Tropical Storm Philippe

Tropical Storm Philippe Track 1700 Hours October 29 2017
Tropical Storm Philippe Track 1700 Hours October 29 2017
Tropical Storm Philippe Satellite 1400 Hours October 29 2017
Tropical Storm Philippe Satellite 1400 Hours October 29 2017

NWS National Hurricane Center Miami FL 500 PM EDT Sun Oct 29 2017  (7:00 AM video below)

During the past few hours, strong vertical wind shear in excess of 50 kt, plus merger with a cold front, has taken its toll on Philippe’s previously well-defined low-level circulation. The system has become elongated north-to-south within the frontal zone, and a new low-level center may have developed about 150 nmi farther north along the frontal boundary near NOAA buoy 41002. Now that Philippe has lost any tropical or subtropical characteristics due to merger with a synoptic-scale cold front, the system is declared to have dissipated.

Much of the latent heat and deep convection associated with Philippe’s remnants will likely be drawn into a larger extratropical low pressure that is developing near the outer banks of North Carolina, aiding in that intensification process. Although the developing powerful low near the Outer Banks is not directly
associated with Philippe, interests along the mid-Atlantic and southern New England coasts should closely monitor forecast products issued by the NOAA Weather Prediction Center, NOAA Ocean Prediction Center, and your local National Weather Service forecast office.

FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 31.0N 75.0W 50 KT 60 MPH
12H 30/0600Z…ABSORBED BY FRONTAL SYSTEM

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Previous Warning  1100 AM EDT Sun Oct 29 2017

Philippe looks the best it ever has, possessing a well-defined low-level center as seen in high-resolution GOES-16 visible imagery, along with at least 45-kt sustained winds based on several recent ship reports. However, the cyclone is sheared with the bulk of the convective cloud shield having been displaced northeast of the center due to southwesterly mid-/upper-level winds of 45-75 kt.

Although the exact center of Philippe was difficult to track overnight, the current position is actually on the previous forecast track. Philippe has been moving due east at about 25-27 kt for the past few hours. However, the NHC model guidance is in decent agreement that the cyclone will turn toward the northeast by this afternoon ahead of an approaching frontal system and a powerful deep-layer trough moving quickly eastward across the eastern Gulf of Mexico and Florida. The cold front is currently located only 90-100 nmi west of Philippe’s center, and merger with the front along with transition to a extratropical low pressure system is expected by 12 hours, if not sooner. As the aforementioned trough becomes more negatively tilted over the next 24 hours, a strong extratropical low is forecast to develop near or just east of the North Carolina Outer Banks, pulling Philippe’s circulation north-northeastward to northward in the 12-24-hour period well offshore of the U.S east coast. Absorption of Philippe’s circulation into the larger extratropical low is expected to be completed by 24 hours when the larger low is located over New England. The official forecast track lies to the right of the previous advisory track, mainly due to the recent eastward jog, and lies along the eastern edge of the guidance envelope near a blend of the HCCA and TVCN consensus models.

Some additional slight strengthening is possible during the next 12 hours or so, mainly due weak baroclinic forcing and the faster forward speed that is forecast. However, most of the baroclinic energy associated with the negatively tilted mid-latitude trough is expected to remain to the west, triggering the development of the above-mentioned significant extratropical coastal low. In fact, some of the latent heat from Philippe’s circulation will likely get drawn into the larger extratropical low developing to its northwest, aiding in that intensification process and increasing the demise of Philippe after 12 hours.

FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 27.8N 77.5W  50 MPH (NE of Vero Beach, FL)
12H 30/0000Z 32.5N 72.5W 60 MPH (E of Charleston SC)
24H 30/1200Z…ABSORBED BY LARGER EXTRATROPICAL LOW

Previous Warning 500 PM EDT Sat Oct 28 2017

…DEPRESSION STRENGTHENS INTO TROPICAL STORM PHILIPPE…
…HEAVY RAINS OCCURRING OVER CENTRAL AND WESTERN CUBA AND SPREADING
NORTHWARD ACROSS THE FLORIDA KEYS AND SOUTH FLORIDA…

Satellite images, radar data from Cuba and Key West, and surface observations indicate the depression has turned northward over the past few hours, and has also strengthened into a tropical storm. The initial intensity of 35 kt is based on a surface observation of 35 kt in a brief squall from Grand Cayman at 1444Z, a recent AMSU estimate of 37 kt, and average Key West Doppler radar velocities of 40 kt between 10,000-12,000 ft just north of the Cuban coast; the latter data equates to an approximate surface wind speed of 36 kt.

