Tropical Cyclone Forecast Track and Intensity Sensitivities to Various Parameterizations using the WRF-ARW Model: Attempt at an Ensemble 2008 Cyclone Workshop

Tropical Cyclone Forecast Track and Tropical Cyclone Forecast Track and Intensity Sensitivities to Various Intensity Sensitivities to Various

Parameterizations using the WRF-ARW Parameterizations using the WRF-ARW Model: Attempt at an EnsembleModel: Attempt at an Ensemble

2008 Cyclone Workshop2008 Cyclone Workshop

Nick P. Bassill Advisor: Michael C. Morgan

2008

This work was supported by ONR Grant 144PN07

National Hurricane Center Discussion National Hurricane Center Discussion for Ernesto from 15 UTC 26 August for Ernesto from 15 UTC 26 August 20062006… … THE FORECAST TRACK IS MORE THE FORECAST TRACK IS MORE PROBLEMATIC AFTER 72 HR. THE PROBLEMATIC AFTER 72 HR. THE LARGE-SCALE MODELS AGREE THAT LARGE-SCALE MODELS AGREE THAT THE MID-LEVEL RIDGE OVER THE THE MID-LEVEL RIDGE OVER THE GULF OF MEXICO WILL WEAKEN AS A GULF OF MEXICO WILL WEAKEN AS A SHORTWAVE TROUGH DIGS SHORTWAVE TROUGH DIGS SOUTHEASTWARD THROUGH THE SOUTHEASTWARD THROUGH THE MISSISSIPPI VALLEY. HOWEVER ... MISSISSIPPI VALLEY. HOWEVER ... THERE ARE DIFFERENCES IN HOW THERE ARE DIFFERENCES IN HOW MUCH WEAKENING WILL OCCUR. THE MUCH WEAKENING WILL OCCUR. THE ECMWF AND NOGAPS CALL FOR ECMWF AND NOGAPS CALL FOR ERNESTO TO RECURVE OVER THE ERNESTO TO RECURVE OVER THE EASTERN GULF OF MEXICO ... WHILE EASTERN GULF OF MEXICO ... WHILE THE UKMET SHOWS ENOUGH RIDGE THE UKMET SHOWS ENOUGH RIDGE TO KEEP ERNESTO MOVING WEST-TO KEEP ERNESTO MOVING WEST-NORTHWESTWARD …NORTHWESTWARD …

WRF* Model VariablesWRF* Model VariablesGrid SpacingGrid SpacingHorizontal: 30km, 45km, or 60km Horizontal: 30km, 45km, or 60km Vertical: 31 or 54 levelsVertical: 31 or 54 levels

Cumulus ParametersCumulus Parameters(1) Kain-Fritsch (cu_physics=1)(1) Kain-Fritsch (cu_physics=1)(2) Betts-Miller-Janjic (*=2)(2) Betts-Miller-Janjic (*=2)(3) Grell-Devenyi ensemble (*=3)(3) Grell-Devenyi ensemble (*=3)

Microphysics ParametersMicrophysics Parameters(1) Kessler (warm rain) (mp_physics=1)(1) Kessler (warm rain) (mp_physics=1)(2) Eta-Ferrier (time efficient) (*=5)(2) Eta-Ferrier (time efficient) (*=5)(3) WSM6 (most complex of these) (*=6)(3) WSM6 (most complex of these) (*=6)

*All simulations performed with the ARW core (version 2.1.2 - 2006 *All simulations performed with the ARW core (version 2.1.2 - 2006 release)release)

North across Cuba and Florida

There are two primary tracks

West across the Yucatan Peninsula

Research GoalsResearch Goals• Attempt a daily “real-time” ensemble for the Attempt a daily “real-time” ensemble for the

tropical North Atlantictropical North Atlantic• Use an ensemble comprised of members Use an ensemble comprised of members

differentiated only by choice of parameterizations differentiated only by choice of parameterizations (i.e. not initial/boundary conditions or dynamical (i.e. not initial/boundary conditions or dynamical core)core)

