Relationships Relationships Between Eye Size and Between Eye Size and Intensity Changes of Intensity Changes of

a N. Atlantic a N. Atlantic HurricaneHurricane

Author: Stephen A. KearneyAuthor: Stephen A. Kearney

Mentor: Dr. Matthew Eastin,Mentor: Dr. Matthew Eastin,

Central CollegeCentral College

IntroductionIntroduction Two primary components to hurricane Two primary components to hurricane

forecasting:forecasting:- Track- Track- Intensity- Intensity

Current research on structure and intensityCurrent research on structure and intensity Knowledge gained about storm structure with Knowledge gained about storm structure with

flight level data (e.g., Jorgensen, 1984)flight level data (e.g., Jorgensen, 1984) Do relationships exist between eye size and Do relationships exist between eye size and

intensity?intensity? Previous studies (e.g., Weatherford and Gray Previous studies (e.g., Weatherford and Gray

1988) show weak correlation between eye size 1988) show weak correlation between eye size and minimum sea level pressure (MSLP)and minimum sea level pressure (MSLP)

Introduction/HypothesisIntroduction/Hypothesis Temporal changes associated with eye wall Temporal changes associated with eye wall

replacement cycles also noted (Willoughby replacement cycles also noted (Willoughby et al. 1990; Willoughby et al. 1982; Black et al. 1990; Willoughby et al. 1982; Black et al. 1992)et al. 1992)

Generally, smaller eye sizes coincident Generally, smaller eye sizes coincident with greater intensitywith greater intensity

Project investigates impact of eye diameter Project investigates impact of eye diameter asymmetries on intensity changesasymmetries on intensity changes

Hypothesis: Eye sizes are characterized by Hypothesis: Eye sizes are characterized by changes in storm intensitychanges in storm intensity

OverviewOverview ProceduresProcedures InvestigationsInvestigations

- Direct relationship- Direct relationship

- Intensity change with eye size - Intensity change with eye size changechange

Effect of eye symmetry on storm Effect of eye symmetry on storm intensity intensity

ProcedureProcedure 88 total flights analyzed, only at 88 total flights analyzed, only at

hurricane strengthhurricane strength Flights analyzed at 850 mb and 700 Flights analyzed at 850 mb and 700

mb levelsmb levels 14 various N. Atlantic hurricanes from 14 various N. Atlantic hurricanes from

1979 through 19951979 through 1995 Included some notable storms: Included some notable storms:

Gilbert, 1988; Andrew, 1992Gilbert, 1988; Andrew, 1992

ProcedureProcedure Flights composed of several legs, or passes Flights composed of several legs, or passes

through eyethrough eye RMW = Radius of Maximum Wind (Shea et RMW = Radius of Maximum Wind (Shea et

al. 1973)al. 1973)- Value of eye size- Value of eye size

Two values for mean RMWTwo values for mean RMW RMWRMW11 = Average of RMW from first four legs = Average of RMW from first four legs RMWRMW22 = Average of RMW from last four legs = Average of RMW from last four legs Only flights with at least eight legs usedOnly flights with at least eight legs used

ProcedureProcedure

Mean times found in same way as Mean times found in same way as mean RMW.mean RMW.

Labeled Labeled t1 and t and t2 2 , respectively, respectively Change in Mean RMW per secondChange in Mean RMW per second

Mean RMW = RMW2 – RMW1

Change t2 – t1

ProcedureProcedure

Calculated change in Maximum Wind Calculated change in Maximum Wind (m/s) and change in MSLP (mb)(m/s) and change in MSLP (mb)

Change values covered separate six-Change values covered separate six-hour periods during and after each hour periods during and after each flightflight

- Immediate or future impact?- Immediate or future impact? RMW Standard Deviation (RMW SD) RMW Standard Deviation (RMW SD)

found separately for RMW-1 and found separately for RMW-1 and RMW-2RMW-2

Investigations of RMWInvestigations of RMW

Direct relationshipDirect relationship Initial Max Wind to RMWInitial Max Wind to RMW11 Final Max Wind to RMWFinal Max Wind to RMW22 Initial MSLP to RMWInitial MSLP to RMW11 Final MSLP to RMWFinal MSLP to RMW22

RMW vs Max WindRMW vs Max Wind

Any direct relationship between RMW and Max Wind?Any direct relationship between RMW and Max Wind?

