TAFB/Marine Product Descriptions
Tropical Weather Discussion
Purpose
The Tropical Weather Discussion describes major synoptic weather features and significant areas of disturbed
weather in the tropics. The product is intended to provide current weather information for those who need to
know the current state of the atmosphere and expected trends to assist them in their decision making. The
product gives significant weather features, areas of disturbed weather, expected trends, the meteorological
reasoning behind the forecast, model performance, and in some cases a degree of confidence.
Content
The Tropical Weather Discussion is a narrative explaining the current weather conditions across the tropics
and the expected short-term changes. The product is divided into four different sections as outlined below:
- SPECIAL FEATURES (event-driven)
The special features section includes descriptions of hurricanes, tropical storms, tropical depressions,
subtropical cyclones, and any other feature of significance that may develop into a tropical or subtropical
cyclone. For active tropical cyclones, this section provides the latest advisory data on the system.
Associated middle and upper level interactions as well as significant clouds and convection are discussed
with each system. This section is omitted if none of these features is present.
- TROPICAL WAVES (event-driven)
This section provides a description of the strength, position, and movement of all tropical waves analyzed
on the surface analysis, from east to west. A brief reason for a wave's position is usually given, citing
surface observations, upper air time sections, satellite imagery, etc. The associated convection is
discussed with each tropical wave as well as any potential impacts to landmasses or marine interests.
This section is omitted if there are no tropical waves present.
- ITCZ
In this section, the Intertropical Convergence Zone (ITCZ) is depicted by coordinates from east to west
with an outline of all associated convection referenced to the axis, if possible. The ITCZ is depicted
based on the following definition: "a zonally elongated axis of surface wind confluence in the tropics,
due to confluence of northeasterly and southeasterly trade winds, and/or confluence at the poleward extent
of cross-equatorial flow into a near-equatorial 'heat trough' or 'monsoon trough.'"
- DISCUSSION
The discussion section makes reference to middle and upper level features and provides connection to
how these features are interacting with or influencing surface features. Convection is outlined with the
features as warranted. This section will also provide short-term (up to 48 hours) trends and forecasts
of features, especially if they are forecast to strengthen and/or affect landmasses. A discussion of
model guidance may also be included. In general, this section is regionalized according to the current
weather pattern (i.e. Gulf of Mexico, Caribbean, Western Atlantic, etc.)
Coverage and intensity for convective and non-convective weather is defined as follows:
COVERAGE FOR CONVECTIVE and NON-CONVECTIVE WEATHER:
Numerous | Widespread | >54% | Scattered | Areas | 25%
- 54% | Widely scattered | Local/Locally | <25% | Isolated | | No
%, implies circumnavigability |
COVERAGE FOR SIGNIFICANT CLOUDS:
Clear | 0 | Few | 1/8 -
2/8 | Scattered | 3/8
- 4/8 | Broken | 5/8
- 7/8 | Overcast | 8/8 |
INTENSITY OF CONVECTION (based on cloud top temperatures):
Strong | <
-70°C (summer) | < -60°C
(winter) | Moderate | between
-45°C and -70°C (summer) | between
-35°C and -60°C (winter) | Weak | >
-45°C (summer) | > -35°C
(winter) |
Coverage
The National Hurricane Center issues two Tropical Weather Discussions, as shown below:
- Atlantic
From the equator to 32°N west of the prime meridian including the Caribbean Sea, Gulf of Mexico, and
adjacent land areas. These areas include the southeast United States [especially Florida], Mexico, Central
America, northern South America, and western Africa
- East Pacific
From the equator to 32°N east of 140°W including coastal areas of Mexico, and Central and South America.
Issuance/Transmission
|
WMO |
NWWS |
Atlantic |
AXNT20 KNHC |
MIATWDAT |
East Pacific |
AXPZ20 KNHC |
MIATWDEP |
|
Issuance Time |
MIATWDAT |
105 AM EST (205 AM EDT) |
705 AM EST (805 AM EDT) |
105 PM EST (205 PM EDT) |
705 PM EST 805 PM EDT) |
MIATWDEP |
0405 UTC |
1005 UTC |
1605 UTC |
2205 UTC |
High Seas Forecasts
Purpose
The world's oceans and seas are divided up into 16 separate regions known as "METAREAS" with different nations having responsibility for
providing high seas marine forecasts for those waters. These high seas forecasts are used mainly by large transoceanic vessels but
can also be used by smaller vessels or those on shorter voyages. The U.S. National Weather Service (through
the National Hurricane Center, the Ocean Prediction Center, and
the Honolulu Weather Forecast Office) has the responsibility to provide high seas marine forecasts
for METAREAS IV, XII, and XVI, which cover most of the North Atlantic Ocean, North Pacific Ocean, and Southeast Pacific Ocean.
