Page 1

THE IMPORTANCE OF PARCEL CHOICE IN ELEVATED CAPE COMPUTATIONS

Scott M. Rochette

Department of Earth Sciences

State University of New York, College at Brockport

Brockport, New York

James T. Moore

Department of Earth and Atmospheric Sciences

Saint Louis University

Saint Louis, Missouri

Patrick S. Market

Department of Soil and Atmospheric Sciences

University of Missouri-Columbia

Columbia, Missouri

Abstract

It has been suggested that one choose the most unstable

parcel in the lowest 300 hPa layer of a sounding when cal-

culating convective available potential energy (CAPE).

This approach is especially useful for cases where insta-

bility is found aloft, and is also applicable when lifting a

surface- or low-level-based parcel or layer as appropriate.

Raising a (near) surface parcel to evaluate CAPE is not

always illustrative of the true nature of the convectively

unstable environment. An example of such a case exists

when elevated CAPE is released from parcels lifted along

and / or north of a frontal boundary. Two brief case stud-

ies of heavy rainfall [>100 mm (24 hPJ episodes in the

midwestern United States are presented, in which thun-

derstorms resulted from the release of elevated CAPE. In

both cases the CAPE computed from lifting the most

unstable parcel (the parcel with the highest Oe in the low-

est 300 hPa layer) was much greater than the CAPE com-

puted by lifting the parcel based on the average thermal

and moisture characteristics of the lowest 100 hPa layer;

in one case the latter "mean-parcel" CAPE was zero.

1. Introduction

Choosing the most suitable parcel to evaluate CAPE

has been a somewhat contentious issue, as actual CAPE

values depend on the particular lifted parcel (Williams

and Renno 1993; Doswell and Brooks 1993; Doswell and

Rasmussen 1994). There are at least three approaches to

this problem: 1) lifting a surface-based parcel (Hales and

Doswell 1982); 2) lifting a parcel representative of the

lowest 100-hPa layer (Prosser and Foster 1966; Miller

1972; Hart and Korotky 1991); and 3) lifting the most

unstable parcel in the lowest 300 hPa (Doswell and

Rasmussen 1994). The third method is more applicable

for evaluating the convective potential of the environ-

ment when a surface-based parcel or layer is not appro-

priate (Doswell and Rasmussen 1994).

20

During our investigation of heavy rainfall-producing

mesoscale convective systems (MCSs) in the midwestern

United States, we found numerous episodes in which the

convection was not rooted in the atmospheric boundary

layer (as is usually the case with deep convection). These

storms, known as elevated thunderstorms (defined in

Colman 1990a, b), occur in response to lifting above a

cool, stable boundary layer ahead of a surface thermal

boundary. The environmental wind profile in the vicinity

of the thermal boundary is typically distinguished by

sharp veering in the lower and middle troposphere. This

type of wind profile results in differential thermal/mois-

ture advection. The cool, stable layer beneath the front is

characterized typically by flow with an easterly compo-

nent. Warm, moist air is transported northward and

upward above/within the frontal zone, while slightly cool-

er and much drier air is advected by westerly flow in the

middle troposphere. The resultant stratification of the

lower troposphere is characterized by elevated convective

instability (and elevated CAPE), with a layer of convec-

tively unstable air (aO

e lap> 0) above the frontal zone

(often found at or around 850 hPa) and convectively sta-

ble air (aOe lap < 0) below.

The large-scale lift associated with the approach of a

short-wave trough and strengthening low-level jet (LLJ)

are instrumental in lifting this convectively unstable

layer to saturation, thereby realizing the latent instabili-

ty. Meso-a lifting at or near the frontal zone due to local-

ized moisture convergence could then lift air parcels to

their level of free convection (LFC), thereby leading to

strong convection over a limited area. This area is gener-

ally found in the exit region of the LLJ where moisture

convergence is maximized.

