Tropical Weather Update – October 17, 2019

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Tropical Weather Outlook

NWS National Hurricane Center Miami FL

800 AM EDT Thu Oct 17 2019

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

1. Showers and thunderstorms associated with a broad area of low

pressure located over the southwestern Gulf of Mexico continue to

show signs of organization.  Environmental conditions are expected

to be conducive for additional development, and a tropical or

subtropical storm is likely to form later today or tonight while the

system moves generally northeastward over the western Gulf of

Mexico.  The low is forecast to approach the northern or

northeastern Gulf Coast on Friday or Saturday and regardless of

development, the system is likely to produce gusty winds and rough

surf over those areas.  Locally heavy rainfall is also possible

across portions of the southeast U.S. late this week and this

weekend. Interests along the northern and northeastern Gulf coast

should monitor the progress of this system.  For more information

about marine hazards while the low moves across the Gulf of Mexico,

see products issued by the Tropical Analysis and Forecast Branch of

the National Hurricane Center. An Air Force Reserve reconnaissance

aircraft is scheduled to investigate the system this afternoon, if

necessary.

* Formation chance through 48 hours…high…80 percent.

* Formation chance through 5 days…high…80 percent.

High Seas Forecasts issued by the National Weather Service

can be found under AWIPS header NFDHSFAT1, WMO header FZNT01

KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

Offshore Waters Forecasts for the Gulf of Mexico issued by the

National Weather Service can be found under AWIPS header MIAOFFNT4,

WMO header FZNT24 KNHC, and online at

www.hurricanes.gov/text/MIAOFFNT4.shtml

Weather Outlook – Monday, October 7, 2019

Wind Fields Friday

 

Tropical Weather Outlook

NWS National Hurricane Center Miami FL

200 PM EDT Mon Oct 7 2019For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. A non-tropical low pressure system located over the central Atlantic

Ocean between Bermuda and the Azores is producing gale-force winds

to the north of its center.  Environmental conditions are forecast

to be generally conducive for the low to acquire some subtropical or

tropical characteristics during the next day or two, and this system

could become a tropical or subtropical storm on Tuesday or Wednesday

while it moves slowly westward.  Upper-level winds are expected to

become unfavorable for further development by Wednesday night.

Additional information on this system can be found in High Seas

Forecasts issued by the National Weather Service.

* Formation chance through 48 hours…medium…50 percent.

* Formation chance through 5 days…medium…50 percent.

2. Showers and thunderstorms located over the western Atlantic

between the southeastern coast of the United States and Bermuda

are associated with a trough of low pressure.  This system is

forecast to move northwestward and a non-tropical low pressure area

is expected to form when the system interacts with a frontal

boundary in a couple of days.  The low could acquire some

subtropical characteristics later in the week while it meanders

off the east coast of the United States.  Additional information on

this system can also be found in High Seas Forecasts issued by the

National Weather Service.

* Formation chance through 48 hours…low…near 0 percent.

* Formation chance through 5 days…low…30 percent.

3. A trough of low pressure extending from the Straits of Florida

northeastward across the southern Florida peninsula is producing

disorganized showers and thunderstorms.  Some slight development of

this system is possible on Tuesday when it moves over the far

western Atlantic.  The disturbance is forecast to merge with a

frontal boundary and developing low off the east coast of the

United States by Wednesday, and no further development is

anticipated after that time.  Regardless of development, this system

is expected to produce locally heavy rainfall over portions of the

the southern Florida peninsula during the next day or so.

* Formation chance through 48 hours…low…10 percent.

* Formation chance through 5 days…low…10 percent.

High Seas Forecasts issued by the National Weather Service

can be found under AWIPS header NFDHSFAT1, WMO header FZNT01

KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

Tropical Update – September 24, 2019

Tropical Storm Karen Discussion Number   9

NWS National Hurricane Center Miami FL       AL122019

500 AM AST Tue Sep 24 2019

During the last pass through Karen’s center around 0430 UTC, the Air

Force reconnaissance aircraft reported some believable SFMR winds of

34-35 kt in the southeastern quadrant and an extrapolated central

pressure of 1006 mb. The 925-mb flight-level height had also

decreased by almost 20 meters in about 2 hours, an indication that

the lower pressure estimate was legitimate. Reflectivity and

velocity data from the San Juan NOAA WSR-88D Doppler radar also

enunciate that Karen’s inner-core has become better defined over

the past few hours. Satellite intensity estimates at 0600 UTC were

T2.5/35 kt from TAFB, and T2.4/34 kt and 40 kt from UW-CIMSS ADT and

SATCON, respectively. Based on the recon and satellite intensity

data, Karen has re-strengthened to tropical storm status.

