warm season frontogenesis forcing applications and implications for convective initiation (or...

Warm Season Frontogenesis Forcing Applications and

Implications for Convective Initiation (or Failure)

Warm Season Frontogenesis Forcing Applications and

Implications for Convective Initiation (or Failure)

Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota

Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota

NWS Duluth Minnesota

Great Lakes Operational Meteorology Workshop – Toronto, Ontario 22 March 2010

Phil SchumacherScience and Operations OfficerNWS/WFO Sioux Falls, South

Dakota

Phil SchumacherScience and Operations OfficerNWS/WFO Sioux Falls, South

Dakota

Greg Mann, PhDScience and Operations Officer

NWS/WFO White Lake, Michigan

Greg Mann, PhDScience and Operations Officer

NWS/WFO White Lake, Michigan

ObjectivesObjectives

1) Review frontogenesis conceptual models

1) Review frontogenesis conceptual models

2) Review cold season frontogenesis applications

2) Review cold season frontogenesis applications

3) Establish a need for FGEN application during the warm season

3) Establish a need for FGEN application during the warm season

4) Develop a warm season frontogenesis conceptual model

4) Develop a warm season frontogenesis conceptual model

5) Warm season case example5) Warm season case example

6) A few thoughts about warm season “parameter space”

6) A few thoughts about warm season “parameter space”

Synoptic Cyclone Frontogenesis RegionsSynoptic Cyclone Frontogenesis Regions

LLLLF > 0

F > 0

AA

BB

CC

Frontogenesis Conceptual ModelsFrontogenesis Conceptual Models

Cold Frontal MovementCold Frontal Movement Dryline MovementDryline

MovementWarm Frontal MovementWarm Frontal Movement

The ascending branch of the ageostrophic circulation resides to the warm side of the FGEN maximum (in the max F vector convergence)

The ascending branch of the ageostrophic circulation resides to the warm side of the FGEN maximum (in the max F vector convergence)

Remember: By convention, we draw the front at the leading edge of the gradient - so FGEN > 0 on the cool side of the front. BUT…

Remember: By convention, we draw the front at the leading edge of the gradient - so FGEN > 0 on the cool side of the front. BUT…

F > 0F > 0

F > 0F > 0

F > 0F > 0

Cross Section A

Cross Section A

Cross Section B

Cross Section B

Cross Section C

Cross Section C

Frontogenesis Conceptual ModelsFrontogenesis Conceptual Models

LLLLF > 0

F > 0

We will focus on this area where “warm” frontogenesis is occurring

Review of Frontogenesis ConceptsReview of Frontogenesis Concepts

LLow Level

Jet

Low Level

Jet

FrontogenesisFrontogenesis Thermal Gradient

Thermal Gradient

Low Level Jet

Low Level Jet

QPF on Cool Side

QPF on Cool Side

Weak Stability or Instability needed for Heavy Precipitation

Weak Stability or Instability needed for Heavy Precipitation

Banded PrecipBanded Precip

Cold Season FGEN Conceptual ModelCold Season FGEN Conceptual Model

Sfc Pres/

QPF

Sfc Pres/

QPF

850 mbT/Wind/Isotach

s

850 mbT/Wind/Isotach

s

800 mb/FGEN

800 mb/FGEN

Sfc Pres/

Temp

Sfc Pres/

Temp


700 mb700 mb

925 mb925 mb

500 mb500 mb

850 mb850 mb

FGEN (image), Isotherms and Wind



FGEN/Theta-

E

FGEN/Theta-

E

EPV*/Theta

EPV*/Theta

RHRH

T/Omega

T/Omega

X-Section Across Frontal ZoneX-Section Across Frontal Zonesouthsouth northnorth

FGEN in the Warm Season?FGEN in the Warm Season?

However… Instability is typically MUCH greater!

…and strong low level jet interaction with a low level baroclinic zone (front or outflow boundary) is quite common

However… Instability is typically MUCH greater!

…and strong low level jet interaction with a low level baroclinic zone (front or outflow boundary) is quite common

So, why are FGEN processes de-emphasized during the warm season?

So, why are FGEN processes de-emphasized during the warm season?

