2012 Atlantic Hurricane Season Birdseye Discussion #63
...JULY 26 2012...3:15 AM EDT...
Atlantic tropics are quiet as strong eastern Atlantic tropical wave will soon encounter unfavorable conditions (see paragraph P12).
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released HPC 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).
...MID-LATITUDES DISCUSSION...
P1...Next surface frontal and its upper trough arriving from the NW US and SW Canada are pushing into the central US and central Canada this early morning. Its upper trough is merging with Texas upper trough mentioned in paragraph P7. Divergence east of this upper trough supports a broad 999 mb depression along this front. Low-level warm air advection ahead of this system is supporting SE US upper ridge mentioned in paragraph P4.
P2...Surface frontal system and upper trough over eastern Canada persists. After losing its first frontal cyclone to the dominating one in paragraph P3....it has re-established a new 996 mb frontal cyclone south of Newfoundland with the support of eastern divergence of the upper trough. Upper convergence on the back side of this upper trough supports a surface 1015 mb ridge that has moved from Michigan to the coast of NC in the past 24 hours.
P3...Surface frontal cyclone near the NE coast of Hudson Bay has weakened from 990 to 997 mb in the past 24 hours...thanks to the less divergent axis of the upper trough in paragraph P2 moving directly overhead of it. Cold front swinging SE on the back side of this 997 mb frontal cyclone has arrived from Hudson Bay into SE Canada.
P4...Upper trough is still east of Greenland...and the system's trailing front is strewn across the north Atlantic. Upper ridge over the central US behind this system has moved into the SE US while becoming associated with the warm air advection ahead of the system in paragraph P1...and hence this upper ridge is moved to that paragraph. The western end of the trailing front...including frontal depression Invest 98-L and its supporting NW Atlantic upper trough...are becoming absorbed into the east sides of the systems in paragraphs P2 and P3. The North Atlantic upper ridge has greatly amplified thanks to low-level warm air advection ahead of Invest 98-L...and ahead of the systems in paragraphs P2 and P3. As this North Atlantic upper ridge amplifies...so has the upper trough east of Greenland such that its south end now reaches the NW coast of Africa. Divergence east of this upper trough supports surface troughing over Spain. There remains another surface frontal depression over the Azores once supported by this upper trough. As the north Atlantic upper ridge amplifies...eastern convergence of the upper ridge will intensify the surface ridge in paragraph P6 to the west...and this surface ridge will hence steer the Azores surface depression southward. Expect no tropical development of this south-tracking Azores frontal depression as it is in highly unfavorable upper convergence east of the north Atlantic upper ridge...and as it tracks into the dry air mentioned in paragraph P6.
P5...Cut-off upper vorticity south of Bermuda persists...and now extends toward Hispaniola (Haiti and the Dominican Republic).
P6...Atlantic surface ridge of 1018 to greater-than-1024 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico to the waters offshore of west Europe....including convergence southeast of the SE US upper ridge (paragraphs P1 and P4)...and convergence east of North Atlantic upper ridge (paragraph P4). In conjunction with the south side of the upper ridge in paragraph P8...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.
...TROPICAL BELT DISCUSSION...
P7...Inverted upper trough over Texas is no longer inverted as it merges with mid-latitude upper trough mentioned in paragraph P1.
P8...East Atlantic upper ridge persists. Weakening upper vorticity is still west of the upper ridge...located in the Caribbean Sea. As this upper vorticity weakens...a south-central Caribbean upper ridge is building in its wake that could soon merge with the west end of this east Atlantic upper ridge. Also...upper vorticity remains embedded in this east Atlantic upper ridge...which has moved southwestward from the Canary Islands while retrograding about the amplifying North Atlantic upper ridge in paragraph P4. Inverted upper trough midway between the Cape Verdes and Lesser Antilles in the previous discussion is also retrograding westward.
P9...Florida Panhandle surface trough persists...stalled between the NW end of the surface ridge in paragraph P6 and SW end of the 1015 mb ridge mentioned in paragraph P2.
P10...Tropical waves in the western and central Caribbean in the previous discussion appear to have merged into a single tropical wave per latest NHC TAFB surface maps. It is largely suppressed by Caribbean upper vorticity mentioned in paragraph P8...although split flow divergence between the south-central Caribbean upper ridge (also mentioned in paragraph P8) and Caribbean upper vorticity is helping some of its t-storm activity.
P11...The tropical wave midway between the Cape Verde Islands and Lesser Antilles remains supressed by dry air mentioned in paragraph P6...and by upper convergece east of the inverted upper trough mentioned in paragraph P8.
P12...Tropical wave SE of the Cape Verde Islands in the previous discussion is now centered just SW of the islands with a well-organized 1012 mb surface low pressure spin. Latent heat release of the t-storms continues to inflate a portion of the east Atlantic upper ridge (paragraph P8) such that it is developing a fair upper outflow structure in this upper ridge. It may also get enhanced NW upper outflow from the upper vorticity retrograding SW from the Canary Islands (also see paragraph P8). Despite all this...tropical cyclone formation will soon be inhibited by dry air ingestion (source of dry air mentioned in paragraph P6)...which appears to be starting on the NW half of this tropical wave judging by above thermo chart. Tropical development also looks to be inhibited as the SW-retrograding upper vorticity is on track to become eventually vertically stacked with this tropical wave...in which case the upper vorticity would suppress upper outflow of the tropical wave.
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