Mobile Ground-Based Mobile Ground-Based Observations Observations

of Landfalling Hurricanes: of Landfalling Hurricanes: Current Capabilities and Current Capabilities and

Future PlansFuture Plans

Kevin Knupp, Walt Peterson and Dan Kevin Knupp, Walt Peterson and Dan CecilCecil

Department of Atmospheric Science Department of Atmospheric Science andand

Earth System Science CenterEarth System Science CenterUniversity of Alabama in HuntsvilleUniversity of Alabama in Huntsville

OutlineOutline

Goals (previous deployments)Goals (previous deployments) InstrumentsInstruments Past research activities – some Past research activities – some

highlightshighlights Future research possibilitiesFuture research possibilities

General Research GoalsGeneral Research GoalsTopics that have been considered at least superficiallyTopics that have been considered at least superficially Atmospheric Boundary Layer (ABL) ProcessesAtmospheric Boundary Layer (ABL) Processes

ABL transitionABL transition: land-to-water and water-to-land: land-to-water and water-to-land Wind profilesWind profiles Structure of ABL eddies, damaging wind streaks, etc.Structure of ABL eddies, damaging wind streaks, etc.

Intensity changeIntensity change around the landfall time around the landfall time What factors, such as What factors, such as cold air productioncold air production over land, over land,

control intensity?control intensity?

Topics not yet addressedTopics not yet addressed QPE (radar) and raindrop size distribution QPE (radar) and raindrop size distribution

variabilityvariability Horizontal and vertical variability; factors controlling Horizontal and vertical variability; factors controlling

variabilityvariability Related mesoscale phenomenaRelated mesoscale phenomena

Rainband/stratiform region kinematics and vertical Rainband/stratiform region kinematics and vertical transportstransports

Tornadoes, gravity waves, fronts (and their interaction)Tornadoes, gravity waves, fronts (and their interaction)

UAH deployments to dateUAH deployments to date1.1. Hurricane Earl (1998),Hurricane Earl (1998), Tallahassee, FL Tallahassee, FL

Adjacent to TLH WSR-88D, east of circulation centerAdjacent to TLH WSR-88D, east of circulation center2.2. Hurricane Georges (1998),Hurricane Georges (1998), N of Gulfport, MS N of Gulfport, MS

Close to two DOW radars, remained within west eyewall Close to two DOW radars, remained within west eyewall for several hoursfor several hours

3.3. Hurricane Irene (1999), NCHurricane Irene (1999), NCIrene turned to the right; no landfallIrene turned to the right; no landfall

4.4. Tropical Storm Helene (2000), Panama City, FLTropical Storm Helene (2000), Panama City, FLModest rain, east of circulation centerModest rain, east of circulation center

5.5. Tropical Storm (Hurricane) Gabrielle (2001),Tropical Storm (Hurricane) Gabrielle (2001), Venice, Venice, FLFL

Center passed over MIPS, co-located with SMART-RCenter passed over MIPS, co-located with SMART-R6.6. Hurricane (Tropical Storm) Isidore (2003), Gulfport, MSHurricane (Tropical Storm) Isidore (2003), Gulfport, MS

Sampled the right side, co-located with TTU towers and Sampled the right side, co-located with TTU towers and SMART-RSMART-R

7.7. Hurricane Ivan (2004),Hurricane Ivan (2004), 5 km N of Orange Beach, AL 5 km N of Orange Beach, ALSampled right eyewall, co-located with DOWSampled right eyewall, co-located with DOW

InstrumentationInstrumentationMobile Integrated Profiling System (MIPS)

1. 915 MHz Doppler wind profiler

2. X-band Profiling Radar (under construction)

3. 12-channel microwave profiling radiometer

4. Lidar ceilometer

5. Surface instrumentation

Mobile Meteorological Measurement Vehicle (M3V)

1. Surface measurements

Mobile Alabama X-band (MAX) radar

1. Dual polarization capability

2. Under construction, will be ready for the 2007 season.

Future

Components of the Mobile Integrated Profiling System (MIPS)1) 915 MHz Doppler wind profiler2) 12 channel microwave profiling radiometer3) Lidar Ceilometer4) Doppler sodar5) Electric field mill6) Surface instrumentation7) Satellite communication8) Parcival disdrometers (new, not shown)