Content
The National Hurricane Center issues three High Seas Forecasts for parts of METAREAS IV and XII and all of
METAREA XVI. Each product is updated every 6 hours and includes a description of winds and waves for the
current time (a nowcast) and a 24- and 48- hour forecast of the winds and waves, using a 20 knot threshold
for the wind and an 8 feet threshold for the seas. Positions and intensities are also given for tropical
cyclones out to the 120-hour forecast. Intermediate forecast times are given for rapidly changing weather events.
The High Seas products also include updated descriptions of convection, particularly along the ITCZ. The
products include marine warnings for gale, storm, hurricane force winds, and tropical cyclone-related
conditions and can also include information on reduced visibility and other marine hazards.
Coverage
- Atlantic Ocean (from 7°N to 31°N west of 35°W, including the Caribbean Sea and the Gulf of Mexico)
- Northeast Pacific Ocean (from the equator to 30°N east of 140°W)
- Southeast Pacific Ocean (from the equator to 18.5°S east of 120°W)
Issuance/Transmission
High seas products are transmitted under World Meteorological Organization (WMO) and NOAA Weather Wire Service
(NWWS) headers as shown in the following table (alternate headers are for high seas products issued by the
Ocean Prediction Center, which append the forecasts of the National Hurricane Center):
|
Primary Headers |
Alternate Headers |
|
WMO |
NWWS |
WMO |
NWWS |
Atlantic |
FZNT02 KNHC |
MIAHSFAT2 |
FZNT01 KWBC |
NFDHSFAT1 |
Northeast Pacific |
FZPN03 KNHC |
MIAHSFEP2 |
FZPN01 KWBC |
NFDHSFEPI |
Southeast Pacific |
FZPN04 KNHC |
MIAHSFEP3 |
|
High seas products are issued on a regular six hourly schedule as shown below:
|
Issuance Time in UTC |
MIAHSFAT2 |
0430 |
1030 |
1630 |
2230 |
MIAHSFEP2 |
0430 |
1030 |
1630 |
2230 |
MIAHSFEP3 |
0515 |
1115 |
1715 |
2315 |
Alternate headers for the Atlantic and Northeast Pacific Forecasts are
where TAFB forecasts are appended to High Seas Forecasts of the
Ocean Prediction Center. In addition,
Atlantic high seas products are transmitted by radiofax.
Offshore Waters Forecasts
Purpose
The Offshore Waters Forecast provides forecast and warning information to mariners who travel the oceanic waters adjacent
to the U.S. and its territorial coastal waters. This forecast serves customers who operate from the coastal waters to
several hundred nautical miles from shore with 10 different products issued by the National Hurricane Center, the Ocean
Prediction Center, the Honolulu Weather Forecast Office, the Anchorage Weather Forecast Office, and the Juneau Weather Forecast Office.
Content
The Offshore Waters Forecast includes a synopsis which describes significant surface weather features that may cause
significant winds and seas over the forecast area during the forecast period. The synopsis identifies major weather
systems and the strength, trend, and movement of each. The most detail is focused in the first 48 hours of the forecast.
The synopsis also includes tropical cyclone forecast positions out to 120 hours.
The offshore waters product provides a forecast for winds and seas over the affected area for roughly the next 5 days.
The forecast also includes significant weather which would pose a hazard to navigation, such as precipitation or restrictions to
visibility. Warnings are issued when conditions are expected to meet the specific warning criteria during the first two periods
of the forecast. Thereafter, a headline is used which shows that the conditions are expected to occur at some time after the
first two periods.
