2016 Atlantic Hurricane Season Birdseye Discussion #179

By: NCHurricane2009 , 10:12 PM GMT on November 25, 2016

**An earlier lack of upper-level wind data for the atmospheric features chart due to data outage...then thanksgiving holiday activities...have prevented me from getting this blog update out by this morning as promised in special update #178A. Apologies for the belated blog post***

...FRIDAY NOVEMBER 25 2016 5:30 PM EDT...
Otto moves into the eastern Pacific Ocean from Costa Rica and Nicaragua while weakening to a tropical storm...but will continue to issue special feature sections with forecasts on Otto on this blog. See the special feature section below for additional details on Otto. Visit www.nhc.noaa.gov for up to the minute latest information on Otto.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1328Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

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 (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

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. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...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...TROPICAL STORM OTTO...
Current Prognosis...Since speical update #178A...Otto weakend to a tropical storm while moving across Nicaragua and Costa Rica...and remains a tropical storm while moving into the eastern Pacific Ocean. Otto is situated south of a southern Mexico upper ridge axis where upper easterlies are shearing thunderstorms slightly to the west of the surface spin. Based on the latest satellite animation...Otto should be approaching 9.5N-90W by 0000Z tonight.

Atmospheric Outlook for the Forecast Period...Otto continues westward while steered by surface ridging across North America. By 72 to 96 hours...a large surface frontal system supported by an upper trough moving into western North America will create a gap between the North America surface ridge and central Pacific surface ridge that will likely cause Otto to slow down and bend northward in track...and its possible that by the end of the 120 hour forecast period Otto turns more westward while reaching the southeastern periphery of the central Pacific surface ridge. Upper-level winds could become more favorable for Otto as the southern Mexico upper ridge mentioned in the above current prognosis section gets pushed southward directly over Otto by the upper trough moving into western North America...in which case the upper ridge will stop shearing and start ventilating Otto. This may allow Otto to re-strenghen late in the forecast period.

Thermodynamic Outlook for the Forecast Period...Otto will be passing over favorable 29 to 30 deg C waters over the eastern Pacific during the forecast period.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Nov 27)...50 mph maximum sustained wind tropical centered over the eastern Pacific at 9.5N-95W

48 Hr Forecast (0000Z Nov 28)...50 mph maximum sustained wind tropical storm centered over the eastern Pacific at 9.8N-100W

72 Hr Forecast (0000Z Nov 29)...70 mph maximum sustained wind tropical storm centered over the eastern Pacific at 10.5N-102.5W

96 Hr Forecast (0000Z Nov 30)...80 mph maximum sustained wind hurricane centered over the eastern Pacific at 11.5N-105W

120 Hr Forecast (0000Z Dec 1)...100 mph maximum sustained wind hurricane centered over the eastern Pacific at 12N-108W

Track Forecast...Otto by 0000Z (6 PM CST) tonight will be arriving to a position that is slightly southwest of my previous forecast track and so I have adjusted my forecast slightly southwest accordingly. Forecast track shows a slow down with a bend to the north at 72 to 96 hours...followed by a turn towards the west at 120 hours...per the steering influences mentioned in the above atmospheric outlook section.

Intensity Forecast...Under easterly vertical shear Otto appears to be on track to weaken further to 50 mph maximum sustained winds in the short term. Then as upper-level winds become more favorable in the 72 to 120 hour forecast timeframe...I show re-strengthening of Otto into a hurricane (see above atmospheric outlook seciton for how upper-level winds are expected to become more favorable). My current intensity forecast is unchanged from my previous one and thus is a continuation of my previous one.

Impact Forecast...The impact swath in the above forecast graphic is an extrapolation of the 3 PM CST NHC tropical storm wind field along my forecast track...with the swath grown in size later in the forecast to reflect the potential for re-strengthening.


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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