the march 01/02 non-winter weather event: part 1 michael w. cammarata anthony w. petrolito

The March 01/02 Non-The March 01/02 Non-Winter Weather Event: Winter Weather Event:

Part 1Part 1

Michael W. CammarataMichael W. Cammarata

Anthony W. PetrolitoAnthony W. Petrolito

WWA TimelineWWA Timeline507 AM EST Sat Feb 28 2009507 AM EST Sat Feb 28 2009

Winter Storm Watch valid Sun March 1 Winter Storm Watch valid Sun March 1

700 pm EST through Mon March 2 700 700 pm EST through Mon March 2 700 am ESTam EST

Far North Midlands (Lancaster, Far North Midlands (Lancaster, Chesterfield, Fairfield)Chesterfield, Fairfield)

Potential for 1 – 3 in of SnowPotential for 1 – 3 in of Snow

WWA TimelineWWA Timeline347 PM EST Sat Feb 28 2009347 PM EST Sat Feb 28 2009

Winter Storm Watch Continued for far northern Winter Storm Watch Continued for far northern Midlands from Sun Mar 1 1200 pm EST through Midlands from Sun Mar 1 1200 pm EST through Mon March 2 700 am ESTMon March 2 700 am EST

Potential for 1 – 3 in of SnowPotential for 1 – 3 in of Snow

Winter Weather Advisory issued for central Winter Weather Advisory issued for central Midlands from Sun Mar 1 1200 pm EST through Midlands from Sun Mar 1 1200 pm EST through Mon March 2Mon March 2

700 am EST700 am EST

Up to 1 in of SnowUp to 1 in of Snow

WWA TimelineWWA Timeline357 AM EST Sun Mar 1 2009357 AM EST Sun Mar 1 2009

All counties in the previous issuance (northern All counties in the previous issuance (northern and central Midlands) were upgraded to Winter and central Midlands) were upgraded to Winter Storm Warning from Sun Mar 1 400 pm EST Storm Warning from Sun Mar 1 400 pm EST through Mon March 2 700 am ESTthrough Mon March 2 700 am EST 3-6 inches of Snow northern Midlands3-6 inches of Snow northern Midlands 2-4 inches of Snow western Midlands2-4 inches of Snow western Midlands 2 inches of Snow Columbia Metro Area2 inches of Snow Columbia Metro Area

Winter Weather Advisory issued for remainder Winter Weather Advisory issued for remainder of CWA (southern Midlands and CSRA) from Sun of CWA (southern Midlands and CSRA) from Sun Mar 1 1200 pm EST through Mon March 2 700 Mar 1 1200 pm EST through Mon March 2 700 am ESTam EST Up to 1 inch of SnowUp to 1 inch of Snow

What Happened?

Not too much 1 – 2 inches of snow in Lancaster

County 0.5 inches of snow in Whitmire in

Newberry County Trace in Columbia metro area

Objective of this Objective of this presentationpresentation

To arrive at an assessment of the To arrive at an assessment of the certainty of snow for this eventcertainty of snow for this event

HPC WWD Graphics issued 1254 am EST Sat Feb 28 HPC WWD Graphics issued 1254 am EST Sat Feb 28 2009 for the period 700 am Sunday Mar 01 2009 to 2009 for the period 700 am Sunday Mar 01 2009 to

700 am Monday Mar 02 2009700 am Monday Mar 02 2009

HPC WWD Graphics issued 1227 pm EST Sat Feb 28 HPC WWD Graphics issued 1227 pm EST Sat Feb 28 2009 for the period 700 pm Sunday Mar 01 2009 to2009 for the period 700 pm Sunday Mar 01 2009 to

700 pm Monday Mar 02 2009 700 pm Monday Mar 02 2009

HPC WWD Graphics issued 1140 pm EST Sat Feb 28 HPC WWD Graphics issued 1140 pm EST Sat Feb 28 2009 for the period 700 am Sunday Mar 01 2009 to2009 for the period 700 am Sunday Mar 01 2009 to

700 am Monday Mar 02 2009 700 am Monday Mar 02 2009

SREF 21-hr forecast probability categorical snow SREF 21-hr forecast probability categorical snow (%) valid 700 pm EST Sunday Mon March 01 2009(%) valid 700 pm EST Sunday Mon March 01 2009

Low snow probabilities central and east midlands

10

20

3040

50

60

70

SREF 21-hr forecast probability categorical rain (%) SREF 21-hr forecast probability categorical rain (%) valid 700 pm EST Sun March 01 2009valid 700 pm EST Sun March 01 2009