Coverage
The National Hurricane Center issues two separate Offshore Waters Forecasts, as shown below:
Gulf of Mexico offshore waters:
- Northwest Gulf (north of 25°N west of 90°W)
- Southwest Gulf (south of 25°N west of 90°W)
- Middle Gulf (between 85°W and 90°W)
- Eastern Gulf (between 81°W and 85°W)
Southwest and Tropical North Atlantic and Caribbean offshore waters:
- Northwest Caribbean (north of 15°N west of 75°W)
- Southwest Caribbean (south of 15°N west of 75°W)
- Eastern Caribbean (east of 75°W to Leeward and Windward Islands)
- Tropical North Atlantic (from 7°N to 22°N between 55°W and 65°W)
- Southwest North Atlantic (south of 31°N west of 65°W including the Bahamas)
Issuance/Transmission
Offshore waters products are transmitted under World Meteorological Organization (WMO) and NOAA Weather Wire
Services (NWWS) headers as shown in the following table:
|
WMO |
NWWS |
Southwest and Tropical North Atlantic and Caribbean |
FZNT23 KNHC |
MIAOFFNT3 |
Gulf of Mexico Forecast |
FZNT24 KNHC |
MIAOFFNT4 |
Offshore waters products are issued on a regular six hourly schedule as shown below:
|
Issuance Time |
MIAOFFNT3 |
430 AM EST (530 AM EDT) |
1030 AM EST (1130 AM EDT) |
430 PM EST (530 PM EDT) |
1030 PM EST 1130 PM EDT) |
MIAOFFNT4 |
330 AM CST (430 AM CDT) |
930 AM CST (1030 AM CDT) |
330 PM CST (430 PM CDT) |
930 PM CST 1030 PM CDT) |
Marine Weather Discussion
Purpose
The Marine Weather Discussion is a semi-technical product, analogous to the Area Forecast Discussion (AFD) issued by the local National
Weather Service Forecast Offices, primarily used as a means to explain the scientific rationale behind the Offshore Waters Forecast and
to summarize the warnings in effect. The Marine Weather Discussion is used to convey forecast and warning information to federal agencies,
weather-sensitive officials, and the media. Part of this goal is to enhance coordination with the coastal Weather Forecast Offices.
Content
The Marine Weather Discussion describes synoptic and mesoscale features expected to affect areas in and adjacent to the offshore waters
of the Gulf of Mexico, Caribbean Sea, and Southwest and Tropical North Atlantic Ocean. The narrative describes weather, wind speed, and
seas with primary focus on the next 48 hours. The product emphasizes timing and issuance of warnings, includes future trends of wind and
sea conditions, discusses the effects of currents such as the Gulf Stream on winds and seas, and addresses how the latest computer model
guidance is handling features of significance to the mariner.
Coverage
The National Hurricane Center issues one Marine Weather Discussion to convey forecast reasoning over both its offshore forecast areas.
This area includes the Gulf of Mexico, the Caribbean Sea, the Tropical North Atlantic, and the Southwest North Atlantic Ocean south of
31°N west of 55°W. The area between 55°W and 65°W is not specifically covered by the Offshore Waters Forecast products, but
conditions in this area are discussed since they often affect the offshore waters in the future.
Issuance/Transmission
The Marine Weather Discussion is transmitted under World Meteorological Organization (WMO) and NOAA Weather Wire Services (NWWS) headers
as shown below:
|
WMO |
NWWS |
Marine Weather Discussion |
AGXX40 KNHC |
MIAMIMATS |
In general, the Marine Weather Discussion is issued twice a day (with updates as needed) shortly before the issuance of the scheduled Offshore
Waters Forecast products. Forecasters will issue a brief discussion to provide information of an impending offshore forecast update. The
scheduled transmission times are shown below:
|
Issuance Time |
MIAMIMATS |
by 230 AM EST (330 AM EDT) |
by 230 PM EST (330 PM EDT) |
Pan-American Temperature and Precipitation Table
Purpose
The Pan-American Temperature and Precipitation Table is a collection of temperature and precipitation data and present weather for
selected cities in Mexico, Central and South America, and the Caribbean area. It provides general weather conditions two times per
day for general public use domestically and internationally.
Content
This product provides general weather conditions, high and low temperatures in degrees Fahrenheit (°F) and degrees Celsius
(°C), and measured precipitation in the previous 6, 12, or 24 hours, as indicated, for selected cities in Mexico, Central
and South America, and the Caribbean area. The morning product contains the low temperature for the current day and the
high temperature for the previous day. The evening product contains the low and high temperature for the current day.
