Bertha

Update, August 10, 1:23 p.m.: Strong winds and flooding, per the BBC. Apparently the system has slowed. Scotland’s Highlands, Grampian, and Eilean Siar are in amber alert for rain. Effects are expected to last through Monday morning.

Update, August 9, 5:27 p.m. Pacific: A bit more coverage, as ex-Bertha is hitting the British Isles tonight. The Daily Mirror says it has live updates. Apparently hundreds of Red Cross volunteers are on standby. Britain’s Met Office website says that the following areas are under a yellow warning: Central, Tayside & Fife, East Midlands, East of England, Grampian, Highlands & Eilean Siar, London & South East England, North East England, North West England, Northern Ireland, Orkney & Shetland, SW Scotland, Lothian Borders, South West England, Strathclyde, Wales, West Midlands, Yorkshire and Humber. On the map, it looks like the entire UK except for the western parts of Ireland. Hope it doesn’t get too bad for anybody there tonight.

Update, August 5, 2:34 p.m. This will be the last update (edit: Europe, however, is anticipating ex-Bertha). Per the current NHC forecast discussion:

000
WTNT43 KNHC 052044
TCDAT3

TROPICAL STORM BERTHA DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014
500 PM EDT TUE AUG 05 2014

Deep convection redeveloped over the center earlier today, but
that convection was subsequently sheared off to the east-northeast.
An ASCAT overpass from a few hours ago indicated that, although
Bertha still had a well-defined surface circulation, the maximum
winds were no more than 45 kt, Based on this, and a Dvorak
classification of T3.0 from TAFB, the advisory intensity is
set at 45 kt…global models show the system becoming embedded within
the frontal zone within 36 hours, so the official forecast indicates
that the transition to a post-tropical/extratropical cyclone will
be complete by that time.

Bertha’s heading is gradually shifting to the right and the motion
is now 030/18 kt. There is little change to the track forecast
philosophy. Over the next couple of days, the tropical, or
post-tropical, cyclone should turn toward the northeast and
accelerate ahead of an amplifying mid-level trough moving off the
northeast United States coast. Later in the forecast period, the
system should move swiftly east-northeastward to eastward in the
mid-latitude westerlies over the North Atlantic.

 

strong>Update, August 4, 4:35 p.m. Pacific: At 11 a.m Eastern the NHC said Bertha is now a low-end Category 1 hurricane. At 5 p.m. Eastern, they’re not sure – a Hurricane Hunter flight was up. They say:

For now, the NHC intensity
forecast calls for gradual weakening, and is a little below most of
the guidance since the shear is predicted to become prohibitively
strong, 50 kt or more, in just 36 hours.

Fixes from the aircraft showed a gradual increase in forward speed
and the initial motion is around 360/15. There are no important
changes to the track forecast or reasoning. During the next couple
of days, Bertha will be moving between a mid-level high pressure
area over the southwestern Atlantic and a broad trough moving off
the northeast United States coast. This should result in a gradual
turn toward the north-northeast and northeast with additional
acceleration during the next 24-48 hours. Later in the forecast
period, Bertha or its post-tropical counterpart should accelerate
east-northeastward in the mid-latitude westerlies over the north
Atlantic. The official forecast is similar to the previous one and
lies between the latest GFS and ECMWF tracks.

Update, August 3, 1:48 p.m. Pacific: Jeff Masters says:

On Monday and Tuesday, Bertha is expected to encounter lower wind shear and a moister atmosphere, and these conditions may allow the storm to briefly intensify into a Category 1 hurricane. Bertha will not be a threat to any more land areas.

 

Not pictured:  A hurricane.  (NOAA)

Not pictured: A hurricane. (NOAA)

Bertha does look healthier than it did yesterday:
 

NOAA

NOAA

The NHC is paying careful attention to the European model that did such a great job predicting Superstorm Sandy in 2012. They say it shows Bertha interacting with a disturbance that’s currently near Florida and moving closer to the US mainland. However, they’ve only nudged the track a little bit closer to shore and don’t show a US landfall.
 
forecast cone

Update, August 2, 5:03 p.m. Pacific: Per the 5 p.m. Eastern NHC discussion:

000
WTNT43 KNHC 022050
TCDAT3

TROPICAL STORM BERTHA DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014
500 PM AST SAT AUG 02 2014

Bertha has maintained some organized convection over the eastern
semicircle during the past several hours. However, the system
barely qualifies as a tropical cyclone, as a combination of NOAA
Hurricane Hunter aircraft and surface data cannot definitively close
off the circulation. The initial intensity is reduced to 40 kt
based on a combination of surface observations and data from the San
Juan WSR-88D Doppler radar. It should be noted that Bertha
continues to suffer from dry air entrainment and northwesterly
vertical shear, and advisories could be discontinued tonight or
Sunday if the system becomes any less organized.