• Evaluate the ability of this type of ensemble to Evaluate the ability of this type of ensemble to reproduce observed spreads seen in more reproduce observed spreads seen in more “conventional” ensembles“conventional” ensembles

• Specifically, we will focus on TC track, intensity, Specifically, we will focus on TC track, intensity, and genesisand genesis

• If this method shows promise, begin accumulating If this method shows promise, begin accumulating statistics on the above variables, with a goal of statistics on the above variables, with a goal of producing a “corrected consensus” of the producing a “corrected consensus” of the ensemble membersensemble members

Current Ensemble InformationCurrent Ensemble Information

• Uses 1200 UTC GFS 1.0Uses 1200 UTC GFS 1.0ºº x x 1.01.0ºº forecast for forecast for initial/boundary conditionsinitial/boundary conditions

• Two domains: the outer Two domains: the outer and inner domains have a and inner domains have a 90 km and 30 km 90 km and 30 km horizontal grid spacing, horizontal grid spacing, respectively. Both have respectively. Both have 31 vertical levels. 31 vertical levels.

• The ARW core of WRFV3 is The ARW core of WRFV3 is the dynamical core usedthe dynamical core used

• The inner domain uses the The inner domain uses the outer domain to create its outer domain to create its boundary conditions (one boundary conditions (one way nest)way nest)

• Currently, there are 10 Currently, there are 10 ensemble members, with ensemble members, with a run-length of 120 hours a run-length of 120 hours

MPMP CPCP BLPBLP

# 1# 1 WSM3WSM3 Kain-FritschKain-Fritsch YSUYSU

# 2# 2 WSM3WSM3 Kain-FritschKain-Fritsch PleimPleim

# 3# 3 WSM3WSM3 Betts-Miller-Betts-Miller-JanjicJanjic

YSUYSU

# 4# 4 WSM3WSM3 Betts-Miller-Betts-Miller-JanjicJanjic

PleimPleim

# 5# 5 WSM3WSM3 Grell-3Grell-3 YSUYSU

# 6# 6 FerrierFerrier Kain-FritschKain-Fritsch YSUYSU

# 7# 7 FerrierFerrier Kain-FritschKain-Fritsch PleimPleim

# 8# 8 FerrierFerrier Betts-Miller-Betts-Miller-JanjicJanjic

YSUYSU

# 9# 9 FerrierFerrier Betts-Miller-Betts-Miller-JanjicJanjic

PleimPleim

#1#100

FerrierFerrier Grell-3Grell-3 YSUYSU

OutlineOutline

• Discuss several examples of storm tracksDiscuss several examples of storm tracks

- Tropical Storm Fay- Tropical Storm Fay

- Hurricane Hanna- Hurricane Hanna

- Hurricane Ike- Hurricane Ike

• Discuss a representative sample of intensity Discuss a representative sample of intensity differencesdifferences

• Discuss several examples of tropical cyclogenesisDiscuss several examples of tropical cyclogenesis

- Alma/Arthur- Alma/Arthur

- Hanna/Ike/Josephine- Hanna/Ike/Josephine

• Offer some preliminary conclusions/explanationsOffer some preliminary conclusions/explanations