Coverage
The Pan-American Temperature and Precipitation Table includes the following stations (as shown in the map above):
Acapulco, Mexio | Merida, Mexico |
Barbados | Mexico City, Mexico |
Bermuda | Montego Bay, Jamaica |
Bogotá, Colombia | Monterrey, Mexico |
Curaçao, Netherlands Antilles | Nassau, Bahamas |
Freeport, Bahamas | San Juan, Puerto Rico |
Guadalajara, Mexico | St. Thomas, Virgin Islands |
Guadeloupe | Tegucigalpa, Honduras |
Havana, Cuba | Trinidad |
Kingston, Jamaica | Veracruz, Mexico |
Mazatlán, Mexico | |
Issuance/Transmission
The Pan-American Temperature and Precipitation Table is transmitted under World Meteorological Organization (WMO) and
NOAA Weather Wire Services (NWWS) headers as shown below:
|
WMO |
NWWS |
Pan-Am Table |
SXCA01 KNHC |
MIATPTPAN |
|
Valid Time |
Issuance Time |
Morning MIATPTPAN |
700 AM EST (800 AM EDT) |
by 950 AM EST (1050 AM EDT) |
Evening MIATPTPAN |
700 PM EST (800 PM EDT) |
by 950 PM EST (1050 PM EDT) |
Satellite Rainfall Estimates (Woodley-Griffith technique)
Purpose
Satellite rainfall estimates are provided for tropical cyclones or other significant convective systems (mainly in the tropics)
when these systems threaten land. The product is issued when convection systems are affecting the WMO RA-IV area. The product
is also issued when system affect the west coast of Mexico. These estimates are based on geostationary infrared satellite
imagery using a method called the Woodley-Griffith Technique.
Content
The satellite rainfall estimate product provides an estimate of the maximum rainfall based on the last four geostationary
satellite images six hours apart (24 hours), as well as the estimated maximum rainfall based on the latest geostationary satellite
image. The product also provides a rainfall distribution within 4° (240 nautical miles) to the left and right of the observed system
motion in 1° (60 nautical miles) increments.
Coverage
One of three satellite rainfall estimate products is issued for each convective system affecting or expected to affect land based on the system.s initial location:
- Eastern Caribbean (areas between 40°W and 67°W)
- Central Caribbean (areas between 67°W and 80°W)
- Western Caribbean / Mexico (areas between 80°W and 120°W)
Issuance/Transmission
The Satellite Tropical Disturbance Rainfall Estimate product is transmitted under World Meteorological Organization (WMO) and NOAA Weather Wire Services (NWWS) headers as shown below:
|
WMO |
NWWS |
Eastern Caribbean |
TCCA21 KNHC |
MIASTDECA |
Central Caribbean |
TCCA22 KNHC |
MIASTDCCA |
Western Caribbean / Mexico |
TCCA23 KNHC |
MIASTDWCA |
The product is issued four times a day as needed near the synoptic times of 0000, 0600, 1200, and 1800 UTC.
The exact issuance time is based on the time of the last satellite image used.
Tropical Surface Analysis / NWS Unified Surface Analysis
Purpose
The Tropical Surface Analysis is created every six hours to depict the current state of atmosphere, specifically the
sea level pressure field and any relevant synoptic surface features. The Tropical Surface Analysis is attached to surface
analyses over North America, the North Atlantic Ocean, the North Pacific Ocean, and the Western Pacific Ocean to create
the National Weather Service Unified Surface Analysis.
Content
The Tropical Surface Analysis and NWS Unified Surface Analysis depict the sea level pressure field by showing lines of
equal pressure, usually in increments of four millibars (mb) but often in increments of two millibars where the pressure
gradient is weaker (especially in the tropics). The analysis also depicts important surface features that affect the
weather, including areas of high and low pressure, frontal systems (cold, warm, stationary, and occluded), troughs,
tropical cyclones, tropical waves, the Intertropical Convergence Zone (ITCZ), drylines, and squall lines.
Coverage
The Tropical Surface Analysis is created by the National Hurricane Center and covers the area approximately from
30°N to 20°S between 0° and 140°W. This area includes the tropical and subtropical areas of the Atlantic and
East Pacific Oceans, Mexico, Florida, the Caribbean, South America, and West Africa. For radiofax purposes, the
analysis is split into three different areas:
- Atlantic (East Half from 5°S to 50°N between 0° and 70°W)
- Atlantic (West Half from 5°S to 50°N between 55°W and 125°W)
- Eastern Pacific (from 20°S to 40°N between 70°W and 150°W)
The NWS Unified Surface Analysis is created by merging the separate surface analysis produced by the National Hurricane
Center, the Hydrometeorological Prediction Center, the Ocean Prediction Center, and the Honolulu Weather Forecast
Office. The total area spans from the equator northward nearly to the North Pole, from 20°E westward to 130°W. This
covers the area from Europe and Central Africa westward across North and South America to East Asia.
