.11" of that coming after the initial line having left.  It just brushed by East Richmond at the airport in Sandston.  I did see on radar, the line perked-up & became wider as it reached Williamsburg.  It's good to finally have my GR3 radar back again, as my PC was in storage so long.    There were a couple volume scans on radar just South of Yale, late Friday night, whose velocities showed about 49 kts on radar at an altitude of 1K ft, about 18 miles out from radar that could have been spot-warned in Sussex county, but didn't.  SPC shows a single tornado report on Friday in Southern Virginia with one red dot, earlier on Friday, the 3rd, Crystal Hill of Halifax county.  Richmond picked up a peak wind gust to 40 mph, though.

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  • 2 weeks later...

Today's rain puts Richmond at 60.28" for the year, which ranks as the 4th wettest on record since 1887. Another 3.02", which is clearly possible in the next 30 days, would put 2018 as the 2nd wettest year. Additionally, there has been 16.22" of rain since September 1st, which means fall 2018 (Sep-Nov) ranks as the 8th wettest fall on record.

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I heard a stat from one of NBC12's meteorologists that there have been more days with rain this year than not, over 50% of days.  I can't remember hearing that one before.  I thought 2003 was pretty rainy, year we had Isabel but that might have just been the summer.  As much as I like storms, I am glad derechos and hurricanes did not find RIC this year given the soil situation.  The tornado breakout was enough excitement to feed my severe weather itch this year.

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Some kind of mix /back and forth is definitely a good early call for how history normally plays out around the Richmond area...Still way to early to get crazy showing the  predicted snow/rain  totals in this area..

Getting some decent precipitation  into the area dosnt look like will be the problem to say the least...

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The main thread is definitely worried about suppression, which would likely be a good thing for us.  But, how many times have we seen the movie where RIC is in the bulls eye 96 hours out only to have it shift inevitably to the north?  Fingers crossed for an event that affects us all but selfish as we are due...want something to fall and stick to enhance the holiday lights.

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4 hours ago, JB Fins said:

The main thread is definitely worried about suppression, which would likely be a good thing for us.  But, how many times have we seen the movie where RIC is in the bulls eye 96 hours out only to have it shift inevitably to the north?  Fingers crossed for an event that affects us all but selfish as we are due...want something to fall and stick to enhance the holiday lights.

Nothing in 12z runs hurt RVA that’s for sure. Still looking snowy.

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4 hours ago, JB Fins said:

The main thread is definitely worried about suppression, which would likely be a good thing for us.  But, how many times have we seen the movie where RIC is in the bulls eye 96 hours out only to have it shift inevitably to the north?  Fingers crossed for an event that affects us all but selfish as we are due...want something to fall and stick to enhance the holiday lights.

 

Imagine how we feel down here in Hampton Roads looking at this. It seems so close...

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4 hours ago, JB Fins said:

The main thread is definitely worried about suppression, which would likely be a good thing for us.  But, how many times have we seen the movie where RIC is in the bulls eye 96 hours out only to have it shift inevitably to the north?  Fingers crossed for an event that affects us all but selfish as we are due...want something to fall and stick to enhance the holiday lights.

In addition to this, we are fighting early December climo. At this point, I'm not going to entertain anything more than 4 or 5" at RIC. I know strange things happen and records can be broken, but amounts more than that just don't happen very often this early in the season. 

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38 minutes ago, RIC Airport said:

In addition to this, we are fighting early December climo. At this point, I'm not going to entertain anything more than 4 or 5" at RIC. I know strange things happen and records can be broken, but amounts more than that just don't happen very often this early in the season. 

Here are all of RIC's official December snow events going back 30 years. There aren't very many over 2" overall. That said, many of the larger ones did happen early in the month. Just posting these for expectation management. 

3.1” December 8-9, 2017

4.3” December 25-26, 2010

2.0” December 16, 2010

1.1” December 13, 2010

0.6” December 4, 2010

7.4” December 18-19, 2009

4.4” December 5-6, 2005

1.3” December 19, 2004

5.0” December 4-5, 2002

1.2” December 26-27, 2000

1.0” December 19, 2000

0.2” December 29, 1997

1.0” December 27, 1997

1.0” December 19, 1996

1.5” December 7, 1995

4.1” December 28-29, 1993

0.1” December 25, 1993

0.9” December 23, 1993

0.8” December 19, 1989

5.0” December 12-13, 1989

5.9” December 8-9, 1989

1.8” December 9, 1988

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Good to see the Richmond thread picking back up, because goodness know we are the "no-mans land" between the heart of the MA forum (Beltway) and the Southeastern forum to our south! And Agree with eaglesin2011, if RIC sees 1/3 of that amount, so say 4-5 inches, that would be a massive win for early December. 

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