2016 Atlantic Hurricane Season Birdseye Discussion #178

By: NCHurricane2009 , 10:28 AM GMT on November 24, 2016

...THURSDAY NOVEMBER 24 2016 5:30 AM EDT...
Hurricane Otto approaching landfall in Nicaragua and Costa Rica...preparations in warned areas should have been completed by now. 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...including watches and/or warnings that are currently in effect.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1946Z-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...HURRICANE OTTO...
Current Prognosis...Since the previous blog update...Otto briefly weakened to a tropical storm while ingesting some cool dry air delivered far south by the 1002 mb frontal cyclone in the western Atlantic. However as the frontal cyclone continues moving eastward and away...Otto has re-developed a large comma shaped thunderstorm field and is back at hurricane strength...even stronger than ever at 85 mph maximum sustained winds while approaching Nicaragua and Costa Rica. As of 0000Z earlier in the night the center of Otto passed over 11.2N-81.5W...and as of 0600Z this morning the center passed over 11.2N-82.2W which provides a current motion of about 0.7W longitude per 6 hours (or 2.8W longitude per 24 hours).

Atmospheric Outlook for the Forecast Period...Otto continues to move westward while steered by surface ridging across North America...but the ridge currently has a weakness generated by a 1012 mb frontal cyclone moving into the eastern US such that Otto is only slow moving to the west at the present time. After 24 hours as the aformentioned frontal cyclone leaves North America...the steering ridge will re-build and accelerate Otto across Central America and into the eastern Pacific. By the end of the 120-hour forecast period...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 again. As Otto moves into the eastern Pacific...it will likely encounter unfavorable easterly vertical shear on the south side of an upper ridge over southern Mexico...but by the end of the 120-hour forecast period this upper ridge will shift southward and possibly ventilate and re-stregnthen Otto while becoming pushed by the aformentioned upper trough moving into western North America.

Thermodynamic Outlook for the Forecast Period...Otto will be over favorable 29 deg C waters in the southern Caribbean...and then by the end of the 120-hour forecast period reach warmer 29 to 30 deg C waters in the eastern Pacific.


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

24 Hr Forecast (0000Z Nov 25)...70 mph maximum sustained wind tropical storm centered inland over the Nicaragua/Costa Rica border at 11N-84.3W

48 Hr Forecast (0000Z Nov 26)...50 mph maximum sustained tropical storm centered over the eastern Pacific at 11N-89.3W

72 Hr Forecast (0000Z Nov 27)...50 mph maximum sustained wind tropical centered over the eastern Pacific at 11N-94.3W

96 Hr Forecast (0000Z Nov 28)...50 mph maximum sustained wind tropical storm centered over the eastern Pacific at 11N-99.3W

120 Hr Forecast (0000Z Nov 29)...70 mph maximum sustained wind tropical storm centered over the eastern Pacific at 11N-102.5W

Track Forecast...The initial first 24 hours of my updated forecast track is based on the current 2.8W longitude rate of progression noted in the above current prognosis section. I then accelerate the westward track after 24 hours as the surface ridge over North America re-builds per the above atmospheric outlook section...now catching up to the latest model guidance which has been going with a faster westward track than my previous forecasts showed. By 120 hours I slow the westward pace of Otto again as Otto gets caught in a gap between the North America surface ridge and central Pacific surface ridge per the above atmospheric outlook section.

Intensity Forecast...Otto is likely to strengthen beyond its current 85 mph maximmum sustained wind intensity before landfall in Nicaragua and Costa Rica...but I have lowered the intensity forecast for the timeframe that is 24 hours away as the updated faster forecast track moves Otto into land sooner and in fact by later today. However I have set the 24-hour forecast point at maximal tropical storm strength (70 mph) to account for the fact Otto will have just made landfall as a strong hurricane not long before the 24-hour forecast point. The updated faster forecast track makes it likely that Otto will survive its passage across Central America into the eastern Pacific. If so...the National Hurricane Center would retain the name Otto and I would continue to issue special feature sections with forecasts on Otto. Over the eastern Pacific...I initially show additional weakening to 50 mph maximum sustained winds due to expected easterly vertical shear mentioned in the above atmospheric outlook section. I then maintain a 50 mph intensity in the forecast through 96 hours as upper wind forecasts suggest the shearing upper-level easterlies will become divergent in nature...which would help ventilate Otto in the shear regime. By the end of the 120 hour forecast period...upper-level winds could become more favorable for Otto per the above atmospheric outlook section...and thus I show re-strengthening by that time.

Impact Forecast...The impact swath in the above forecast graphic is an extrapolation of the 4 AM EDT NHC tropical storm wind field along my forecast track...with the swath initially shrunken to reflect forecast weakening...and then re-expanded at the end of the forecast period to reflect forecast 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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