1) To minimize the threat of tropical cyclones to military and civilian
interests world-wide that are affected by tropical cyclone activity.
2) To combine geostationary and polar orbiting satellite data together so
that the Navy and the rest of the military community can have a centralized
real-time source of data pertaining to tropical cyclones.
Main Page Overview
This section describes the general features on the main page of the
Tropical Cyclone Web Page. More detailed explanations of the buttons are given
below under a following section.
The page is divided into two sections. On the left hand side, there is a
list containing all of the current actively-monitored storms (highlighted by a
red dot on the left hand side of the storm or invest area) over six predefined
regions of the globe. The geographical boundaries for each region with their
letter identifiers are:
Atlantic(L): North of the equator between N. America and Africa
East Pacific(E): North of the equator between 140W and N. America
Central Pacific(C): North of the equator between 180W and 140W longitude
West Pacific(W): North of the equator between 100E and 180E longitude
(A) North of the equator between Africa and 77E longitude
(B) North of the equator between 77E and 100E longitude
(P) South of the equator between 135E and S. America
(S) South of the equator between Africa and 135E longitude
Letter identifiers are assigned to the storm's basin of origin. If a storm
passes over a basin boundary, the storm will maintain it's basin of origin
letter identifier even though it has entered a new region. For example, storm
"Alpha" originates in the Eastern Pacific and is assigned 01E. If it makes its
way into the Central Pacific it will still maintain its number and name
designation even though it is seen under the Central Pacific header.
The storm number can be an eighty series (80-89), ninety series (90-99), or a number between 1 and 50. Storms seen with a number between 80 and 89
are usually used for testing purposes only. Storms with numbers between 90 and
99 are areas that forecasters use to monitor suspect regions typically with
disorganized large-scale convection that has a chance to develop into a more
organized system such as a tropical depression. Storms with numbers between
1 and 50 are/were storms that reached tropical storm strength or higher.
The naming convention after the number/basin pair can be called INVEST,
NONAME, or assigned name. All storms will start with an INVEST name. When
the system becomes a tropical storm this name will change to either NONAME or
assigned name. NONAME is assigned to storms which do not have an official
assigned name yet. Assigned names are given to tropical storms according to
the World Meteorological Organization (WMO). Typically, storms that form in the
Indian Ocean north of the equator will have NONAME. There are a few occasions
where a tropical storm name will have an INVEST or a ONE, TWO,... following the
number/basin pair. This name is only temporary and typically lasts for only
a couple of hours. This is caused by the timing of the position updates
generated by the Automated Tropical Cyclone Forecasting (ATCF) system and
when forecasters determine that the system has become a tropical storm.
The by default main window on the right hand side displays the first
system that is listed on the left in blue. The priority of the basins is listed
as they appear from top to bottom. Any storm can be selected from this menu
just by clicking on the links. At the top of the window, there are three
buttons. The "Active" button (already highlighted) only displays the active
systems. The "All" button displays all the systems for the year up to present.
The "Year" button points to the storm archive for previous years' storms.
The main window of the tropical cyclone web page contains a menu at the
top that displays the sensors and products associated with the displayed
system. At the top, the button highlighted "Latest" is displayed in yellow.
This indicates that the image displayed is the latest data available. The "1-
km" menu has IR and VIS buttons that will display either a visible or IR
image at a 1 km resolution from a geostationary satellite. The 1 km data is
received from GOES east and west, Meteosat 5 or 7, or GMS depending on the
region of coverage. A histogram equalization is applied to the visible images
to provide contrast in the clouds.
The following two menu bars in grey are used for displaying products
associated with a SSM/I or TRMM overpass. The IR and VIS buttons will be
discussed here. Please see below for a more detailed explanation of the
remaining products in these menus. The IR and VIS buttons on the SSM/I menu
are the geostationary images generated closest in time to the latest SSM/I
overpass. Only geostationary IR and VIS data are displayed through these two
buttons. For TRMM, the IR and VIS buttons may contain two types of products.
The first type of product is similar to the SSM/I VIS/IR buttons and the
1-km VIS/IR buttons in that they only display geostationary data closest in
time to the TRMM overpass. The second product seen through the TRMM VIS/IR
buttons is the TRMM VIS/IR sensor (VIRS) overlayed on top of the geostationary
Below the SSM/I and TRMM menus is the upcoming pass display along with
the current zulu time. This box displays the date and time of the SSM/I and
TRMM data that currently makes up the products seen in the images. It also
displays the next set of passes and their distance from the system's center
for SSM/I and TRMM. The "more" button will display the upcoming passes for
the next day.
At the bottom, the current 1 km visible data is displayed each time. There will also be an ATCF forecast graphic on the left hand side when there is
a tropical storm. In the upper left portion of the displayed images, there
is information given on the date and time and type of sensors used to
generate the image. The top line is always the date and time of the ATCF
warning or bogus message that fixes the center of the image. It is followed
by the system's number and name. The lines that follow the name are the date
and time of the sensors that make up the images. If the image is a composite
image (an image where there are two of more sensors), then there will be two
or more lines indicating the dates and times of the data.