Issuance/Transmission
The Tropical Surface Analysis is transmitted by radiofax via New Orleans, Pt. Reyes, and Honolulu according to the
following table:
|
New Orleans, LA (East
Half) |
New Orleans, LA (West
Half) |
Pt. Reyes, CA |
Honolulu, HI |
---|
Valid Time
(UTC) |
Transmit Time (UTC) |
Filename |
Transmit Time (UTC) |
Filename |
Transmit Time (UTC) |
Filename |
Transmit Time (UTC) |
Filename |
0000 |
0620 |
PYEA86.TIF |
0605 |
PYEB86.TIF |
0408 |
PYFA96.TIF |
0356 |
PYFA96.TIF |
0600 |
1220 |
PYEA87.TIF |
1205 |
PYEB87.TIF |
0945 |
PYFA97.TIF |
0954 |
PYFA97.TIF |
1200 |
1820 |
PYEA85.TIF |
1805 |
PYEB85.TIF |
1608 |
PYFA98.TIF |
1556 |
PYFA98.TIF |
1800 |
0020 |
PYEA88.TIF |
0005 |
PYEB88.TIF |
2150 |
PYFA99.TIF |
2154 |
PYFA99.TIF |
latest |
|
PYEA11.TIF |
|
PYEB11.TIF |
|
PYFA90.TIF |
|
PYFA90.TIF |
The analyses are also updated on the NHC webpage by 0300, 0900, 1500, and 2100 UTC for the 0000, 0600, 1200, and 1800
UTC surface analyses, respectively.
Significant Wave Height Analysis
Purpose
The Significant Wave Height Analysis is created every 12 hours, at 0000 and 1200 UTC, to depict the current significant wave height and
primary swell direction field over the tropical and subtropical Atlantic and East Pacific waters.
Content
The significant wave height is contoured at intervals of three feet, with additional contours added if necessary in areas of
little spatial variation. The significant wave height is defined as the average height of the highest 1/3 of the waves
(individual waves may be more than twice the significant wave height). Maximum and minimum significant wave height values
are indicated as necessary. Arrows are also depicted showing the primary swell direction at specific points.
Coverage
The National Hurricane Center produces two separate significant wave height analyses twice a day:
- Atlantic (from the equator to 31°N between 35°W and 100°W, including the Pacific east of 100°W)
- East Pacific (from 20°S to 30°N east of 145°W)
Issuance/Transmission
|
New Orleans, LA |
Pt. Reyes, CA |
Honolulu, HI |
Valid Time (UTC) |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
0000 |
0215 |
PJEA88.TIF |
0205 |
PKFA88.TIF |
0240 |
PKFA88.TIF |
1200 |
1415 |
PJEA90.TIF |
1425 |
PKFA89.TIF |
1440 |
PKFA89.TIF |
latest |
|
PJEA11.TIF |
|
PKFA10.TIF |
|
PKFA10.TIF |
Tropical Cyclone Danger Graphic (Mariner's 1-2-3 Rule)
Purpose
The tropical cyclone danger graphic is intended to depict the forecast track and corresponding area of avoidance
for all active tropical cyclones and to depict areas for which tropical cyclone formation is possible within
the next 36 hours over the Atlantic and East Pacific waters between May 15 and November 30.
Content
The 3-day forecast track of each active tropical cyclone is depicted along with a shaded "danger" region, or area of
avoidance. The danger area is determined by adding 100, 200, and 300 nautical miles to the tropical storm force radii
(34 knots) at the 24-, 48-, and 72-hour forecast positions, respectively (hence the Mariner's 1-2-3 rule).
Users operating in the vicinity of these systems are advised to continually monitor the latest forecasts and advisories
issued by the National Hurricane Center. Areas are also shaded for systems in which NHC forecasters believe there is
an adequate chance of tropical cyclone formation within the next 48 hours.
Coverage
The National Hurricane Center produces tropical cyclone danger graphics covering the following areas:
- Atlantic (from the equator to 60°N between 0° and 100°W, including the Pacific east of 100°W)
- East and Central Pacific (from the equator to 40°N between 80°W and 175°W,
including the Gulf of Mexico and Western Caribbean)
Issuance/Transmission
The tropical cyclone danger graphics are transmitted by radiofax via Boston, New Orleans, and Pt. Reyes according to the following table:
|
Boston, MA (Atlantic) |
New Orleans, LA (Atlantic) |
Pt. Reyes, CA (East Pacific) |
Valid Time (UTC)
| Transmission Time (UTC)
| Filename
| Transmission Time (UTC)
| Filename
| Transmission Time (UTC)
| Filename
|
0300 |
0452 |
PWEK89.TIF |
0735 |
PWEK89.TIF |
0357 |
PWFK88.TIF |
0900 |
1028 |
PWEK90.TIF |
1335 |
PWEK90.TIF |
1009 |
PWFK89.TIF |
1500 |
1824 |
PWEK91.TIF |
1935 |
PWEK91.TIF |
1557 |
PWFK90.TIF |
2100 |
2228 |
PWEK88.TIF |
0135 |
PWEK88.TIF |
2214 |
PWFK91.TIF |
latest |
|
PWEK11.TIF |
|
PWEK11.TIF |
|
PWFK11.TIF |
High Wind and Associated Seas
Purpose
The high wind and associated seas graphic is produced by the National Hurricane Center to depict areas of high winds and related
seas over the Atlantic and East Pacific waters between December 1 and May 14 (outside of hurricane season).