20 30 40 50 60 70 80 90

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

Initial Max Wind (m/s)

RM

W-1

(km

)

20 30 40 50 60 70 80 90

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

Final Max Wind (m/s)

RM

W-2

(km

)

RMW vs MSLPRMW vs MSLP

Any direct relationship between RMW and MSLP?Any direct relationship between RMW and MSLP? Very low pressures with small RMW values Very low pressures with small RMW values

(Gilbert, 888 mb) (Gilbert, 888 mb)

880 900 920 940 960 980 1000 1020

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

Initial MSLP (mb)

RM

W-1

(km

)

875 900 925 950 975 1000

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

110.00

120.00

130.00

Final MSLP (mb)

RM

W-2

(km

)

Investigations of RMW Investigations of RMW ChangeChange

Intensity change relationship with Intensity change relationship with eye changeeye change

Max Wind Change during flightMax Wind Change during flight Max Wind Change after flightMax Wind Change after flight MSLP Change during flightMSLP Change during flight MSLP Change after flightMSLP Change after flight

RMW Change vs Max Wind RMW Change vs Max Wind Change During FlightChange During Flight

Any immediate Any immediate effect on Max effect on Max Wind?Wind?

Little to no Little to no correlation foundcorrelation found

Statistics:Statistics:

y = 2.496 - 1.095 y = 2.496 - 1.095 xx

R=0.039804 R=0.039804 -15 -10 -5 0 5 10 15

-60

-40

-20

0

20

40

60

80

100

120

Max Wind Change (m/s)

RM

W C

hang

e (m

/s)

RMW Change vs Post Flight RMW Change vs Post Flight Max Wind ChangeMax Wind Change

Any future effect Any future effect on Max Wind?on Max Wind?

Little to no Little to no correlation foundcorrelation found

Statistics:Statistics:

y = 1.888 - 0.298 xy = 1.888 - 0.298 x

R= 0.003811R= 0.003811

-20 -15 -10 -5 0 5 10

-60

-40

-20

0

20

40

60

80

100

120

Post Flight Max Wind Change (m/s)

RM

W C

hang

e (m

b)

RMW Change vs MSLP RMW Change vs MSLP Change During FlightChange During Flight

Any immediate Any immediate effect on MSLP?effect on MSLP?

Little to no Little to no correlation foundcorrelation found

Statistics:Statistics:

y = 2.722 + 0.602 y = 2.722 + 0.602 xx

R= 0.034097 R= 0.034097

-40 -30 -20 -10 0 10 20 30

-60

-40

-20

0

20

40

60

80

100

120

MSLP Change (mb)

RM

W C

hang

e (k

m)

RMW Change vs Post Flight RMW Change vs Post Flight MSLP ChangeMSLP Change

Any future effect Any future effect on MSLP Change?on MSLP Change?

Little to no Little to no correlation foundcorrelation found

Statistics:Statistics:

y = 1.534 + 0.392 y = 1.534 + 0.392 xx

R=0.01604R=0.01604

-30 -20 -10 0 10 20 30 40

-60

-40

-20

0

20

40

60

80

100

120

MSLP Change (mb)

RM

W C

hang

e (k

m)

ResultsResultsDirect RelationshipDirect Relationship Very little correlation presentVery little correlation present

Relationship to RMW ChangeRelationship to RMW Change Not much correlationNot much correlation Agrees with findings of Weatherford Agrees with findings of Weatherford

and Gray (1988)and Gray (1988)

RMW Std DevRMW Std Dev

Approximate measure of eye Approximate measure of eye structure symmetrystructure symmetry

Larger RMW SD: RMW values Larger RMW SD: RMW values dissimilardissimilar

Indicated more asymmetric eye Indicated more asymmetric eye structurestructure

Smaller RMW SD: RMW values similarSmaller RMW SD: RMW values similar Indicated more symmetric eye structureIndicated more symmetric eye structure

MSLP vs RMW SDMSLP vs RMW SD

MSLP and RMW SD had noticeable MSLP and RMW SD had noticeable correlationcorrelation

Found ranges of RMW SD to get Found ranges of RMW SD to get different “levels” of eye symmetry different “levels” of eye symmetry (i.e., < 3, 3 to 6, 6 to 9)(i.e., < 3, 3 to 6, 6 to 9)

Calculated Mean and Std Dev of Calculated Mean and Std Dev of MSLP Change within each RMW SD MSLP Change within each RMW SD range range

< 3 3 to 6 6 to 10 10 to 21 > 21

-15

-10

-5

0

5

10

15

RMW-1 Std Dev Range

MSL

P C

hang

e du

ring

flight

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00

-15

-10

-5

0

5

10

15

RMW-1 Std Dev.