The initial motion estimate is now 355/25 kt based on radar data and high-resolution GOES-16 visible satellite imagery over the past 2-3 hours. The low-level wind flow pattern for the next 6 hours or so is forecast to be complex, with a new non-tropical surface low having recently formed about 100 nmi west of Key West, Florida. This feature appears to have developed beneath an upper-level jet entrance region ahead of an approaching cold front. The global, regional, and even the convective-scale models are now showing the center of Philippe moving general northward across the Straits of Florida this evening and merging with the non-tropical low around 0000Z. After the merger over Florida Bay, the various models are in good agreement on Philippe moving northeastward to east-northeastward across extreme southern Florida or the Florida Keys overnight as the cyclone is accelerated ahead of the aforementioned frontal system and strong mid-/upper-level trough.

After reaching the northwestern Bahamas by 1200Z Sunday morning, Philippe is forecast to accelerate further towards the northeast at forward speeds of 30-35 kt, by Sunday afternoon and evening, remaining well offshore of the Carolinas. By 36 hours, Philippe is expected to pass about midway between Bermuda and the southeastern United States, and gradually getting pulled north-northeastward up the east side of a powerful baroclinic low that is forecast to develop near Cape Hatteras and move northward near the U.S. east coast. The NHC track guidance is in reasonable agreement on this developing track scenario, and lies between the GFS model, which takes Philippe across the Florida Keys, and the ECMWF model, which moves the cyclone farther north over South Florida.

The vertical wind shear affecting Philippe is expected to remain favorable for strengthening to occur for the next 24 hours, along with an additional baroclinic boost from the aforementioned upper-level jet maximum. By 36 hours, strong baroclinic forcing associated with the approaching frontal system are forecast to induce additional strengthening before the cyclone merges with the frontal system and becomes an extratropical low by 48 hours. Dissipation or absorption by a larger extratropical low is expected by 72 hours when the system is located over the cold waters of the North Atlantic.

KEY MESSAGES:

1. Although the center of Philippe is now forecast to move across the Florida Keys or extreme south Florida, most of the strongest winds are expected to remain east and southeast of the center. However, tropical-storm-force winds, mainly in gusts, could occur in brief heavy squalls across the upper Florida Keys and southeast Florida overnight. For that reason, a tropical storm watch remains in effect for these areas.

2. Regardless of the exact track of Philippe, the primary threat from this system will be heavy rainfall that can cause localized flooding across portions of Cuba, the Florida Keys, and South Florida.

FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 23.0N 82.6W 40 MPH (SE of Playa Baracoa, Cuba)
12H 29/0600Z 26.0N 80.1W 50 MPH (E of Hollywood Beach, FL)
24H 29/1800Z 31.5N 75.3W 60 MPH (SE of Hilton Head Island, SC)
36H 30/0600Z 36.6N 70.5W 65 MPH (E of Virginia Beach, VA)
48H 30/1800Z 42.0N 66.0W 60 MPH (E of Provincetown, MA)
72H 31/1800Z…DISSIPATED

Previous Warning 200 PM EDT Sat Oct 28 2017

…TROPICAL DEPRESSION PRODUCING HEAVY RAINS ACROSS CENTRAL CUBA
AND SPREADING NORTHWARD OVER THE FLORIDA KEYS AND SOUTH FLORIDA…

SUMMARY OF 200 PM EDT…1800 UTC…INFORMATION
———————————————-
LOCATION…21.8N 82.4W
ABOUT 30 MI…45 KM ENE OF THE ISLE OF YOUTH
ABOUT 80 MI…130 KM S OF HAVANA CUBA
MAXIMUM SUSTAINED WINDS…35 MPH…55 KM/H
PRESENT MOVEMENT…NNE OR 20 DEGREES AT 25 MPH…41 KM/H
MINIMUM CENTRAL PRESSURE…1005 MB…29.68 INCHES

OUTLOOK
——————————
At 200 PM EDT (1800 UTC), the center of Tropical Depression Eighteen was located by weather radars from Cuba and Grand Cayman near latitude 21.8 North, longitude 82.4 West. The depression is moving toward the north-northeast near 25 mph (41 km/h) and this motion is expected to continue today. A motion toward the northeast with an increase in forward speed is expected to begin tonight and continue through Sunday. On the forecast track, the center will move across west-central Cuba this afternoon and evening, across the Straits of Florida and near the Florida Keys overnight, and across the northwestern Bahamas Sunday morning.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast during the next 48 hours, and the depression is expected to become a tropical storm overnight.

The estimated minimum central pressure is 1005 mb (29.68 inches).

Previous Warning  1100 AM EDT Sat Oct 28 2017 

Data from an Air Force Reserve reconnaissance aircraft indicate that the low pressure system located over the northwestern Caribbean Sea has developed a well-defined low-level circulation center. Satellite imagery also shows more central deep convection has developed and persisted in the inner-core region since yesterday. Based on these data, the disturbance has been upgraded to Tropical Depression Eighteen.