Example 1: Tropical Storm Example 1: Tropical Storm FayFay

... WITH THE LARGE-SCALE MODELS ... WITH THE LARGE-SCALE MODELS FORECASTING A WEAKNESS IN THE RIDGE FORECASTING A WEAKNESS IN THE RIDGE OVER THE EASTERN GULF OF MEXICO OR OVER THE EASTERN GULF OF MEXICO OR FLORIDA THAT SHOULD ALLOW FAY TO FLORIDA THAT SHOULD ALLOW FAY TO TURN TOWARD THE NORTH-NORTHWEST TURN TOWARD THE NORTH-NORTHWEST OR NORTH AFTER 36 HR. OR NORTH AFTER 36 HR. THERE IS A THERE IS A LARGE SPREAD IN THE MODEL LARGE SPREAD IN THE MODEL GUIDANCE ON WHEN AND HOW GUIDANCE ON WHEN AND HOW SHARPLY FAY WILL TURNSHARPLY FAY WILL TURN. THE . THE ECMWF...CANADIAN ... AND NAM ARE ECMWF...CANADIAN ... AND NAM ARE FARTHEST TO THE EAST ... CALLING FOR FARTHEST TO THE EAST ... CALLING FOR FAY TO MOVE ACROSS CUBA TO THE FAY TO MOVE ACROSS CUBA TO THE SOUTHEASTERN COAST OF FLORIDA. THE SOUTHEASTERN COAST OF FLORIDA. THE GFDL IS A LITTLE FARTHER WEST. THE GFDL IS A LITTLE FARTHER WEST. THE GFS ... HWRF ... FLORIDA STATE GFS ... HWRF ... FLORIDA STATE SUPERENSEMBLE ... AND THE CONSENSUS SUPERENSEMBLE ... AND THE CONSENSUS MODELS FORECAST FAY TO CROSS WEST MODELS FORECAST FAY TO CROSS WEST CENTRAL CUBA AND MAKE LANDFALL CENTRAL CUBA AND MAKE LANDFALL ALONG THE SOUTHWEST COAST OF ALONG THE SOUTHWEST COAST OF FLORIDA. THE UKMET AND GFDN ARE FLORIDA. THE UKMET AND GFDN ARE FARTHER WEST...FORECASTING FAY TO FARTHER WEST...FORECASTING FAY TO MOVE TOWARD THE FLORIDA MOVE TOWARD THE FLORIDA PANHANDLE. THE NOGAPS IS THE PANHANDLE. THE NOGAPS IS THE FARTHEST WEST ... FORECASTING FAY TO FARTHEST WEST ... FORECASTING FAY TO MOVE TOWARD THE NORTHERN GULF MOVE TOWARD THE NORTHERN GULF COAST. COAST.

*http://euler.atmos.colostate.edu/~vigh/guidance/northatlantic/archive/

#http://cimss.ssec.wisc.edu/tropic2/archive/atlantic.php

*

#

Example 2: Hurricane Example 2: Hurricane HannaHanna

TRACK MODELS INSIST THAT HANNA WILL START ITS MUCH-ANTICIPATED TURN TOWARD TRACK MODELS INSIST THAT HANNA WILL START ITS MUCH-ANTICIPATED TURN TOWARD THE NORTHWEST SOON...AS A LARGE MID-LATITUDE TROUGH OVER THE WESTERN THE NORTHWEST SOON...AS A LARGE MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC LIFTS NORTHWARD AND THE SUBTROPICAL RIDGE BUILDS BACK IN. SUCH A ATLANTIC LIFTS NORTHWARD AND THE SUBTROPICAL RIDGE BUILDS BACK IN. SUCH A TRACK WOULD TAKE THE CYCLONE NORTHWESTWARD THROUGH THE CENTRAL AND TRACK WOULD TAKE THE CYCLONE NORTHWESTWARD THROUGH THE CENTRAL AND NORTHWESTERN BAHAMAS DURING THE NEXT TWO DAYS. HANNA IS THEN EXPECTED TO NORTHWESTERN BAHAMAS DURING THE NEXT TWO DAYS. HANNA IS THEN EXPECTED TO ACCELERATE AS IT MAKES ITS APPROACH TO THE SOUTHEASTERN UNITED STATES. ACCELERATE AS IT MAKES ITS APPROACH TO THE SOUTHEASTERN UNITED STATES. HOWEVER ... UNTIL HANNA BEGINS A MORE DEFINITIVE MOTION ... IT WILL BE HOWEVER ... UNTIL HANNA BEGINS A MORE DEFINITIVE MOTION ... IT WILL BE DIFFICULT TO NARROW THE POTENTIAL IMPACT AREA. DIFFICULT TO NARROW THE POTENTIAL IMPACT AREA. IN ADDITION ... THE IN ADDITION ... THE ANTICIPATED ANGLE OF APPROACH TO THE SOUTHEAST UNITED STATES COAST MEANS ANTICIPATED ANGLE OF APPROACH TO THE SOUTHEAST UNITED STATES COAST MEANS THAN ONLY A SMALL DEVIATION LEFT OR RIGHT OF THE TRACK WILL HAVE LARGE THAN ONLY A SMALL DEVIATION LEFT OR RIGHT OF THE TRACK WILL HAVE LARGE IMPLICATIONS IN BOTH TIME AND LOCATION OF LANDFALL. IMPLICATIONS IN BOTH TIME AND LOCATION OF LANDFALL.