The initial motion is now northward or 360/06 kt. Karen’s forecast

track hinges heavily on the future intensity and associated vertical

structure of the cyclone. The GFS, GFS-Legacy, UKMET, and HRWF

dynamical models take a much weaker and more vertically shallow

cyclone northeastward after 48 hours and either continue with that

motion through day 5 or dissipate the system. In contrast, the ECMWF

and many of its stronger ensemble members stall Karen around days

3-4 and then turn the somewhat stronger and deeper cyclone westward

to west-southwestward to the south of a building ridge. Given that

Karen is forecast to be stronger and vertically deeper than the

weaker models, the current track forecast leans more toward the

stronger ECMWF and ECMWF-Ensemble model solutions. The new NHC

forecast is to the right of the previous advisory track and slower,

especially on days 3-5, but the new track does not extend as far

east as the weaker GFS, UKMET, and HWRF models or the consensus

models that incorporate those three models.

None of the dynamical models, including the HWRF and HMON hurricane

models, show much in the way of strengthening once Karen moves

north of Puerto Rico and Virgin Islands except for the ECMWF model,

despite the very low vertical wind shear conditions that the cyclone

will be moving into by 24 hours and beyond. Given Karen’s decent

wind field and vertical structure, the expected low shear

conditions, moist mid-level environment, and SSTs of more than 29

deg C for the next 48 hours or so, forecasting at least slow but

steady strengthening seems to be quite reasonable. By days 3-5, the

mid-level environment dries out significantly, which the weaker

models seem to be keying on. However, if Karen strengthens as

currently expected, then the cyclone’s robust circulation should

be able to mix out any dry air intrusions, allowing for at least

additional modest intensification to occur in the 72-120 hour

period. The official intensity forecast is a little above the

previous advisory, and is basically an average of the weaker

dynamical models and the stronger GFS- and ECMWF-based

statistical-dynamical models Decay-SHIPS and LGEM.

Key Messages:

1.  Karen is expected to bring heavy rainfall, flash floods and

mudslides to Puerto Rico and the U.S. and British Virgin Islands

today, where a tropical storm warning is in effect.  The rainfall

and potential flooding will likely continue on Wednesday even as the

center of Karen moves away from Puerto Rico and the Virgin Islands.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 16.8N  65.8W   35 KT  40 MPH

12H  24/1800Z 18.1N  65.9W   35 KT  40 MPH

24H  25/0600Z 20.1N  65.5W   40 KT  45 MPH

36H  25/1800Z 22.6N  64.7W   45 KT  50 MPH

48H  26/0600Z 24.6N  64.0W   50 KT  60 MPH

72H  27/0600Z 27.3N  62.7W   55 KT  65 MPH

96H  28/0600Z 28.0N  63.0W   60 KT  70 MPH

120H  29/0600Z 27.7N  65.5W   60 KT  70 MPH

Tropical Update – September 19, 2019

Tropical Weather Outlook

NWS National Hurricane Center Miami FL

800 AM EDT Thu Sep 19 2019

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

The National Hurricane Center is issuing advisories on Hurricane

Humberto, located several hundred miles northeast of Bermuda,

and on Tropical Storm Jerry, located several hundred miles east of

the Leeward Islands.

1. A tropical wave located about 1000 miles west of the Cabo Verde

Islands is producing disorganized cloudiness and showers. Some

development of this system is possible while the system approaches

the Windward Islands this weekend or when it moves across the

eastern Caribbean Sea early next week.

* Formation chance through 48 hours…low…near 0 percent.

* Formation chance through 5 days…low…30 percent.

2. An elongated area of low pressure associated with a tropical wave

is located just south of the Dominican Republic. Although

upper-level winds are not conducive for significant development,

thunderstorm activity has become more concentrated since yesterday.

Some slight development is still possible before the system begins

to interact with the high terrain of Hispaniola. Regardless of

development, locally heavy rainfall is possible over portions of the

Dominican Republic and Haiti during the next day or two. The

disturbance is forecast to move slowly northwestward through the

weekend.

* Formation chance through 48 hours…low…10 percent.

* Formation chance through 5 days…low…10 percent.

3. A tropical wave is forecast to move off the west coast of Africa in

a few days. Environmental conditions are expected to be conducive

for at least gradual development thereafter while the system moves

westward over the far eastern tropical Atlantic.

* Formation chance through 48 hours…low…near 0 percent.

* Formation chance through 5 days…low…20 percent.

 

Tropical Storm Jerry – September 18, 2019

TS Jerry has formed in the Atlantic and looks like based on the official forecast that most land masses will be missed. At the end of five days the NHC forecast has TS Jerry turning and may not pose a threat to the US Coast. Still a long way out, so keep watching.

