NCHurricane2009's Blog

2016 Atlantic Hurricane Season Birdseye Discussion #1A (Special Update)

By: NCHurricane2009, 12:47 PM GMT on January 16, 2016

...SATURDAY JANUARY 16 2015 7:47 AM EDT...
As expected...Hurricane Alex has transitioned to a non-tropical remnant gale. It is currently producing severe weather and rough seas in the far north Atlantic and will affect southern Greenland today as well.

It is quiet elsewhere in the Atlantic tropics. Will resume daily blog updates when the threat of tropical activity returns to the Atlantic basin.

2016 Atlantic Hurricane Season Birdseye Discussion #1

By: NCHurricane2009, 6:22 AM GMT on January 15, 2016

...FRIDAY JANUARY 15 2015 1:20 AM EDT...
Unusual January Hurricane Alex continues accelerating northward toward the Azores Islands in the northeastern Atlantic...expect tropical storm and hurricane conditions to strike within the next 6 to 12 hours. See special feature section below for additional details on Alex. Visit www.nhc.noaa.gov for up to the minute latest information on Alex including information on watches and warnings in effect for the Azores.

Tropical cyclone formation is not expected elsewhere over the next several days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

Hurricane Alex Genesis Graphic...showing the events leading up to the formation of Alex several days prior.


This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1936Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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. 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, 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 ALEX...
Genesis Discussion...A special Hurricane Alex Genesis Graphic has been inserted in the above atmospheric features section...reference this graphic for the following genesis discussion. Alex can be traced to a frontal zone that left the North American continent on the 4th to 5th of January...driven by a major wintertime gale centered near southern Greenland. By the 5th of January the associated upper trough began to split into upper troughs "A" and "B"...with divergence on the east side of southern cut-off upper trough "B" supporting the formation of a surface frontal low near western Cuba (pre-Alex). Through January 8 upper ridge "F" began to form and amplify to the west of upper trough "B" due to warm air advection ahead of a developing winter storm over the United States...with the amplification of the upper ridge causing upper trough "B" to also amplify into an upper vortex. Strengthening upper divergence ahead of amplifying upper trough/vortex "B" caused the pre-Alex surface frontal low to intensify into a gale as it moved northeastward from Cuba and across the western Atlantic...and by January 8 satellite pictures suggested it had some subtropical characteristics. During this time the back side of the major gale near southern Greenland pulled in a cold Canadian air mass (upper trough "C") southeastward such that upper trough "C" merged with the parent upper vortex "B" over the pre-Alex surface gale...and it is this delivery of cold air over pre-Alex that initially caused it to lose tropical character while moving eastward over the open Atlantic from the 8th to the 11th...but later this cold air helped to de-stabilize the atmosphere such that pre-Alex could acquire tropical characteristics and become a hurricane (see thermodynamic outlook section below). Upper ridge "F" to the west of pre-Alex continued to amplify through the 13th due to warm air advection ahead of the intensifying winter storm over North America...causing the base of cold upper trough "C" to cut-off into an upper vortex "J" on the 13th when pre-Alex was south of the Azores. Pre-Alex proceeded to build a core of thunderstorms (and a resulting low-level warm core) due to the de-stabilzing cold air of upper vortex "J"...transitioning in the following 24 hours into Subtorpical Storm Alex and then Hurricane Alex when an eye popped open in the thunderstorm core.

