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April Fool’s Day Storm

1. Incipient Disturbance (March 31,1997)

On March 31st at 00z-06z

there was an initial lowover Virginia.

There was also a jet strea

at 200mb to the west of

the Low and cold fronts,

over Tennessee, because

the strong thermal gradi

The indirect circulation is

corresponding with the

surface low and the area

maximum PVA anddivergence.

It can be seen on the IR

that a baroclinic leaf was

formed.

Based on the 500mb steering method of forecastin

is assumed that the low would move towards the

East, because of the height gradients being the

tightest just south of the low.

There is a subtropical jet that is bringing moisture

into the area of interest (towards the polar). This i

what looks to make this into a high precipitation

system.



Rapid Development Stage (15z March 31, 1997)

It is notable that due to the temperature

gradient over the Atlantic brought by the

subtropical jet has created a warm front over

the Atlantic, off the coast of Virginia.

If the low moves as predicted above

(500mb steering) it should join with the warm

front to strengthen the disturbance.

The pressure minimum deepened slightly which is causing the cyclonic flow to intensify.

The vorticity has increased at the base of the trough as it moved east due to the increase

in curvature and shear. This increased the PVA and divergence on the downstream side

of the trough.

Warm air advections enhanced the dipole in vertical motions.

The increased thermal advections are lowering the heights upstream and increasing the

heights downstream

A comma cloud is beginning to form because of the divergence behind the cold front.

The surface cyclone should follow the warm front, which is the largest thickness gradient,

so it should go towards the East and a little north.





Mature Stage (18z March 31, 1997)

The limiting streamine is

becoming evident (can be

seen over Pennsylvania and

Delaware)

There is also evidence of an

enhanced warm conveyor

belt in the Atlantic (off the

coast of the Carolinas) and

cold conveyor belt coming

from the Atlantic.

At this point in the cyclone life cycle, the cloud and precipitation areas have

expanded, and the cyclone is at maximum intensity.

The surface map shows that the system is already occluding but, by analyzing

the upper air charts, the trough is not vertically stacked yet, which signals that

although this system is very close to decay at 18z it has not occluded yet.

In this stage both the vorticity and advections are at their maximum, and so isPVA.

Using 500mb steering the gradient will make the low go north, which will

weaken it, leading to the decay stage.





Decay (00z April 1, 1997)

In this stage the cyclone is vertically stacked and a secondary speed maximum has formed over the

downstream ridge so there is no more PVA being fed into the low (occlusion has occurred).

The tail of the comma cloud narrows and the head expands. As seen in the satellite image the cold

air is beginning to cut off the low so that there is no longer warm air advection to the initial low.

Because the cyclone is weakening it is going to go north, and develop a secondary low following the

warm front where thermal and vorticity advections are still strong.







The “April Fool’s Day Storm” was a fast moving and short lived snowstorm that affected so uthern

New England in 1997. The storm brought damaging winds and record snowfall to a large portion of

the area. Areas saw snowfall totals as high as 36” from this storm.

References

200mb charts, weatherchannel surface maps and satellite images:

http://www.njfreeways.com/weather/1997/31-Mar-97.html

http://weather.unisys.com/archive/

4-panel charts:

http://www.meteo.psu.edu/~gadomski/NARR/1997/us0331.php

weather maps:

http://nomads.ncdc.noaa.gov/ncep-charts/archives/19970331

GOES satellite image:

http://dcdbs.ssec.wisc.edu/inventory/image.php?sat=GOES-8&date=1997-03-

31&time=19:02&type=Imager&band=1&thefilename=goes08.1997.090.190144.INDX&coverage=CONUS

&count=1&offsettz=0

Summation of the storm:

http://ccams.eas.cornell.edu/ithacation/ith_feb03.pdf









http://dcdbs.ssec.wisc.edu/inventory/image.php?sat=GOES-8&date=1997-03-31&time=19:02&type=Imager&band=1&thefilename=goes08.1997.090.190144.INDX&coverage=CONUS&count=1&offsettz=0














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