Most of the graphic and text warning information is provided to FNMOC
through ATCF. A smaller subset of location and intensity information is
obtained locally through the TAPPS system which provides one line QC'd data
to NAVGEM. An automated decoder is placed on the front end of the tropical
cyclone web page to decode the messages generated by TAPPS and ATCF.
The storm track graphic seen on the main page (when appropriate) shows
the official 72 hour forecast track issued by the regional centers. The
graphic also shows the forecast wind radii (provided by Buck Sampson, NRL-MRY):
Red = gale force winds > 34 kts
Blue = 50 kt wind radius
Green = hurricane force winds > 74 kts
Purple = 100 kt wind radius
SSM/I AND TRMM PRODUCTS
The section discusses the products located in the SSM/I and TMI menus
on the main page. One of the main goals of the web page is to provide products
that contain information from multiple satellites. The images are triggered
on either a SSM/I or TRMM pass. The appropriate geostationary data is then
obtained based on the storm's location. First a search is made from an
archive (usually one day) and then the data is used. The SSM/I or TRMM data
sets are then merged to the same grid as the geostationary data to provide
collocated products. Time differences between the geostationary and SSM/I
are typically less than 30 minutes. Below summarizes the products in the SSM/I
and TMI menus.
1) Vis -- visible geostationary data closest in time to a SSM/I pass
2) IR -- infrared geostationary data closest in time to a SSM/I pass
3) IR-BD -- IR image containing a BD enhancement curve. The BD
enhancement is used as part of the Dvorak method for determining
tropical cyclone intensity. The enhancement brings out the
cloud tops which helps determine whether a storm is strengthening
4) Multi-Sensor -- This image contains four panels: upper right -
IR, upper left - visible (only during the day), lower left SSM/I
Polarization Corrected Temperature (PCT), and lower right -
composite SSM/I. The IR and visible have already been discussed
above. The PCT and composite are explained below. The four panels
allows researchers to readily access many sources of data on a single
image to determine features as eyewall strength and shear.
5) 85 Ghz horizontal - The resolution of these images as 12.5 km.
This means that forecasters can see features nearing the mesoscale.
Alone this channel acts like a total precipital water indicator.
Total precipital water is combination of water vapor, cloud liquid
water, and rain drops. In strong convection, 85 GHz starts
scattering and "depressions" can be see in the images. This due
to the ice located 1 to 2km below the cloud tops. The more
scattering, the heavier the precipitation. Units are in Kelvins.
6) 85 GHz horizontal-weak -- This product enhances a portion of the
color table used in (5). It stretches the brightness temperatures
in the "warmer" portions of the channel to provide contrast
in the warmer cloud tops. Units are in Kelvins.
7) PCT -- A product that is a linear ratio between the 85 GHz V and H
channels. Units are in Kelvins.
8) color composite -- The composite SSM/I image creates a false color
image using red (85 GHz PCT), green (85 GHz vertical), and blue
(85 GHz horizontal).
9) rain -- This SSM/I algorithm uses the combination of 85 Ghz
scattering (for rain over land areas and cold cloud top rain
signatures) and an emission component using the lower frequency
channels. The emission portion of the algorithm senses "warm"
rain where the cloud tops are lower. This is helpful to identify
cloud structure in weaker systems. Current units are in inches/hr.
10) wind speed -- The SSM/I algorithm retrieves the wind speed at
19.5 meters above the ocean surface. It is based on the lower
frequency channels. The algorithm does not retrieve wind in
rain areas. These are indicated by black areas within the clouds
and rain bands. The wind speed retrieval is screened using the
rain flag that determines the wind speed error based on cloud
contamination. Currently only wind speed values with a rain flag
of zero ( < 2/ms error) are allowed to be displayed in the images.
Therefore, wind speed data can only be seen on the edges of the
systems. Units are in knots.
11) water vapor -- This product represents the total precipital water
in a column of the atmosphere. The algorithm uses the lower
frequency channels and cannot retrieve water vapor in the presence
of rain. This product is the most accurate SSM/I algorithm. Units
are in mm (kg/m^2).
Buttons for VIS, IR, IR-BD, Multi-sensor, 85 GHz, PCT, and color are
the same as SSM/I but using the frequencies from TMI.
1) rain rate -- This product is provided directly to FNMOC. Units are in
2) wind speed -- This algorithm is calculated at FNMOC. It takes advantage
of the 10 GHz channel to compute surface wind. It is also screened
for cloud/rain contamination using the 37 GHz differential. Units are
3) color 37 -- Same as for the composite color using 85 GHz except this
algorithm uses 37 GHz instead.
4) 37 GHz vertical -- One of the lower frequency channels on TMI. This
frequency is the most sensitive to clouds and cloud liquid water
content. Units are in Kelvins.
5) 37 GHz horizontal -- same as in (4) except the horizontal polarization
provides more dynamic range.
6) cloud liquid water -- This product is provided directly to FNMOC.
Cloud liquid water is the amount of non-raining cloud in the
atmosphere. Units are in mm (kg/m^2).
26 JUL 2021 0420Z
Half-sized, ( 139 K) click image to get full-size ( 305 K).