Future: X-band Profiling Radar (XPR) will replace the sodar

http://vortex.nsstc.uah.edu/mips

1

234 5

6 7

An ideal MIPS location on 23 June 2003 (BAMEX)

3. Mobile Meteorological Measurement

Vehicle(M3V)

1. MIPS van and instrument trailer

2. Pickup & power trailer

6/23/03

Past research topicsPast research topics Examination of wind profiles and their Examination of wind profiles and their

variabilityvariability Boundary layer propertiesBoundary layer properties Fronts – in hurricanes? – yes Fronts – in hurricanes? – yes

Cooling over land can be prominent and importantCooling over land can be prominent and important Cool air + convergence can produce frontogenesisCool air + convergence can produce frontogenesis

Intensity change?Intensity change? Gravity wavesGravity waves

Prominence (Gabrielle)Prominence (Gabrielle) A noteworthy gravity wave event in Hurricane A noteworthy gravity wave event in Hurricane

EarlEarl The most active weather was associated with a gravity The most active weather was associated with a gravity

wavewave Impact – unknown Impact – unknown

Analysis of TS Gabrielle Analysis of TS Gabrielle (NASA CAMEX-4 campaign)(NASA CAMEX-4 campaign)

Boundary layer Boundary layer transitiontransition for for both on-shore and both on-shore and off-shore flow. off-shore flow. (The circulation (The circulation center passed center passed very close to the very close to the MIPS)MIPS)

Generation of Generation of shallow warm shallow warm and cold frontsand cold fronts

Production of Production of cold aircold air over land over land

Leading Rainband

x

Intense deep convection

Reflectivity from Tampa Bay WSR-88D

MIPS & SMART-R

915 MHz profiler moments

Regions in terms of precipitation characteristics:

1. Leading stratiform2. Convective region3. Inner core region4. West flank stratiform

Flow regimes

Off-shore: 0400-1100 UTCOn-shore: after 1200 UTC

The stable off-shore regime does not exhibit enhanced spectral width, but the on-shore regime does.

Core

915 MHz 915 MHz wind profileswind profiles at 30 min at 30 min intervalsintervals

off-shore, veering with heightcool surface air, stable BL

on-shore, backing with heightwarmer surface air, neutral to stable ABL

TS Gabrielle

Surface fluxes produced from cool air flowing Surface fluxes produced from cool air flowing over warm water over warm water production of temperature production of temperature

gradient along the coastal watersgradient along the coastal waters

coas

tline

landwater

Cool air, 22 CWarm water, 28 C

Surface fluxes

Off-shore flow

Spatial variability across the coastal zoneSpatial variability across the coastal zone

MIPSprofile

Isotachs (m s-1)

Descending jet

Analysis based on Doppler radar + profiler

Spatial variability across the Spatial variability across the coastal zonecoastal zone

a) Flow deceleration is apparent at flow levels over land.b) Flow deceleration begins over water, prior to air reaching

the land surface. Implication: perturbation pressure gradient force from dynamic forcing.

c) BL height is not well defined by the isotachs.d) Vertical shear above the jet over water is greater than that

over land.

Near surface winds are slowed by increase in surface roughness

Temporal variability in the Temporal variability in the 915 MHz wind profiles, 915 MHz wind profiles,

1330-1430 UTC1330-1430 UTCSystematic wind variation

during this period:

a) Rapid changes in the wind profile close to the core region

b) General backing below 1 km

c) Sharp backing of wind with height is large initially.

d) Wind speed profile evolves from maximum at 200 m to a jet profile in which the maximum ascends with time. Thus, the jet is initially within the turbulent BL (consistent with Kepert 2001).

Jet location near the surface

05530553 0853

Cool air (T≤23 C) covers a large area (50,000 km2).

Stratiform rainfall is widespread downshear of the core of Gabrielle.

A warm front formed as Gabrielle approached. This front was associated with tornadoes near 0800 UTC

Surface

Analysis

MIPSlocation

Fronts

Cool air

Tornadoes formed along a warm front

1153 1453

Surface

Analysis

A cold front appeared after 1200 UTC; occlusion by 1453 UTC.

