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2013 Atlantic Hurricane Season Birdseye Discussion #39

By: NCHurricane2009 , 8:37 AM GMT on July 11, 2013

...THURSDAY JULY 11 2013 4:37 AM EDT...
Chantal degenerates into a tropical wave currently affecting Haiti...the Dominican Repbulic...and the eastern Bahamas with thunderstorm activity. See paragraph P9 for update statement on the remnants of Chantal.

The eastern of the two tropical waves behind Chantal has become better organized southwest of the Cape Verde Islands. Due to the forecast favorable upper winds for the next few days...I have upgraded this tropical wave to a special feature on this blog. See special feature section below for additional details.

 photo Jul_10_2013_2345Z_zps67025f01.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0130Z-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.

 photo Jul_10_2013_2345Z_zps86a11351.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).

Tropical wave previously southeast of the Cape Verde Islands is now southwest of the islands. While taking advantage of low shear...enhanced outflow...and moisture re-surgence toward Africa (all associated with low-latitude upper ridge axis mentioned in paragraph P7)...thunderstorms in the western vicinity of the tropical wave appear to be organizing into a low pressure area with some spiral banding. As the paragraph P3 upper vortex currenlty east of Bermuda retrogrades westward...models show the favorable low-latitude upper ridge axis expanding westward in its wake. Therefore these favorable conditions are likely to last as the tropical wave continues westward while steered by the south side of the paragraph P5 surface ridge. With the early signs of organization beginning and the favorable conditions that lie ahead...I am gambling that this system has a high probability of eventually becoming a tropical cyclone and have upgraded it to a special feature this early morning.

P1...Upper trough from western Canada has entered the northern US and eastern Canada. Eastern divergence of the upper trough supports 993 mb surface frontal cyclone centered over NE Hudson Bay...and western convergence of the upper trough supports 1017 mb ridge over the north-central US. Warm air advection ahead of the 993 mb cyclone supports upper ridge over the NE US and eastern tip of Canada.

P2...Western US upper ridge...mentioned in paragraph P2 of the previous discussion...persists.

P3...Upper trough...with attendant surface frontal cyclone featuring a 1005 mb center over southern Greenland...is located in the Atlnatic high seas over and south of Greenland. Western convergence of this upper trough system supports 1024 mb surface ridge between Newfoundland and Greenland. In the last 96 hrs a fragment of this upper trough has split southeastward and is currently located over the Azores (and a southwest portion of this upper trough fragment has evolved into relatively new upper vortex east of Bermuda). Low-level warm air advection ahead of the 1005 mb center is supporting an amplifying upper ridge east of Greenland just outside of the above charts.

P4...Upper vortex has moved southwest from the W Bahamas and into the Florida straits while steered by paragraph P2 western US upper ridge.

P5...Surface ridge dominates much of the open Atlantic basin. Its northern Gulf of Mexico extension currently with a 1018 mb center is supported by southeast convergence of western US upper ridge...but this Gulf portion is expected to erode due to eastern divergence of paragraph P1 upper trough. A 1022 mb center over Bermuda is supported by eastern convergence of NE US upper ridge mentioned in paragraph P1. This surface ridge continues to have a northeastern lobe extending into western Europe supported by eastern convergence of upper ridge east of Greenland mentioned at the end of paragraph P3.

P6...Upper troughing persists over parts of the Gulf of Mexico in relatively lower pressures south of the western US upper ridge in paragraph P2.

P7...Anticyclonic upper ridging in the eastern half of the Atlantic persists and remains expanded into the the Caribbean. This upper ridging still has upper anticyclonicity SE of the Azores...and also a new upper anticyclone SW of the Azores located between upper vortex E of Bermuda and upper trough fragment over the Azores both mentioned in paragraph P3. This upper ridging also continues to have a low-latitude axis present over the Cape Verde Islands extending into W Africa...with the west end of this upper ridge axis splitting off over the eastern Caribbean while becoming associated with the latent heat release of Chantal's t-storms (eastern convergence of this eastern Caribbean upper ridge axis is supporting sinking motion that re-enforces Saharan dry air midway between the Cape Verde Islands and Lesser Antilles). Inverted upper trough vorticity persists in the south-central Caribbean such that the Caribbean upper anticyclonicity is split into the aformentioned eastern Caribbean upper ridge axis and upper anticyclone over Costa Rica. Embedded SW-NE oriented string of upper vorticity persists over the Canary Islands...and into the waters NW of the Cape Verde Islands. Days ago the south end of all the upper ridging mentioned in this paragraph (in conjunction with the south end of the paragraph P5 surface ridge) advected dry Saharan air from Africa...large swaths of which still remain as shown by brown shading in the above thermo chart. Since this upper ridging developed a low-latitude axis over the Cape Verde Islands that created upper outflow and resulting moistening lift over the ocean surface...the supply of dry Saharan air has ended as indicated by the current shades of white and blue toward Africa in the lower-right of the above thermo chart (see paragraph P7 of discussion #32 for development of low-latitude upper ridging over the Cape Verde Islands).

P8...Tropical wave previously over the Yucatan has exited the picture while sliding over southeastern Mexico and the eastern Pacific.

P9...Remnant tropical wave of Chantal was looking to be headed into Jamaica overnight and into this early morning...but instead has slowed significantly over Haiti perhaps while becoming associated with the outflow of the paragraph P7 eastern Caribbean upper ridge axis pumped up by the latent heat release of the associated t-storm mass. As the Gulf of Mexico portion of the paragraph P5 ridge erodes...expect the tropical wave to round the west side of the remainder of the ridge...which should take it across Cuba...the Bahamas...Florida...and into the southeastern US region within the next 72 hours. Unfavorable factors going against Chantal's regenesis include land interaction...paragraph P4 upper vortex...paragraph P3 upper vortex east of Bermuda expected to retrograde westward toward Chantal's area...as well as the paragraph P1 and P6 upper troughs. The only favorable factors for Chantal's regenesis include any exposure to warm waters in the region...the aformentioed eastern Caribbean upper ridge axis...and any new upper ridging that could develop in between all aforementioned upper voritces. Will not be re-upgrading Chantal to a special feature on this blog until it is clear the favorable factors are winning against the numerous unfavorable factors.

P10...As mentioned in paragraph P7...west end of low-latitude upper ridge axis has broke off into east Caribbean upper ridge axis associated with Chantal's t-storm latent heat release. Tropical wave previously souhtwest of the Cape Verde Islands is now midway between the Cape Verdes and Lesser Antilles...and has become inactive while suppressed by dry Saharan air also midway between the Cape Verdes and Lesser Antilles re-enforced by convergent east side of the east Caribbean upper ridge axis. The tropical wave is also suppressed inverted upper trough that exists due to relatively lower pressures southeast of this upper ridge axis.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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