Presumably because…Presumably because…

1) Thermal gradients are weaker in the warm season

1) Thermal gradients are weaker in the warm season

2) Frontal zones are shallower in the warm season

2) Frontal zones are shallower in the warm season

3) Synoptic waves are generally weaker during the warm season (weaker dynamic forcing)

3) Synoptic waves are generally weaker during the warm season (weaker dynamic forcing)

Frequency of FGEN in Warm Season?Frequency of FGEN in Warm Season?

From Bettwy/Donofrio/Lonka, et al for 2006 warm seasonFrom Bettwy/Donofrio/Lonka, et al for 2006 warm season

MUCH more common that previously acknowledged!

MUCH more common that previously acknowledged!

FGEN processes need additional scrutiny in the warm season as well

FGEN processes need additional scrutiny in the warm season as well

Warm Season FGEN Conceptual ModelWarm Season FGEN Conceptual Model

Sfc Pres/

QPF

Sfc Pres/

QPF

850 mbT/Wind/FGEN

850 mbT/Wind/FGEN

MUCAPE

MUCAPE

Sfc Pres/Sfc CAPE

Sfc Pres/Sfc CAPE


700 mb

925 mb

500 mb

850 mb



FGEN/Theta

FGEN/Theta

CAPE/Omega

CAPE/Omega

RHRH

Theta-E/

Ageo Circ

Theta-E/

Ageo Circ

X-Section Across Frontal ZoneX-Section Across Frontal Zonesouthwe

stsouthwe

stnorthea

stnorthea

st

Case Example: 13 August 2007Case Example: 13 August 2007

1630 UTC Hail Outlook


1630 UTC Wind Outlook


1630 UTC Tornado Outlook


1630 UTC Categorical Outlook


Case Example: 13 August 2007Case Example: 13 August 2007









13 August 2007: Convective Initiation13 August 2007: Convective Initiation

KDLH Reflectivity Loop 2159-2341 UTC

KDLH Reflectivity Loop 2159-2341 UTC

13 August 2007: Objective Analysis13 August 2007: Objective Analysis

Surface CAPE 21ZSurface CAPE 21Z

Most Unstable CAPE 21Z


13 August 2007: Objective Analysis13 August 2007: Objective Analysis

Surface CAPE 23ZSurface CAPE 23Z



13 August 2007: Volumetric Reflectivity13 August 2007: Volumetric Reflectivity

KDLH Reflectivity 4-panel 2353 UTC

KDLH Reflectivity 4-panel 2353 UTC

~12,000ft agl

~12,000ft agl

~33,000ft agl

~33,000ft agl

~41,000ft agl

~41,000ft agl

~21,000ft agl

~21,000ft agl

Is the Frontal Zone Active?Is the Frontal Zone Active?

Wind(green barbs)/Wind Isotachs (peach lines) and Divergence (image)

Wind(green barbs)/Wind Isotachs (peach lines) and Divergence (image)

Active Part of Frontal ZoneActive Part of Frontal Zone

Frontolysis/Frontogenesis couplet indicates active part of the frontal zone (Sawyer-Eliassen Equation)

Frontolysis/Frontogenesis couplet indicates active part of the frontal zone (Sawyer-Eliassen Equation)

Cold Season Warm Season

Ageostrophic ResponseAgeostrophic Response

Active Frontogenetic/Frontolytic circulations develop

Active Frontogenetic/Frontolytic circulations develop

Cold SeasonCold Season Warm SeasonWarm Season

Impact on Parcel TrajectoriesImpact on Parcel Trajectories

Parcels hit a “speed bump” and weak subsidence just before entering the ascending branch of the frontogenetic circulation resulting in further dynamic strengthening of an already strong cap

Parcels hit a “speed bump” and weak subsidence just before entering the ascending branch of the frontogenetic circulation resulting in further dynamic strengthening of an already strong cap

Cold SeasonCold Season Warm SeasonWarm Season

Layer Lifting ProcessesLayer Lifting Processes

Significant limitation of Parcel Theory:

Layer Lifting Processes

Significant limitation of Parcel Theory:

Layer Lifting ProcessesParcel Computed CAPE can

underestimate Actual Realized CAPE by 2 to 4 times!!

Parcel Computed CAPE can underestimate Actual Realized CAPE by 2 to 4 times!!

