Tropical (Zehr, Hilgendorf, Knaff, Vaughn)
An investigation of the vertical wind shear forcing on the intensity and
track changes of Hurricane Erika has identified ten different environmental
vertical wind profiles, each of which are for consecutive time periods
of 12 to 45 hr, covering September 1-12, 1997. Those profiles evaluate
the mean wind over a 5 degree latitude radius circle around the tropical
cyclone (TC) center. Three different approaches are used. Numerical
model analyses, storm center IR average images, and high density satellite
winds are used. The results show that a two-level analysis of vertical
shear may at times be inadequate, and that the direction of vertical shear
is important to the analysis. The three methods combined with sea-surface
temperature analyses, observed intensity changes, and TC motion are shown
to fit a simple model approach.
A new project is planned for analysis of inner core upper winds from 1-minute
visible imagery. Training and planning meetings with Kelly Findeisen
(CSU graduate student), John Knaff, and Dr. William Grays project have
taken place. This project will focus on use of SRSO manual winds
in the inner core region of Hurricane Marilyn. SRSO imagery was collected
on 5 consecutive days with Hurricane Marilyn (1995). Dave Watson
is supporting this project with data processing and CD-ROM archiving.
Significant and interesting tropical cyclones were analyzed in near real
time. Such analyses included digital IR intensity analyses, storm
relative average images, and equatorial westerly wind burst analysis.
The tropical cyclones were located in both Northern and Southern Hemisphere
and included Hurricanes Guillermo, Linda, Nora, and Pauline in the eastern
Pacific, Typhoons Ivan, Joan, Keith and Paka in the western Pacific, and
Cyclones Pam, Ron and Susan in the South Pacific. Super typhoon Paka
which hit Guam with considerable damage and Cyclone Pam formed as twin
cyclones unusually far east in the central Pacific, in response to the
ongoing strong El Nino.
High resolution (10 sec) flight (10,000 ft) level observations form the
Air Force Reserve Hurricane Hunter C-130 reconnaissance flights for the
entire 1995 season have been obtained from the Hurricane Research Division,
Miami. Previously, these data have been successfully converted to
MCIDAS format so that flight level information can be displayed along with
the satellite imagery. In addition, programs to place these data
in a storm relative position at common synoptic times (00Z, 06Z,
12Z, and 18Z) or snapshots, interpolate azimuthally around the storm in
a high resolution manner, and break these data into individual radial legs
have been successfully written.
Cloud track winds have been manually derived from rapid and super
rapid scan images for Erika 1997, and for Luis (1995) (for only one super
rapid scan period). Programs have been written to remove storm motion,
and place these data in similar storm relative synoptic snapshots.
It has been shown that data from the manually derived cloud track winds
derived the rapid and super rapid scan imagery, high resolution water vapor
winds from the University of Wisconsin, and the radially interpolated Air
Force C-130 reconnaissance can be combined to form a superior synoptic
and mesoscale wind analysis around Atlantic tropical cyclones. An
outline for a paper to be submitted to either Weather and Forecasting or
The Journal of Atmospheric and Ocean Technology discussing this methodology
has been created.
Work has begun on a case study of Hurricane Luis (1995). This study
will utilize the super rapid scan satellite imagery, Air Force reconnaissance
data, NCEP reanalysis data, and high resolution water vapor winds.
To date individual radial legs, and azimuthally interpolated synoptic snapshots
have been created using the flight level observations, and the water vapor
winds and NCEP reanalysis data have been obtained from various sources.
Seasonal predictions of Atlantic tropical cyclone activity for the 1998
hurricane season (LAD multiple linear regression forecast of Atlantic
tropical cyclone activity for 1998), and future El Nino/Southern Oscillation
conditions (Application of the El Nino - Southern Oscillation CLImatology
and PERsistence (CLIPER) forecasting scheme) were prepared in December
and were informally published in the Climate Predictions Centers Experimental
Long-Lead Forecast Bulletin.
Two Super Typhoons
occurring simultaneously in the West Pacific were studied, using GMS-5
satellite imagery. Ivan and Joan were the 8th and 9th
Super Typhoons to form this year in this area of the Pacific. It
was an unusual occurrence for two storms of this strength to occur at the
same time and both of them being so close to satellite subpoint.
Because of the close proximity to subpoint, the stadium effect (inward
sloping of the eyewall), can be seen. The outflows of the two storms
were unique also. Ivan's extends to the north-east while Joan's stretches
to the south-west. The significance of this, is that even with
their close proximity, the two outflows are not affecting one another.
Daily Global Analysis SST anomaly charts, a product of NOAA/NESDIS, show
that the storms produce a cold wake through upwelling. (Click on
image for full size display.)