Highest rain probabilities across the Eastern Midlands

10

20

30

405060

70

80

SREF 24-hr forecast probability categorical snow SREF 24-hr forecast probability categorical snow (%) valid 1000 pm EST Sun March 01 2009(%) valid 1000 pm EST Sun March 01 2009

Snow probabilities CAE CWA 60-70%

Highest snow probabilities in the SC/NC Piedmont

1020

3040

50 6070

80

SREF 24-hr forecast probability categorical rain (%) SREF 24-hr forecast probability categorical rain (%) valid 1000 pm EST Sun March 01 2009valid 1000 pm EST Sun March 01 2009

Low probabilities rain across CAE CWA at 03z. Probabilities favored snow over rain

10

20

30

40

50

50

60

70

30

NAM12 3-hr QPF (in.) and mean sea level surface NAM12 3-hr QPF (in.) and mean sea level surface pressure valid 1000 pm EST Sun March 01 2009pressure valid 1000 pm EST Sun March 01 2009

0.25-0.50 inches QPF forecast across Western Midlands and Piedmont

GFS40 6-hr QPF (in.) and mean sea level surface GFS40 6-hr QPF (in.) and mean sea level surface pressure valid 100 am EST Mon March 02 2009pressure valid 100 am EST Mon March 02 2009

GFS QPF similar to NAM with highest amounts West and North of CAE

Models show sufficient QPF for accumulating snowfall across Central South Carolina/CSRA of Georgia with higher amounts north and west of CAE.

SREF 03-hr forecast mean sea level pressure and SREF 03-hr forecast mean sea level pressure and precipitable water (in.) valid 100 am ESTprecipitable water (in.) valid 100 am EST

Sun March 01 2009 Sun March 01 2009

Surface low over South Central Georgia

SREF 12-hr forecast mean sea level pressure and SREF 12-hr forecast mean sea level pressure and precipitable water (in.) valid 1000 am precipitable water (in.) valid 1000 am

Sun March 01 2009Sun March 01 2009

Surface low tracking northeast along SC coast

Climatological favorable surface low track for heavy snow in central SC/CSRA is across central Florida

Climatologically favored storm track

BUFKIT CAE Sounding and Precipitation Type BUFKIT CAE Sounding and Precipitation Type Nomogram from 700 pm EST Sat Feb 28 run Nomogram from 700 pm EST Sat Feb 28 run of NAM12 valid at of NAM12 valid at 1000 pm EST Sun Mar 01 1000 pm EST Sun Mar 01

20092009

BUFKIT CAE Time Section Overview BUFKIT CAE Time Section Overview 700 pm EST Sat Feb 28 2009 run of 700 pm EST Sat Feb 28 2009 run of

NAM12NAM12

BUFKIT CAE 2m T and Precipitation BUFKIT CAE 2m T and Precipitation from 700 pm EST Sat Feb 28 2009 run from 700 pm EST Sat Feb 28 2009 run

of NAM12 of NAM12

BUFKIT CAE Energy Precipitation type diagram BUFKIT CAE Energy Precipitation type diagram NAM12NAM12

23-hr forecast valid 6 pm Sunday evening Mar 01 23-hr forecast valid 6 pm Sunday evening Mar 01 20092009


29-hr forecast valid 12 am Mon Mar 02 2009 29-hr forecast valid 12 am Mon Mar 02 2009

GFS MOS Guidance GFS MOS Guidance 700 pm EST model run Sat Feb 28 2009700 pm EST model run Sat Feb 28 2009

Columbia, SC.Columbia, SC.

Temperatures above freezing from 0000-0600 UTC.

6-hr Probability of Precipitation 71 % ending at 0600 UTC.

Conditional Probability of Snow 70-85 % from 0000-0600 UTC.

Conditional Precipitation type from 0000-0600 UTC = snow.

24-hr snowfall accumulation ending at 1200 UTC = none to a trace.

NAM MOS Guidance NAM MOS Guidance 700 pm EST model run Sat Feb 28 2009700 pm EST model run Sat Feb 28 2009

Columbia, SC.Columbia, SC.

Temperatures at or above freezing from 0000-0600 UTC.


24-hr snowfall accumulation ending at 1200 UTC = none to a trace.

CAE Hourly Temperature verification vs. GFS/NAM CAE Hourly Temperature verification vs. GFS/NAM MOS Guidance 700 am EST Sun March 01 2009 to MOS Guidance 700 am EST Sun March 01 2009 to

900 am EST Mon March 02 2009900 am EST Mon March 02 2009

Guidance and observed temperatures were above freezing during the critical time period when snow was possible.

