September 24, 2020

TS FAY headed towards Bermuda, but 90L [now TS Gonzalo] is the one to watch

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at201407_satBy: Dr. Jeff Masters, From Weather Underground (See UPDATE and Gonzalo Discussion from NHC below)

NOTE: Since this BLOG from Dr. Masters SD7 is now Tropical Storm FAY and 90L is Tropical Storm Gonzalo

Subtropical Depression Seven formed in the Atlantic at 11 am EDT Friday [now TS FAY]

The depression, located about 590 miles south of Bermuda, was headed northwest at 10 mph, and Bermuda is the only land area the storm poses a threat to. A tropical storm watch has been posted for the island, and the 11 am EDT Wind Probability Forecast from NHC gave Bermuda a 14% chance of seeing tropical storm-force winds of 39+ mph, with the strongest winds expected to affect the island Saturday evening into Sunday morning. Satellite loops showed STD 7 had very little heavy thunderstorm activity near its center, with most of the action in a curved band well to the north of the center. This is characteristic of a storm that is not fully tropical, thus the designation of the storm as a subtropical depression. Sea Surface Temperatures (SSTs) were warm, near 29°C (84°F), and wind shear was moderate, 5 – 15 knots. These conditions are favorable for slow development, and the depression is likely to get the name Fay Friday evening or Saturday morning. Disturbances getting their start from a cold-cored upper level low like STD 7 have plenty of cold, dry air aloft, which retards development into a tropical system. I expect STD 7 will be named Subtropical Storm Fay instead of Tropical Storm Fay, if it intensifies at expected. STD 7 will recurve to the northeast out to sea on Sunday without troubling any other land areas. An Air Force hurricane hunter aircraft has been tasked to investigate STD 7 on Friday afternoon.

at201490_sat

Pay attention to Invest 90L east of the Lesser Antilles [now TS Gonzalo]023623W5_NL_smgraphicast_at_latestat201490_model

An area of disturbed weather associated with a tropical wave located about 700 hundred miles east of the northern Lesser Antilles Islands on Friday morning has been designated Invest 90L by the National Hurricane Center. This disturbance has the potential to be trouble, and needs to be watched carefully. Invest 90L was headed west to west-northwest at about 10 mph. Satellite loops showed 90L had a modest amount of spin and heavy thunderstorm activity, and these thunderstorms were poorly organized. Water vapor satellite loops show a good degree of dry air surrounding 90L, and this will retard development. Sea Surface Temperatures (SSTs) were warm, near 28.5°C (83°F), and wind shear was light, 5 – 10 knots. These conditions are favorable for development. The 8 am Friday run of the SHIPS model predicted that conditions would remain favorable for slow development through Monday, with light to moderate wind shear and SSTs near 29°C (84°F), though the atmosphere is expected to dry as the disturbance moves to the north of Puerto RIco early next week. All three of our reliable computer models for predicting tropical storm formation, the European, GFS, and UKMET models, showed 90L developing by the middle of next week in their 00Z Friday runs. When multiple models predict development, the odds of formation are increased. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 10% and 20%, respectively. Given the high model support for 90L’s development, I put the 5-day odds of development higher, at 40%. 90L’s west-northwest trajectory will carry it to a point about 100 – 200 miles north of Puerto Rico on Monday, and near the Southeast Bahamas and Turks and Caicos Islands on Wednesday.

IMAGES:

Figure 1. Latest satellite image of Subtropical Depression Seven.

Figure 2. Latest satellite image of Invest 90L near the Lesser Antilles.

For more on this story go to: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2825

Other Images:

http://www.nhc.noaa.gov/tafb_latest/graphicast_at_latest.png

http://www.sfwmd.gov/portal/page/portal/xweb%20weather/hurricane%20model%20plots

Tropical Storm Fay hits Bermuda

(AP) Tropical Storm Fay toppled utility poles and knocked out power to thousands of people in Bermuda before moving out over open ocean on Sunday, just as a new storm raced toward the eastern rim of the Caribbean threatening to become a hurricane.

