The Rapid Evolution of Convection Approaching New York City and Long IslandMichael Charles and Brian A. ColleInstitute for Terrestrial and Planetary SciencesSUNY at Stony Brook

Secondary Author:Jeffrey TongueNOAA/NWS Upton, NY

Probability of Detection (POD) in % Warned events/total events(Svr tstm/torn.) ALY, BOX, OKX, and PHI Warnings from 1/1/1986 10/16/2003

False Alarm Rate (FAR) in % Unverified warnings/total warnings (Svr tstm/torn.) ALY, BOX, OKX, and PHI Warnings from 1/1/1986 10/16/2003

Motivational QuestionsWhat is the thunderstorm distribution over the coastal Northeast?How do severe thunderstorms evolve as they approach the coast?Does the evolution of severe convection change as the sea surface temperatures warm during the summer?How well can mesoscale models forecast these convective events?

OutlineClimatology:Severe thunderstorm/tornado reports.Lightning climatology.Results:Results of lightning climatology.Case study (18 May 2000):Squall line evolution.NWP model simulation of case study.

Severe thunderstorm/tornado reports per 100 km2 per 1 million peopleStorm reports from 1/1/1950 to 10/31/2002

CG Lightning Strike DataNational Lightning Detection Network (NLDN)Global AtmosphericsCG lightning to represent convection over NE (similar to Wasula et al 2002)June vs. August convection (2000-2002)5-7 C difference in sea-surface temp.

NLDN sensor locations in the US

Sea Surface Temperatures15 June 200015 August 2000

Grid domain

Objective Analysis Routine

June Density 2000-2002 - strikes per 100 km2

August Density 2000-2002 - strikes per 100 km2

June Lightning Hours 2000-2002

August Lightning Hours 2000-2002

Case Study 18 May 2000 Squall LineTotal Storm Reports 18 May 2000 through 19 May 2000Total of 99 storm reports across southern New EnglandThe only warned county that didnt verify was Nassau county, LI.The only damage report in Suffolk county LI was a downed tree.

18 May 2000 1200 UTC Surface Analysis

Temperature (every 2 F) Analysis 18 May 2000 18 UTC

.5 reflectivity loop 20 UTC 18 May 2000 to 02 UTC 19 May 2000

Above: 21:36 UTC reflectivity indicating cross section.Top Right: Reflectivity cross sectionshowing vertical storm structure.Right: Velocity cross section.

Left: 23:33 UTC reflectivity indicatingcross section.Above: Cross section showing verticalstorm structure.

18 May 2000 Lightning Distribution

18 May 2000 2100 UTC Soundings (9-hr Eta model forecast)KOKX (Brookhaven, NY)KPOU (Poughkeepsie, NY)

Eta CAPE 9-hr forecast valid 21 UTC

MM5 description36, 12, and 4 km domains.Initialized with GFS at 0000 UTC 18 May 2000.Ran 36/12 km MM5 with Grell convective parameterization, explicit only in 4 km domain.

Model Verification Surface Temperature 1800 UTC 18 May 20004km MM5 (hr-18) MSLP and T (C)Surface Analysis

Model Verification Precipitation 1800 UTC 18 May 2000Reflectivity Mosaic12km SBU MM5 MSLP and 1-hr precip.

Model Verification Precipitation 2200 UTC 18 May 2000 Reflectivity4km SBU MM5 MSLP and 1-hr precip.

MM5 CAPE

Future WorkNeed to better understand the model difficulties in forecasting squall lines over the NE (MM5 rarely has them under weak to moderate CAPE; this is not an Oklahoma environment!!)With a good simulation, one can diagnose three-dimensionally the rapid evolution of severe convection approaching the coast.

ReferencesNLDN Details:http://ghrc.msfc.nasa.gov/uso/readme/gai.htmlWasula, Alicia C., Bosart, Lance F., LaPenta, Kenneth D. 2002: The Influence of Terrain on the Severe Weather Distribution across Interior Eastern New York and Western New England. Weather and Forecasting: Vol. 17, No. 6, pp. 12771289.

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Small-scale Interannual VariabilityJune 2000 DensityJune 2001 DensityJune 2002 Density

Small-scale Interannual VariabilityAugust 2000 DensityAugust 2001 DensityAugust 2002 Density

Velocity Cross Section