2013 Atlantic Hurricane Season Birdseye Discussion #31

By: NCHurricane2009 , 1:18 PM GMT on July 02, 2013

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...TUESDAY JULY 2 2013 9:30 AM EDT...
Whatever weak computer model support for western Gulf of Mexico development from tropical wave activity is diminshing. And with a large swath of Saharan dry air building westward in the tropical latitudes...all should be quiet in the Atlantic tropics during the next few days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jul_2_2013_0615Z_UPDATED_zps095c6b5c.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0730Z-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...
 photo Jul_2_2013_0615Z_UPDATED_zps51546be5.png
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).

...MID-LATITUDES DISCUSSION...
P1...Large upper trough spanning eastern North America and Gulf of Mexico has split into a few features in the last 36 hrs. Frontal cyclone that was previously south of Greenland in the previous discussion is heading into western Europe while its cool air advection on its back side has carved out a supporting shortwave upper trough (frontal cyclone's upper trough marked with blue-dashed line...and frontal cyclone's warm front also marked...in upper-right corner of above atmo chart). Frontal cyclone over eastern Canada in the previous discussion has ejected northeastward into the Atlantic high seas SSW of Greenland while deepening to 999 mb...and it too with its cool air advection had carved out its own supporting shortwave upper trough (western convergence of this shortwave supports surface 1027 mb ridge over eastern Canada to the SE of Hudson Bay). Remainder of upper troughing is cut-off over the eastern US and Gulf of Mexico as a large-scale upper vortex...with eastern divergence of the upper vortex supporting 1012 mb surface frontal depression currently over Tennessee. Western convergence of this upper vortex meanwhile supports 1023 mb ridge building into central North America as shown by the red-zig-zag line in the upper-left corner of the above atmo chart. NW Atlantic upper ridge is currently supported by warm air adevction ahead of the aforementioned Tennesse 1012 mb depression.

P2...Large upper vortex persists in the open central Atlantic. Surface trough southeast of Bermuda persists while supported by split flow upper divergence between westerlies flowing into this upper vortex and easterlies flowing into the Lesser Antilles-Bermuda upper vortex mentioned in paragraph P5. Another surface trough is beneath the east side of the upper vortex while supported by the vortex's eastern divergence. The central Atlantic upper vortex in the days ahead is expected to retrograde westward around the building NW Atlantic upper ridge mentioned in paragraph P1 above.

P3...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1030 mb...is near the western Azores. It is supported by southeastern convergence of NW Atlantic upper ridge mentioned in paragraph P1 as well as northeastern convergence of east Atlnatic upper anticyclonic ridge mentioned in paragraph P7.

...TROPICAL BELT DISCUSSION...
P4...Tropical wave previously over the western Caribbean has split into a southern fragment that has evolved into an eastern Pacific tropical disturbance...and a northern fragment currently over interior SE Mexico. This tropical wave is currently suppressed by non-divergent region and westerly shear directly south of the paragraph P1 upper trough.

P5...Upper vortex previously midway between the Lesser Antilles and Bermuda is retrograding westward about the paragraph P1 NW Atlnatic upper ridge...and is currently located north of Hispaniola.

P6...Tropical wave previously in the eastern Caribbean is now in the north-central Caribbean region. T-storm activity in its vicinity is enhanced by divergent northerly flow at the boundary between the SW side of the paragraph P5 upper vortex and tropical upper ridging from the west previously mentioned in discussion #30 paragraph P5.

P7...Tropical wave previously midway between the Lesser Antilles and the Cape Verdes is now en route to the Lesser Antilles. It is currently below a favorable SW extension of anticyclonic eastern Atlantic upper ridge...but is suppressed by unfavorable dry Saharan air (seen by brown shading in lower-right of above thermo chart) advected from Saharan Africa by deep-layered easterly wind current on the south side of the upper ridge and south side of the paragraph P3 surface ridge.

P8...Tropical wave previously SE of the Cape Verde Islands is now SW of the islands. It too is suppressed by dry Saharan air mentioned in paragraph P7 above.

P9...Tropical wave is about to roll off the west African coast as marked in lower-right corner of above atmo chart. Although it has an associated t-storm cluster...expect it to also choke on dry Saharan air mentioned in paragraph P7 above.

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