Atlantic Tropical Weather Discussion

National Hurricane Center - Tropical Weather Discussion (Atlantic)

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    AXNT20 KNHC 261726

    Tropical Weather Discussion
    NWS National Hurricane Center Miami FL
    126 PM EDT Wed Jul 26 2017

    Tropical Weather Discussion for North America, Central America
    Gulf of Mexico, Caribbean Sea, northern sections of South
    America, and Atlantic Ocean to the African coast from the
    Equator to 32N. The following information is based on satellite
    imagery, weather observations, radar and meteorological analysis.

    Based on 1200 UTC surface analysis and satellite imagery through
    1715 UTC.


    A tropical wave is over the easter Atlantic with axis extending
    from 16N26W to 06N26W, moving westward at 10 kt. Although
    TPW imagery shows that the wave is in an area of moderate to deep
    moisture, it remains under Saharan dry air and dust at lower
    levels inhibiting significant convection. A few showers are
    observed along the waves axis mainly below the monsoon trough
    south of 12N between 22W-28W.

    A tropical wave is in the central Atlantic with axis extending
    from 12N36W to 04N36W, moving westward at about 5 kt. The SSMI
    Total Precipitable Water imagery (TPW) indicates that deep
    moisture prevails within this wave. Scattered moderate convection
    is where the wave crosses the monsoon trough mainly from 08N-11N
    between 35W-38W.

    A large amplitude tropical wave has its axis extending from near
    24N55W to 12N54W, moving westward near 15 kt. The northern
    portion of this wave is observed as a very noticeable area of
    moisture, as seen on SSMI TPW imagery. The wave has a distinct
    signal at 650-700 mb as suggested in global model guidance.
    Saharan dry air and dust is following the wave, as noted in the
    latest METEOSAT-9 imagery. Scattered showers are observed along
    the northern portion of the wave mainly north of 22N between

    An eastern Caribbean tropical wave has its axis along 66W between
    06N-18W, moving westward at 10-15 kt. The wave has a distinct
    moist area as seen on SSMI TPW imagery. A broad 700 mb troughing
    is covering much of the eastern Caribbean. At this time, dry air
    dominates the eastern portion of the Caribbean therefore, no
    convection is related to this wave.


    The monsoon trough extends from 13N16W to 09N35W. The ITCZ begins
    near 08N41W and continues to 10N61W. Besides convective activity
    described above in association with the tropical waves, scattered
    moderate convection is within 60-90 nm north of the ITCZ between



    A broad surface ridge extends across the basin from the east,
    anchored by a 1020 mb high centered over northern Florida. A
    diffluent flow aloft is supporting scattered moderate convection
    along 25N and east of 90W. Another area of scattered moderate
    convection prevails over the Bay of Campeche mainly south of 25N
    and west of 94W. Scatterometer data depicts a light to gentle
    anticyclonic flow across the basin. Little change is expected
    with the current synoptic pattern over the next couple of days.


    A tropical wave is over the eastern Caribbean. Refer to the
    section above details. Scattered moderate convection is quickly
    increasing over the far southwest Caribbean south of 13N and west
    of 75W. This activity is due mainly to the presence of the
    monsoon trough that extends from the eastern Pacific to across
    Costa Rica and Panama, and the nearby southern extent of an upper-
    level trough that stretches from Hispaniola to the southwest
    Caribbean. Scatterometer data depicts moderate trades across most
    of the basin except between 72W-78W where fresh easterlies
    prevail. Expect for the tropical wave moving through the eastern
    Caribbean to provide additional moisture and instability to that
    portion of the area over the next 48 hours.


    Isolated showers are observed just north of the eastern section
    of the Dominican Republic as an upper-level cyclonic shear axis
    nearby is providing additional instability to an already very
    moist and unstable environment present over the island. Water
    vapor imagery depicts that moisture has increased in the upper-
    levels compared to the previous days. With plenty of deep layer
    moisture and instability in place, and with the added factor of
    the eastern Caribbean tropical wave forecast to pass near the
    island within the next 48 hours, expect for deep convection to
    become scattered to locally numerous over most sections of
    Hispaniola through at least Thursday night. Some of this activity
    may produce locally heavy rain and frequent lightning.


    Three tropical waves are moving across the basin. Refer to the
    section above for details. The basin is under the influence of a
    surface ridge, anchored by a 1026 mb high centered near 32N39W. A
    large area of Saharan dust is present over the eastern Atlantic,
    and much of the central Atlantic behind the tropical wave along
    55W. No major changes expected through next couple of days.

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