Content
Areas depicted on the high wind and seas graphic are extracted from the high seas forecasts produced by the National Hurricane
Center, the Ocean Prediction Center, and the Honolulu Weather Forecast Office. South of 30°N, areas are depicted for winds higher
than 25 knots with the corresponding seas noted. North of 30°N, areas are depicted for winds of gale force (34 knots) or higher
with the corresponding seas noted. Ranges in which the 25/34 knot thresholds are the upper limit (i.e. 25-35 knots) are included
on the graphic.
Coverage
The National Hurricane Center produces high wind and seas charts covering the following areas:
- Atlantic (from the equator to 40°N between 35°W and 100°W, including the Pacific east of 100°W)
- East Pacific (from the equator to 40°N between 80°W and 150°W)
Issuance/Transmission
The high wind and associated seas graphics are transmitted by radiofax via Boston, New Orleans, and Pt. Reyes according to the
following table:
|
New Orleans, LA |
Pt. Reyes, CA |
Honolulu, HI |
Valid Time(UTC) |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
0000 |
0452 |
PWEK89.TIF |
0735 |
PWEK89.TIF |
0357 |
PWFK88.TIF |
0600 | 1028 | PWEK90.TIF | 1335 | PWEK90.TIF | 1009 | PWFK89.TIF |
1200 |
1824 |
PWEK91.TIF |
1935 |
PWEK91.TIF |
1557 |
PWFK90.TIF |
1800 |
2228 |
PWEK88.TIF |
0135 |
PWEK88.TIF |
2214 |
PWFK91.TIF |
latest |
|
PWEK11.TIF |
|
PWEK11.TIF |
|
PWFK11.TIF |
Wind/Wave Forecasts
Purpose
Wind/wave forecasts are produced to depict the 24-, 48-, and 72-hour forecasts of surface features, surface wind speed and direction, and
significant wave heights over the tropical and subtropical Atlantic and East Pacific waters.
Content
The wind/wave forecasts include relevant surface features, including areas of high and low pressure, frontal systems (cold, warm,
stationary, and occluded), troughs, ridges, tropical waves, and tropical cyclones. Wind barbs indicate the forecast wind speed and
direction at specific points where long barbs indicate 10 knots and short barbs indicate 5 knots. The significant wave height is
contoured at intervals of three feet, with additional contours added if necessary in areas of little spatial variation. The significant
wave height is defined as the average height of the highest 1/3 of the waves (individual waves may be more than twice the significant
wave height). Maximum and minimum significant wave height values are indicated as necessary.
Coverage
The National Hurricane Center produces wind/wave forecasts covering the following areas:
- Atlantic (from the equator to 31°°N between 35°W and 100°W, including the Pacific east of 100°W)
- East Pacific (from 20°S to 30°N east of 145°W)
Issuance/Transmission
The Wind/wave forecasts are transmitted by radiofax via New Orleans, Pt. Reyes, and Honolulu according to the following table:
|
|
New Orleans, LA (Atlantic) |
Pt. Reyes, CA (East Pacific) |
Honolulu, HI (East Pacific) |
Forecast Period |
Valid Time (UTC) |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
24-hour |
0000 |
0635 |
PWEE89.TIF |
0959 |
PWFE01.TIF |
1008 |
PWFE01.TIF |
1200 |
1835 |
PWEE91.TIF |
2204 |
PWFE03.TIF |
2208 |
PWFE03.TIF |
latest |
|
PWEE11.TIF |
|
PWFE10.TIF |
|
PWFE10.TIF |
36-hour |
1200 |
1350 |
PWED98.TIF |
- |
- |
- |
- |
48-hour |
0000 |
0645 |
PWEI88.TIF |
1208 |
PWFI88.TIF |
1500 |
PWFI88.TIF |
1200 |
1845 |
PWEI89.TIF |
0225 |
PWFI90.TIF |
0300 |
PWFI90.TIF |
latest |
|
PWEI11.TIF |
|
PWFI10.TIF |
|
PWFI10.TIF |
72-hour |
0000 |
0655 |
PJEK88.TIF |
1218 |
PWFK92.TIF |
1510 |
PWFK92.TIF |
1200 |
1855 |
PJEK89.TIF |
0235 |
PWFK93.TIF |
0310 |
PWFK93.TIF |
latest |
|
PJEK11.TIF |
|
PWFK10.TIF |
|
PWFK10.TIF |
Surface Forecasts
Purpose
Surface forecasts are produced to depict the 24-, 48-, and 72-hour forecasts of sea level pressure and surface features over the tropical
and subtropical Atlantic and East Pacific waters.