Elevated thunderstorms can produce copious rainfall

(Rochette and Moore 1996) or severe weather (Grant

1995), with large hail being the primary severe weather

threat. The following is an excerpt from a forecast dis-

cussion from the National Weather Service Forecast

Office (NWSFO) in Twin Cities/Chanhassen, Minnesota,

Volume 23 Number 4 December 1999

which illustrates the conditions associated with a partic-

ular episode of elevated thunderstorms that occurred on

14 October 1998:

WSR-88D radar reflectivity returns lighting

up across much of far southwest and south-

central [sicl Minnesota with a number of 3/4

inch hail reports with some of the activity.

Convection is elevated but the mixing ratios

showing up at 850 mb on LAPS generated

soundings is [sic] incredible for so late in the

season. At 19Z near KMKT [Mankato,

Minnesotal ... the 850 mb mixing ratio was 9

gm/kg with elevated [sic] CAPE of 575 J/kg.

The purpose of this paper is to discuss the importance

of selecting the most unstable parcel in the lowest 300

hPa when computing CAPE. Toward this end, brief diag-

nostic analyses oftwo heavy rainfall episodes in the mid-

western United States in which lifting the most unstable

parcel resulted in a significant increase in CAPE will be

presented. As such, data from these two cases are pro-

vided only to serve as background to the problem, not to

stand alone as exhaustive case

studies. The reader is directed to

the original sources for further

insight.

2. Illustrative Cases

a. 6 June 1993

73

090

08

21

MISSOURI

24 Hour Precipitation Totals

Ending 7 June 1993

Fig. 1. 24-hour total rainfall (mm) ending at 1200 UTC 7 June

1993 for Missouri, as measured by NWS cooperative network rain

gauges (after Rochette and Moore 1996).

2

10

During the morning and

early afternoon hours of 6 June

1993, an MCS developed over

west-central Missouri and trav-

eled southeastward, resulting in

a narrow swath of heavy precip-

itation as it traversed central

and eastern portions of the

state. Rainfall amounts in

excess of 150 mm (6 in.) fell in

localized areas of central

Missouri (Fig. 1). The opera-

tional community was caught off

guard by this event, as there

was little mention of rain in the

national guidance or local fore-

casts. The heavy rainfall-pro-

ducing thunderstorms devel-

oped well north of a quasi-sta-

tionary surface boundary

extending from the lower

Mississippi Valley across north-

central Oklahoma into western

Kansas. Figure 2 reveals that

surface temperatures over

Missouri ranged from 11 to 16

°C (52 to 62 OF), indicative of a

cool, stable boundary layer, an

environment not usually associ-

ated with the potential for deep

Fig. 2. Surface analysis for 1200 UTC 6 June 1993. Solid lines are isobars in 2 hPa increments

(1012 = 12). Station model as follows: upper left, temperature in OF; bottom left, dewpoint in OF;

upper right, surface pressure in hPa (1020.4 = 204); lower right, 3-h pressure tendency inhPa.

Wind reported as follows: full feather and half feather denote 5.0 and 2.5 ms" respectively. C indi-

cates calm, M signifies missing data. Scalloped region signifies area of initial storm development

(adapted from Rochette and Moore 1996).

22

National Weather Digest

CONVECTIVE STABILITY ANALYSIS

I

J

6/6/93

stable layer around 800 hPa) superimposed on

a stable frontal zone layer (surface to 850

hPa). The Monett profile reveals a similar pat-

tern, with a higher maximum 8e value lower

along the frontal boundary. As a result, the

environment associated with the MCS in

question is characterized by elevated potential

convective instability.

12 UTe

TO PEKA, KS -

:'/

MONETT, M O-· --- -

Elevated thunderstorms require the

release of convective instability via lifting at or

above the frontal zone. In the case of elevated

convection, lifting is not surface-based but

takes place along or ahead of the frontal

boundary, often best diagnosed utilizing an

isentropic perspective. In order to illustrate

the elevated nature of the lifting in this case,

the 306 K isentropic surface at 1200 UTC

6 June 1993 (Fig. 4) is presented. The isen-

tropic perspective is presented to show how

rising air parcels from Texas and Oklahoma

were part of the large-scale lifting process.

