Tropical Cyclone Processingfor the CFS Reanalysis

Bob Kistler

NWP TC Review

• tcvital files– Worldwide observations of TC’s

• Tropical Storm Relocation– TC in guess is located and bodily moved to

tcvital location

• Bogus vortex winds– If TC not found in guess, bogus vortex wind

profiles are created to “spin-up” storm in GSI

tcvitals• NHC 16L NOEL 20071101 0000 229N 0785W 360 015 0995 1008 0334 26 093 0185 0185 -999 0185 D

• Formatted storm text messageidentification, location, movement, strength

• historical sources1. Mike Fiorino’s bogus wind profiles

2. HURDAT archive

3. /nwprod archive

4. Mike Fiorino’s “mdeck” merge of 1,2,3

tcvitalstype tcvcard ! Define a new type for a TC Vitals card sequence character*4 tcv_center ! Hurricane Center Acronym character*3 tcv_storm_id ! Storm Identifier (03L, etc) character*9 tcv_storm_name ! Storm name integer tcv_yyyymmdd ! Date of observation integer tcv_hhmm ! Time of observation (UTC) integer tcv_lat ! Storm Lat (*10), always >0 character*1 tcv_latns ! 'N' or 'S' integer tcv_lon ! Storm Lon (*10), always >0 character*1 tcv_lonew ! 'E' or 'W' integer :: tcv_stdir = -99 ! Storm motion vector (in degr) integer :: tcv_stspd = -99 ! Spd of storm movement (m/s*10) integer :: tcv_pcen = -999 ! Min central pressure (mb) integer :: tcv_penv = -999 ! val outermost closed isobar(mb) integer :: tcv_penvrad = -999 ! rad outermost closed isobar(km) integer :: tcv_vmax = -9 ! max sfc wind speed (m/s) integer :: tcv_vmaxrad = -99 ! rad of max sfc wind spd (km) integer :: tcv_r15ne = -999 ! NE rad of 15 m/s winds (km) integer :: tcv_r15se = -999 ! SE rad of 15 m/s winds (km) integer :: tcv_r15sw = -999 ! SW rad of 15 m/s winds (km) integer :: tcv_r15nw = -999 ! NW rad of 15 m/s winds (km) character*1 :: tcv_depth = 'X' ! Storm depth (S,M,D) X=missingend type tcvcard

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19NHC 16L NOEL 20071101 0000 229N 0785W 360 015 0995 1008 0334 26 093 0185 0185 -999 0185 D

1 NHC

2 16L

3 NOEL

4 20071101

5 0000

6 229N

7 0785W

8 360

9 015

10 0995

11 1008

12 0334

13 26

14 093

15 0185

16 0185

17 -999

18 0185

19 D

Hurricane Initializations in NCEP Numerical Models

Qingfu Liu

Acknowledgement: Naomi Surgi Steve Lord Hua-Lu Pan

EMC/NCEP/NOAA/SAIC

Brief History of Hurricane Forecast in NCEP global model (GFS)

• Prior to 1995, no storm genesis in NCEP global model. Bogus data are added in 1989. tropical storms in the initial conditions defined by the bogus data weakened and becomes open wave in medium range forecast

• In Oct. 1995, the newly implemented version of the NCEP global model started to generate and deepen tropical storms. The new version not only forecast real storm genesis, but also created many false storms. The false storms passed to next cycle through first guess, and continue to develop and lead to many bad forecast in a row.

• In 2000, cloud momentum mixing was added to the simplified Arakawa-Schubert scheme, significantly suppressed the false storm formation

• Two vortices in the global analysisStorms existing in the first guess often are weak and large compared to the observed storms, and the center located away from the real storm center. Adding bogus storm data (and forcing the GSI to accept the data) will often lead to two vortices in the same region, one from the first guess and the other from the bogus data.

This two vortices interact each other and often leads to very bad forecast.

• Prompted development of TC relocation

9 hour forecast at time t-3, t, t+3

GSI analysis at time t-6

Relocate hurricane vortices

GSI analysis at time t

5 or more day forecast

Hurricane initialization in GFS GSI analysis cycle at time t:

t t+6

Hurricane Relocation in GFS

• Locate vortex center in t-3, t and t+3 forecast fields TC vital message

lon, lat, max surface wind, min central press, etc. Tracker software

700 & 850 mb: max relative vorticity, min wind speed and min geopotential height

sea-level press

• Separate hurricane vortex from environmental fields• Relocate hurricane vortex to the observed storm

position (divergence, vorticity, surface pressure, temperature, and mixing ratio)

• If the storm is too weak in the forecast fields, storm bogus data will be added in GSI analysis

Advantages Compared to Storm Bogus

• Removes the possibility of double vortices in the analysis field

• Guess field is more consistent with observation data, and less data are rejected

• Model generated vortex is more consistent with model dynamics, and less adjustment needed once forecast starts

• Hurricane dynamic structures, such as tilted hurricane vortex in shear or baroclinic environment, will be maintained in hurricane relocation

Bogus vortex winds

• Program SYNDATA – – requires full tcvital report

• i.e central p, max wind, radius max winds • Will fail with incomplete HURDAT or Fiorino report

– 2nd execution performs QC near TC vortex• Flag non-representative reports

– central pressure reports– dropwindsone winds

TC processing in earlier reanalyses

• NCEP/NCAR I and II – none– Wind bogus tested – produce double vortices

• NASA / DAO - none

• ERA-15 - none

• ERA-40, NCEP Regional Reanalysis– Fiorino wind bogus was availalble– Was not used

• JRA-25 – Fiorino wind bogus was used

1. Fiorino Wind Bogus

• 6 hour frequency Jan 1979 – Feb 2001• All basins• 5 bufr wind profiles

– 1000,925,850,700,500, 400 Hpa – central location , +/- 1 deg N,S,E,W– Storm name same from storm id: TC021 21L– No tcvital strength information

• Neither radius of max winds nor max wind• No central pressure

• Storm location has been converted to a tcvital report• End result is a report pair:

– tcvitl.gdas.yyyymmddhh - tcvital entry– tcbogw.gdas.yyyymmddhh - 5 wind profiles

2. HURDAT

• 1850’s – present “Best Track”• 4xdaily for reanalysis period 1978 - present• Atlantic (L) and Eastern Pacific (E) only• Uses historical names (e.g. Camille, Katrina)• Has central pressure and max wind

– Lacks radius of max winds

• Storm id (03L) usually equates with Fiorino id• Supercedes Fiorino tcbog report

– Has ‘W’ added when tcbogw winds are available

3. NCEP tcvital production archive

• From 1997 – on• Complete tcvital reports

– Supercede HURDAT and Fiorino wind tcvital

• 1997 -2002 – Indian, Pacific oceans spotty• 1997-1998 – non Y2K• Multiple differing reports

– GFS (~t+2:45) then GDAS(~t+5:50)– Correction of error or later info received – Upgrade from depression # to storm name– Required manual inspection and editing

Bogus vortex winds

• New program: TCBOG_SYNDATA – Alternative to existing SYNDATA

• Runs identical QC of central p., drop. winds

– invoked for incomplete tcvital records• Hurdat reports marked “W” • Fiorino tcvital reports

– If relocation indicates vortex spin-up:• matches tcvitl and tcbogw reports• Converts the tcbogw profiles for input to GSI

Fiorino “mdeck”

• Just received on Monday, 11/05/2007– Awaiting comparison with existing sets

• Fills a gap in production archive – missing Jan – Mar 2002

• Merge of historical best tracks – HURDAT/TCVITAL type files for all basins– Contains historical names