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2012 Atlantic Hurricane Season Birdseye Discussion #127
By: NCHurricane2009 , 3:56 AM GMT on October 08, 2012
...OCTOBER 7 2012...11:55 PM EDT...
An outage persists with GOES-E satellite imagery in the last several days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops.
In the western part of the Atlantic tropical basin...continuing to watch the surface low of Invest 97-L (paragraph P5)...a surface tropical wave (paragraph P7)...and the melding together of a western Atlantic upper ridge (paragraph P5) and southern Caribbean upper ridge (paragraph P4). So far the surface low of Invest 97-L has been the only focal point of attention...but it shows no signs of tropical cyclone formation as noted in paragraph P5.
In the central part of the Atlantic tropical basin...although t-storms remain curved and organized northeast of the Lesser Antilles...this activity is associated with a long-lasting central Atlantic upper vortex rather than a surface feature (paragraph P4).
In the eastern part of the tropical Atlantic basin...a tropical wave has not gotten any better organized. See paragraph P9 below for details on its window of opportunity.
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-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).
P1...Upper vortex over E Canada has de-amplified into an upper trough on the east coast of Canada...with the 994 and 993 mb gale centers it supports with its eastern divergence combining into one gale center that has intensified to 984 mb heading for Greenland. Despite the departure of the upper trough onto the east coast of Canada...upper troughing over North America is being re-enforced by cool air advection from 1002 mb Canadian frontal depression and other Canadian frontal depressions soon to follow. Western convergence of the upper troughing continues supporting strong central US surface ridge (now 1028 mb) that continues driving in unseasonably cold air.
P2...Deep-layered cyclone in the eastern open Atlantic is shifting toward Europe. Upper-levels of this system continues to be marked by impressive upper trough. Western convergence of this upper trough is supporting a 1022 to 1018 mb W Atlantic surface ridge. Strong surface center of the deep-layered cyclone...supported by eastern divergence of the upper trough...is shifting NNE from the Azores.
P3...Based on Meteosat-9 animation over the last day...shortwave upper trough has moved into Europe and left the scope of the above birdseye charts. NE Atlantic surface ridge was formerly supported by western convergence of the upper trough activity in this area. Due to the GOES-E satellite outage...in the above atmo chart I do not have satellite-derived 200 mb (upper-level) wind barbs in this region. However...I speculate their is an upper ridge ahead of the paragraph P2 upper trough whose eastern convergence is now supporting this NE Atlantic surface ridge.
...TROPICAL BELT DISCUSSION...
P4...Central tropical Atlantic upper vortex persists...still extending to a smaller upper vortex near Haiti. While t-storms remain curved and organized at a location NE of the Lesser Antilles...this organization is occurring about the central Atlantic upper vortex rather than a surface feature. Upper convergence on west side of both upper vortices supports pocket of Caribbean dry air. As both upper vortices gradually weaken (as all cut-off upper vortices do)...a southern and western Caribbean upper ridge continues building in their wake. Scattered t-storms across the south-central Caribbean...Panama..Costa Rica...and a portion of the eastern Pacific is supported by outflow of this building upper ridge. Yet another upper ridge persists in relatively higher pressures east of these upper vortices...located across the eastern tropical Atlantic. The east end of this eastern tropical Atlantic upper ridge is de-amplified by a pair of upper vortices that have been dropped off by paragraph P2 upper trough (Even though I have no satellite-derived 200 mb (upper wind) barbs in this area from the GOES-E satellite outage...the upper vortex NW of the Cape Verde Islands is confirmed by Meteosat-9 water vapor imagery...and both upper vortices are confirmed by looking at initialization of 1200Z and 1800Z GFS model 200 mb fields).
P5...W Atlantic upper ridge is shifting southward in advance of large-scale paragraph P1 upper troughing pushing in. Disturbance Invest 97-L over the eastern Bahamas...supported by the upper outflow of this upper ridge...has gotten a little better organized with curved cloud bands while the surface low (now 1008 mb) is more embedded in the t-storm cluster (albeit the surface low is still on the south edge of the t-storm cluster). Expect this disturbance to continue drifting westward while steered by a merger of the 1028 mb central US surface ridge (paragraph P1) and W Atlantic surface ridge (paragraph P2). The t-storm activity has been intermittent rather than persistent...and the continued westward drift will bring the disturbance increasingly into hostile westerly vertical shear delivered by paragraph P1 upper troughing. These reasons are why I am not upgrading this disturbance to a special feature on this blog.
P6...Disturbed weather across the Bay of Campeche...southern Gulf of Mexico...at times overspreading Florida (mentioned in paragraph P8 of previous discussion #126) remains supported by eastern divergence of paragraph P1 upper troughing. Surface forcing for this area of weather is also coming from cold front extending from 984 mb center in paragraph P1...and coming from surface trough in the Bay of Campeche. The Bay of Campeche surface trough is formerly the tropical wave mentioned in paragraph P9 of previous discussion #126.
P7...Tropical wave moving across the eastern Caribbean in the previous discussion has crossed the central Caribbean and is about to enter the western Caribbean. It is currently suppressed by pocket of dry air mentioned in paragraph P4.
P8...I had been tracking a westward-moving t-storm cluster in Meteosat-9 infrared satellite animation...and marking it as a suspect tropical wave. Although the t-storm cluster has disappeared since 1200Z October 5...I am still marking the suspect tropical wave for continuity's sake...which I believe this evening is positioned in the open tropical Atlantic midway between the Cape Verde Islands and Lesser Antilles.
P9...Tropical wave with 1010 mb low pressure spin in the eastern Atlantic...SW of the Cape Verde Islands...has not gotten any better organized in the last 24 hours. It continues to be enhanced by upper outflow of paragraph P4 eastern tropical Atlantic upper ridge...and so far has managed to avoid oppressive effects of pair of upper vortices that have de-amplified the east end of this upper ridge. This is because the tropical wave is in between both upper vortices. Based on animation of this evening's 1800Z GFS model...this tropical wave should continue west...and has about 48 hours to develop before encountering hostile westerly vertical shear by 72 hours delivered by the pair of cut-off upper vortices mentioned in paragraph P4.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.