The fronts were shallow, confined to the ABL.

The strongest frontal signature occurred at the MIPS site (near the center of the storm)

Cold front

Fronts

With regard to cold air With regard to cold air production over land, the production over land, the observations suggest the observations suggest the

following hypothesis:following hypothesis:

Hypothesis: Hypothesis: Landfalling hurricanes weaken at an Landfalling hurricanes weaken at an accelerated rate upon ingesting cold accelerated rate upon ingesting cold (low-valued (low-valued ee) continental air from ) continental air from the ABLthe ABL

The presence of The presence of cold air within the ABL cold air within the ABL will produce a rapid weakeningwill produce a rapid weakening in the in the storm if entrained into the core region.storm if entrained into the core region.

The cold air is produced by The cold air is produced by rainfall rainfall evaporation within mesoscale evaporation within mesoscale downdraftsdowndrafts whose characteristics (relative whose characteristics (relative distribution relative to the center, minimum distribution relative to the center, minimum ee) are predictable.) are predictable.

This hypothesis is consistent with observed This hypothesis is consistent with observed rapid weakening over cool water. rapid weakening over cool water. In fact, the In fact, the weakening from cold air intrusion may be weakening from cold air intrusion may be even more dramatic.even more dramatic.

Cooling within Cooling within stratiform stratiform

precipitationprecipitation

Significant Significant mesoscale mesoscale downdrafts downdrafts provided provided downward downward transport of low-transport of low-valued valued ee air, air, and thereby and thereby produced produced appreciable appreciable cooling at low cooling at low levels.levels.

w derived from EVAD analyses

Gabrielle

Is this process observed in other Is this process observed in other storms?storms?

The case of Ivan:The case of Ivan:Cold air from the continent may have Cold air from the continent may have

produced weakening in the NW flank just produced weakening in the NW flank just before landfallbefore landfall

Surface 0043 16 Surface 0043 16 September 2004September 2004

Cold feeder flowe = 343 K

Extensive stratiform precipitation is present to the north of the circ center.

Ivan appeared to Ivan appeared to weaken rapidly weaken rapidly around the time of around the time of landfall, more so landfall, more so than was forecast.than was forecast.

Future work in this area:Future work in this area:

Further examine the “cold air” Further examine the “cold air” hypothesis.hypothesis.

Relate the production of cold air to:Relate the production of cold air to: Thermodynamic vertical profiles in Thermodynamic vertical profiles in

advance of the hurricaneadvance of the hurricane Rainband kinematics, i.e., a more detailed Rainband kinematics, i.e., a more detailed

description of the mesoscale downdrafts description of the mesoscale downdrafts within rainbands and stratiform within rainbands and stratiform precipitationprecipitation

Precipitation propertiesPrecipitation properties

Future plansFuture plansMore of the same, plus:More of the same, plus: QPE (Quantitative Precipitation QPE (Quantitative Precipitation

Estimation)Estimation) Disdrometers Disdrometers profiler profiler radar calibration radar calibration

and improved Z-R (and eventually and improved Z-R (and eventually polarimetric) relationspolarimetric) relations

Improved real-time QPE with the WSR-88D Improved real-time QPE with the WSR-88D networknetwork

Precipitation growth processes (and drop Precipitation growth processes (and drop breakup)breakup)

Mesoscale dynamicsMesoscale dynamics Rainband and stratiform kinematicsRainband and stratiform kinematics Inner core processesInner core processes Thermodynamics – cooling within stratiform Thermodynamics – cooling within stratiform

precipitationprecipitation

Rainband Kinematics: A future research thrustKinematic structure of rainbands in TS Gabrielle (dual Doppler analysis using SMART-R and TBW WSR-88D)

Peak values of updrafts and reflectivity in the rainband : 20 m s-1 and >50 dBZ

Vertical E-W section

TS Gabrielle

Convolved distribution Observed distribution

Hydrometeor size distribution

Raindrop spectrum and size distributions

Time: 060226 UTC Ht : 3.578km Vobs: 8.06m/s Dm: 1.67mm Spectral width: 2.52m/s = 3

Doppler spectra Size distributions

Develop a better understanding of precipitation processes, and drop break-up in the turbulent boundary layer.