Vertical motion on an isentropic surface can be

expressed via the following:

Ii

< •• • • -.- ••• - • • ,~

/-'-"

~ --- -------- . -. --

--7"

I

) 10

315

no

315

330

33S

340

345

350

3 55

3 60

Fig. 3. 1200 UTe 6 June 1993 convective stability analysis for Topeka, Kansas

(solid) and Monett, Missouri (dashed). Abscissa is 8e (K), ordinate is pressure

(hPa) (after Rochette and Moore 1996).

ap _

de ap

\

\ \ --,--\ - \

"

'

\ "',\ '\

I

" '" " ., ,

~ "

' ..

WIND VECTORS

- - ---- PRESSURE (MB)

-.--

We = at + v . v p + dt ae

(1)

'-...-' '---v---' '----..r--'

A B C

Note that the strongest lifting is present

over central and northern Missouri, which is

characterized by winds oriented normal to the

closely spaced isobars, blowing from higher to

lower pressure; this is the contribution of term

B of (1), the pressure advection term. In this

case, rising motion is indicated in the vicinity

of 850 hPa, within the layer of elevated con-

vective instability. It should be noted that dia-

batic heating associated with the convection

[term C of (1)] will generally increase the

upward vertical motion, while the local pres-

sure tendency on the isentropic surface [term

A of (1)] will detract from the upward motion

37 +----<> M / S

(Moore 1993). Examination of the surface

divergence field at 1200 UTC (not shown) indi-

Fig. 4. 1200 UTe 6 June 1993306 K isentropic surface. Arrows represent wind

vectors, dashed lines are isobars (hPa).

cates generally weak convergence (> -1.0 x

10.5 S·I) to weak divergence « +1.0 x 10.5 S·I)

over Missouri, further corroborating the ele-

convection. Further details of this episode may be found

in Rochette and Moore (1996).

A simple method of evaluating the convective instabil-

ity of a local environment (and the potential for elevated

convection) is to examine the vertical profile of equivalent

potential temperature (8e). Figure 3 is the distribution of

8e with respect to pressure at Thpeka, Kansas (solid) and

Monett, Missouri (dashed) for 1200 UTC 6 June 1993.

Given the location of MCS initiation, the Topeka profile

most closely approximated the ambient environment in

the cool sector, while the Monett profile was representa-

tive of the inflow air. The Topeka profile is characterized

by a potentially convectively unstable thermal stratifica-

tion from 850 to 660 hPa (with the exception of a shallow

vated nature of the large-scale lift.

High moisture content is also essential for the release

of convective instability. Examination of the relative

humidity (RR) field on the 306 K surface at 1200 UTC 6

June 1993 (not shown) reveals that the majority of

Missouri is characterized by RHs in excess of 70%, while

the 80% isohume encloses the northern third of Missouri,

most of Iowa, and a north-south sliver through the cen-

tral portion of Minnesota. This verifies that the initial

thunderstorms developed in a region characterized by

high values of relative humidity (-80%).

The effect of parcel choice in CAPE computation is

demonstrated in Fig. 5, a skew T-Iog P diagram for

Monett, Missouri, at 1200 UTC 6 June 1993. The cross-

hatched region represents the CAPE based upon the

Volume 23 Number 4 December 1999

23

100

l

150

l:

~

~

250

'---

300

~

350

~

400

450

500 ~

550

600

650 ~

700

~

750

800

850

~

900

950

1000

72349 06/06/93 12 UTe MONETT, MO

Fig. 5. 1200 UTC 6 June 1993 skew T-Iog P diagram for Monett, Missouri. Horizontal lines depict pressure (hPa), straight slanting (lower

left to upper right) lines are isotherms (0C), and slightly curved sloping (lower right to upper left) lines are dry adiabats (K). Winds follow stan-

dard notation, with full and half feathers representing 5.0 and 2.5 ms·" respectively, and pennants representing 25.0 ms·'. Cross-hatched

region indicates convective available potential energy (CAPE) based upon lifting the mean 1 OO-hPa parcel, stippled region represents addi-

tional CAPE based on lifting the parcel with the highest ee value in the lowest 300 hPa (after Rochette and Moore 1996).

lifting of a parcel based on the average thermal and mois-

ture characteristics of the lowest 100-hPa layer (here-

after referred to as mean-parcel CAPE), while the stip-

pled region represents the additional CAPE realized by

lifting the most unstable parcel (i.e., the parcel with the

highest ee, located around 910 hPa) in the lowest 300-hPa

layer (hereafter referred to as 'best CAPE'). The Monett

sounding revealed a mean-parcel CAPE of 2258 J kgl,

suggestive of a moderately unstable environment.

