Hurricane Henri

[WxWatcher007]

Not expecting a ton but this one has flown under the radar. Advisories likely by 11pm.

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Sun Aug 15 2021

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical 
Storm Fred, located over the east-central Gulf of Mexico, and on 
Tropical Depression Grace, located about 100 miles south-southeast 
of the Dominican Republic. 

1. Satellite imagery and radar data from Bermuda indicate that showers 
and thunderstorms associated with a small but well-defined area of 
low pressure located northeast of Bermuda have continued to become 
better organized during the past few hours. If this trend continues, 
advisories will likely be initiated on a new tropical depression 
later tonight. The system is forecast to move slowly toward the 
south or southwest during the next day or so, and then turn westward 
on Tuesday, passing near or just east and south of Bermuda. 
Interests in Bermuda should monitor the progress of this system, 
and a Tropical Storm Watch could be required for that island 
tonight.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

Forecaster Zelinsky

 

[GaWx]

 Here's the end of the 18Z Euro. It would likely recurve rather sharply soon after because the 500 mb ridge is then weakening rapidly and prior Euro runs did recurve it then. However, this run  is the strongest yet and it is the furthest west. So, even though odds per current models strongly favor a safe recurve, the more important thing here to note may be the Euro trend. Also, how does Grace affect the steering, a possible fly in the ointment?

Also, let's see what the 18Z Euro ens members do. The 0Z and 6Z both had a handful of E coast threats (5-10% of the members). Then the 12Z pretty much backed off.

 

[GaWx]

The 18Z Euro ens goes back to having a few US threats from 96L, similar to the 0Z and 6Z, with 3 members showing a TS+ moving toward the SE US at the end of the run though keep in mind that's only 6% of the members thus making them outliers:

 

 

[MattPetrulli]

Now have TD 8, NHC notes a 65 MPH peak and a low confidence forecast

Tropical Depression Eight Discussion Number   1
NWS National Hurricane Center Miami FL       AL082021
1100 PM AST Sun Aug 15 2021

A small well-defined low pressure system located just 
east-northeast of Bermuda has produced persistent deep convection 
since this morning. Radar imagery from Bermuda along with 
geostationary and polar orbiting microwave satellite data show that 
the convection is sufficiently well organized to meet the 
definition for a tropical cyclone. Therefore advisories have been 
started on Tropical Depression Eight.  The initial intensity is set 
at 25 kt, based on believable winds near that value in a pair of 
recent ASCAT overpasses. Dvorak estimates from TAFB and SAB were a 
little higher, so this estimate could be slightly conservative.

Confidence in the forecast is reasonably high for the next 48 to 
72 h. The depression should make a slow clockwise turn around 
Bermuda, steered by a mid-level ridge currently centered off the 
coast of the Carolinas. Warm SSTs should provide ample fuel to 
support at least slight strengthening during this period, despite 
expected northerly shear, and this is shown by all of the intensity 
guidance. The NHC forecast is very near the multi-model consensus 
for both track and intensity through that period.

Beyond 72 h, the track and intensity models diverge quickly. The 
HWRF and COAMPS-TC models rapidly intensify the system to major 
hurricane strength. A stronger, deeper vortex would likely be 
steered generally westward through the end of the forecast period, 
influenced by a deeper-layer steering flow.  However, the global 
models have a much weaker, shallower system which turns northward, 
and then possibly accelerates northeastward by day 5. As a result, 
the spread in the track guidance is nearly 800 n mi by day 5, with 
the GFS and HWRF taking the extreme positions to the northeast and 
southwest, respectively. The official track forecast takes a middle 
approach, and is between the various consensus aids at days 4 and 
5. The NHC intensity forecast is slightly more conservative, and is 
below the consensus at the end of the period. Significant changes 
to the forecast may be required in subsequent advisory packages.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 33.2N  62.7W   25 KT  30 MPH
 12H  16/1200Z 32.4N  62.8W   30 KT  35 MPH
 24H  17/0000Z 31.5N  63.3W   35 KT  40 MPH
 36H  17/1200Z 31.1N  64.0W   40 KT  45 MPH
 48H  18/0000Z 31.0N  64.9W   45 KT  50 MPH
 60H  18/1200Z 31.0N  66.1W   50 KT  60 MPH
 72H  19/0000Z 31.2N  67.4W   55 KT  65 MPH
 96H  20/0000Z 32.0N  68.5W   55 KT  65 MPH
120H  21/0000Z 33.5N  68.0W   55 KT  65 MPH

[WxWatcher007]

@GaWx this one is a little more interesting this morning, right? For now at least?

I took a look at the EPS and there were certainly a few interesting members. Looks like most go OTS, but with a stronger system perhaps we get a further west push. NHC has really highlighted how uncertain a forecast this one is at D4 & D5. 