Content
The surface forecasts include the forecast sea level pressure field depicted by isobars contoured every four millibars (mb). Intermediate
two millibar isobars are sometimes included in areas where the pressure gradient is relatively light. Relevant surface features
are also shown, including areas of high and low pressure, frontal systems (cold, warm, stationary, and occluded), troughs, ridges,
drylines, tropical waves, and tropical cyclones. The 72-hour forecast chart also includes a depiction of the 96-hour forecast
positions of highs, lows, and tropical cyclones.
Coverage
The National Hurricane Center produces surface forecasts covering the following areas:
- Atlantic (from the equator to 31°N between 35°W and 100°W, including the Pacific east of 100°W)
- East Pacific (from 20°S to 30°N east of 145°W)
Issuance/Transmission
The surface forecasts are transmitted by radiofax via New Orleans and Honolulu according to the following table:
|
|
New Orleans, LA (Atlantic) |
Honolulu, HI (East Pacific) |
Pt. Reyes, CA (East Pacific) |
Forecast Period |
Valid Time (UTC) |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
24-hour |
0000 |
0705 |
PYEE79.TIF |
1400 |
PYFE79.TIF |
- |
- |
1200 |
1905 |
PYEE80.TIF |
0200 |
PYFE80.TIF |
- |
- |
latest |
|
PYEE10.TIF |
|
PYFE10.TIF |
|
- |
48-hour |
0000 |
0715 |
PYEI81.TIF |
1410 |
PYFI81.TIF |
1435 |
PYFI81.TIF |
1200 |
1915 |
PYEI82.TIF |
0210 |
PYFI82.TIF |
0215 |
PYFI82.TIF |
latest |
|
PYEI10.TIF |
|
PYFI10.TIF |
|
- |
72-hour |
0000 |
0725 |
PYEK83.TIF |
1420 |
PYFK83.TIF |
- |
- |
1200 |
1925 |
PYEK84.TIF |
0220 |
PYFK84.TIF |
- |
- |
latest |
|
PYEK10.TIF |
|
PYFK10.TIF |
|
- |
Peak Wave Period and Direction Forecasts
Purpose
Peak wave period and direction forecast charts are produced to depict the 48- and 72-hour forecasts of how much time exists
between the most energetic waves and what direction these waves are coming from over the tropical and subtropical Atlantic and
East Pacific waters.
Content
The peak wave period (in seconds) is defined as the wave period associated with the most energetic waves in the total wave
spectrum at a specific point. Wave regimes that are dominated by wind waves tend to have smaller peak wave periods, and
regimes that are dominated by swell tend to have larger peak wave periods. It is important to note that these charts only
depict the peak wave period and that there still could be other significant waves at a specific point that just happen to have
less energy. Peak wave periods are contoured by isolating different swell events with a single line – not contouring at a specific
interval as in other forecast graphics. Labels within the contours indicate the peak wave period in that general area. Arrows
are also shown depicting the direction that the most energetic waves are traveling.