However, by lifting the most unstable parcel, the best

CAPE was 4256 J kgl, an increase of more than 88%. The

Topeka sounding for the same time (Fig. 6) was even

more dramatic; the mean-parcel CAPE was 699 J kgI,

while the best CAPE was 2814 J kgI, an increase of more

than 300%. It is noteworthy that both soundings exhibit-

ed virtually no convective inhibition (CIN), and that both

represent weakly sheared environments.

Further corroboration of this difference is unveiled by

the comparison of plan views of mean-parcel CAPE (Fig.

7) and best CAPE (Fig. 8). Note that northern Missouri is

only slightly unstable at best, with mean-parcel CAPE

values generally less than 500 J kgl. In contrast, the best

CAPE field over the initiation region reveals a much

more unstable environment, with values in excess of

1500 J kgl. Thus, the pre-MCS environment north of the

warm front on the morning of6 June 1993 had the poten-

tial for strong convection, and conventional CAPE com-

putations would not disclose this fact.

24

National Weather Digest

~

~

~--~--~~~--~~----~~----~~~~~--~~~~-r~----~~--~~450 ~

~----~~----~----~~----~~--~~~~~~~~----~~----~~~500 ~

~L-~~ __ ~~~ __ ~~ ____ ~~ ____ ~~=-__ ~~~ __ ~~~ __ ~ __ ~~~~::: ~

~------~----~~----~,,~--~~~--~~-r--~~~~~----~~----~650

~~--~--~--~--~--~~~----~~-----r~--~~~~~~~----~~~700 ~

~--~------~------~L-----~~----~~~--~~~~~~~--~~~~~750

~~--~--~~~--~~~----~~~--~~~----~~~~~~----~~--~800 ~

~~----~L-----~~----~.r~--~~~--~~~----~~~~~~~--~~850 ~

~~--~~~----~~----~~~--~~~----~~-----r~~--~rA~----~900 ~

I------*---~~~~~~~:::" 41

72456 06/06/93 12 UTe TOPEKA, KS

Fig. 6. As in Fig. 5, except for Topeka, Kansas.

The threat for deep convection is even further isolated

by the examination of analyses of convective inhibition

(CIN), computed via the mean-parcel and best methods.

In this case, the mean-parcel CIN for 1200 UTC 6 June

1993 (Fig. 9) reveals that the atmosphere over the central

U.S. (including the region affected by the MCS) is strong-

ly capped (~50 J kg!), further downplaying the potential

for thunderstorm development at this time. However,

CIN computed through the lifting of the most unstable

parcel (best CIN, Fig. 10) is generally weaker and much

smaller in areal extent, with values below 50 J kg! over

northern Missouri, indicating a much more conducive

environment for the elevated thunderstorms and exces-

sive precipitation that occurred in this region.

b. 27-28 April 1994

From the late afternoon of 27 April 1994 into the

morning of 28 April 1994, a series of thunderstorm

complexes produced heavy rainfall from north-central

Oklahoma across southeast Kansas into east-central

Missouri (Moore et al. 1998). Rainfall amounts exceed-

ing 125 mm (5 in.) occurred over portions of southeast

Kansas and southwest Missouri (Fig. 11). The heavy

rainfall-producing MCSs developed north of a distinct

quasi-stationary surface boundary extending from the

Missouri bootheel through southeast Oklahoma into

north-central Texas. Figure 12 is the 0000 UTC

28 April 1994 surface analysis, showing a strong baro-

clinic zone with warm-sector temperatures from 28 to

31°C (82 to 88 OF) and cool-sector temperatures of 5 to

15 °c (41 to 59 OF). Convective stability profiles at

0000 UTC 28 April 1994 for Monett, Missouri (solid)

and Norman, Oklahoma (dashed) are shown in Fig. 13.