SummarySummary Mobile instruments have been used to Mobile instruments have been used to

examine:examine: Flow transition within the ABL across the Flow transition within the ABL across the

coastal zonecoastal zone Gravity waves in the hurricane environmentGravity waves in the hurricane environment Cold air production over land, which appears Cold air production over land, which appears

to exert a large impact on hurricane intensity to exert a large impact on hurricane intensity around the time of landfallaround the time of landfall

Future work should continue to investigate Future work should continue to investigate the above plusthe above plus Investigations of rainband & stratiform Investigations of rainband & stratiform

kinematics and thermodynamicskinematics and thermodynamics Precipitation physics and improved Z-R Precipitation physics and improved Z-R

relations for accurate QPE, with applications to relations for accurate QPE, with applications to the future dual-pol capability of the WSR-88Dthe future dual-pol capability of the WSR-88D

But, this will require a dedicated But, this will require a dedicated multi-year field campaign utilizing multi-year field campaign utilizing

other resourcesother resources

WC-130 NOAA P-3 (2)

In situ, dropsondes, radarIn situ, Dropsondes

Radars, Cloud physics

radar Doppler radar

Atmospheric & BL profiling(wind, T, v, cloud, precipitation)

Mobile Doppler radars

Towers(~10)

Questions?Questions?

E-mail: E-mail: kevin@nsstc.uah.edukevin@nsstc.uah.edu Web site: Web site:

http://vortex.nsstc.uah.edu/mipshttp://vortex.nsstc.uah.edu/mips

Hurricane Earl Hurricane Earl (1998)(1998)

Cold air at the surface Cold air at the surface can provide an can provide an environment conducive environment conducive to gravity wavesto gravity waves

Doppler profiler Doppler profiler observations of a observations of a gravity wave associated gravity wave associated with Hurricane Earl at with Hurricane Earl at landfall (M.S. thesis by landfall (M.S. thesis by Barry Roberts)Barry Roberts)

Combined analysis

Maximum updraft and downdraft of +13 and -9 m s-1 near the 0.8 km AGL level

Low uniform cloud base within the updraft

FutureFutureX-band Profiling Radar X-band Profiling Radar

(XPR)(XPR) 9.4 GHz (9.4 GHz ( = 3.3 cm) = 3.3 cm) Peak power: 50 kWPeak power: 50 kW Min detectable Z at 4 km: -20 Min detectable Z at 4 km: -20

dBZdBZ Time resolution 1-20 sTime resolution 1-20 s PRF ~ 2500 sPRF ~ 2500 s-1-1

Minimum gate spacing: ~30 mMinimum gate spacing: ~30 m

Profiles of Z, W, Doppler Profiles of Z, W, Doppler spectraspectra

Precipitation & cloudsPrecipitation & clouds Boundary Layer PropertiesBoundary Layer Properties 915 XPR

Surface instrumentationSurface instrumentation

TT RHRH pp WindWind Solar radiationSolar radiation Rainfall rateRainfall rate Electric fieldElectric field DSD (Parcival optical disdrometers)DSD (Parcival optical disdrometers)

Conclusions (ABL Conclusions (ABL transition)transition)

a)a) Significant temporal variabilitySignificant temporal variability in airflow at the in airflow at the MIPS site related to gravity waves, large eddies MIPS site related to gravity waves, large eddies (and boundaries).(and boundaries).

b)b) Stable off-shore flow exhibited a jet profile that Stable off-shore flow exhibited a jet profile that descended from land to water. Wind shear descended from land to water. Wind shear below the jet decreased over water.below the jet decreased over water.

c)c) On shore flow produced a more unstable BL.On shore flow produced a more unstable BL.

d)d) In both cases, flow adjustment within the BL In both cases, flow adjustment within the BL occurred within about 5 km of the coast lineoccurred within about 5 km of the coast line

e)e) A transition in flow occurs in the onshore (off-A transition in flow occurs in the onshore (off-shore) cases as deceleration (acceleration) is shore) cases as deceleration (acceleration) is observed to occur before air passes over the observed to occur before air passes over the coast line.coast line.