Cristobal

Update, August 27, 3:23 p.m.: NASA studied the storm today. Per the NHC in its current forecast discussion, Cristobal is going to remain strong even after it transitions into an extratropical storm (links and comment added):

The intensity forecast shows gradual intensification to 75
kt in 36 to 48 hours, as Cristobal will have the opportunity to
intensify as a tropical cyclone and then via baroclinic processes
during extratropical transition. Global model fields show Cristobal
deepening during transition and acquiring a warm seclusion structure
in 48 to 72 hours. [This is not good news for anything in the storm’s path] Slow decay is expected after 72 hours before the
cyclone is absorbed at high latitudes.

Cristobal has begun moving north-northeastward, with an initial
motion estimate of 030/13. The cyclone should continue to accelerate
around the subtropical ridge into the mid-latitude westerlies
tonight and remain on a general northeastward heading through 72
hours before bending northward. The track model guidance remains in
good agreement on this scenario, and the NHC track is close to the
previous forecast and the middle of the guidance envelope.

The extratropical portion of the forecast has been coordinated with
the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 32.7N 71.4W 65 KT 75 MPH
12H 28/0600Z 34.4N 69.2W 65 KT 75 MPH
24H 28/1800Z 37.3N 63.7W 70 KT 80 MPH
36H 29/0600Z 41.0N 55.3W 75 KT 85 MPH
48H 29/1800Z 45.3N 47.8W 75 KT 85 MPH…POST-TROPICAL
72H 30/1800Z 53.5N 34.5W 70 KT 80 MPH…POST-TROP/EXTRATROP
96H 31/1800Z 60.0N 27.5W 50 KT 60 MPH…POST-TROP/EXTRATROP
120H 01/1800Z…ABSORBED

$$
Forecaster Brennan

Update, August 27, 1:43 p.m. Cristobal is just southeast of Cape Hatteras and the NHC expects it to head out to sea. I was mistaken yesterday. It probably will hit Iceland as a storm, but the UK will be spared. Actually, there was a story in the Telegraph yesterday expressing hope that ex-Cristobal will bring some sunny weather in its wake.

Update, August 26, 12:50 p.m. Pacific: Cristobal is now a hurricane, in spite of strong wind shear that had left part of its center of circulation exposed, per the NHC. However, I think it’s getting covered as the storm gathers strength. That’s quite impressive convection firing now:
 

NOAA

NOAA

It remains on track to bypass Bermuda, though the Bermuda Weather Service still considers it a potential threat.

Cristobal has a much better profile on the global wind map now. Check out Cristobal in the Atlantic and Maria in the Pacific:
 

As for Cristobal’s future, the NHC says:

Model guidance indicates that the
upper-level winds will become less hostile during the next day or so
as Cristobal moves underneath and then north of the aforementioned
trough, which should allow for some intensification. The NHC
forecast shows Cristobal peaking in 36-48 hours in agreement with
the latest IVCN intensity consensus. After that time, Cristobal
will be moving over cooler waters and into a higher shear
environment, which should result in the system losing tropical
characteristics in about 3 days. However, as this occurs the global
models show Cristobal moving in a favorable position for baroclinic
intensification ahead of a mid-latitude trough. This should result
in Cristobal transitioning to a powerful extratropical cyclone over
the north Atlantic late in the period.

The current wind maps show it missing both the UK and Iceland.

Update, August 25, 12:57 p.m. Pacific: Very strong wind shear has exposed the lower level of circulation, which is an amazing sight, but the rest of Cristobal seems to be going great guns at the moment.
 

NOAA

NOAA

The NHC says in its current discussion that Cristobal will become a hurricane in 48-72 hours as it passes to the west and north of Bermuda. The Bermuda Weather Service is expecting it to be a Category 1 (in line with NHC models) and calling it a potential threat.