The profiles from both stations are similar to those

shown for 1200 UTC 6 June 1993, with strong stable

layers from the surface to 850 hPa (beneath the frontal

inversion) and potential convectively unstable layers

-

Volume 23 Number 4 December 1999

above to 650-700 hPa (with shallow

stable layers in-between). This ver-

tical stratification is indicative of

elevated convective instability sup-

porting the MCS over the surface

cool-sector environment.

25

06-06 - 19 93

12UTe

The 304 K isentropic surface at

0000 UTC 28 April 1994 (Fig. 14) is

presented to diagnose lifting above

the boundary layer within the frontal

zone. The strongest lifting on this

isentropic surface was present over

northeastern Oklahoma, northern

Arkansas, extreme southeastern

Kansas and southwestern Missouri in

the 850-800 hPa layer. An analysis of

surface divergence at 0000 UTC (not

shown) depicted weak divergence (2.0

to 4.0 x 10-5 S-l) over most of Missouri;

these findings suggest that the lifting

was not surface-based. Isentropic

uplift above the frontal zone was

responsible for the release of the ele-

vated convective instability, although

it should be noted that existing con-

vection could disrupt the continuity of

isentropic surfaces throughdiabatic

heating.

Fig. 7. 1200 UTC 6 June 1993 objective analysis of mean-parcel CAPE (J kg-1).

As was the case in the previously

described episode, high moisture was

present in the storms' initial environ-

ment at 0000 UTC 28 April 1994. A

large swath of high RH values (~70%)

was indicated on the 304 K isentropic

surface (not shown), covering eastern

Nebraska, the eastern two-thirds of

Kansas, southwestern Missouri, cen-

tral and eastern Oklahoma, and most

of Arkansas. The initial thunder-

storms developed in an area where

RH values were in excess of 70%.

06-06 - 1993

1 2 UTe

The differences between the mean-

parcel CAPE and the best CAPE are

rather dramatic, as evidenced by the

soundings from Monett, Missouri

(Fig. 15) and Norman, Oklahoma

(Fig. 16). Lifting a mean parcel in

either sounding results in a CAPE

value of 0 J kg-I, while the best CAPE

values were 1793 J kg-I (Monett) and

2479 J kg-I (Norman). This supports

the assertion that the thunderstorms

occurring at this time were the result

of the release of elevated CAPE.

Comparison of the analyses of mean-

Fig. 8. As in Fig. 7, except for best CAPE (J kg-1).

parcel CAPE (Fig. 17) and best CAPE (Fig. 18) at this

time yields further evidence. Mean-parcel CAPE values

indicate modestly unstable air in central Oklahoma

(::;500 J kg-I), increasing to the south and east, while the

best CAPE analysis reveals values in excess of 2000 J kg-I

over the same area. It should be noted that any discrep-

ancies in CAPE values between those derived from the

soundings and those shown in plan view are most likely

attributable to the Barnes (1973) objective analysis

scheme.

Analysis of mean-parcel CIN (Fig. 19) reveals that the

Southern Plains region (including Oklahoma, Arkansas,

and Missouri) is characterized by weak values «50 J kg-l).

Meanwhile, the best CIN field (Fig. 20) illustrates that the

26

06 -06-1993

12UTC

National Weather Digest

3. Discussion

Fig. 9. 1200 UTG 6 June 1993 objective analysis of mean-parcel convective inhibition (GIN;

J kg-').

