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By: NCHurricane2009 , 2:14 AM GMT on July 23, 2013
...MONDAY JULY 22 2013 10:15 PM EDT...
High probablity of a tropical cyclone this week in the waters between the Cape Verde Islands and Lesser Antilles from vigorous tropical wave that has emerged from Africa. See special feature section below for additional details. It is quiet elsewhere in the Atlantic tropics.
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1925Z-released WPC analysis.
In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.
In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.
...THERMODYNAMICS BIRDSEYE CHART...
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.
Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).
...SPECIAL FEATURE...TROPICAL WAVE INVEST 98-L...
Impressive tropical wave with organized thunderstorm activity has emerged from the west coast of Africa and into the tropical waters SE of the Cape Verde Islands as seen in the lower-right corner of the above atmo chart. The tropical wave is in a favorable atmoshperic environment of low shear and enhanced upper outflow due to the development of its own upper anticyclone within the large-scale low-latitude upper ridge covering the eastern tropical Atlantic mentioned in paragraph P7. Over the last three days...the GFS and CMC computer models have shown development potential from this tropical wave while generally suggesting this tropical wave will continue to maintain this upper anticyclone...and even the conservative Euro (ECMWF) model has joined the bandwagon in the last 24 hrs. And because the surface convergence of the tropical wave...coupled with the upper divergence of the upper anitcyclone...has created a large enough moisture field that is warding off the dry Saharan air layer to the northwest (mentioned in paragraph P7)...this system has a high risk of becoming an Atlantic tropical cyclone...which is why I upgraded it to a special feature as of special update #48A earlier this afternoon.
Marine interests in the Atlantic tropical waters between the Cape Verde Islands and the Lesser Antilles should monitor the progress of this tropical wave over the next few days as it gets steered generally westward by deep-layered easterlies south of the paragraph P6 surface ridge and paragraph P2 north-central Atlantic upper ridge. Even though the paragraph P7 upper vortex midway between the Lesser Antilles and Cape Verde Islands will retrograde westward while getting pushed by this tropical wave's upper anticyclone and south side of paragraph P2 north-central Atlantic upper ridge...longer-range computer model runs suggest this tropical wave will eventually catch up to the unfavorable environment of the upper vortex as it nears the Lesser Antilles. However interests in the Lesser Antilles should also keep a wary eye on this tropical wave.
P1...Next upper trough in the mid-latitude westerlies has entered the upper-left corner of the above charts and is currently positioned over central Canada and the central US. Its eastern divergence supports 999 mb surface frontal cyclone just SW of Hudson Bay.
P2...Upper trough and associated 990 mb surface frontal cyclone persists over eastern Canada. Low-level warmer air ahead and south of the 990 mb surface frontal cyclone's cold fronts (in addition to the warmer air south of the 999 mb cyclone mentioned in paragraph P1) supports upper ridge over the SW US...another upper ridge over the eastern Gulf of Mexico that has recently expanded into the waters offshore of the SE US...and also the persistent upper ridge in the north-central Atlantic.
P3...Large NE Atlantic upper trough remains stationary as its eastward progression is blocked by deep-layered ridge over Europe. At the surface...the dominant feature below this upper trough is an intensfying 1005 mb center that is taking advantage of the eastern divergence of this upper trough while it moves NE toward the British Isles.
P4...East-west surface troughing in the open central Atlantic...mentioned in paragraph P3 of the previous discussion...currently persists south of the Azores and west of the Canary Islands while generally supported by split flow upper divergence between easterlies southeast of the north-central Atlantic upper ridge mentioned in paragraph P2 and mainstream mid-latitude westerlies.
P5...SE US to western Gulf of Mexico upper trough mentioned in paragraph P4 of the previous discussion has largely been absorbed by the south end of the paragraph P1 upper trough. What has not been absorbed is currently an upper vortex over the Bay of Campeche.
P6...Surface ridge dominates much of the open Atlantic basin...with a current westward extension into the Gulf of Mexico. The westward extension is supported by SE convergence of paragraph P2 SW US upper ridge. The remainder of the surface ridge is supported by southeastern convergence of paragraph P2 north-central Atlantic upper ridge and western convergence of paragraph P7 upper trough SW of Bermuda.
...TROPICAL BELT DISCUSSION...
P7...Low-latitude upper ridge covering the eastern tropical Atlantic has split into one upper anitcyclone centered over the northern Lesser Antilles and another upper anticyclone associated with the t-storm latent heat release of tropical wave Invest 98-L...with inverted upper trough midway between the Lesser Antilles and Cape Verde Islands (mentioned in paragraph P6 of the previous discusison) evolving into an upper vortex between the two upper anticyclones. Due to latent heat release of southern Caribbean thunderstorms mentioned in paragraph P8...Central America upper vortex has been pushed back east into the central Caribbean as a weakened upper trough while an upper ridge has flared up over SE Mexico and Central America. Upper trough persists SW of Bermuda. South end of aforementioned northern Lesser Antilles upper anticyclone...in conjunction with the south end of the paragraph P6 surface ridge and south end of paragraph P2 north-central Atlantic upper anticyclone...is advecting dry Saharan air from Africa as seen by low-latitude brown shading in the above thermo chart. Open central Atlantic upper vortex continues retrograding westward around the paragraph P2 north-central Atlantic upper ridge...and as it moves toward sea-surface temps greater than 28 deg C (as indicated by above thermo chart) it appears the vertical contrast between the warm waters and cold air of the upper vortex has supported an increase in instability and t-storms east of Bermuda.
P8...Thundestorm activity in the southern Caribbean persists while supported by split flow upper divergence between westerlies flowing across south side of paragrpah P7 Central Caribbean upper trough and easterlies flowing across south side of paragraph P7 Central America upper ridge. Pop-up t-storm clusters continue east of Florida and offshore of SE US due to outflow of eastern Gulf of Mexico upper ridge mentioned in paragraph P2. Thunderstorm activity along the US Gulf coast is supported by split flow upper divergence at the boundary between paragraph P2 SW US upper ridge and paragraph P2 eastern Gulf of Mexico upper ridge.
P9...Tropical wave previously moving toward the Lesser Antilles has crossed the islands and into Puerto Rico. Now that it has escaped the stream of Saharan dry air mentioned in paragraph P7...its thunderstorms have increased due to outflow of northern Lesser Antilles upper anticyclone also mentioned in paragraph P7.
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