Update, August 24, 5:25 p.m.: Wind map – compare Category 5 Maria in the East Pacific with Tropical Storm Cristobal over by the Bahamas:
 
Maria

Update, August 24, 1:21 p.m. Pacific: At 6:20 a.m. Eastern, the NHC recognized Tropical Storm Cristobal. Just now it doesn’t look at that great:
 

NOAA

NOAA

Meanwhile, I think the NHC’s five-day cone is about where the GFS is currently tracking Cristobal, but that’s not what they say in their current discussion:

five-day cone

The overall cloud pattern of Cristobal has changed little since
the previous advisory. Flight-level wind data from the Air Force
Reserve and NOAA reconnaissance aircraft investigating Cristobal
earlier this morning indicated that the low-level and mid-level
circulations were not vertically aligned, suggesting that the
inner-core wind field of the cyclone is still trying to form…

The initial motion is an uncertain 345/6 kt. There are significant
differences noted between the various NHC models. The GFS model and
the GFS ensemble mean shear the mid-level circulation southward from
the current position, and take the remaining shallow and weak
low-level circulation quickly northeastward, which seems unlikely at
this time given the overall large structure of the cyclone noted in
recon, satellite, and upper-air data. In contrast, the ECMWF, UKMET,
and NAVGEM models keep Cristobal as a deeper, stronger, and more
vertically coherent cyclone, moving the system only slowly
north-northwestward or northwestward for the next 72 hours or so as
a strong mid-latitude trough over the Carolinas lifts out to the
northeast. As the trough lifts out, the subtropical ridge is
expected to build back in to the north of Cristobal until a second
trough moves off the U.S. east coast in 4-5 days and weakens the
ridge again, allowing Cristobal to move slowly northward and then
accelerate off to the northeast. More weight has been placed the on
the ECMWF-UKMET-NAVGEM solutions, and the official forecast track
remains near the left side of the guidance envelope.

The Bermuda Weather Service says Cristobal is not a threat to Bermuda at the present time.

Update, 5 p.m., Pacific: We’ve got Tropical Depression 4, per the NHC. Head’s up, Florida (Atlantic coast), Georgia and the Carolinas:
 

Five-day warning cone.  NHC

Five-day warning cone. NHC

Here is the first forecast discussion at 5 p.m. Eastern:

000
WTNT44 KNHC 232048
TCDAT4

TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM AST SAT AUG 23 2014

The Air Force Reserve Hurricane Hunter aircraft investigating the
disturbance near the southeastern Bahamas found a well-defined
circulation this afternoon. Even though the convective presentation
is somewhat ragged, there is enough organization to classify the
system as a tropical cyclone. The intensity is set to 30 kt based
on flight level wind data from the aircraft and an earlier ASCAT
pass, and the central pressure of 1005 mb is based on a recent
surface observation from Providenciales in the Turks and Caicos. The
SHIPS model shows light to moderate shear over the cyclone for the
next couple of days, which should allow for intensification given
that the cyclone will be moving over waters of 29 to 30C. The NHC
forecast shows slow strengthening in the first 24 to 36 hours as
the cyclone organizes. Global models show more favorable upper-
level winds over the system in a couple of days, which should allow
for strengthening to a hurricane in by 3 days. The official forecast
is close to the IVCN intensity consensus through the period.

The initial motion estimate is a relatively uncertain 310/10 given
the recent formation of the center. The cyclone should continue
moving northwestward and north-northwestward into a developing break
in the subtropical ridge cause by a mid/upper-level trough off the
U.S. east coast. As the trough begins to lift out and steering
currents weaken, a slow motion is expected in 36 to 48 hours. Then
as a subtropical ridge rebuilds to the east of the cyclone later in
the period, the system is expected to turn northward and then
northeastward. However, there is significant disagreement in
the timing and sharpness of the turn in this and previous dynamical
model cycles. Currently the GFDL and GFS are along the western
edge of the guidance envelope showing a more westward track and
a slower motion at day 5. The ECMWF, GEFS mean, and HWRF show a
sharper turn and a more northeastward motion by day 5 on the east
side of the guidance envelope. The NHC forecast is near the TVCA
multi-model consensus through most of the period and a little to the
left of it at day 5. Given the spread in the guidance and the recent
formation of the system, confidence in the details of the track
forecast is lower than normal.

FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 21.8N 72.3W 30 KT 35 MPH
12H 24/0600Z 22.9N 73.6W 35 KT 40 MPH
24H 24/1800Z 24.0N 74.4W 40 KT 45 MPH
36H 25/0600Z 24.6N 74.8W 45 KT 50 MPH
48H 25/1800Z 25.0N 75.0W 55 KT 65 MPH
72H 26/1800Z 26.5N 76.0W 65 KT 75 MPH
96H 27/1800Z 29.0N 77.5W 65 KT 75 MPH
120H 28/1800Z 32.0N 76.5W 70 KT 80 MPH

$$
Forecaster Brennan

Update, August 23, 12:44 p.m.: The GFS shows this developing over the Bahamas, just kind of sitting there and intensifying – not good news to the Bahamians, if it verifies. Then it approaches and maybe makes landfall over the Atlantic coast of Florida and threatens Georgia and the Carolinas before moving out to sea. Again, this may eventually be bad news for the UK.