#http://www.wunderground.com/hurricane/at200808.asp

*

#

Example 3: Hurricane IkeExample 3: Hurricane IkeTHE RIDGE IS FORECAST TO SHIFT EASTWARD DURING THE NEXT COUPLE OF THE RIDGE IS FORECAST TO SHIFT EASTWARD DURING THE NEXT COUPLE OF DAYS ALLOWING IKE TO MAKE A TURN WESTWARD. IN 3 TO 4 DAYS ... A DAYS ALLOWING IKE TO MAKE A TURN WESTWARD. IN 3 TO 4 DAYS ... A SHORTWAVE TROUGH MOVING OVER THE EASTERN UNITED STATES IS SHORTWAVE TROUGH MOVING OVER THE EASTERN UNITED STATES IS EXPECTED TO CREATE A WEAKNESS TO THE NORTH OF IKE RESULTING A TURN EXPECTED TO CREATE A WEAKNESS TO THE NORTH OF IKE RESULTING A TURN TOWARD THE WEST-NORTHWEST OR NORTHWEST. THIS SHORTWAVE TROUGH TOWARD THE WEST-NORTHWEST OR NORTHWEST. THIS SHORTWAVE TROUGH WILL BE A CRITICAL PLAYER IN IKE'S EVENTUAL TRACK AT THE EXTENDED WILL BE A CRITICAL PLAYER IN IKE'S EVENTUAL TRACK AT THE EXTENDED RANGES. RANGES. DYNAMICAL MODELS ARE SPLIT INTO TWO CAMPS AT THIS DYNAMICAL MODELS ARE SPLIT INTO TWO CAMPS AT THIS TIME ... WITH SOME MODELS SHOWING THE SHORTWAVE PASSING TIME ... WITH SOME MODELS SHOWING THE SHORTWAVE PASSING SUFFICIENTLY FAR TO THE NORTH TO KEEP IKE MOVING WEST-SUFFICIENTLY FAR TO THE NORTH TO KEEP IKE MOVING WEST-NORTHWESTWARD ... WHILE OTHER MODELS SHOW IKE TURNING NORTHWESTWARD ... WHILE OTHER MODELS SHOW IKE TURNING NORTHWARD INTO THE WEAKNESS. NORTHWARD INTO THE WEAKNESS.


#http://cimss.ssec.wisc.edu/tropic2/archive/atlantic.php

*

#

Kain-Fritsch Members

Betts-Miller-Janjic Members

Grell-Devenyi Members

MP:MP:

CP:CP:

BLPBLP::

WSMWSM33

KFKF

YSUYSU

WSMWSM33

KFKF

PleimPleim

WSMWSM33

BMJBMJ

YSUYSU

WSMWSM33

BMJBMJ

PleimPleim

WSMWSM33

Grell-Grell-??

YSUYSU

FerrieFerrierr

KFKF

YSUYSU

FerrieFerrierr

KFKF

PleimPleim

FerrieFerrierr

BMJBMJ

YSUYSU

FerrieFerrierr

BMJBMJ

PleimPleim

FerrieFerrierr

Grell-Grell-??