The initial motion is now 300/19. Bertha is approaching the
southwestern edge of the subtropical ridge and should turn
northwestward during the next several hours. A turn toward the
north should occur in about 48 hours as Bertha moves between the
ridge and a deep-layer trough over the southeastern United States.
After that, the cyclone should turn northeastward as it enters the
mid-latitude westerlies. The track guidance remains in good
agreement on this scenario, and the new forecast track is
again generally similar to the previous track.

There are now three possible scenarios for the intensity of Bertha.
The scenario for the official forecast is that Bertha survives its
current lack of structure, land interaction, and dry air
entrainment long enough to reach a more favorable environment in
about 36 hours. At that point, it would likely intensify until
the onset of extratropical transition in 96-120 hours. Using this
scenario, the new intensity forecast is similar to the previous
forecast and calls for Bertha to become a hurricane in about 96
hours. The second scenario is that Bertha degenerates to a tropical
wave as it passes over Hispaniola, with possible regeneration later
when the system reaches the more favorable environment. A new third
possibility involves a low pressure area currently developing over
the northwestern Bahamas. The UKMET and NAVGEM forecast this low to
get strong enough to absorb Bertha in 48 hours or so, while the
other models are less bullish on the its development. Later model
runs should help determine the likelihood of this scenario.

Update, August 2, 1:20 p.m. Pacific: The NHC still maintains Bertha as a tropical storm but in their current forecast discussion admits that it may go back into a tropical wave before reaching better conditions and regenerating into a full-fledged hurricane (after 72 hours, per the GFS). If their forecast and the GFS are correct, this “Hurricane Bertha” will be a fish (no threat to land).

000
WTNT43 KNHC 021454
TCDAT3

TROPICAL STORM BERTHA DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014
1100 AM AST SAT AUG 02 2014

Bertha remains a disorganized tropical cyclone this morning, as
even with the aid of Doppler radar data it is difficult to find
a closed circulation. The low-level center is near the western edge
of the main convective mass, which indicates the system is still
affected by vertical wind shear. However, the convection has become
a little better organized during the past 24 hours, and the outflow
is improving over the eastern semicircle. The initial intensity
remains 45 kt based on a combination of continuity and Doppler radar
data.

The initial motion is 290/19. Bertha is approaching the
southwestern edge of the subtropical ridge and should turn
northwest during the next 6-12 hours. A turn toward the north
should occur in about 48 hours as Bertha moves between the ridge
and a deep-layer trough over the southeastern United States. After
that, the cyclone should turn northeastward as it enters the
mid-latitude westerlies. The track guidance is in excellent
agreement on this scenario, and the new forecast track is generally
similar to the previous track. There has been a small westward
shift during the first 12-24 hours, with the center now forecast to
make landfall over the eastern Dominican Republic.

Little change in strength is expected during the next 36 hours or
so as Bertha deals with lingering shear, dry air entrainment, and
passage over the mountains of Hispaniola. After that, the cyclone
is expected to move into a more favorable environment that could
allow strengthening. The new intensity forecast is unchanged from
the previous advisory, calling for Bertha to become a hurricane
for a short time after recurvature. It is possible that passage
over the Dominican Republic could cause Bertha to degenerate to a
tropical wave. Should that happen, there would be a chance for
regeneration when the system reaches the more favorable environment
to the north.

FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 17.2N 66.7W 45 KT 50 MPH
12H 03/0000Z 18.8N 68.9W 45 KT 50 MPH…INLAND
24H 03/1200Z 21.2N 71.5W 45 KT 50 MPH…OVER WATER
36H 04/0000Z 23.6N 73.4W 45 KT 50 MPH
48H 04/1200Z 26.4N 74.1W 50 KT 60 MPH
72H 05/1200Z 32.5N 71.5W 60 KT 70 MPH
96H 06/1200Z 37.5N 64.5W 65 KT 75 MPH
120H 07/1200Z 42.0N 55.0W 55 KT 65 MPH

 

That's a terrible shape for a tropical cyclone of any intensity, but look at that convection!  Bertha still packs some muscle.  (Image: NOAA)

That’s a terrible shape for a tropical cyclone of any intensity, but look at that convection! Bertha still packs some muscle. (Image: NOAA)

Update, August 1, 2:45 p.m. Pacific: Last night, the NHC identified this as Tropical Storm Bertha.

The storm is currently in an area of vertical shear and there is plenty of dry air nearby, but the NHC says (and the current run of the GFS shows) that Bertha will hang together until it reaches an area where conditions are more favorable. However, as it intensifies again, it will curve away from land and head out into the Central Atlantic.

Satellite imagery shows its most intense activity currently is over the Lesser Antilles.
 

