matthew cote, lance bosart, and daniel keyser state university of new york, albany, ny

Predecessor Rainfall Events (PRE) in Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Tropical Cyclones - Results from a

Recent Northeastern U.S. Collaborative Recent Northeastern U.S. Collaborative Science, Technology, and Research Science, Technology, and Research

(CSTAR) Project(CSTAR) Project

Predecessor Rainfall Events (PRE) in Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Tropical Cyclones - Results from a

Recent Northeastern U.S. Collaborative Recent Northeastern U.S. Collaborative Science, Technology, and Research Science, Technology, and Research

(CSTAR) Project(CSTAR) Project

Matthew Cote, Lance Bosart, and Daniel Keyser

State University of New York, Albany, NY

Michael L. Jurewicz, Sr.

National Weather Service, Binghamton, NY

July 10, 2008 – HPC, Camp Springs, MD

Matthew Cote, Lance Bosart, and Daniel Keyser

State University of New York, Albany, NY

Michael L. Jurewicz, Sr.

National Weather Service, Binghamton, NY

July 10, 2008 – HPC, Camp Springs, MD

OutlineOutlineOutlineOutline

• Data Sources

• Definition of PRE

• Motivating factors / goals for this session

• Methodologies for the project

• Categorize PRE / Establish climatologies for the Eastern U.S. / Atlantic Basin TC

• Provide operational forecasting resources

– Composites / Conceptual models

• Case Study Examples

• Summary

• Data Sources

• Definition of PRE

• Motivating factors / goals for this session

• Methodologies for the project

• Categorize PRE / Establish climatologies for the Eastern U.S. / Atlantic Basin TC

• Provide operational forecasting resources

– Composites / Conceptual models

• Summary

Data SourcesData SourcesData SourcesData Sources

• WSI NOWRAD Radar Imagery

• HPC Surface / Radar Analyses

• SPC Upper-Air / Mesoanalyses

• Archived TC Tracks / Positions from TPC

• NARR 32-km Datasets

• NWS WES Imagery

• NPVU QPE Data from NWS RFC’s

• WSI NOWRAD Radar Imagery

• HPC Surface / Radar Analyses

• SPC Upper-Air / Mesoanalyses

• Archived TC Tracks / Positions from TPC

• NARR 32-km Datasets

• NWS WES Imagery

• NPVU QPE Data from NWS RFC’s

PRE – What are They ?PRE – What are They ?PRE – What are They ?PRE – What are They ?

• Coherent areas of heavy rainfall observed poleward of Tropical Cyclones (TC)

– Distinct from the main precipitation shields of TC, or their extra-tropical remnants

– Yet, still indirectly tied to TC

• Coherent areas of heavy rainfall observed poleward of Tropical Cyclones (TC)

– Distinct from the main precipitation shields of TC, or their extra-tropical remnants

– Yet, still indirectly tied to TC

PRE Example – Frances (2004)PRE Example – Frances (2004)PRE Example – Frances (2004)PRE Example – Frances (2004)

Main Precipitation Shield of the TC

Results of the Frances PREResults of the Frances PREResults of the Frances PREResults of the Frances PRE

Motivation for Research Motivation for Research Motivation for Research Motivation for Research

• PRE can be particularly challenging phenomena for operational meteorologists

– NWP models often underestimate / misplace heavy rainfall associated with PRE

• Poor handling of diabatic heating transfer / upper-jet intensification

– Attention is frequently diverted to different areas / times

• Closer to where TC make landfall

• Future time periods when the more direct impacts of TC or their remnants may be expected

• PRE can be particularly challenging phenomena for operational meteorologists

– NWP models often underestimate / misplace heavy rainfall associated with PRE

• Poor handling of diabatic heating transfer / upper-jet intensification

– Attention is frequently diverted to different areas / times

• Closer to where TC make landfall

• Future time periods when the more direct impacts of TC or their remnants may be expected

GoalsGoalsGoalsGoals

• To provide NWS forecasters / operational meteorologists with:

– Background Knowledge / Awareness of PRE

– Forecast Tools

• PRE Climatologies

• Conceptual Models / Composite Charts

• To provide NWS forecasters / operational meteorologists with:

– Background Knowledge / Awareness of PRE

– Forecast Tools

• PRE Climatologies

• Conceptual Models / Composite Charts

Methodology Methodology Methodology Methodology

• We restricted classifications of PRE to systems that met the following criteria:

– 100 mm (4”) of rainfall needed to be observed within a 24-hour period

– Such rainfall had to be connected with a well defined region of precipitation

• Not scattered / isolated convection

• We restricted classifications of PRE to systems that met the following criteria:

– 100 mm (4”) of rainfall needed to be observed within a 24-hour period

– Such rainfall had to be connected with a well defined region of precipitation

• Not scattered / isolated convection

Frequency of OccurrenceFrequency of OccurrenceFrequency of OccurrenceFrequency of Occurrence

• Our period of study ran from 1998 to 2006

• 47 PRE were identified, which were tied to a total of 21 TC

– An average of about 2 PRE per PRE-producing TC (PPTC)

• About 1/3 of all Atlantic Basin TC that made U.S. Landfall for this period were PPTC

– A few outlier PPTC did not actually make landfall

• Our period of study ran from 1998 to 2006

• 47 PRE were identified, which were tied to a total of 21 TC

– An average of about 2 PRE per PRE-producing TC (PPTC)

• About 1/3 of all Atlantic Basin TC that made U.S. Landfall for this period were PPTC

– A few outlier PPTC did not actually make landfall

Separation DistanceSeparation Distance

1086 1086 ±± 482 km 482 km Median: 935 kmMedian: 935 km

Bosart and Carr (1978) conceptual model of antecedent rainfall indirectly associated with TC Agnes (from 1972)

PRE StatisticsPRE Statistics

Agnes PRE

Separation Distance

1086 ± 482 km Median: 935 km

Event DurationEvent Duration

14 ± 7 h Median: 12 h

PRE Statistics (Continued)PRE Statistics (Continued)

Agnes PRE

PRE Statistics (Continued)PRE Statistics (Continued)

Separation Distance

1086 ± 482 km Median: 935 km

Event Duration

14 ± 7 h Median: 12 h

Time LagTime Lag

45 ± 29 h Median: 36 h

ROT AT

PRE Locations Relative to TC Track (1998-2006)

PRE Left of TC Track PRE Along TC Track PRE Right of TC Track

Relative Locations

PRE Track-Relative PositionsPRE Track-Relative Positions

Relative Locations

Potential for excessive flooding beginning before arrival of TC rainfall

Relative Locations

Potential for flooding in areas not directly impacted by TC rainfall

Further Sub-ClassificationsFurther Sub-ClassificationsFurther Sub-ClassificationsFurther Sub-Classifications

• Separation by Similarity of TC Track:

– Southeast Recurvatures (SR)

• Highest percentage of PPTC

– Atlantic Recurvatures (AR)

• Most common TC Track

– Central Gulf Landfalls (CG)

• Lower percentage of PPTC, but high frequency PRE production within those PPTC

– Other “Hybrid” TC that were harder to categorize

• Separation by Similarity of TC Track:

– Southeast Recurvatures (SR)

• Highest percentage of PPTC

– Atlantic Recurvatures (AR)

• Most common TC Track

– Central Gulf Landfalls (CG)

• Lower percentage of PPTC, but high frequency PRE production within those PPTC

– Other “Hybrid” TC that were harder to categorize

SR TC Tracks and PRE LocationsSR TC Tracks and PRE LocationsSR TC Tracks and PRE LocationsSR TC Tracks and PRE Locations

All SR TC Tracks All SR PPTC Tracks; with PRE centroids (colored dots)

AR TC Tracks and PRE LocationsAR TC Tracks and PRE LocationsAR TC Tracks and PRE LocationsAR TC Tracks and PRE Locations

All AR TC Tracks All AR PPTC Tracks; with PRE centroids (colored dots)

CG TC Tracks and PRE LocationsCG TC Tracks and PRE LocationsCG TC Tracks and PRE LocationsCG TC Tracks and PRE Locations

All CG Tracks All CG PPTC Tracks; with PRE centroids (colored dots)

Favorable Locations for PRE Favorable Locations for PRE Favorable Locations for PRE Favorable Locations for PRE

• Within the Right-rear quadrant (RRQ) of an Upper-level Jet

• Ahead of the Mean Long-Wave Trough Axis at Mid-levels (trough axis is west of the parent TC’s longitude)

– Near or just upstream from Short-wave Ridging

• Near a Low-level Front / Baroclinic Zone

• On the periphery of a Tropical Moisture Plume

• Near or just west of a Low-level Theta-E Ridge Axis

• Within the Right-rear quadrant (RRQ) of an Upper-level Jet

• Ahead of the Mean Long-Wave Trough Axis at Mid-levels (trough axis is west of the parent TC’s longitude)

– Near or just upstream from Short-wave Ridging

• Near a Low-level Front / Baroclinic Zone

• On the periphery of a Tropical Moisture Plume

• Near or just west of a Low-level Theta-E Ridge Axis

SR PPTC Composites (PRE - 12)SR PPTC Composites (PRE - 12)

Center of composite TC

Trough axis

Ridge axis

θe-Ridge axis

700 mb heights (dam) and upward vertical motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds

(shaded, m s-1)

SR PPTC Composites (At Time of PRE)SR PPTC Composites (At Time of PRE)

700 mb heights (dam) and upward vertical

motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds (shaded, m

s-1)Center of composite TCCentroid of 1st composite PRE

Trough axis

Ridge axis

θe-Ridge axis

SR PPTC Composites (PRE + 12)SR PPTC Composites (PRE + 12)

Centroid of 1st composite PRE

Centroid of 2nd composite PRE

Trough axis

Ridge axis

θe-Ridge axis

700 mb heights (dam) and upward vertical motion

(shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds

(shaded, m s-1)

Common Detracting Elements for Common Detracting Elements for PRE FormationPRE Formation

• A Zonal Flow Pattern is in place Poleward of the TC

– Lack of merdional flow discourages northward return of deep tropical moisture away from the TC itself

• The Long-wave Mid-level Trough Axis is already east of the TC’s Longitude

• A Low-level Blocking Ridge is located north / northeast of the TC

– Tends to prevent significant moisture inflow into any frontal boundaries or jet circulations that may be poleward of the TC

• A Zonal Flow Pattern is in place Poleward of the TC

– Lack of merdional flow discourages northward return of deep tropical moisture away from the TC itself

• The Long-wave Mid-level Trough Axis is already east of the TC’s Longitude

• A Low-level Blocking Ridge is located north / northeast of the TC

– Tends to prevent significant moisture inflow into any frontal boundaries or jet circulations that may be poleward of the TC

SR Null-Case CompositesSR Null-Case CompositesSR Null-Case CompositesSR Null-Case Composites

700 mb heights (dam) and upward vertical motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds (shaded, m s-1)

Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)

• CG Landfall PPTC

– Several PRE were associated with Erin (typical of CG PPTC)

• Erin’s PRE exhibited many of the “classic” synoptic-scale ingredients

– Within RRQ of an upper-level jet

– Deep moisture was fed northward into the PRE / pronounced theta-e ridging developed

– A low-level boundary was in the vicinity

• CG Landfall PPTC

– Several PRE were associated with Erin (typical of CG PPTC)

• Erin’s PRE exhibited many of the “classic” synoptic-scale ingredients

– Within RRQ of an upper-level jet

– Deep moisture was fed northward into the PRE / pronounced theta-e ridging developed

– A low-level boundary was in the vicinity

Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)

18/12z

19/00z19/06z

19/12z20/00z

Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)

PRE #1 – 3-6” (75-150 mm) of rain late on 8/17/07 (“Along-track” PRE)

PRE #2 – 4-8” (100-200 mm) of rain early on 8/18/07

Erin’s 3Erin’s 3rdrd PRE PREErin’s 3Erin’s 3rdrd PRE PRE

Locally 10+ “ Locally 12+” (300+ mm) of

rain on the evening of

8/18/07

Ramifications of PRE #3Ramifications of PRE #3Ramifications of PRE #3Ramifications of PRE #3

• 12” - 15” of rain fell in 6 hours or less over parts of Southeastern MN and Southwestern WI

– Record flooding

– Several fatalities

• 12” - 15” of rain fell in 6 hours or less over parts of Southeastern MN and Southwestern WI

– Record flooding

– Several fatalities

Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07

Significant PRE

Erin’s Moisture Plume

MSLP Isobars and Mean 925-850 mb Winds

TD Erin

300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07

Jet Entrance Region

850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07

TD Erin

Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07

Flooding PicturesFlooding PicturesFlooding PicturesFlooding Pictures

Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)

• Became a Tropical Storm over the western Atlantic, before brushing the Outer Banks of NC

– Then recurved towards the east-northeast over the open Atlantic (Would be categorized as an AR TC)

• No PRE were associated with this TC

– Expansive ridge axis blocked advection of deeper moisture into the U.S.

• Became a Tropical Storm over the western Atlantic, before brushing the Outer Banks of NC

– Then recurved towards the east-northeast over the open Atlantic (Would be categorized as an AR TC)

• No PRE were associated with this TC

– Expansive ridge axis blocked advection of deeper moisture into the U.S.

Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)

24 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 2007

Localized 1-2” (25-50 mm) rainfall amounts in a 24 hour period – Available

moisture was not associated with Gabrielle

Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07

Gabrielle

Dry Wedge

Frontal Plume of Moisture…Disconnected from Gabrielle

MSLP Isobars and Mean 925-850 mb Winds

300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07

Gabrielle

Trough Axis

Ridge Axis

850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07

Gabrielle

Axis of minimum Theta-e

Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07

Ridge axis blocks inflow of moisture towards poleward front

ML Streamlines

Representative TC Tracks

TC Rainfall

LL θe-Ridge Axis

See inset

UL Jet

Conceptual Model: LOT PRE (SR/AR TC)Conceptual Model: LOT PRE (SR/AR TC)

Revised and updated from Fig. 13 of Bosart and Carr (1978)

ML Streamlines

TC Tracks

TC Rainfall

LL θe-Ridge Axis

UL Jet

LL θe-Ridge Axis

Mountain Axes

Idealized LL Winds

LL Temp/ Moisture Boundary

Conceptual Model (More Detailed Inset)Conceptual Model (More Detailed Inset)

Summary – Forecast ChallengesSummary – Forecast ChallengesSummary – Forecast ChallengesSummary – Forecast Challenges

• NWP models are often poor with the placement / intensity of PRE

• Attention is frequently diverted away from potential PRE development

• PRE can impact almost any area of the CONUS

• NWP models are often poor with the placement / intensity of PRE

• Attention is frequently diverted away from potential PRE development

• PRE can impact almost any area of the CONUS

Summary – PRE StatisticsSummary – PRE StatisticsSummary – PRE StatisticsSummary – PRE Statistics

• About 1/3 of U.S. Landfalling TC in our period of study (1998-2006) were PPTC

• LOT PRE were the most common

– Typically the best synoptic enhancement

• AT PRE can be the most dangerous

– Double-shot of heavy rainfall

• ROT PRE tended to display the highest rainfall rates

– Typically slower moving PRE, with less synoptic forcing

– Orography perhaps more important

• About 1/3 of U.S. Landfalling TC in our period of study (1998-2006) were PPTC

• LOT PRE were the most common

– Typically the best synoptic enhancement

• AT PRE can be the most dangerous

– Double-shot of heavy rainfall

• ROT PRE tended to display the highest rainfall rates

– Typically slower moving PRE, with less synoptic forcing

– Orography perhaps more important

Summary – Similarity of TC TracksSummary – Similarity of TC TracksSummary – Similarity of TC TracksSummary – Similarity of TC Tracks

• SR TC had the highest percentage of PPTC

• AR TC were the most common in our period of study

– However, had a lower percentage of PPTC

• CG TC had the lowest percentage of PPTC

– However, CG PPTC were the most prolific PRE producers (an average of 3-4 PRE per TC)

• SR TC had the highest percentage of PPTC

• AR TC were the most common in our period of study

– However, had a lower percentage of PPTC

• CG TC had the lowest percentage of PPTC

– However, CG PPTC were the most prolific PRE producers (an average of 3-4 PRE per TC)

Summary – Favored PRE LocationsSummary – Favored PRE LocationsSummary – Favored PRE LocationsSummary – Favored PRE Locations

• Within the RRQ of a strengthening poleward upper-level jet streak

• Downstream of a mid-level trough, which is well west of the parent TC’s longitude

• Near a low-level boundary

• On the northern or western fringes of a deep tropical moisture plume (evident on water vapor imagery)

• Near or just west of a low-level theta-e ridge axis

• Within the RRQ of a strengthening poleward upper-level jet streak

• Downstream of a mid-level trough, which is well west of the parent TC’s longitude

• Near a low-level boundary

• On the northern or western fringes of a deep tropical moisture plume (evident on water vapor imagery)

• Near or just west of a low-level theta-e ridge axis

Summary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRE

• A de-amplified, zonally oriented flow pattern is in place north of the TC

• The main poleward mid-level trough axis is already at, or east of the TC’s longitude

• A low-level blocking ridge is north / northeast of the TC

• A de-amplified, zonally oriented flow pattern is in place north of the TC

• The main poleward mid-level trough axis is already at, or east of the TC’s longitude

• A low-level blocking ridge is north / northeast of the TC

Future WorkFuture WorkFuture WorkFuture Work

• Expand PRE database to include the western U.S. (Pacific Basin TC)

• Add composites / conceptual models for AT and ROT PRE, and possibly other TC tracks (i.e. CG)

• Develop a technique to identify / quantify PRE rainfall in TC precipitation analyses

• Perform modeling studies to interrogate the role that TC have in modulating the strength of poleward jets

• Expand PRE database to include the western U.S. (Pacific Basin TC)

• Add composites / conceptual models for AT and ROT PRE, and possibly other TC tracks (i.e. CG)

• Develop a technique to identify / quantify PRE rainfall in TC precipitation analyses

• Perform modeling studies to interrogate the role that TC have in modulating the strength of poleward jets

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• Bosart and F. H. Carr, 1978: A case study of excessive rainfall centered around Wellsville, New York, 20-21 June 1972. Mon. Wea. Rev., 106, 348–362.

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