In two episodes of Midwestern

heavy rainfall associated with ele-

vated convective instability, it was

shown that the choice of lifted par-

cel in the computation of CAPE

made a distinct difference in evalu-

ating the environmental support of

convection. It was illustrated that

the CAPE computed by lifting a

parcel based on the average ther-

mal and moisture characteristics of

the lowest 100-hPa layer (mean-

parcel CAPE) was often much less

than that computed by lifting the

most unstable parcel in the lowest

300 hPa layer (best CAPE). In one

of the cases examined the best

CAPE was sufficiently large to sup-

port strong convection, even though

the mean-parcel CAPE was nonex-

istent. Analyses of best CIN can fur-

ther isolate regions of potential

excessive precipitation via elevated

thunderstorms.

Regions of non-zero best CAPE

will typically be associated with

environments characterized by lay-

ers of convective instability, either

surface-based or elevated. However,

best CAPE quantifies this instabili-

ty and relates it directly to parcel

accelerations in a more-recognized

form. The ideal situation would be

to examine CAPE and CIN fields in

plan view and vertical profiles of 8e

for specific soundings (observed or

forecast) to determine the convec-

tive potential for a given region.

06-06-1993

12UTC

MAX THETA-E CIN (1Ikg)

In summary, there are convective

episodes that result in heavy rain-

fall and severe weather that occur

in environments that do not appear

to have sufficient instability to sup-

port convection. A thorough analy-

sis ofthe environment that includes

examining both mean-parcel CAPE

(CIN) and best CAPE (CIN) will

highlight situations where elevated

thunderstorms may occur, and

should result in better prediction of

a potentially dangerous situation.

Fig. 10. As in Fig. 9, except for best GIN (J kg-').

region of elevated convection lies in an area of minimum

CIN «50 J kgl). However, western Kansas and the

Oklahoma Panhandle are experiencing a localized maxi-

mum of CIN (-150 J kg!), further isolating eastern

Oklahoma and southwestern Missouri as the region of

excessive convective precipitation.

In addition, the presence of modest

values of best CAPE might indicate

regions where convective winter

precipitation (e.g., thundersnow) may occur.

Modification of existing (and development of future)

computer software packages should make such a com-

parison relatively simple.

..

Volume 23 Number 4 December 1999

Acknowledgments

The authors would like to thank Mr. Sean Nolan of

Saint Louis University for his support during the prepa-

ration of this manuscript. The lead author is indebted to

his colleagues in the Departments of Earth Sciences at

St. Cloud State University and SUNY Brockport for

their assistance and support during his tenures at these

institutions. Messrs. Fred Glass and Dan Ferry

(NWSFO St. Louis) provided guidance and insight dur-

ing the preparation of this manuscript. Messrs. Rich

N aistat and William Togstad (NWSFO Twin

Cities/Chanhassen, MN) are due thanks for providing

the text of the forecast discussion cited in Section 1. The

contributions of Mr. Pete Browning (NWSFO Pleasant

Hill, MO) and an anonymous reviewer were particular-

ly helpful in producing a clarified end result. The

patience and understanding of Major Pete Roohr during

the preparation of this manuscript are greatly appreci-

ated. The authors would also like to thank the

Cooperative Program for Operational Meteorology,

Education and Training (COMET). This research was

27

Fig. 11. 24-h total rainfall (mm) ending at 1200 UTC 28 April 1994

as measured by NWS cooperative network rain gauges .

Fig. 12. As in Fig. 2, except for 0000 UTC 28 April 1994. Station model follows that of Fig. 2, with the following exceptions: solid lines are

isopleths of altimeter setting (in Hg), cloud cover and genera are included, along with pressure trend symbol. Number preceded by "G" i~di­

cates wind gust in knots. Bold 'B' denotes location of bubble high. Dashed-double dotted line indicates outflow boundary. Scalloped region

signifies area of initial storm development (adapted from Moore et al. 1998).

28

National Weather Digest

CONVECTIVE STABILITY ANALYSIS

0

//

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0

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/.' ,,~ .....

.

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.

,

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MONETT. MO -

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328

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Fig. 13. 0000 UTC 28 April 1994 convective stability analysis for Monett, Missouri (solid) and Norman,

Oklahoma (dashed). Abscissa is 8e (K), ordinate is pressure (hPa).

t·

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WIND VECTORS

PRESSURE (MB)

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Fig. 14. 0000 UTC 28 April 1994304 K isentropic surface. Notation follows that of Fig. 4.