Here is the NHC’s current tropical weather outlook. Thus far, they haven’t even designated it a tropical depression, though it looks to me as though it’s already got good rotation and may be trying to develop an eye:
 

Amateur forecast:  I suspect the NHC will wait until a closed center of location is located, perhaps by the Hunters later this afternoon, and then will issue a special outlook by or before 8 p.m. in which we will have Cristobal.

Amateur forecast: I suspect the NHC will wait until a closed center of location is located, perhaps by the Hunters later this afternoon, and then will issue a special outlook by or before 8 p.m. in which we will have Cristobal.

Update, August 22, 5:20 p.m. Within the hour, the NHC upped the its estimate of the chances this will develop through five days to 90%. They still show it as a Bahamian threat, not touching the US mainland:

000
ABNT20 KNHC 222334
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT FRI AUG 22 2014

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

An Air Force Reserve Hurricane Hunter aircraft investigating the
area of disturbed weather near Puerto Rico and Hispaniola reported
winds of tropical storm force over the open waters north of those
islands. However, the aircraft data and surface observations
indicate that the system still lacks a well-defined surface
circulation. Another Air Force Reserve Hurricane Hunter aircraft is
scheduled to investigate the system on Saturday morning, if
necessary.

Showers and thunderstorms associated with the system are gradaully
becoming better organized, but the proximity of the system to
Hispaniola could limit development tonight. Conditions are expected
to become more conducive for development when the disturbance moves
near or over the southeastern Bahamas on Saturday. Gusty winds and
heavy rains are expected across Puerto Rico and the Virgin Islands
tonight, and over portions of Hispaniola and the southeastern and
central Bahamas tonight and Saturday. These heavy rains could cause
life-threatening flash floods and mudslides, especially in the
mountainous areas of Hispaniola and Puerto Rico. Interests in the
southeastern and central Bahamas should monitor the progress of this
disturbance, since tropical storm watches or warnings could be
required with little advance notice.
* Formation chance through 48 hours…high…80 percent.
* Formation chance through 5 days…high…90 percent.

$$
Forecaster Beven

Update, August 22, 3:56 p.m. It probably would be Cristobal, if it weren’t interacting with Hispaniola right now. Those mountains usually tear a cyclone up badly, but this system is intensifying:
 

Current loop.  Source:  NOAA.

Current loop. Source: NOAA.

Per NHC:

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
450 PM EDT FRI AUG 22 2014

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

Special outlook issued to discuss results of aircraft
reconnaissance mission.

1. Updated…An Air Force Reserve Hurricane Hunter aircraft is
continuing to investigate the area of disturbed weather moving
over and north of Puerto Rico and Hispaniola. Aircraft reports
indicate that the system is producing winds of tropical storm force
over the open waters north of those islands, although the aircraft
data and surface observations indicate that the system still lacks a
well-defined surface circulation. Given the lack of a well-defined
surface circulation, tropical cyclone advisories are not being
initiated at this time.

The overall organization of the showers and thunderstorms has been
increasing today, but the proximity of the system to Hispaniola
could limit development tonight. Conditions for development are
expected to be more conducive when the disturbance moves near or
over the southeastern Bahamas on Saturday. Gusty winds and heavy
rains are expected across Puerto Rico and the Virgin Islands
tonight, and over portions of Hispaniola and the southeastern and
central Bahamas tonight and Saturday. Interests in the southeastern
and central Bahamas should monitor the progress of this disturbance,
since tropical storm watches or warnings could be required with
little advance notice.
* Formation chance through 48 hours…high…70 percent.
* Formation chance through 5 days…high…80 percent.

The models won’t really become reliable until this system develops a closed center of circulation. This is still a system to watch carefully.

Update, August 22, 12:58 p.m. Well, this is tracking a bit further east on the GFS. NHC has also moved the track east. Right now it appears to be mostly a Bahamas threat, though the GFS does show it intensifying after its Bahamian passage. I wonder if this is going to go on and make trouble in Britain.
 