CAE Temperature Trend/Precipitation Type March 1-2 2009

28

32

36

40

44

48

52

Date/Time (UTC)

Tem

p (

F)

CAE Temp Verification CAE GFS MOS CAE NAM MOS

RA RA RA RA RA RA RA RA RA RA RA RA RA RA UP SN UP

Rain was the predominant precip type during the event. Brief period of light snow at the end of the event.

Soil/Surface TemperaturesSoil/Surface Temperatures

The three days preceding the event The three days preceding the event were relatively mild. Max and Min were relatively mild. Max and Min temperatures at CAE were as follows:temperatures at CAE were as follows:

Feb 26 69 46Feb 26 69 46 Feb 27 69 52Feb 27 69 52 Feb 28 64 48Feb 28 64 48

Soil temperatures were in the low to mid Soil temperatures were in the low to mid 50s50s

So what can we say about So what can we say about certainty?certainty?

Storm track was not the Storm track was not the climatologically favored trackclimatologically favored track

Reliance upon wrap around Reliance upon wrap around precipitation on back side of dry slot in precipitation on back side of dry slot in weak cold advectionweak cold advection

Model forecasts did show adequate Model forecasts did show adequate moisture in snow growth region and moisture in snow growth region and ample QPFample QPF

Above freezing layer near surfaceAbove freezing layer near surface

So what can we say about So what can we say about certainty?certainty?

Mild weather prior to event and warm soil Mild weather prior to event and warm soil temperatures would be an inhibiting factor temperatures would be an inhibiting factor to snow accumulationto snow accumulation

SREF probabilities favored snow but were SREF probabilities favored snow but were not certainnot certain

MOS Temperature forecasts were above MOS Temperature forecasts were above freezing during the time of expected snowfreezing during the time of expected snow

Energy Precipitation Type diagrams Energy Precipitation Type diagrams indicate that surface based warm layer indicate that surface based warm layer would be a significant inhibiting factor for would be a significant inhibiting factor for accumulating snow especially at CAEaccumulating snow especially at CAE

The End (Part 1)

Questions?

BUFKIT CLT Sounding and Precipitation type BUFKIT CLT Sounding and Precipitation type Nomogram (NAM12 27-hr forecast) validNomogram (NAM12 27-hr forecast) valid

10 pm EST Sunday March 1 10 pm EST Sunday March 1

BUFKIT CLT Overview – from theBUFKIT CLT Overview – from the 700 pm EST NAM model run Sat March 01 700 pm EST NAM model run Sat March 01

20092009

BUFKIT CLT Energy Ptype diagram BUFKIT CLT Energy Ptype diagram from 0000 UTC runfrom 0000 UTC run

of NAM March 1 2009 of NAM March 1 2009

UZA GFS MOS Guidance 0000 UTC Sun March 01 UZA GFS MOS Guidance 0000 UTC Sun March 01 20092009

Rock Hill, SC.Rock Hill, SC.

Temperatures at or above freezing from 0000-0600 UTC.


Conditional Probability of Snow 73-83 % from 0000-0600 UTC.

Conditional Precipitation type from 0000-0600 UTC = snow.

24-hr snowfall accumulation ending at 1200 UTC = > trace < 2 inches.

UZA NAM MOS Guidance 0000 UTC Sun March 01 UZA NAM MOS Guidance 0000 UTC Sun March 01 20092009

Rock Hill, SC.Rock Hill, SC.

Temperatures above freezing from 0000-0600 UTC.


24-hr snowfall accumulation ending at 1200 UTC >= 8 inches.

UZA Temperature Trend/ Precipitation Type March 1-2 2009

25

29

33

37

41

45

49

1/12

00

1/14

00

1/16

00

1/18

00

1/20

00

1/22

00

2/00

00

2/02

00

2/04

00

2/06

00

2/08

00

2/10

00

2/12

00

2/14

00

Date/Time (UTC)

Tem

p (

F)

UZA Temp Verification UZA GFS MOS UZA NAM MOS

UZA Hourly Temperature verification vs. GFS/NAM UZA Hourly Temperature verification vs. GFS/NAM MOS Guidance 700 am EST Sun March 01 2009 to MOS Guidance 700 am EST Sun March 01 2009 to

0900 am EST Mon March 02 20090900 am EST Mon March 02 2009

Guidance and observed temperatures were at or above freezing during the critical time period when snow was possible.

Rain mixing with snow at times early in the event…then a change over to snow after 700 pm.

UP RA RA RA RA RA RA RA SN RA RA RA SN SN SN SN SN SN SN

the march 01/02 non-winter weather event: part 1 michael w. cammarata anthony w. petrolito

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