Volume 23 Number 4 December 1999

29

100

~

150

~

s!

200

~

250 ~

300 ~

350

400

~

450

'\:y/

500

~

550

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600

650

700

750

800

850

900

950

1000~---7~------~------~~--~--~~----~~------~~----~~------~~~ 1000

~~

72349 04/28/94 00 UTe MONETT, MO

Fig. 15. 0000 UTC 28 April 1994 skew T-Iog P diagram for Monett, Missouri. Notation follows that of Fig. 5. Stippled region represents CAPE

based on lifting the parcel with the highest ee value in the lowest 300 hPa.

funded in part from a sub award (UCAR S97-86991)

under a cooperative agreement between the National

Oceanic and Atmospheric Administration (NOAA) and

the University Corporation for Atmospheric Research

(UCAR). The views expressed herein are those of the

authors and do not necessarily reflect the views of

NOAA, its subagencies, or UCAR.

Authors

Scott M. Rochette is an assistant professor of

meteorology in the Department of the Earth Sciences

at the State University of New York, College at

Brockport, Brockport, New York. In addition, he is

serving as Weather Center Director. He received his

B.S. in meteorology from Lyndon State College,

Vermont in 1988. Mter a four-year hiatus from higher

education, during which he worked as a forecaster

(among other things), he entered Saint Louis

University in January 1992 as a teaching assistant.

He received his M.S.(R) and Ph.D. in meteorology from

Saint Louis University in 1994 and 1998, respectively.

Prior to his appointment at SUNY Brockport, Dr.

Rochette served as a visiting assistant professor in the

Department of Earth Sciences at Saint Cloud State

University, Saint Cloud, Minnesota. His main

research focus is the analysis and modelling of the

synoptic/mesoscale environments associated with

excessive rainfall, especially those that result from the

release of elevated convective instability. Dr.

Rochette's teaching and research interests include

synoptic and dynamic meteorology, weather forecast-

ing, severe local storms, and mesoscale modelling.

James T. Moore is a professor of meteorology in the

30

National Weather Digest

200 ~

250

~

300

~

350

400

~

450

500

550

~

600

dt

650

700

750

800~~--~--~~~~---r~~----~~~---7~~----~~---T~~------~~--~

8S0~------~~----~~~----~~----~~~--~~~----~~~--~~-r--~~~

900~~--~~~~--~~~--~~~~--~~~--~~~~~~~~----~~~----~

950~~~~----~--~--~~-+----~~7---~~~~~~~~--~~~~--~~-r~

800

850

900

950

j

r~

1000~--~?-------~------~~------~~----~~------~~------~-------7~~ 1000

72357 04/28/94 00 UTe NORMAN,OK

Fig. 16. As in Fig. 15, except for Norman, Oklahoma.

Department of Earth and Atmospheric Sciences at Saint

Louis University. He received his B.S. in meteorology

from New York University in 1974, and his M.S. and

Ph.D. in meteorology from Cornell University in 1976

and 1979, respectively. He has taught at the National

Weather Service Training Center and COMET, and has

given workshops at many NWS forecast offices through-

out the central, southern and eastern regions. Jim is com-

pleting work on a three-year COMET cooperative project

with NWS Forecast Offices in St. Louis, Louisville,

Paducah, and Slidell on quantitative precipitation fore-

casting. He is also an incorrigible punster and co-author

ofthe book Jokes and Puns for Groan-Ups. Dr. Moore has

also authored numerous articles in Monthly Weather

Review, Weather and Forecasting, and National Weather

Digest. He was President of the National Weather

Association for 1999.

Patrick S. Market is an assistant professor in the

Department of Soil and Atmospheric Sciences at the

University of Missouri in Columbia, Missouri. In 1994, he

graduated from Millersville University of Pennsylvania

with a B.S. in Meteorology. Two years later, he earned his

Master's degree from Saint Louis University and immedi-

ately entered the Doctoral program there, receiving his

Ph.D. in July 1999. His dissertation work involved the

latent heating influences onjet streak propagation and the

resultant heavy precipitation that can occur under certain

conditions. Dr. Market's other research interests include

the extratropical cyclone occlusion process, precipitation

efficiency, and atmospheric motions over complex terrain.