YSUYSU

66thth 950.1950.1 942.5942.5 970.5970.5 956.8956.8 995.1995.1 946.9946.9 940.5940.5 971.0971.0 956.7956.7 992.5992.5

77thth 952.4952.4 940.4940.4 972.4972.4 958.8958.8 989.5989.5 954.3954.3 942.8942.8 974.2974.2 963.6963.6 989.4989.4

99thth 947.2947.2 933.0933.0 969.4969.4 952.3952.3 949.9949.9 948.7948.7 937.5937.5 977.2977.2 961.8961.8 955.4955.4

1010thth 950.7950.7 935.7935.7 967.0967.0 954.1954.1 950.2950.2 950.3950.3 936.6936.6 973.9973.9 960.1960.1 959.7959.7

AvgAvg::

950.1950.1 937.9937.9 969.8969.8 955.5955.5 950.1950.1 939.4939.4 974.1974.1 960.1960.1

A Comparison of Maximum A Comparison of Maximum IntensitiesIntensities

The above table shows the minimum sea level pressure The above table shows the minimum sea level pressure attained by Hurricane Ike in the Gulf of Mexico at any point attained by Hurricane Ike in the Gulf of Mexico at any point during the 120 hour duration of each simulation, over four during the 120 hour duration of each simulation, over four

different days of simulationsdifferent days of simulations

MP:MP:

CP:CP:

BLPBLP::

WSMWSM33

KFKF

YSUYSU

WSMWSM33

KFKF

PleimPleim

WSMWSM33

BMJBMJ

YSUYSU

WSMWSM33

BMJBMJ

PleimPleim

WSMWSM33

Grell-Grell-??

YSUYSU

FerrieFerrierr

KFKF

YSUYSU

FerrieFerrierr

KFKF

PleimPleim

FerrieFerrierr

BMJBMJ

YSUYSU

FerrieFerrierr

BMJBMJ

PleimPleim

FerrieFerrierr

Grell-Grell-??

YSUYSU

66thth 950.1950.1 942.5942.5 970.5970.5 956.8956.8 995.1995.1 946.9946.9 940.5940.5 971.0971.0 956.7956.7 992.5992.5

77thth 952.4952.4 940.4940.4 972.4972.4 958.8958.8 989.5989.5 954.3954.3 942.8942.8 974.2974.2 963.6963.6 989.4989.4

99thth 947.2947.2 933.0933.0 969.4969.4 952.3952.3 949.9949.9 948.7948.7 937.5937.5 977.2977.2 961.8961.8 955.4955.4

1010thth 950.7950.7 935.7935.7 967.0967.0 954.1954.1 950.2950.2 950.3950.3 936.6936.6 973.9973.9 960.1960.1 959.7959.7

AvgAvg::

950.1950.1 937.9937.9 969.8969.8 955.5955.5 950.1950.1 939.4939.4 974.1974.1 960.1960.1




MP:MP:

CP:CP:

BLPBLP::

WSMWSM33

KFKF

YSUYSU

WSMWSM33

KFKF

PleimPleim

WSMWSM33

BMJBMJ

YSUYSU

WSMWSM33

BMJBMJ

PleimPleim

WSMWSM33

Grell-Grell-??

YSUYSU

FerrieFerrierr

KFKF

YSUYSU

FerrieFerrierr

KFKF

PleimPleim

FerrieFerrierr

BMJBMJ

YSUYSU

FerrieFerrierr

BMJBMJ

PleimPleim

FerrieFerrierr

Grell-Grell-??

YSUYSU

66thth 950.1950.1 942.5942.5 970.5970.5 956.8956.8 995.1995.1 946.9946.9 940.5940.5 971.0971.0 956.7956.7 992.5992.5

77thth 952.4952.4 940.4940.4 972.4972.4 958.8958.8 989.5989.5 954.3954.3 942.8942.8 974.2974.2 963.6963.6 989.4989.4

99thth 947.2947.2 933.0933.0 969.4969.4 952.3952.3 949.9949.9 948.7948.7 937.5937.5 977.2977.2 961.8961.8 955.4955.4

1010thth 950.7950.7 935.7935.7 967.0967.0 954.1954.1 950.2950.2 950.3950.3 936.6936.6 973.9973.9 960.1960.1 959.7959.7

AvgAvg::