In fact, looking deeper at the EPS, the ones that do develop TD 8 do make it more of an EC threat. Interesting.

[LongBeachSurfFreak]

Regardless of the direct US landfall threat this will be a prolific swell producer for the east coast. As it’s prime beach season the rip current threat will be real. Offshore hurricanes have killed dozens of people at east coast beaches over the years. 

[WxWatcher007]

8 minutes ago, LongBeachSurfFreak said:

Regardless of the direct US landfall threat this will be a prolific swell producer for the east coast. As it’s prime beach season the rip current threat will be real. Offshore hurricanes have killed dozens of people at east coast beaches over the years. 

Very good point. 

[cptcatz]

Have we had a storm this season where the NHC didn't highlight the uncertainty of the forecast?

[MJO812]

HWRF at 6z 

Loops and goes back west

[Kevin Reilly]

Henri will be very interesting to track the East Coast is pretty open without a strong trough coming in from the west.  There is a pretty good blocking area of high pressure off of the New England Coast for days and that would appear to be a key to where Henri goes.  Pretty much a east southeasterly flow pointing up along the East Coast this week into the weekend. It's interesting I do remember a few GFS runs last week showing this system making a run to the Carolina coast then blocked up the coast last week. 

[GaWx]

8 hours ago, WxWatcher007 said:

@GaWx this one is a little more interesting this morning, right? For now at least?

I took a look at the EPS and there were certainly a few interesting members. Looks like most go OTS, but with a stronger system perhaps we get a further west push. NHC has really highlighted how uncertain a forecast this one is at D4 & D5. 

In fact, looking deeper at the EPS, the ones that do develop TD 8 do make it more of an EC threat. Interesting.

Indeed, the 0Z EPS had some members threatening the E coast as you showed. However, the 12Z was less threatening. 

[WxWatcher007]

39 minutes ago, GaWx said:

Indeed, the 0Z EPS had some members threatening the E coast as you showed. However, the 12Z was less threatening. 

Yeah—I think smart money is on out to sea, but still worth a casual eye I suppose since Grace wants to drive toward the equator now  

[GaWx]

   12Z UKMET: comes slowly west for 3 days and then turns back safely OTS

 TROPICAL DEPRESSION 08L        ANALYSED POSITION : 31.9N  63.0W

     ATCF IDENTIFIER : AL082021

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    1200UTC 16.08.2021    0  31.9N  63.0W     1013            23
    0000UTC 17.08.2021   12  31.0N  63.2W     1012            24
    1200UTC 17.08.2021   24  30.7N  63.8W     1012            25
    0000UTC 18.08.2021   36  30.7N  65.0W     1012            26
    1200UTC 18.08.2021   48  30.7N  66.6W     1014            26
    0000UTC 19.08.2021   60  31.1N  68.2W     1014            25
    1200UTC 19.08.2021   72  31.1N  69.6W     1013            25
    0000UTC 20.08.2021   84  31.7N  70.1W     1011            27
    1200UTC 20.08.2021   96  32.9N  69.9W     1010            29
    0000UTC 21.08.2021  108  34.4N  68.4W     1009            30
    1200UTC 21.08.2021  120  35.6N  65.7W     1010            29
    0000UTC 22.08.2021  132  35.9N  62.3W     1010            29
    1200UTC 22.08.2021  144  35.0N  59.1W     1010            30

[WxWatcher007]

Tropical Storm Henri Discussion Number   4
NWS National Hurricane Center Miami FL       AL082021
500 PM AST Mon Aug 16 2021

Deep convection has persisted near and southeast of the center 
of the small tropical cyclone today, and subjective Dvorak 
intensity estimates were a consensus T2.5 (35 kt) at 1800 UTC.  
Objective estimates from ADT and SATCON also support tropical 
storm status, therefore the depression has been upgraded to a 
35-kt tropical storm with this advisory.  Henri (ahn-REE) becomes 
the eighth named storm of the 2021 Atlantic hurricane season.  This 
is the fourth-earliest eighth storm on record with only 2020, 
2005, and 1936 having the eighth-named storm form earlier in the 
season.

Henri is located over warm waters, but is currently being affected 
by light to moderate northerly shear and dry mid-level air in the 
surrounding environment.  Although these conditions are not overly 
conducive for strengthening, most of the intensity guidance 
supports gradual intensification over the next 24 to 48 hours.  
After that time, a significant increase in northeasterly 
upper-level winds is depicted by the global models over the system, 
which is likely to halt further strengthening.  In fact, given the 
small size of Henri, it is likely to be more susceptible to the 
increase in shear, and it could weaken faster than indicated below. 
The HWRF remains more aggressive, but given the expected increase in 
shear, that solution still does not seem likely.  The NHC intensity 
forecast is in best agreement with the LGEM model, and is slightly 
below the IVCN intensity consensus.