Tropical Storm Jerry Discussion Number   5

NWS National Hurricane Center Miami FL       AL102019

1100 AM AST Wed Sep 18 2019

Satellite images indicate that Jerry continues to become better

organized, with a large curved band wrapping around the center.

While microwave data does not show an inner core yet, the overall

satellite presentation has improved during the past several hours.

The initial wind speed is set to 45 kt, which closely matches

almost all of the available Dvorak estimates and a just-arrived

ASCAT-C scatterometer pass.

Further intensification of Jerry is expected during the next day or

two as the cyclone moves over very warm waters within light shear.

While this type of environment could support even more

strengthening than forecast, there is some substantial dry air

around the cyclone, which is forecast to limit the intensification

rates for now.  This forecast leans heavier on the regional

hurricane models HWRF, HMON and COAMPS-TC, which all show a weaker

cyclone than the statistical/dynamical LGEM and SHIPS models.

Most of the guidance shows increasing shear in a couple of days, and

the shear could become somewhat strong by next week.  While little

change in strength is indicated beyond Friday, this usually doesn’t

happen in reality, and further changes will be necessary as the

environmental factors become more clear.

The initial motion continues to be west-northwestward, or 290/12

kt.  The subtropical ridge to the north should steer Jerry at a

faster forward speed for the next couple of days.  Afterward, a

northwest to north-northwestward turn, influenced by a weakness in

the aforementioned ridge left behind by Humberto, is expected. The

NHC track forecast is basically an update from the previous advisory

and lies on the left side of the guidance suite, nearest the ECMWF

model and the corrected-consensus forecasts.

Key Messages:

1. Jerry is expected to strengthen and be a hurricane when it moves

near the northern Leeward Islands Friday, although it is too soon to

determine the direct impacts to the islands. Interests there should

ensure they have their hurricane plan in place and monitor the

progress of this system.  Watches could be issued for a portion of

this area this afternoon or evening.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 14.6N  49.2W   45 KT  50 MPH

12H  19/0000Z 15.3N  51.0W   55 KT  65 MPH

24H  19/1200Z 16.3N  53.7W   60 KT  70 MPH

36H  20/0000Z 17.3N  56.5W   65 KT  75 MPH

48H  20/1200Z 18.4N  59.5W   65 KT  75 MPH

72H  21/1200Z 20.5N  65.3W   65 KT  75 MPH

96H  22/1200Z 23.3N  69.1W   65 KT  75 MPH

120H  23/1200Z 26.5N  70.5W   60 KT  70 MPH

 

Tropical Depression #10 – September 17, 2019

Weekly_Outlook (2)

 

Tropical Depression Ten Discussion Number   1

NWS National Hurricane Center Miami FL       AL102019

1100 AM AST Tue Sep 17 2019

Deep convection associated with the area of low pressure over the

central Atlantic has become more persistent and better organized

this morning.  Data T-numbers from both SAB and TAFB are 2.0 on the

Dvorak scale, therefore advisories are being initiated on a tropical

depression.  The initial intensity is set at 30 kt, in line with the

satellite estimates.  The depression is forecast to move over

gradually increasing sea surface temperatures within a favorable

upper-level environment.  The only negative factor for

intensification appears to be some nearby dry air, but with low

shear conditions expected, so steady strengthening is forecast

during the next several days.  The NHC forecast calls for the

depression to become a tropical storm later today, and attain

hurricane status within 72 hours. The NHC intensity forecast is in

good agreement with the SHIPS and LGEM statistical models.

Since the depression is still in the development phase, the initial

motion is a somewhat uncertain 295/10 kt.  A strong deep-layer

ridge to the north of the cyclone should steer the depression

generally west-northwestward at a faster forward speed during the

next few days.  The track guidance is in relatively good agreement

through 72 hours, and brings the cyclone near the northern Leeward

Islands in about 3 days.  By late in the period, the cyclone is

expected to reach the western periphery of the ridge, and there is

increasing spread among the guidance.  The global model ensemble

means are along the right side of the envelope while the HWRF and

UKMET are along the left side.  The NHC track lies close the

consensus aids, which is also in good agreement with the latest

ECMWF.

Interests in the northern Leeward Islands should monitor the

progress of this system.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 12.9N 44.9W  30 KT  35 MPH

12H  18/0000Z 13.8N 46.1W  35 KT  40 MPH

24H  18/1200Z 14.7N 47.9W  40 KT  45 MPH

36H  19/0000Z 15.5N 50.2W  45 KT  50 MPH

48H  19/1200Z 16.3N 52.9W  55 KT  65 MPH

72H  20/1200Z 18.2N 59.2W  65 KT  75 MPH

96H  21/1200Z 20.2N 64.7W  75 KT  85 MPH

120H  22/1200Z 22.5N 69.0W  80 KT  90 MPH

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