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2012 Atlantic Hurricane Season Birdseye Discussion #134
By: NCHurricane2009 , 4:30 AM GMT on October 16, 2012
...TUESDAY OCTOBER 16 2012...12:30 AM EDT...
Tropical Storm Rafael of 70 mph max winds explosively intensified into a strong category 1 hurricane of 85 mph max winds as of 8 PM EDT. The center of the hurricane is expected to pass east of Bermuda in the next 24 hours...so only tropical storm conditions is the worst case scenario for Bermuda. A tropical storm warning is currently in effect for Bermuda. See Rafael special feature section below for additional details.
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.
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1923Z-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).
...SPECIAL FEATURE...HURRICANE RAFAEL...
Since special update #133A...the surface center of Rafael made an early northward turn while regenerating into its heavy t-storm activity...and moreover this heavy t-storm activity has become symmetric and impressive around the surface center in the last 24 hours. The latent heat release from the unexpected amount of t-storms has inflated the warm core upper ridge over the storm such that the wind shear from the incoming paragraph P2 upper trough has been warded off. Originally the shear was expected to increase by 11 AM yesterday morning...but now we can expect the shear to increase by 11 AM tomorrow morning. However...their are signs that the shear has wanted to encroach into the storm in since 11 AM yesterday...because despite Rafael's impressiveness...he has struggled to become a hurricane until 8 PM. It is hard to say whether the incoming shear will prevent Rafael from additional strengthening..or whether the latent heat release of the t-storms and associated warm core upper ridge will continue to ward off the shear and allow more strengthening. I am fairly impressed with Rafael's uncolorized (black and white) infrared satellite appearance to the degree I think a rapid intensification episode is possible...so I forecast a peak strength 12 hours from now (by 11 AM Tue) that is a little higher than the NHC's forecast. After that...I show steady weakening as the shear and increasingly cooler waters should affect Rafael...but I flatten the weakening rate at the end of the forecast as the eastern upper divergence of the paragraph P2 upper trough should support Rafael as he transitions to non-tropical over cool waters. I have delayed the non-tropical transition time by 12 hours from the previous due to the unexpectedly high initial strength the storm currently exhibits.
Track-wise...because of Rafael's earlier than expected northward turn during special update #133A...all forecasts have adjusted to the right-of-previous...which has reduced the threat to Bermuda and eliminated the threat to Newfoundland. I agree with the current NHC track forecast shown in Figure 1...which in the short-term very consistent with the most recent NNE angle of the recorded storm track...and in the long-term gradually bends to the right consistent with when the GFS model passes the paragraph P2 994 mb cyclone to the north of Rafael such that Rafael bends in the more westerly flow on the south side of the cyclone.
Figure 1: My forecast generated for Hurricane Rafael at midnight
Impact swath in Figure 1 is based on the 11 PM tropical storm wind radius...and extrapolating that along the forecast track. The swath barely clips Bermuda for the next 24 hrs. If my impact swath forecast verifies exactly..this would mean Bermuda would barely experience significant weather from Rafael if at all. However...Bermuda is under a tropical storm warning...which should have been acted upon in case the storm bends more leftward in track for some reason.
P1...Next surface frontal system in the mid-latitude westerlies is entering the upper-left corner of the above atmo chart from western Canada. Warm air advection ahead of this system supports sprawling upper ridge across the Gulf of Mexico and western US.
P2...Upper trough and surface frontal system moving across the western US in the previous discussion is now moving into the eastern US. Western convergence of the upper trough supports 1019 to 1022 mb ridge over western US extending into the W Gulf and Central America. Eastern divergence of the upper trough supports frontal depression that has intensified from 999 to 994 mb in the last 24 hrs while moving across the Great Lakes into SE Canada. Warm air advection of the 994 mb depression supports an upper ridge shifting from the eastern US into the NW Atlantic. This upper ridge is merging with large-scale upper ridge mentioned in paragraph P5.
P3...Upper trough over the W Atlantic and Caribbean has fractured into two during the last 24 hrs. One fragment is over the W Caribbean whose western convergence supports dry air in the southern Gulf of Mexico...SE Mexico...and W Caribbean. Second fragment is associated with intense surface gale near the south tip of Greenland that has weakened from 958 to 982 mb in the last 24 hrs while whirling beneath the less-divergent upper trough axis. Western convergence of this upper trough supports 1027 mb surface ridge in the W Atlantic.
...TROPICAL BELT DISCUSSION...
P4...Remnant surface trough of Patty near the central Bahamas has been shown fracturing into two in NHC TAFB maps over the last 24 hrs. One fragment is shown moving WSW toward SE Mexico while now steered by paragraph P2 1019 to 1022 mb surface ridge. Other fragment is shown to be stationary while becoming drawn toward the low pressure field of Hurricane Rafael to its east.
P5...Large-sized central Atlantic upper ridge remains melded with warm core upper ridge/outflow structure produced by the latent heat release of Hurricane Rafael's immense t-storm activity.
P6...1026 mb eastern Atlantic surface ridge in the previous discussion has weakened to 1019 mb. The dominant surface ridge over the Atlantic is becoming the 1027 mb center mentioned in paragraph P3.
P7...In the eastern tropical Atlantic...cut-off upper vortex persists. Tropical wave in the vicinity in the previous discussion is moving toward the Lesser Antilles while suppressed by a pocket of sinking dry air associated with the western convergence of the upper vortex. Meanwhile...the t-storm cluster once associated with this tropical wave persists W of the Cape Verde Islands while enhanced by outflow from a relatively new E tropical Atlc upper ridge that has developed in relatively higher pressures E of the upper vortex. A second tropical wave recently added into NHC TAFB maps appears to also be enhancing this t-storm cluster. Tropical development with this second wave will be dependent on how far west the shearing upper vortex retrogrades westward and away. Based on the lack of computer model support for this second tropical wave...it appears this wave will not develop while instead moving westward into the shearing upper vortex.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.