MSLP Change vs RMWMSLP Change vs RMW11 SD SD During FlightDuring Flight

Std Dev bars on left - Variability of MSLP ChangeStd Dev bars on left - Variability of MSLP Change Diagonal lines indicate mean MSLP in each “level”Diagonal lines indicate mean MSLP in each “level” MSLP change values plotted on right against RMWMSLP change values plotted on right against RMW11 SD SD

MSLP Change vs RMWMSLP Change vs RMW22 SD During SD During FlightFlight

< 3 3 to 5 5 to 8 8 to 20 > 20

-15

-10

-5

0

5

10

RMW-2 Std Dev Range

MS

LP

Ch

an

ge

du

rin

g fl

igh

t (m

b)

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00

-20

-15

-10

-5

0

5

10

RMW-2 Std Dev.

Std Dev bars on left - Variability of MSLP ChangeStd Dev bars on left - Variability of MSLP Change Diagonal lines indicate mean MSLP in each “level”Diagonal lines indicate mean MSLP in each “level” MSLP change values plotted on right against RMWMSLP change values plotted on right against RMW22 SD SD

< 3 3 to 6 6 to 9 10 to 21 > 21

-10

-5

0

5

10

15

RMW-1 Std Dev Range

Futu

re M

SLP

Cha

nge

(mb)

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00

-15

-10

-5

0

5

10

15

RMW-1 Std Dev.

Post Flight MSLP Change vs Post Flight MSLP Change vs RMWRMW11 SD SD

Std Dev bars on left - Variability of MSLP ChangeStd Dev bars on left - Variability of MSLP Change Diagonal lines indicate mean MSLP in each “level”Diagonal lines indicate mean MSLP in each “level” MSLP change values plotted on right against RMWMSLP change values plotted on right against RMW11 SD SD

Post Flight MSLP Change vs Post Flight MSLP Change vs RMWRMW22 SD SD

Std Dev bars on left - Variability of MSLP ChangeStd Dev bars on left - Variability of MSLP Change Diagonal lines indicate mean MSLP in each “level”Diagonal lines indicate mean MSLP in each “level” MSLP change values plotted on right against RMWMSLP change values plotted on right against RMW22 SD SD

0.00 5.00 10.0015.0020.0025.0030.0035.0040.0045.0050.00

-15

-10

-5

0

5

10

15

RMW-2 Std Dev.< 3 3 to 5 5 to 8 8 to 20 > 20

-15

-10

-5

0

5

10

15

RMW-2 Std Dev Range

Futu

re M

SLP

Cha

nge

(mb)

Summary and ConclusionSummary and Conclusion

Very little relationship between eye Very little relationship between eye diameter and intensity change, diameter and intensity change, current or futurecurrent or future

Symmetric structure indicated by Symmetric structure indicated by RMW SDRMW SD

Lower MSLP Std Dev trended with Lower MSLP Std Dev trended with higher RMW SDhigher RMW SD

MSLP changed the most with more MSLP changed the most with more symmetric structuresymmetric structure

Summary and ConclusionSummary and Conclusion

More asymmetric structure: negative impact on More asymmetric structure: negative impact on stormstorm

More time for vertical shearMore time for vertical shear More time for colder SST’s to inhibit More time for colder SST’s to inhibit

strengtheningstrengthening

More symmetric structure: positive impact on More symmetric structure: positive impact on stormstorm

Allows winds to increase quickerAllows winds to increase quicker Other studies (e.g. Shapiro and Willoughby Other studies (e.g. Shapiro and Willoughby

1982) show more symmetric structure has 1982) show more symmetric structure has better “spin-up” effectbetter “spin-up” effect

Summary and ConclusionSummary and Conclusion

Eye symmetry important to forecastingEye symmetry important to forecasting Case study by Willoughby et al. 1990Case study by Willoughby et al. 1990

- Outer eye wall observed to contract - Outer eye wall observed to contract before becoming asymmetricbefore becoming asymmetric

- Retained intensity on one side, then - Retained intensity on one side, then weakened on the otherweakened on the other

- Can create different effects on a local - Can create different effects on a local area, depending on landfall time and area, depending on landfall time and locationlocation

Points to ConsiderPoints to Consider Only flights from 1979 to 1995 were Only flights from 1979 to 1995 were

usedused Tropical cyclones stronger and more Tropical cyclones stronger and more

frequent in past ten yearsfrequent in past ten years Further studies, especially on 2005 Further studies, especially on 2005

record breaking season, can be donerecord breaking season, can be done More frequent flights into storms todayMore frequent flights into storms today Higher resolution data may indicate Higher resolution data may indicate

further relationshipsfurther relationships

AcknowledgementsAcknowledgements Author would like to thank the following:Author would like to thank the following:

Dr. Matthew Eastin - mentorship, Dr. Matthew Eastin - mentorship, guidance, and dataguidance, and data

Dr. Takle - advice Dr. Takle - advice NOAA’s Hurricane Research Division - NOAA’s Hurricane Research Division -

datadata Classmates and Professors - moral supportClassmates and Professors - moral support

Any Questions?Any Questions?