For more:

http://entertainment.verizon.com/news/read/category/AP%20Online%20National%20News/article/the_associated_press-tropical_storm_aims_for_nighttime_pass_by_bermuda-ap

 

Tropical Storm Gonzalo forms in Caribbean Sea

TROPICAL STORM GONZALO DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014
1100 PM AST SUN OCT 12 2014

The circulation of Gonzalo, which has shown some signs of inner-core
features, is apparent in radar imagery from Guadeloupe, but the
cyclone’s overall convective pattern is somewhat disorganized in
satellite imagery. A small area of central convection is noted near
the center, along with a rather linear convective band in the
eastern semicircle. Little deep convection is noted west of the
center, perhaps due to westerly shear of around 10 kt and some dry
air in the mid and upper levels seen in radiosonde data from St.
Maarten. The initial intensity remains 40 kt based on the earlier
aircraft data and a blend of the latest Dvorak data-T numbers from
TAFB and SAB. The SHIPS model shows the shear weakening in 12 to 18
hours, and most of the intensity guidance shows Gonzalo reaching
hurricane status in about 36 hours. Additional intensification is
forecast after that time in a low-shear environment over warm
waters. The new NHC intensity forecast is largely an update of the
previous one and is close to the IVCN consensus through the period.

The initial motion estimate is 275/10, as Gonzalo is being steered
by a mid-level ridge to its northeast. During the next 36 to 48
hours, the cyclone will gradually turn northwestward as it moves
around the western periphery of this ridge. Overall, the guidance
envelope has shifted a little to the right through the first 2 days,
and the NHC forecast has been adjusted in that direction but lies
south of the multi-model consensus and close to the ECMWF. After
that time, most of the guidance shows the cyclone turning northward
into a weakness in the ridge and then accelerating northeastward
ahead of a mid-latitude trough by day 5. There is still a large
amount of along-track spread at these time ranges, with the GFS,
HWRF, GFDL, and GEFS ensemble mean showing a faster northeastward
acceleration, and the slower ECMWF showing the trough missing
Gonzalo and leaving the cyclone moving slowly northeastward
by the end of the period. At days 3 through 5, the NHC forecast is
faster and shows more of a northeastward motion compared to the
previous one, but is much slower than the GFS and south of the
consensus out of respect for the ECMWF model.

FORECAST POSITIONS AND MAX WINDS

INIT 13/0300Z 16.6N 60.2W 40 KT 45 MPH
12H 13/1200Z 16.9N 61.9W 50 KT 60 MPH
24H 14/0000Z 17.7N 63.8W 55 KT 65 MPH
36H 14/1200Z 18.8N 65.3W 65 KT 75 MPH
48H 15/0000Z 20.0N 66.5W 70 KT 80 MPH
72H 16/0000Z 22.5N 68.0W 85 KT 100 MPH
96H 17/0000Z 24.5N 68.0W 95 KT 110 MPH
120H 18/0000Z 27.0N 66.0W 90 KT 105 MPH

$$
Forecaster Brennan

 

TROPICAL STORM GONZALO FORECAST/ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014
0300 UTC MON OCT 13 2014

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY…

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

A HURRICANE WATCH IS IN EFFECT FOR…
* PUERTO RICO
* VIEQUES AND CULEBRA
* U.S. VIRGIN ISLANDS
* BRITISH VIRGIN ISLANDS

A TROPICAL STORM WARNING IS IN EFFECT FOR…
* GUADELOUPE…DESIRADE…LES SAINTES…AND MARIE GALANTE
* ST. MARTIN
* ST. BARTHELEMY
* ST. MAARTIN
* SABA AND ST. EUSTATIUS
* BARBUDA
* ANTIGUA
* ANGUILLA
* ST. KITTS AND NEVIS
* MONTSERRAT
* PUERTO RICO
* VIEQUES AND CULEBRA
* U.S. VIRGIN ISLANDS
* BRITISH VIRGIN ISLANDS

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