2016 Atlantic Hurricane Season Birdseye Discussion #176

By: NCHurricane2009 , 7:26 AM GMT on November 22, 2016

...TUESDAY NOVEMBER 22 2016 2:30 AM EDT...
The area of disturbed weather in the southern Caribbean Sea supported by a surface low rapidly develops into strong Tropical Storm Otto. Additional rapid intensification is possible before Otto makes landfall in southern Nicaragua and Costa Rica later this week...therefore interests in these areas and offshore southern Caribbean islands should be preparing now for a possible severe strike from a strong hurricane. 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 1929Z-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...The surface low that has persisted in the south-central Caribbean Sea has finally strengthened into tropical depression sixteen...and then Tropical Storm Otto...in the last 24 hours. Newly-named Otto appears to already be developing at a brisk pace while already reaching an intensity of 60 mph maximum sustained winds. As of 0000Z earlier this evening the center of Otto was pinwheeling stationary at 10.5N-79W. The thunderstorm activty of Otto is biased to the west of the center as the tropical storm is under light easterly shear while being under the west side of (instead of directly below) the upper ridge that has been ventilating this system over the last few days. The upper ridge has been suppressed to the east of Otto due to strong 986 mb frontal cyclone and its upper trough dominating eastern North America and the west Atlantic.

Atmospheric Outlook for the Forecast Period...Otto is currently stationary while trapped between the westerly steering flow from the upper trough and 986 mb surface frontal cyclone over the western Atlantic and eastern North America...and easterly steering flow of a strong 1030 mb surface ridge over central North America. As the upper trough/surface frontal cyclone shift eastward and away...the current easterly shear regime mentioned in the above current prognosis section should subside as there will be room for the ventilating upper ridge to re-locate and expand over directly over Otto...espeically while bolstered by the latent heat release of Otto's thundrestorm activity. In addition Otto will likely begin moving westward toward Nicaragua and Costa Rica while the 1030 mb ridge shifts to the north of Otto and pushes it. By 48 to 96 hours...a pair of frontal cyclones moving into eastern North America will weaken the ridge which could cause Otto's westward track to slow down. However unlike previous forecasts...I no longer show Otto stalling during this timeframe as the models have trended with weaker frontal cyclones. In fact already by 96 hours the latest model runs show the ridge re-building...and so I have increased the westward pace of my forecast track for the 72 to 96 hour timeframe. I further increase the westward pace under the re-building ridge for the 96 to 120 hour forecast period.

Thermodynamic Outlook for the Forecast Period...Otto will be over favorable 29 deg C waters in the southern Caribbean supportive of tropical development.


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

24 Hr Forecast (0000Z Nov 23)...70 mph maximum sustained wind tropical storm centered at 10.5N-80.5W

48 Hr Forecast (0000Z Nov 24)...85 mph maximum sustained wind hurricane centered offshore of Nicaragua and Costa Rica at 10.5N-81.5W

72 Hr Forecast (0000Z Nov 25)...100 mph maximum sustained wind hurricane centered just offshore of Nicaragua and Costa Rica at 10.5N-82.5W

96 Hr Forecast (0000Z Nov 26)...100 mph maximum sustained wind hurricane making landfall on the Nicargua/Costa Rica border at 10.5N-83.7W

120 Hr Forecast (0000Z Nov 27)...35 mph maximum sustained wind tropical depression weakening to a remnant low over northwestern Costa Rica coast...centered at 10.5N-85.7W

Track Forecast...Once again I have had to shift my forecast track south and east as Otto continued to shift south and east during its formative stages...likely due to northwesterly flow on the southwest side of the large upper trough/surface frontal cyclonic system that has been over eastern North America/west Atlantic. Per the above atmospheric outlook section...I have incrased the westward pace of Otto for 48 hours and beyond...see atmopsheric outlook section for details.

Intensity Forecast...With Otto becoming a compact tropical cyclone and a history of compact tropical cyclone rapidly intensifying...with warm waters of 29 deg C (thermodynamic outlook section)...and with atmopsheric conditions expected to become even more favorable with a reduction in shear (atmoshperic outlook section)...I have no choice but to raise the intensity forecast especially considering that Otto has jumped well ahead of my previous intensity forecast in the last 24 hours. The intensity forecast in fact may have to be raised even further to show Otto becoming a major hurricane (115+ mph) in the next day or so should signs of rapid development indeed manifest...and therefore interests in southern Nicaragua and Costa Rica should be taking Otto seriously and begin making preparations for a potentially severe strike late this week. Rapid weakening is then shown by 120 hours as compact tropical cyclones tend to rapidly weaken at landfall...even for smaller land masses such as Central America.

Impact Forecast...The impact swath in the above forecast graphic is an extrapolation of the 10 PM EDT NHC tropical storm wind field along my forecast track...with some slight growth in the swath to reflect the anticipated strengthening. The rather small wind field at 10 PM EDT indicates that Otto is structured as a compact tropical cyclone...although it may not seem that way with a field of cloudiness attached to Otto extending to the east-northeast. However note that these clouds are associated with the tail end of cold fronts associated with the large 986 mb frontal cylcone moving into the west Atlantic...and not necessarily associated with the compact tropical storm.


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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