AXNT20 KNHC 201740

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
140 PM EDT Fri Oct 20 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 1745 UTC.


A tropical wave is in the central Atlc with axis extending from 20N35W to 08N41W, moving W at 10-15 kt. Satellite derived data indicate the wave is in a strong vertical wind shear environment. CIRA LPW imagery show dry air in the majority of the wave environment. The wave is underneath diffluent flow aloft between an upper low centered near 21N41W and a ridge over the tropical eastern Atlc. This is supporting scattered moderate convection from 13N-22N between 33W-40W.

A tropical wave is in the central Caribbean with axis extending from 20N72W to 11N73W, moving W at 5 kt. The wave is in a region of strong vertical wind shear. However, deep layer moisture along with upper level diffluent flow between the base of an upper trough in the SW Atlc and an anticyclone in the W Caribbean support scattered heavy showers and isolated tstms from 13N-20N between 71W-78W.

A tropical wave is in the western Caribbean with axis extending from 21N80W to adjacent waters of Costa Rica near 09N82W, moving W at 20 kt. The wave is in a region of low to moderate vertical wind shear and CIRA LPW imagery show abundant moisture in its low to middle level environment. However, the wave is underneath a broad upper level high, which associated subsidence limits the convection to isolated showers W of 78W.


The monsoon trough extends from the African coast near 07N12W to 06N19W. The Intertropical Convergence Zone axis extends from 06N19W to 04N30W to 07N39W. Scattered moderate convection is from 02N-09N E of 17W, from 06N-09N between 26W-36W and from 07N-12N W of 48W.



Middle to upper level ridging prevails across the Gulf E of 93W while an upper level trough extends from the southern Plains to a base over the western Bay of Campeche. The troughing aloft supports scattered heavy showers and tstms over Louisiana adjacent waters N of 27N between 91W-95W and between 90W-93W just east of a surface trough that extends from 25N94W to 17N94W. Strong dry air subsidence across the basin supports fair weather elsewhere. The southern periphery of a broad surface ridge anchored over West Virginia by a 1027 mb high covers the remainder northern half of the Gulf. The gradient between high pressure to the N and lower pressure associated with the trough in the SW basin continue to support moderate to occasional fresh NE to E winds N of 22N E of 90W and SE flow of the same magnitude in the NW Gulf. By Saturday, moderate to fresh E-SE flow will re-establish itself across the Gulf as an area of low pressure develops across the central Plains. Return flow is expected to continue through Sunday afternoon.


An upper level anticyclone is centered over the western Caribbean near 18N82W providing an overall divergent environment W of 70W. The divergence along with two tropical waves moving across the basin are generating scattered showers and tstms from 11N-20N W of 72W, including inland portions of Central America, Jamaica and SW Haiti. Plenty of atmospheric moisture in associated with the ridge and will likely continue to produce relatively active convection through the weekend. Otherwise, fresh to strong trades prevail E of 80W as the pressure gradient strengthens while strong high pressure moves off the Mid-Atlc coast and into the western North Atlc. The trades are expected to remain strong through Monday night.


A tropical wave is moving across Haiti today bringing scattered showers and tstms to the SW portions of the island and the Windward Passage. Fresh to strong trades are expected through the weekend as high pressure builds in N of the region.


A cold front extends SW from a 1007 mb low centered near 34N60W continuing along 30N63W to 25N71W then dissipating to the central Bahamas near 23N74W. Scattered showers prevails within 150 nm E of the cold front. This system is supported aloft by a middle-level low and reinforced by an upper level trough. The remainder of the eastern Atlc is under the influence of a surface ridge anchored by a 1031 mb high centered near 40N38W.

For additional information please visit http://www.hurricanes.gov/marine

$$ Ramos