The tropical storm is moving south-southwestward or 200/6 kt. Henri 
is forecast to move west-southwestward during the next 12-24 hours 
around the southeastern side of a mid-tropospheric high over the 
western Atlantic.  After that time, Henri should turn westward as 
the ridge shifts eastward to the north of the tropical cyclone, and 
after 72 hours Henri is expected to approach the western extent of 
the ridge and should turn northward and then north-northeastward. 
The dynamical model guidance is in somewhat better agreement during 
the next 48-72 hours, but there remains some spread later in 
the period as to how sharp of northward turn occurs.  The new NHC 
track forecast is similar to the previous advisory and lies near 
the center of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 31.0N  62.9W   35 KT  40 MPH
 12H  17/0600Z 30.5N  63.4W   40 KT  45 MPH
 24H  17/1800Z 30.3N  64.2W   45 KT  50 MPH
 36H  18/0600Z 30.2N  65.4W   50 KT  60 MPH
 48H  18/1800Z 30.2N  66.9W   50 KT  60 MPH
 60H  19/0600Z 30.3N  68.5W   50 KT  60 MPH
 72H  19/1800Z 30.5N  69.9W   45 KT  50 MPH
 96H  20/1800Z 31.8N  70.2W   45 KT  50 MPH
120H  21/1800Z 34.2N  68.4W   45 KT  50 MPH

$$
Forecaster Brown

 

[Wannabehippie]

Definite signs of shear, but also looks like it has good outflow.

[Yeoman]

I hope the fish don't get too wet

[yoda]

BULLETIN
Tropical Storm Henri Advisory Number   6
NWS National Hurricane Center Miami FL       AL082021
500 AM AST Tue Aug 17 2021

...HENRI STRENGTHENS A LITTLE MORE AS IT CONTINUES TO MOVE SLOWLY
SOUTHWESTWARD...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...30.6N 63.7W
ABOUT 135 MI...215 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WSW OR 240 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES

[yoda]

Tropical Storm Henri Discussion Number   6
NWS National Hurricane Center Miami FL       AL082021
500 AM AST Tue Aug 17 2021

Earlier this evening Henri was undergoing a sheared bursting 
pattern, with intermittent deep convection trying to develop near 
the center, but northwesterly shear would quickly diminish the 
convective coverage. However, over the past several hours the 
convection has become more persistent, and covers at least the 
southeastern portion of the low-level center. As such, the latest 
subjective Dvorak intensity estimates from TAFB and SAB are now 
both 3.0 (45 kt), and therefore 45 kt will be the initial advisory 
intensity.

Henri is forecast to remain over warm waters and in an environment 
of light to moderate northerly shear for the next 24 h, so some 
strengthening is expected during that time. After 24 h, global 
models indicate that the shear magnitude will double, which should 
prevent any further strengthening and possibly weaken the cyclone. 
The latest NHC intensity forecast was adjusted a little higher than 
the previous due to both the increase in initial intensity, and 
slight increase in the model intensity guidance. This forecast 
closely follows the LGEM solution and is just a little lower than 
the IVCN consensus.

The tropical storm continues to move slowly southwest, or 240/04 kt 
to the southeast of a mid-level ridge. This ridge is forecast to 
shift to the east over the next several days, which would result in 
the tropical storm making a gradual clockwise turn throughout much 
of the forecast period. Tonight, Henri is forecast to turn westward 
with a increase in forward motion and pass well south of Bermuda. In 
a few days, the cyclone should turn to the northwest then north, 
followed by a turn to the northeast around the western periphery of 
the ridge. There continues to be some spread in how far west Henri 
will go before it begins to turn to the north, and the latest 
guidance has made a slight shift to the left. The official NHC 
forecast is near the previous one through 48 h, then is a little 
left of it thereafter, yet still remains to the right of the bulk of 
the consensus guidance beyond 48 h.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0900Z 30.6N  63.7W   45 KT  50 MPH
 12H  17/1800Z 30.4N  64.4W   50 KT  60 MPH
 24H  18/0600Z 30.3N  65.7W   55 KT  65 MPH
 36H  18/1800Z 30.2N  67.1W   55 KT  65 MPH
 48H  19/0600Z 30.3N  68.6W   55 KT  65 MPH
 60H  19/1800Z 30.8N  69.8W   55 KT  65 MPH
 72H  20/0600Z 31.6N  70.6W   55 KT  65 MPH
 96H  21/0600Z 34.0N  69.1W   55 KT  65 MPH
120H  22/0600Z 36.0N  66.0W   55 KT  65 MPH

$$
Forecaster Latto

[jconsor]

 

[Vice-Regent]

It's not low risk at all. For it to come towards 75W from a starting position east of Bermuda (even east of Hebert Box) is highly anomalous and portends to unusual outcomes potentially.

