2012 Atlantic Hurricane Season Birdseye Discussion #25

By: NCHurricane2009 , 2:48 AM GMT on June 12, 2012

...JUNE 11 2012...10:53 PM EDT...
The following is an update on three prospect areas of tropical development mentioned in previous discussion #24:

The cut-off upper low forecasted by numerical models to occur in the NW Atlantic...by June 13 to 15...is coming to fruition as explained by tonight's paragraph P3. I believe there is a slight chance of a subtropical cyclone in the NW Atlantic during the June 13 to 15 timeframe from this system...see paragraph P3 for further details.

1009 mb Gulf coast low is translating across the SE US as a 1017 mb feature tonight...and headed towards the west Atlantic (see paragraph P1). The only upper atmospheric feature that can help it become a tropical system is upstream upper ridge mentioned towards the end of paragraph P1. The numerical models seem to squeeze out the upper ridge between upper trough in paragraph P1 and upper vortex in paragraph P3...so I don't expect this area to become a W Atlantic tropical cyclone. Instead...I expect it will eventually get absorbed/assimilated into the SW side of weather system in paragraph P3 in the coming days.

Computer models continue flaring Caribbean upper ridging (paragraph P7 below) and suggesting a possible tropical cyclone beneath it for the latter part of June. However...the "tropical cyclone" displayed by the models is a bit scattered about...and I still don't know which current surface feature (if any) will come into play. One could argue that the surface tropical wave in paragraph P9 below maybe what the models are talking about...but I am suspicious because the tropical wave has made a recent NW jog toward the deep-layered cyclonic system of paragraph P3 instead of a direct W jog into the Caribbean.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1921Z-released HPC analysis.

In light blue is upper air anlaysis, 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 indicating surface lows, Hs indicating 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...Surface frontal cyclone from west coast of North America has moved rapidly eastward while intensifying to 989 mb...and reaching Canada's Hudson Bay. Intensification of the surface cyclone is supported by divergence ahead of vigorous west US upper trough. West US upper trough has absorbed central US upper trough mentioned in paragraph P1 of yesterday's discussion. 1009 mb Gulf coast low (paragraph P1 of yesterday's discussion) has moved NE into W North Carolina and is at 1017 mb while guided by southwesterly flow ahead of strong 989 mb frontal cyclone. This has brought the heavy rains along the Gulf coast into interior sections of the SE US. Strong warm air advection ahead of 989 mb cyclone has amplified the east US upper ridge ahead of this system. The upper ridge's eastern convergence supports surface ridge centers of 1024 mb offshore of Carolinas...1026 mb centers over Atlantic Canada...and 1028 mb over S Greenland.

P2...What is left ofupper vortex SE of Greenland is an upper trough exiting the picture while heading toward W Europe. Decaying surface low of 1019 mb SE of Greenland in the above charts...once supported by this upper vortex...will soon dissipate.

P3...Relatively new upper vortex in NW Atlantic continues pushing southward and amplifying while the adjacent upper ridge...mentioned towards the end of paragraph P1...amplifies to its west. This is something numerical models have been predicting to occur. 24 hrs ago...this upper vortex supported a 1011 mb cyclone with divergence at its NE periphery...which is now almost vertically stacked with the upper vortex and is currently at 1010 mb. Also 24 hrs ago...accelerational divergence SE of this upper vortex supported a new 1010 mb frontal low in the central Atlantic...but all that is left now is a bare surface front across the central Atlantic tonight. I beleive there is a slight chance that the 1010 mb surface low near the upper vortex could begin firing t-storms and hence become more subtropical...that is if the upper vortex is cold enough to de-stabilize the atmosphere despite waters in the area in the low 20s of deg C. I will be calling off this area for subtropical development if t-storm clouds do not begin showing near the 1010 mb center by June 13.

P4...Deep-layered anticyclone S of the Azores has begun to vertically de-couple...with surface 1030 mb center remaining S of the Azores while the upper anticyclonic center has been displaced eastward toward the Canary Islands thanks to the vigor of the upper vortex in paragraph P3.

P5...Upper ridge on east coast of Canada has merged with east US upper ridge mentioned towards the end of paragraph P1.

...TROPICAL BELT DISCUSSION...
P6...East-west upper trough straddling the Atlantic tropics has split into a fragment across the Caribbean and upper vortex midway between the Antilles and Azores. Remainder of the dry air in the tropical belt at this time has collected beneath this upper trough when looking at tonight's thermodynamic birdseye chart.

P7...Long-lived Caribbean upper ridging persists...currently forked in half by east-west upper trough of paragraph P6. The northern half is an upper anticyclone near Cuba...the southern half is an upper anticyclone over Panama which has helped to fire strong t-storms over the surface ITCZ in the area.

P8...Upper ridge in E tropical Atlantic continues moistening the air in the area thanks to its upper outflow.

P9...Tropical wave nearing the Lesser Antilles in yesterday's discussion has made it to the northern Antilles while gaining a SW-NE tilt in latest NHC TAFB maps...suggesting it is gravitating NW toward subtropical ridge weakness caused by deep-layered low pressure system in paragraph P3 above. Currently...this tropical wave is inactive while suppressed by dry air of east-west upper trough mentioned in paragraph P6.

P10...Tropical wave that emerged from Africa yesterday is passing S of the Cape Verde Islands tonight. It is travesring favorable moistening air and upper outflow caused by upper ridge in paragraph P8...so there is a chance that it may get increasingly impressive on satellite imagery in the short-term. This tropical wave is doomed for a one-two punch of dry air & westerly vertical shear in the long-term thanks to upper trough mentioned in paragraph P6 above.


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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4. NCHurricane2009
3:29 AM GMT on June 13, 2012
Quoting KoritheMan:
Nice blog, although I do not see an upper low collocated with the western Atlantic system on the models, so I think any development would be tropical, albeit sheared.

I don't even understand why the models would develop a tropical cyclone in the first place. After they squeeze out the upper ridge...the models show perfectly straight 200 mb upper winds out of the west. I even checked the 500 mb upper wind forecasts...still straight out of the west. Tropical cyclones develop beneath upper anticyclones that ventilate them instead of straight (and shearing) upper westerly winds.
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3. KoritheMan
2:40 AM GMT on June 13, 2012
Nice blog, although I do not see an upper low collocated with the western Atlantic system on the models, so I think any development would be tropical, albeit sheared.
Member Since: December 31, 1969 Posts: Comments:
2. NCHurricane2009
3:12 AM GMT on June 12, 2012
Quoting HurricaneDean07:
Great Entry, Thanks for your thoughts!

Thanks back at you for the commment....
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1. HurricaneDean07
3:07 AM GMT on June 12, 2012
Great Entry, Thanks for your thoughts!
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