National Hurricane Center

National Hurricane Center


 

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT FRI AUG 22 2014

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

1. Shower and thunderstorm activity has increased during the past few
hours in association with a small area of low pressure located just
north of the Mona Passage between Puerto Rico and the Dominican
Republic. Satellite wind data and preliminary reports from an Air
Force Reserve Hurricane Hunter aircraft indicate that the
circulation associated with the low is poorly defined. Some
additional development of this system is possible today, but
environmental conditions are expected to be more conducive for the
development of a tropical depression or tropical storm when the
disturbance moves near or over the southeastern Bahamas on Saturday.
Regardless of whether the system becomes a tropical cyclone, gusty
winds and heavy rainfall are expected across Puerto Rico and the
Virgin Islands today, and over portions of Hispaniola and the
southeastern and central Bahamas tonight and Saturday. Interests in
the southeastern and central Bahamas should monitor the progress of
this disturbance, as tropical storm watches or warnings could be
required with short notice.
* Formation chance through 48 hours…high…70 percent.
* Formation chance through 5 days…high…80 percent.

Forecaster Brennan

five day outlook

Update, August 21, 1:34 p.m Pacific: The NHC issued this within the hour:

Tropical Weather Outlook Text

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
400 PM EDT THU AUG 21 2014

Updated for reconnaissance information

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

1. Data from an Air Force Reserve Hurricane Hunter aircraft indicate
that the circulation associated with the small low pressure area
approaching the Leeward Islands is poorly defined. In addition, the
associated shower activity has decreased during the past few hours.
The aircraft did, however, find a small area of tropical-storm-force
winds on the northeast side of the low. Environmental conditions
are expected to be conducive for some development during the next
day or so, and a tropical depression or tropical storm could still
form while the system moves west-northwestward at around 20 mph
across the Lesser Antilles. The mountainous terrain of Hispaniola
could limit development during the first part of the weekend, but
conditions are expected to become more conducive for development by
Sunday when the system is forecast to move near or over the Bahamas.
Regardless of tropical cyclone formation, gusty winds and heavy
rainfall are expected across portions of the Lesser Antilles, Puerto
Rico, and the Virgin Islands through Friday, and over Hispaniola
late Friday and Saturday. Interests in those islands and in the
Bahamas should closely monitor the progress of this disturbance. An
Air Force Reserve Hurricane Hunter aircraft is scheduled to
investigate this system again tomorrow afternoon.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…high…70 percent.

Forecaster Brennan/Blake

h/t to James Reynolds for this – I hadn’t found it on the NHC site

Update, August 21, 12:44 p.m. Pacific: The GFS looks a lot better today, showing the disturbance further east. It appears to end up over the Bahamas for a while, intensifies five days from now (hoodooland – it’s a computer model), but then turns out to sea. Will see how that pans out.

Here is the current NHC tropical outlook:

000
ABNT20 KNHC 211750
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 21 2014

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

Satellite data indicate that an area of low pressure located about
275 miles east of Guadeloupe has become a little better defined
today. However, the associated shower and thunderstorm activity
remains limited and disorganized. Environmental conditions are
expected to be conducive for some development during the next day or
so, and a tropical depression could form while the system moves
west-northwestward at around 20 mph across the Lesser Antilles. The
mountainous terrain of Hispaniola could limit development during the
first part of the weekend, but conditions are expected to become
more conducive for development by Sunday when the system is
forecast to move near or over the Bahamas. Regardless of tropical
cyclone formation, gusty winds and heavy rainfall are possible
across portions of the Lesser Antilles, Puerto Rico, and the Virgin
Islands through Friday, and over Hispaniola late Friday and
Saturday. Interests in those islands and in the Bahamas should
closely monitor the progress of this disturbance. An Air Force
Reserve Hurricane Hunter aircraft is currently investigating the
system.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…high…70 percent.

Keeping my fingers crossed that this one remains harmless…

Update, August 20, 12:42 p.m. Pacific: The GFS run today shows the storm still developing but further to the east…over Florida. Again, at this point the model is so far advanced that you just can’t rely on it. Still, it’s well worth your while to keep an eye on the tropical Atlantic for the next week to ten days, especially if you live in Florida or the eastern Gulf coast.