950.1950.1 937.9937.9 969.8969.8 955.5955.5 950.1950.1 939.4939.4 974.1974.1 960.1960.1




Some ObservationsSome Observations

• Choice of CP seems to determine storm track Choice of CP seems to determine storm track much more than either choice of MP or BLPmuch more than either choice of MP or BLP

• Conversely, choice of BLP seems to impact Conversely, choice of BLP seems to impact storm intensity to a similar degree as choice storm intensity to a similar degree as choice of CPof CP

• For these parameterizations, choice of MP For these parameterizations, choice of MP seems to affect track and intensity seems to affect track and intensity surprisingly littlesurprisingly little

• Storms using the same CP can have much Storms using the same CP can have much different intensities, but this does not appear different intensities, but this does not appear to influence the storm track significantlyto influence the storm track significantly

TC Cyclogenesis: TC Cyclogenesis: Alma/ArthurAlma/Arthur

From Jeff Masters’ Wunderground Blog* from 26 May 2008:Possible development in the Western Caribbean or Eastern Pacific late this week

For the past 3-6 days, our most reliable global computer weather forecast models have been predicting the development of a low pressure system near or over Central America by Friday of this week. Given the persistence in the models in developing this low, we need to be alert to the possibility of a tropical depression forming in either the Western Caribbean or Eastern Pacific, on either side of Costa Rica and Nicaragua. It is uncertain which ocean basin such a storm might form in, and whether or not there will be a tropical wave around to help kick off development. It may be that the low pressure region will stay anchored over land south of the Yucatan Peninsula, preventing any development. This is the solution preferred by the ECMWF model in its last few runs. However, the GFS, NOGAPS, and Canadian models all predict a tropical depression might form in the Western Caribbean near Mexico's Yucatan Peninsula. In contrast, the UKMET shows development in the Eastern Pacific, on the Pacific side of Central America. Climatologically, May tropical storms are much more common in the Eastern Pacific than the Western Caribbean, so we should not discount the UKMET solution, even though it is an outlier. All five models predict that the Central American low pressure area will move northward towards the Gulf of Mexico, and wind shear may fall enough to allow a tropical depression to form should the low's center emerge over water. I'll be posting daily updates on the situation this week.

- Jeff Masters- Jeff Masters

*http://www.wunderground.com/blog/JeffMasters/comment.html?*http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=947&tstamp=200805entrynum=947&tstamp=200805

Inner Grid 84 Hour Forecast Initialized 1800 UTC 26 May

Inner Grid 120 Hour Forecast Initialized 1200 UTC 28 August

Preexisting Hurricane Gustav

Future Hurricane Hanna

Future Hurricane Ike

Future Tropical Storm Josephine

The “Unnamed Storms”

Outer Grid 120 Hour Forecast Initialized 1200 UTC 28 August

Conclusions & Future WorkConclusions & Future Work

• Initial results suggest this method of ensemble Initial results suggest this method of ensemble generation can effectively reproduce spreads more generation can effectively reproduce spreads more typical of a “traditional” ensembletypical of a “traditional” ensemble

• This is true for track, intensity, and TC cyclogenesisThis is true for track, intensity, and TC cyclogenesis• Ideally, the ensemble size could be increased to include Ideally, the ensemble size could be increased to include

additional CPs, MPs, BLPs, or additional categories of additional CPs, MPs, BLPs, or additional categories of parameterizationsparameterizations

• Given enough data, hopefully statistics could be created Given enough data, hopefully statistics could be created that would enhance the usefulness of this ensemblethat would enhance the usefulness of this ensemble

• Additional variables could be studied, such as radius of Additional variables could be studied, such as radius of maximum wind or precipitation amountsmaximum wind or precipitation amounts

• More detailed comparisons between the two types of More detailed comparisons between the two types of ensembles need to be performedensembles need to be performed

http://aurora.aos.wisc.edu/tropical/WRF.shtml

Documents

Tropical Cyclone Forecast Track and Intensity Sensitivities to Various Parameterizations using the WRF-ARW Model: Attempt at an Ensemble 2008 Cyclone Workshop