[NorthHillsWx]

Henri looks very healthy this morning. Still feeling effects of some northwesterly shear, but the system has a vigorous mid level center seen clearly in the intense convective envelope it developed overnight and with morning visible it does not seem to be too far displaced from the llc. Given the current look, it would not shock me to see this small system ramp up quickly today, maybe becoming a hurricane 

[Windspeed]

Henri looks very healthy this morning. Still feeling effects of some northwesterly shear, but the system has a vigorous mid level center seen clearly in the intense convective envelope it developed overnight and with morning visible it does not seem to be too far displaced from the llc. Given the current look, it would not shock me to see this small system ramp up quickly today, maybe becoming a hurricane 

I do like the hurricane potential this weekend when Henri turns north towards the gulf stream. If timed right, it will be between two upper troughs with good thermodynamic support. Should be sufficient ventilation for a stronger hurricane as it heads into the maritimes by early next week.

[WxWatcher007]

43 minutes ago, Windspeed said:

53 minutes ago, NorthHillsWx said:

Henri looks very healthy this morning. Still feeling effects of some northwesterly shear, but the system has a vigorous mid level center seen clearly in the intense convective envelope it developed overnight and with morning visible it does not seem to be too far displaced from the llc. Given the current look, it would not shock me to see this small system ramp up quickly today, maybe becoming a hurricane 

I do like the hurricane potential this weekend when Henri turns north towards the gulf stream. If timed right, it will be between two upper troughs with good thermodynamic support. Should be sufficient ventilation for a stronger hurricane as it heads into the maritimes by early next week.

The guidance has been unusually slow catching up to this one, so it’d fit the theme of the season, and this storm, for it to produce a “surprise”.

As you both said—it looks quite good this morning.

[WxWatcher007]

[NorthHillsWx]

6 minutes ago, WxWatcher007 said:

Yep. I believe we have a hurricane incoming

[ldub23]

May end  up the strongest  of the season.

[NorthHillsWx]

Oh how I wish we had recon in Henri atm…

[jconsor]

 

[WxWatcher007]

Tropical Storm Henri Discussion Number   7
NWS National Hurricane Center Miami FL       AL082021
1100 AM AST Tue Aug 17 2021

Henri remains a sheared tropical storm.  Geostationary satellite 
images and microwave data show a relatively large area of deep 
convection (~200 miles across), but the center of the storm is 
located near the western edge of the thunderstorms due to ongoing 
northwesterly vertical wind shear.  The latest Dvorak estimates have 
been steady at 3.0/45 kt from TAFB and SAB, and based on that data, 
the initial intensity is held at 45 kt.  The center of Henri is 
located roughly 130 miles south-southeast of Bermuda currently, and 
this will likely be as close as the storm gets to the island.

The tropical storm is gradually turning to the west, as expected, 
and the initial motion is estimated to be 255/5 kt.  A subtropical 
ridge over the western Atlantic is building eastward to the north of 
Henri, and this feature should steer the storm westward at a 
slightly faster pace during the next two or three days.  After that 
time, the ridge is expected to weaken and shift farther east as a 
cut off low or negatively-tilted trough develops over the northeast 
U.S.  This change in the steering pattern should cause Henri to turn 
northeastward between Bermuda and the east coast of the U.S in the 
72-120 h period.  The NHC track forecast is a little faster than the 
previous one in the short term and farther west than the previous 
one from days 3-5, trending toward the latest consensus models.

The northwesterly shear currently affecting Henri is expected to 
subside later today, and that should allow the storm to gain 
strength during the next 12-24 hours.  However, a round of moderate 
northerly shear is expected to setup over Henri during the 24-96 
hour period.  Although this shear would typically cause some 
weakening, the combination of warm SSTs and increasing mid-level 
moisture could offset the negative influences of the shear.  
Therefore, no change in strength is predicted beyond the 24 h 
period.  Some of the models suggest that the shear could lessen 
again this weekend, so although not explicitly forecast, some 
strengthening is possible then.


FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 30.4N  64.3W   45 KT  50 MPH
 12H  18/0000Z 30.4N  65.1W   50 KT  60 MPH
 24H  18/1200Z 30.3N  66.5W   55 KT  65 MPH
 36H  19/0000Z 30.3N  68.2W   55 KT  65 MPH
 48H  19/1200Z 30.4N  69.7W   55 KT  65 MPH
 60H  20/0000Z 30.7N  70.6W   55 KT  65 MPH
 72H  20/1200Z 31.6N  71.3W   55 KT  65 MPH
 96H  21/1200Z 34.1N  69.6W   55 KT  65 MPH
120H  22/1200Z 37.4N  66.0W   55 KT  65 MPH

$$
Forecaster Cangialosi

[SnowenOutThere]

If we are looking for where an eye would be I think I found it, the lightning on the band would be the eyewall trying to wrap around. Seems like it’s just a matter of time before an eye forms.