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  ![](media/image1.jpeg){width="6.0in"   **TROPICAL WEATHER DISCUSSION**                    ![](media/image3.png){width="0.7791666666666667in"
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-   **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 outline
below:

1.  **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.

2.  **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.

3.  **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.'"

4.  **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:

1.  **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

2.  **East Pacific**

> From the equator to 32°N east of 140°W including coastal areas of
> Mexico, and Central and South America.

-   **Issuance / Transmission**

The Tropical Weather Discussion is transmitted under World
Meteorological Organization (WMO) and NOAA Weather Wire Services (NWWS)
headers as shown below:

  ----------------------- ----------------------- -----------------------
                          **WMO**                 **NWWS**

  **Atlantic**            AXNT20 KNHC             MIATWDAT

  **East Pacific**        AXPZ20 KNHC             MIATWDEP
  ----------------------- ----------------------- -----------------------

Tropical Weather Discussions are issued on a regular six hourly schedule
as shown below:

+-------------+-------------+-------------+-------------+-------------+
|             | Issuance    |             |             |             |
|             | Time        |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| MIATWDAT    | **105 AM    | **705 AM    | **105 PM    | **705 PM    |
|             | EST**       | EST**       | EST**       | EST**       |
|             |             |             |             |             |
|             | *(205 AM    | *(805 AM    | *(205 PM    | *(805 PM    |
|             | EDT)*       | EDT)*       | EDT)*       | EDT)*       |
+-------------+-------------+-------------+-------------+-------------+
| MIATWDEP    | **0405      | **1005      | **1605      | **2205      |
|             | UTC**       | UTC**       | UTC**       | UTC**       |
+-------------+-------------+-------------+-------------+-------------+