Lynne, one of the last things I said before you headed to Florida was “Mind the hurricanes.” Doubt you’ll see this post, but if you do, and if the GFS run verifies…told ya so.

OK, here is the relevant part of the NHC’s latest tropical weather outlook (emphasis added):

000
ABNT20 KNHC 201749
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT WED AUG 20 2014

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

Shower and thunderstorm activity associated with an elongated area
of low pressure located several hundred miles east of the Windward
Islands has become a little better organized during the past few
hours. Additional slow development of this system is possible during
the next day or two, and a tropical depression could form as the
system moves west-northwestward at 10 to 15 mph across the Lesser
Antilles and into the Caribbean Sea. After that time, land
interaction could limit development potential over the weekend.
Regardless of tropical cyclone formation, gusty winds and heavy
rainfall are possible across portions of the Lesser Antilles, Puerto
Rico, and the Virgin Islands on Thursday night and Friday. Interests
in those islands should closely monitor the progress of this system.

An Air Force Reserve Hurricane Hunter aircraft is scheduled to
investigate this system tomorrow afternoon, if necessary.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…high…60 percent.

Per Jeff Masters today, this system has managed to moisten its environment despite lots of dry air nearby – quite an impressive accomplishment this early in the cycle, at least in an amateur’s opinion.

The GFS takes the system, still undeveloped, over the mountains of Hispaniola, where interactions with land will really do a number on it. This may be on Saturday. There will also be a lot of dry air over the Caribbean to further keep it weak. However, I see the system then intensifying quickly, per the GFS run, after it gets into the Florida straits and heading right up the Florida peninsula.

That’s hoodooland, though. We’ll take this day by day and see how it goes.

Update, August 19, 4:51 p.m. Pacific: The 8 p.m. NHC tropical outlook notes:

000
ABNT20 KNHC 192334
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE AUG 19 2014

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

Disorganized shower and thunderstorm activity continues in
association with an elongated area of low pressure that extends from
the northeastern coast of South America into the central tropical
Atlantic. Environmental conditions are forecast to be more conducive
for gradual development of this system during the next few days as
it approaches the Lesser Antilles and moves into the Caribbean Sea.
* Formation chance through 48 hours…medium…30 percent.
* Formation chance through 5 days…medium…50 percent.

Jeff Masters said in his earlier post today that the Hurricane Hunters are on call to check this possible system out on Thursday.

I saw a news report earlier this month that the Hunters are having planes retrofitted with more modern equipment. Wonder if and how that will affect missions into this storm.

 


 

The current run of the GFS shows a tropical system forming close to the Lesser Antilles soon. This run, if you follow it out into hoodooland, shows the system crossing the Antilles and entering the northern Caribbean in 72 hours, and eventually crossing western Cuba and entering the Gulf. That far out, for a storm that hasn’t even developed yet, a model can’t be relied on. However, it would be a good idea to keep a close watch on this one.

If it does form, if will be Cristobal.

Per the National Hurricane Center today:

 
000
ABNT20 KNHC 191742
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE AUG 19 2014

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

Disorganized shower and thunderstorm activity continues in
association with an elongated area of low pressure that extends from
the northeastern coast of South America into the central tropical
Atlantic. Environmental conditions are forecast to be more conducive
for gradual development of this system during the next few days as
it approaches the Lesser Antilles and moves into the Caribbean Sea.
* Formation chance through 48 hours…medium…30 percent.
* Formation chance through 5 days…medium…40 percent.

Per Dr. Jeff Masters, it’s a threat to develop:

The wave should pass through the Lesser Antilles Islands Thursday night or Friday morning, then track west to west-northwest through the Caribbean a few hundred miles south of Puerto Rico. The 12Z Tuesday run of the GFS and European models showed 96L tracking through the Central Caribbean early next week, and arriving in the Western Caribbean on Tuesday. The UKMET model showed a more northerly component of motion, with a path over Hispaniola. Two of our three reliable models for predicting tropical cyclone genesis, the UKMET and GFS models, predicted that 96L would develop into a tropical storm after passing through the Lesser Antilles. When both of these models show development, the odds increase that development will occur. The UKMET model showed 96L developing on Saturday, and the GFS showed it developing on Friday. Given the presence of so much dry air near the disturbance, the risk of development is low through Wednesday, but development odds will increase on Thursday as ocean temperatures warm and the atmosphere becomes moister.



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