With the recent redevelopment of the inner-core region this morning, the initial motion estimate is an uncertain 020/19 kt. The global models remain in excellent agreement on an approaching frontal system and deep mid-tropospheric trough accelerating the cyclone north-northeastward across west-central Cuba today, followed by a motion toward the northeast tonight and Sunday, with the system passing about midway between Bermuda and the southeastern United States in 36-48 hours. The new NHC forecast track is essentially just an update of the previous advisory due to the good agreement in the global and consensus models, which lie along or just a tad to the west of the official forecast track.

The vertical wind shear affecting the cyclone is expected to remain somewhat favorable for strengthening to occur for the next 24 hours or so, with the depression expected to become a tropical storm by tonight. Thereafter, baroclinic processes associated with the aforementioned frontal system are forecast to induce some additional strengthening before the cyclone merges with the frontal system and becomes an extratropical low by 48 hours. Dissipation is expected by 72 hours when the system is located over the far North Atlantic.

KEY MESSAGES:

1. While the forecast track of the center lies about 35 miles southeast of the Upper Florida Keys and extreme southeast Florida and most of the winds are expected to remain east of the center, only a slight deviation to the west of the expected track or an increase in the size of the wind field could bring tropical-storm- force winds across these land areas. For that reason, a tropical storm watch has been issued for these areas.

SITUATION OVERVIEW
——————
Tropical depression eighteen in the western Caribbean Sea will continue to move north northeast and likely become Tropical Storm Philippe as it moves into the outer Straits of Florida late today and then offshore of the southeast Florida east coast early Sunday morning.

FORECAST POSITIONS AND MAX WINDS

INIT 28/1500Z 20.8N 82.9W 35 MPH (S of Nueva Gerona, Cuba)
12H 29/0000Z 23.0N 81.8W 40 MPH (W of Matanzas, Cuba)
24H 29/1200Z 26.6N 78.5W 45 MPH (NE of Freeport, Bahamas)
36H 30/0000Z 31.5N 74.0W 50 MPH (SE of Hilton Head Island, SC)
48H 30/1200Z 37.5N 69.5W 60 MPH (E of Virginia Beach. VA)
72H 31/1200Z…DISSIPATED

Previous Warning 200 AM EDT Sat Oct 28 2017

SUMMARY OF 200 AM EDT…0600 UTC…INFORMATION
———————————————-
LOCATION…18.9N 84.6W
ABOUT 220 MI…355 KM SSW OF THE ISLE OF YOUTH
ABOUT 330 MI…530 KM SSW OF HAVANA CUBA
MAXIMUM SUSTAINED WINDS…35 MPH…55 KM/H
PRESENT MOVEMENT…N OR 360 DEGREES AT 7 MPH…11 KM/H
MINIMUM CENTRAL PRESSURE…1005 MB…29.68 INCHES

DISCUSSION AND 48-HOUR OUTLOOK

——————————
At 200 AM EDT (0600 UTC), the disturbance was centered near latitude 18.9 North, longitude 84.6 West. The system is moving toward the north near 7 mph (11 km/h). An acceleration toward the northeast is expected to begin later today and continue through Sunday. On the forecast track, the system will move across western Cuba later today and move through the northwestern Bahamas tonight and early Sunday.

Satellite-derived wind data indicated that maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast during the next 48 hours, and the system is expected to become a tropical storm later today. Formation chance through 48 hours, high, 80 percent
Formation chance through 5 days, high, 80 percent.

Previous Warning 500 PM EDT Fri Oct 27 2017 

 Aircraft investigating the disturbance over the northwestern Caribbean Sea indicate that the system does not yet have a well-defined center. In fact, the aircraft data and satellite imagery suggest that there are multiple circulations embedded within a broader circulation at this time. Given the lack of a well-defined center, the system is not a tropical cyclone, but since tropical storm conditions are expected to affect Cuba and the northwestern Bahamas in the next 24 to 36 hours, advisories are being initiated on the system as a potential tropical cyclone at this time.

The initial intensity is set to 35 kt based on aircraft data, with these winds found well south of the broad circulation center. However, NOAA buoy 42057 also reported a peak 1-minute wind of 31 kt earlier today. Aircraft data suggest that the central pressure is around 1006 mb. The system is situated in a low-shear environment and over warm waters, so some slow strengthening is expected in the first 24 hours before the system reaches Cuba. The official forecast follows the trend of the intensity consensus in showing a peak of around 45 kt at 36 and 48 hours before the system is absorbed by an approaching cold front in 60-72 hours.