References

Barnes, S.L., 1973: Mesoscale objective map analysis

using weighted time series observations. NOAA Tech.

Memo. ERL NSSL 62,60 pp. [NTIS COM-73-10781.l

Volume 23 Number 4 December 1999

Colman, B.R., 1990a: Thunderstorms

above frontal surfaces in environ-

ments without positive CAPE. Part I:

A climatology. Mon. Wea. Rev., 118,

1103-1121.

____ , 1990b: Thunderstorms

above frontal surfaces in environ-

ments without positive CAPE. Part

II: Organization and instability mech-

anisms. Mon. Wea. Rev., 118, 1123-

1144.

Doswell, C.A. III, and H.E. Brooks,

1993: Comments on "Anomalous

cloud-to-ground lightning in an F5

tornado-producing supercell thunder-

storm on 28 August 1990." Bull.

Amer. Meteor. Soc., 74, 2213-2218.

____ , and E.N. Rasmussen,

1994: The effect of neglecting the vir-

tual temperature correction on CAPE

calculations. Wea. Forecasting, 9, 625-

629.

Grant, B.N., 1995: Elevated cold-sec-

tor severe thunderstorms: A prelimi-

nary study. Natl. Wea. Dig., 19:4, 25-

31.

Hales, J.E., Jr., and C.A. Doswell III,

1982: High resolution diagnosis of

instability using hourly surface lifted

parcel temperatures. Preprints, 12th

Conf Severe Local Storms, San

Antonio, TX, Amer. Meteor. Soc., 172-

04·28 · 1994

OO UTC

Fig. 17. 0000 UTC 28 April 1994 objective analYSis of mean-parcel CAPE (J kg").

175.

'------

Hart, J.A., and W.D. Korotky, 1991:

The SHARP workstation+v1.50. A

skew T / hodograph analysis and

research program for the IBM and

compatible PC. User's Manual.

NOAAlNWS Charleston, wv, 62 pp.

Henry, w., 1987: The skew T, log P

Diagram. National Weather Service

Training Center, 83 pp. [Available

from National Weather Service

Training Center, 7220 N.W. 101st

Terrace, Kansas City, MO 64153.]

Miller, R.C., 1972: Notes on analysis

and severe-storm forecasting proce-

dures of the Air Force Global Weather

Central. TR 200 (Rev.), Air Weather

Service, 181 pp.

Fig. 18. As in Fig. 17, except for best CAPE (J kg").

31

32

Moore, J .T., 1993: Isentropic Analysis

and Interpretation: Operational

Applications to Synoptic and

Mesoscale Forecast Problems.

National Weather Service Training

Center, Kansas City, MO. 99 pp.

[Available from National Weather

Service Training Center, 7220 N.W.

101st Terrace, Kansas City, MO

64153.]

____ , A.C. Czarnetzki, and P. S.

Market, 1998: Heavy precipitation

associated with elevated thunder-

storms formed in a convectively

unstable layer aloft. Meteorol. Appl. 5,

373-384.

Prosser, N.E., and D.E. Foster, 1966:

Upper air sounding analysis by use of

an electronic computer. J. Appl.

Meteor., 5, 296-300.

Rochette, S.M., and J.T. Moore, 1996:

Initiation of an elevated mesoscale

convective system associated with

heavy rainfall. Wea. Forecasting, 11,

443-457.

Williams, E., and N. Renno, 1993: An

analysis of the conditional instability

ofthe tropical atmosphere. Mon. Wea.

Rev., 121,21-36.

National Weather Digest

Fig. 19. 0000 UTC 28 April 1994 objective analysis of mean-parcel CIN (J kg·').

04-28-1994

o o UTe

Fig. 20. As in Fig. 19, except for best CIN (J kg·').

MAX THETA-E CIN (J/kg)