Coverage
The National Hurricane Center produces peak wave period and direction forecasts covering the following areas:
- Atlantic (from the equator to 31°N between 35°W and 100°W, including the Pacific east of 100°W)
- East Pacific (from 20°S to 30°N east of 145°W)
Issuance/Transmission
The peak wave period and direction forecasts are transmitted by radiofax via New Orleans, Pt. Reyes, and Honolulu
according to the following table:
| |
New Orleans, LA (Atlantic) |
Pt. Reyes, CA (East Pacific) |
Honolulu, HI (East Pacific) |
Forecast Period |
Valid Time(UTC) |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
Transmission Time (UTC) |
Filename |
48-hour |
0000 |
0750 |
PJEI88.TIF |
1228 |
PJFI87.TIF |
1430 |
PJFI87.TIF |
1200 |
1950 |
PJEI89.TIF |
2346 |
PJFI88.TIF |
- |
- |
latest |
|
PJEI11.TIF |
|
PJFI11.TIF |
|
|
72-hour |
0000 | 0825 | PKEK88.TIF | 2356 | PJFK93.TIF | 0230 | PJFK93.TIF |
Tropical/Subtropical Cyclone Position and Intensity Estimates
TAFB provides the National Hurricane Center with position estimates of
tropical cyclones every three hours and intensity estimates every six
hours. Intensity estimates use the Dvorak technique, which is a statistical system using observed satellite
cloud pattern and a set of rules to produce a current estimate of a cyclone's strength. Estimates can be
made from both visible and infrared satellite imagery. The Dvorak technique is the main tool for determining
tropical cyclone strength when it is out of range of reconnaissance
aircraft.
TAFB also provides NHC with position and intensity estimates for
subtropical cyclones (a hybrid between tropical cyclones and frontal or
extratropical cyclones) using the
Herbert-Poteat technique.
TAFB's position and intensity estimates are not currently available to the public. However, the
intensity estimates (called T numbers, CI numbers, and ST numbers), are often referred to in NHC's
Tropical Cyclone Discussions and
Preliminary Reports. The following table (taken from the reports
mentioned below) gives the approximate wind and pressure values for the CI
and ST numbers.
CI Number |
Sustained winds |
Atlantic Min. Pres. |
W Pacific Min. Pres. |
ST Number |
Sustained winds |
1.0 | 25 kt | – | – | – | – |
1.5 | 25 kt | – | – | 1.5 | 25-30 kt |
2.0 | 30 kt | 1009 mb | 1000 mb | – | – |
2.5 | 35 kt | 1005 mb | 997 mb | 2.5 | 35-40 kt |
3.0 | 45 kt | 1000 mb | 991 mb | 3.0 | 45-50 kt |
3.5 | 55 kt | 994 mb | 984 mb | 3.5 | 55-65 kt |
4.0 | 65 kt | 987 mb | 976 mb | – | – |
4.5 | 77 kt | 979 mb | 966 mb | – | – |
5.0 | 90 kt | 970 mb | 954 mb | – | – |
5.5 | 102 kt | 960 mb | 941 mb | – | – |
6.0 | 115 kt | 948 mb | 927 mb | – | – |
6.5 | 127 kt | 935 mb | 914 mb | – | – |
7.0 | 140 kt | 921 mb | 898 mb | – | – |
7.5 | 155 kt | 906 mb | 879 mb | – | – |
8.0 | 170 kt | 890 mb | 858 mb | – | – |
NHC uses the Atlantic pressure table for eastern Pacific
tropical cyclones. Note that these are intensity estimates and may be
superceded by reconnaissance and/or surface observations.
More information on the Dvorak technique is found in NOAA Technical Report NESDIS 11 - Tropical Cyclone
Intensity Analysis Using Satellite Data - by Vernon F. Dvorak. More infomation on the
Herbert-Poteat technique is found in NOAA Technical Memorandum NWS SR-83 - A Satellite
Classification Technique for Subtropical Cyclones - by Paul J. Herbert and K.O. Poteat.
TAFB is currently testing an objective version of the Dvorak technique. This could
provide intensity estimates every 30 minutes. More information can be obtained from
Ray Zehr at the
Cooperative Institute for Research in the Atmosphere,
Colorado St. University, or from Chris Velden or
Tim Olander at the
Cooperative Insititute for Meteorological Satellite
Studies, University of Wisconsin.
Marine Radiofax Broadcast Schedule
The Tropical Analysis and Forecast Branch
(TAFB) provides marine analyses and forecasts for the Gulf of Mexico,
Caribbean Sea, and the tropical and subtropical Atlantic and Pacific.
Products available include: surface analyzes, sea state analyses, wind/seas
forecasts, wave period/swell direction forecasts, tropical cyclone danger
area forecaasts (during the hurricane season), text High Seas Forecasts, and
GOES satellite imagery. These products are transmitted through the U.S.
Coast Guard Stations at New Orleans, Louisiana, and Pt. Reyes, California.
These and other Tropical Prediction Center products are also available from
the National Weather
Service Marine Fax page. Here is more
information on receiving NWS marine products at sea.
The complete list of radiofax broadcasts can be found on the TAFB Radiofax
Broadcast Schedule page.
|