Given the lack of a well-defined center, the initial position is and the initial motion of 330/05 are highly uncertain. A faster northward motion should begin soon as the disturbance begins to recurve ahead of an approaching mid/upper-level trough moving into the southeastern United States. This trough should cause a faster northeastward acceleration at 24 through 48 hours. The track model guidance is in generally good agreement on the overall scenario, with more along than cross track spread. The NHC forecast leans toward a blend of the ECMWF and GFS models and is a little slower than the current multi-model consensus. Not surprisingly, given the disorganized initial state of the system, the track forecast uncertainty is larger than usual.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 17.5N 84.5W 40 MPH – (E of Belize City, Belize)
12H 28/0600Z 19.1N 84.1W 40 MPH  – (W of Cayman Islands)
24H 28/1800Z 21.7N 82.4W 45 MPH  – (N of Cayos Boca de Alonso, Cuba)
36H 29/0600Z 24.6N 79.6W 50 MPH  – (E of Marathon, Florida)
48H 29/1800Z 28.0N 75.5W 50 MPH  – (SE of Melbourne, Florida)

Previous Warning 200 PM EDT Fri Oct 27 2017

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 northwestern Caribbean Sea are beginning to show signs of organization. Environmental conditions are expected to be conducive for additional development, and a tropical depression or tropical storm is likely to form later today or Saturday as the system moves northward over the northwestern Caribbean Sea before turning northeastward by late Saturday. Tropical storm watches and warnings may be needed for the Cayman Islands, central and western Cuba, and the central and northwestern Bahamas later today or tonight. Interests in the Florida Keys and South Florida should also monitor the progress of this disturbance. An Air Force Reserve reconnaissance aircraft is en route to investigate this system.

Regardless of development, this disturbance is expected to produce locally heavy rainfall over the Cayman Islands, Jamaica, and portions of Cuba during the next day or two. Rainfall is also forecast to spread northward across portions of South Florida and the Keys on Saturday, and over the northwestern and central Bahamas Saturday night and Sunday. Formation chance through 48 hours, high, 80 percent. Formation chance through 5 days, high, 80 percent.

Previous Warning 800 AM EDT Fri Oct 27 2017

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

1. Shower and thunderstorm activity has increased and become more concentrated in association with a trough of low pressure over the northwestern Caribbean Sea. Environmental conditions are expected to be conducive for development today and Saturday, and a tropical depression could form as the system moves northward over the northwestern Caribbean Sea. Increasing upper-level winds will make conditions less favorable when the system moves north of Cuba and merges with a cold front on Sunday. Interests in the Cayman Islands and central and western Cuba should monitor the progress of this system. Regardless of development, this disturbance is expected to produce locally heavy rainfall over the Cayman Islands, Jamaica, and portions of Cuba during the next day or two. These rains are forecast to spread northward across portions of South Florida and the Keys on Saturday, and over the northwestern Bahamas Saturday night and Sunday. An Air Force Reserve reconnaissance aircraft is scheduled to investigate this system this afternoon, if necessary. Formation chance through 48 hours, medium, 60 percent. Formation chance through 5 days, medium, 60 percent.

Previous Warning 200 PM EDT Wed Oct 25 2017

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 western Caribbean Sea and Central America have become a little better organized over the past few hours. Close proximity to land is likely to limit development of this system for the next day or so. However, environmental conditions are expected to be conducive for the system to become more organized later this week as it moves slowly northward over the northwestern Caribbean Sea.

Strong upper-level winds associated with an approaching cold front will likely prevent further development by Sunday. Regardless of development, locally heavy rains are likely over portions of Central America and Cuba during the next several days.

Formation chance through 48 hours, low, 20 percent. Formation chance through 5 days, medium, 40 percent.

Previous Warning 800 AM EDT Wed Oct 25 2017

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

1. A broad area of low pressure located over the western Caribbean Sea continues to produce disorganized showers and thunderstorms over Nicaragua, Honduras, and the adjacent waters. Close proximity to\ land is likely to limit development of this system for the next day or so.

However, environmental conditions are expected to be conducive for the system to become more organized later this week as it moves slowly northward over the northwestern Caribbean Sea. Strong upper-level winds associated with an approaching cold front will likely prevent further development by Sunday. Regardless of development, locally heavy rains are likely over portions of Central America and Cuba during the next several days. Formation chance through 48 hours, low, 20 percent. Formation chance through 5 days, medium, 40 percent.

Previous Warning 800 AM EDT Tue Oct 24 2017

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

1. Widespread cloudiness and showers associated with a broad area of low pressure are located over the western Caribbean Sea, near the Central American coast.

Close proximity to land is likely to limit development of this system for the next day or two, however, environmental conditions are expected to be conducive for some development to occur thereafter while the system moves slowly northward over the northwestern Caribbean Sea.

Formation chance through 48 hours, low, 10 percent. Formation chance through 5 days, medium, 50 percent.

If this system forms into a tropical storm, it will be named Tropical Storm Philippe

Watch Cruise Ship Weather for more real time graphics of this storm system

Video: Tropical Storm Philippe outlook 10/29/17 – 7am