Current Prognosis...The center of North American winter storm in the Hurricane Alex genesis graphic has whirled back westward into central Canada (currently marked as the 1005 mb center in the top-left of the above atmospheric features chart) while the clipper that was diving on its back side from the 11th to 13th has arrived to the east coast of Canada while rapidly deepening to the 964 mb gale marked in the atmospheric features chart (there is also another clipper following behind...marked at 997 mb in the top-left of the atmospheric features chart). As upper trough "C" has moved into Europe...its western convergence is producing a surface 1032 mb ridge due north of Alex. This ridge is blocking Alex from moving northeastward to Europe...and as a result Alex is currently accelerating northward while getting pulled toward the 964 mb gale on the east coast of Canada. The parent upper vortex "J" over Alex has recently opened into an upper trough while merging with the upper trough associated with the 964 mb gale...causing an increase in southerly vertical shear over Alex that has recently blasted its thunderstorm core to the north half of the center (resulting in Alex losing its closed eye and now having only a "half-eye" on the north half of its center). From 0000Z to 0300Z the center of Alex has moved northward toward the Azores from 33.7N-27.5W to 34.5N-27.2W.

Atmospheric Outlook for the Forecast Period...Through the forecast period the 964 mb gale over the east coast of Canada will weaken as it is now beneath the non-divergent axis of its parent upper trough...but another strong frontal cyclone will form beneath the eastern divergent side of the upper trough. This frontal cyclone will cyclonically whirl and accelerate Alex north-northwestward toward southern Greenland after it crosses the Azores. Alex will also be supported by the divergence on the east side of the upper trough. The asymmetric cloud pattern noted toward the end of the above current prognosis section is showing early signs of regaining symmetry as Alex slides beneath a lower shear environment below the upper ridge axis ahead of the 964 mb frontal cyclone (marked by blue-zig-zag line to the right of the cyclone in the above atmopsheric features chart). Therefore Alex maybe in a low enough shear environment to attain symmetry in its cloud pattern as he crosses the Azores later this morning...and for much of the remainder of its lifespan.

Thermodynamic Outlook for the Forecast Period...Alex is an amazing specimen of a tropical cyclone...retaining tropical characteristics while over 20 deg C waters largely due to de-stabilizing cold upper-level air temperatures. However thunderstorm core and resulting tropical warm core should fade as the tropical cyclone gets slingshotted into far north cold water temperatures...and transition to non-tropical status is expected in the next 24 hours.


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

12 Hr Forecast (1200Z Jan 15)...75 mph maximum sustained wind hurricane with center passing over eastern half of Azores at 38.1N-27W

24 Hr Forecast (0000Z Jan 16)...75 mph maximum sustained wind non-tropical remnant gale centered at 45N-27.8W

Track Forecast...The motion from 0000Z to 0300Z in the above current prognosis shows a slight east lean in the current track of Alex...and appears to be slightly right of the NHC forecast. Therefore my forecast track is slightly to the right of the NHC's.

Intensity Forecast...I agree with the NHC forecast of maintaining hurricane strength (75 mph maximum sustained wind) through the transition to non-tropical as strong upper air divergence on the east side of the upper trough mentioned in the above atmospheric outlook maintains Alex's strength.

Impact Forecast...Impact swath in the above forecast graphic is extrapolation of the 10 PM EDT NHC advisory tropical storm wind field along the forecast track. Tropical storm conditions are expected across the Azores later this morning...with hurricane force conditions near the storm center. All preparations should have been completed by last night.

2016 Atlantic Hurricane Season Birdseye Discussion #0A (Special Update)

By: NCHurricane2009, 11:35 PM GMT on January 14, 2016

...THURSDAY JANUARY 14 2016 7:35 PM EDT...
Unusual January hurricane forms in the northeastern Atlantic...heading northwards towards the Azores...preparations in the Azores should be rushed to completion by tonight as tropical storm conditions are imminent over the next 24 hours and hurricane conditions near the storm center will be possible!

Hurricane Alex has taken me by surprise as I had not been monitoring the Atlantic tropics considering its the middle of the Northern Hemisphere winter! This system has been mentioned in the National Hurricane Center tropical (NHC) weather outlook over the last seven days...so kudos to the NHC for plenty of forewarning on this system. I apologize for not monitoring the tropics as aggressively in the off-season. After this event I will now be checking the tropics on a daily basis to also provide some better forewarning during the off-season.

I will be providing a full blog update on Alex and the rest of the Atlantic tropics later tonight.


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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