From: Bryan et al

CI: 13 August 2007 Case - 21 UTCCI: 13 August 2007 Case - 21 UTC

Surface Warm Front

Surface Warm Front

Location of Initiation


Thermodynamics North of BoundaryThermodynamics North of Boundary

**



North of Boundary: Initial ProfileNorth of Boundary: Initial Profile

MU layer: ~860-830 mb


2100 UTCCAPE: 491CIN: 455LFC: ~16000

ft/agl ~570 mb

2100 UTCCAPE: 491CIN: 455LFC: ~16000

ft/agl ~570 mb2100 UTC

Sustained Layer Forced Ascent due to frontogenesis


North of Boundary: Profile ChangesNorth of Boundary: Profile Changes

2200 UTC



2200 UTCCAPE: 980CIN: 276 LFC: ~14400

ft/agl ~602 mb

2200 UTCCAPE: 980CIN: 276 LFC: ~14400

ft/agl ~602 mb




2300 UTC



2300 UTCCAPE: 1320CIN: 130LFC: ~13800

ft/agl ~616 mb

2300 UTCCAPE: 1320CIN: 130LFC: ~13800

ft/agl ~616 mb






2400 UTC2400 UTC

2400 UTCCAPE: 1737CIN: 72LFC: ~13205

ft/agl ~630 mb

2400 UTCCAPE: 1737CIN: 72LFC: ~13205

ft/agl ~630 mb



North of Boundary: Forcing ModificationsNorth of Boundary: Forcing Modifications

MU Parcel Layer

MU Parcel Layer

3 Hour ChangeCAPE: 1737

(+1247)CIN: 72 (-383)

3 Hour ChangeCAPE: 1737

(+1247)CIN: 72 (-383)LCL/LFC

heights lower by ~3000 feet!

LCL/LFC heights lower by ~3000 feet!

Sustained Layer Forced Ascent

Sustained Layer Forced Ascent

Thermodynamics South of BoundaryThermodynamics South of Boundary

**

Warm Sector Profile

Warm Sector Profile

South of Boundary: Initial ProfileSouth of Boundary: Initial Profile

Sustained Layer Forced Weak Subsidence due to Frontolysis


2100 UTCCAPE: 3605CIN: -125LFC: ~10745

ft/agl ~694 mb

2100 UTCCAPE: 3605CIN: -125LFC: ~10745


South of Boundary: Profile ChangesSouth of Boundary: Profile Changes



2200 UTCCAPE: 3717CIN: -129LFC: ~10745

ft/agl ~694 mb

2200 UTCCAPE: 3717CIN: -129LFC: ~10745





2300 UTCCAPE: 3756CIN: -133LFC: ~10745

ft/agl ~694 mb

2300 UTCCAPE: 3756CIN: -133LFC: ~10745





2400 UTCCAPE: 3919CIN: -147LFC: ~10700

ft/agl ~695 mb

2400 UTCCAPE: 3919CIN: -147LFC: ~10700


South of Boundary: Forcing ModificationsSouth of Boundary: Forcing Modifications

MU ParcelMU Parcel

2200 UTCCAPE: 3919

(+314)CIN: 147 (+22)

2200 UTCCAPE: 3919

(+314)CIN: 147 (+22)

LCL/LFC height nearly unchanged

LCL/LFC height nearly unchanged

Dynamic Cap Strengthening: CI FailureDynamic Cap Strengthening: CI Failure

Agrees well with Weisman/Wieseler Study (St. Cloud State University)Conv Vs. NonConv Lid Strength

0

2

4

6

8

10

12

14

16

18

20

22

Lid Strengths (°C)

Nu

mb

er o

f O

ccu

rren

ces

CI cases = redCI cases = red

CI failure cases = greenCI failure cases = green

Dynamic Cap Strengthening

Parameter Space vs. ProcessesParameter Space vs. Processes

Sharp precip/cloud cutoff on warm side of boundary

Sharp precip/cloud cutoff on warm side of boundary

Severe Weather Parameter Space is Maximized

Severe Weather Parameter Space is Maximized

Parameter “Sufficiency” + Maximized Processes

Parameter “Sufficiency” + Maximized Processes

Thanks For Your Attention

Thanks For Your Attention

Questions/Comments/Discussion?

Questions/Comments/Discussion?dan.j.miller@noaa

.govdan.j.miller@noaa

.gov

warm season frontogenesis forcing applications and implications for convective initiation (or...

Documents

warm frontogenesis

fgen processes

mb fgen image

frequency of fgen

fgen maximum

fgen application

warm season case example

michigan slide