That's a very disorganized-looking storm, but the setting sun nicely highlights the tops of Bertha's ongoing thunderstorm.  This one will hang on!  (Image: NOAA)

That’s a very disorganized-looking storm, but the setting sun nicely highlights the tops of Bertha’s ongoing thunderstorm. This one will hang on! (Image: NOAA)

The NHC’s current warning cone shows it at tropical storm strength throughout its path northward – no landfall on the US mainland.
 

I wonder why they weren’t fooled by yesterday’s GFS showing it not really developing further.

Update, July 31, 5:21 p.m: About half an hour ago, the NHC did a new tropical weather outlook, saying:

000
ABNT20 KNHC 312342
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU JUL 31 2014

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

An Air Force Reserve reconnaissance aircraft this afternoon and
evening investigated the well-defined low pressure system located
about 350 miles east-southeast of Barbados, and found surface winds
of 40 to 45 mph across the northern and eastern portions of the
circulation. Showers and thunderstorms have increased east of the
center during the past couple of hours, and if this development
trend continues a tropical storm could form later tonight or early
Friday. Regardless of development, gale-force winds are likely to
spread across portions of the central Lesser Antilles beginning by
midday Friday. Interests in these areas should continue to monitor
the progress of this disturbance as it moves west-northwestward near
20 mph, since watches or warnings could be required for some of
these islands later tonight or Friday.
* Formation chance through 48 hours…high…80 percent.
* Formation chance through 5 days…high…80 percent.

$$
Forecaster Stewart

Maybe this thing will get a name before it dissipates!

Update, July 31, 1:44 p.m. Pacific: The GFS, as I read it (and I’m an amateur), now shows this thing not developing, passing over the Lesser Antilles and Puerto Rico, and then fizzling over the Bahamas. This variation from yesterday to today shows the importance of not relying totally on computer models.

The NHC, as of about half an hour ago in a special tropical weather outlook, is bullish:

000
ABNT20 KNHC 312013
TWOAT

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
415 PM EDT THU JUL 31 2014

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

A Hurricane Hunter aircraft has continued to investigate the
low pressure system located about 500 miles east of the Windward
Islands. Observations from the aircraft indicate that this system
is producing winds of up to 40 to 45 mph in the northern portion of
the circulation. Showers and thunderstorms could redevelop over
the low tonight or Friday, which could result in tropical cyclone
formation. Regardless of development, winds of gale force are
likely to spread across portions of the Lesser Antilles beginning
early Friday. Interests in the Lesser Antilles should continue
to monitor the progress of this disturbance as it moves
west-northwestward near 20 mph, and watches or warnings may be
required for some of these islands later tonight or Friday.
* Formation chance through 48 hours…high…70 percent.
* Formation chance through 5 days…high…70 percent.

$$
Forecaster Pasch

Jeff Masters is impressed enough by its circulation and thunderstorm activity to suspect it will be classified a tropical depression later today. Moderate wind shear and dry air, he says, will limit its growth in the near future, and the models still agree that it will recurve without hitting mainland USA.

Update, July 30, 1:17 p.m. Pacific: Well, the GFS shows this still developing, but only the northern Antilles taking a hit. Then, instead of curving out to sea as shown in earlier runs, it heads toward the Bahamas, weakens, and at the end of the run appears to be strengthening again. This is in hoodoo-land, though. The NHC is less bullish in the current tropical weather outlook:

000
ABNT20 KNHC 301734
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT WED JUL 30 2014

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

Showers and thunderstorms associated with an area of low pressure
located about 1000 miles east of the southern Windward Islands have
been gradually decreasing since yesterday. However, environmental
conditions are marginally conducive for the development of this
system into a tropical depression during the next couple of days.
Interests in the Lesser Antilles should monitor the progress of this
system as it moves west-northwestward near 15 mph.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…medium…50 percent.

$$
Forecaster Pasch

Jeff Masters notes that only two out of the originally scheduled five Hurricane Hunter flights are now going out to investigate this on daily alternating flights, starting today. He says the models do show it eventually recurving without hitting the mainland US.

Update, July 28, 2:41 p.m. Pacific: The GFS still shows this thing developing slowly and then lasting through the length of the run. The NHC has increased the chances for tropical cyclone formation to 70% over the next five days; it’s 30% over the next 48 hours.

Update, July 27, 3:52 p.m. Pacific: The GFS still shows development over the coming days. The NHC gives this Cape Verde wave a 40% chance of development this week. Jeff Masters says:

The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday. The GFS is slower, predicting a Saturday arrival in the islands…Most of the 20 members of the 06Z Sunday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea early next week, but it is too early to assess the odds of this.

Stay tuned!

The GFS is showing a system developing soon and moving into the southern Caribbean next week. Things are not definite for modeling that many days out, but the National Hurricane Center already has their eye on a possibility:
 

If it develops far enough, it will be named Bertha.



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