Using Lightning Data to Monitor the Intensification of Tropical Cyclones in
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Using Lightning Data to Monitor the Intensification of Tropical Cyclones in the Eastern North Pacific. By: Lesley Leary 1 , Liz Ritchie 1 , Nick Demetriades 2 , Ron Holle 2 1-University of Arizona 2-Vaisala Inc . Acknowledgement: Sponsor Office of Naval Research Marine Meteorology Program.

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Using Lightning Data to Monitor the Intensification of Tropical Cyclones inthe Eastern North Pacific

By: Lesley Leary1, Liz Ritchie1,

Nick Demetriades2, Ron Holle2

1-University of Arizona

2-Vaisala Inc.

Acknowledgement: Sponsor Office of Naval Research Marine Meteorology Program


Introduction
Introduction: Tropical Cyclones in

  • One cluster dissipates within 24 hrs.

  • One cluster develops into a category 2 hurricane

  • Which cluster will develop?

Cluster 1

Cluster 2


Understanding genesis
Understanding Genesis Tropical Cyclones in

  • Definition:

    • Processes that occur in a tropical disturbance prior to tropical depression designation.

  • Forecasting:

    • When and where tropical systems will develop

    • Which clusters will develop

  • Important factors:

    • Synoptic-scale pattern

    • SSTs

    • Vorticity

    • Vertical profile of atmosphere


Back to the clusters
Back to the clusters… Tropical Cyclones in

24 hours later

Cluster 1

Cluster 1

Cluster 2

Cluster 2


24 more hours hurricane hector
24 more hours… Tropical Cyclones inHurricane Hector

  • Began as a convective cluster on August 13 at 0000 UTC (4 pm Pacific)

  • Skipped TD status

  • TS status - August 16 at 0000 UTC (4 pm Pacific)

  • Maximum intensity - August 18 at 0600 UTC (10 pm Pacific)

  • Dissipated – August 24 at 1200 UTC (4 am Pacific)


Why lightning is interesting
Why Lightning is Interesting Tropical Cyclones in

  • Lightning requires deep convection

  • Intensity of convection may indicate development of the cloud cluster into a TC

  • Frequency of lightning can imply intensity of convection

  • Periods of increased activity in lightning can indicate diurnal cycle in organized systems

  • Means of tracking convective tropical systems


Hypothesis
Hypothesis Tropical Cyclones in

  • If lightning can be used as a measure of convective activity, it may be able to be an indicator of whether tropical cyclogenesis and/or intensification will occur in a given disturbance.

Hurricane Floyd: September 14, 1999


Long range lightning detection network
Long-Range Lightning Detection Network Tropical Cyclones in

  • Extension of National Lightning Detection Network

  • Detects VLF signals trapped by ionosphere

  • Efficiency of network decreases with

    • Distance from coast

    • Time of day

  • Using data from 2006

30 N

130 W

80 W

Equator


Methodology developing systems
Methodology: Developing Systems Tropical Cyclones in

  • Genesis:

    • No time requirement for genesis period

    • Track system with IR imagery every 6 hrs. for entire lifetime of the system

    • Allows the capture of any possible pattern during genesis period

  • Classify as land or water storm

  • Create a longitude/latitude boundary for each period

  • Filter lightning data per 6 hr. period for each system


Methodology non developing clusters
Methodology: Non-Developing Clusters Tropical Cyclones in

  • Track persistent clusters within the region

    • Exclude clusters lasting less than 72 hrs unless:

      • Out of range

      • Joins another cluster

  • Classify storm as land or water cluster

  • Create boundaries and filter lightning data with same method as developing systems

Cluster 3

Cluster 1

Cluster 2

9/7/06 three clusters between 110 W and 130 W


Systems over water

Developing Storms for 2006 Tropical Cyclones in

Systems Over Water

Flash Counts (#/6h)

Non-Developing Clusters for July 2006

Flash Counts (#/6h)


Results water systems
Results: water systems Tropical Cyclones in

  • Developing Storms: 9 tropical storms

    • Average flashes per 6 hrs: 270

    • Average flashes per storm: 5635

    • Total number flashes: 50713

  • Presence of Diurnal Cycle

  • Non-Developing Clusters: 47 tropical clusters

    • Average flashes per 6 hrs: 37

    • Average flashes per storm: 632

    • Total number flashes: 29734

  • Presence of Diurnal Cycle


Systems over land

Developing Storms for 2006 Tropical Cyclones in

Systems Over Land

Flash Counts (#/6h)

Non-Developing Clusters for 2006 season

Flash Counts (#/6h)


Results for land systems
Results for land systems Tropical Cyclones in

  • Developing Storms: 5 tropical storms

    • Average flashes per 6 hrs: 1164

    • Average flashes per storm: 19362

    • Total number flashes: 96632

  • Presence of Diurnal Cycle

  • Non-Developing Clusters: 12 tropical clusters

    • Average flashes per 6 hrs: 336

    • Average flashes per storm: 5997

    • Total number flashes: 71962

  • Presence of Diurnal Cycle


Is lightning really an accurate measure of intensification
Is lightning really an accurate measure of intensification? Tropical Cyclones in

Non-Developing Clusters for August 2006

  • Notice cluster 6 – resembles results seen for developing systems

  • Is it really a developing system, or is lightning an inaccurate measure of tropical intensification?


Quikscat
QuikSCAT Tropical Cyclones in

Cluster 6

  • Turning of winds

  • 45 kt observation – underestimate

  • Why not designate as TD?


Conclusions
Conclusions Tropical Cyclones in

The results we have presented indicate that lightning activity is a good indicator of whether a cloud cluster will develop into a tropical depression

Lightning is a proxy for deep convection, so this leads us to the question of how convective processes are important in the genesis process

Storms over land have more convective activity than storms over water – it appears to be easier to differentiate between developing and non-developing systems over water


Future work
Future Work Tropical Cyclones in

  • Expand the data set to include multiple seasons and look for statistically significant trends in the data

  • Investigate the reasons for the unusual diurnal signal in the land-based systems

  • Analyzing lightning data for storms after TS designation to look for signatures in intensification

  • Examine other remotely sensed data that may differentiate between tropical clusters and developing storms

  • Identify a signature that can predetermine whether genesis will occur in a cluster


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