TROPICAL STORM GASTON FORMS, FIONA STRONGER, NEW SYSTEMS EAST OF FLORIDA

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TROPICS ARE ALIVE. TWO NAMED STORMS. TWO WAVES.

Two waves, two named storms, as of Tuesday afternoon, September 20, 2022. (National Hurricane Center).

BY: WEATHER TEAM | BocaNewsNow.com

BOCA RATON, FL (BocaNewsNow.com) (Copyright © 2022 MetroDesk Media, LLC) — Tropical Storm Gaston was born late Tuesday afternoon as Hurricane Fiona continues to get stronger. Two new waves — including one that may become a tropical depression within days — are east of Florida. The quiet hurricane season is over.

There is a lot of information this evening from the National Hurricane Center. We start with the latest on Fiona. We then update Gaston, and then end with the two tropical waves:

Hurricane Fiona Discussion Number 26 NWS National Hurricane Center Miami FL AL072022 500 PM EDT Tue Sep 20 2022

Deep convection around Fiona’s eye is intense, but is in a rather asymmetrical pattern at this time. Upper-tropospheric outflow remains somewhat restricted over the western semicircle of the system. The last Air Force Hurricane Hunter fix in the center of the hurricane around 17Z showed a slight fall of central pressure from earlier in the day, but the flight-level and SFMR-observed surface winds indicated that the maximum winds were still near 100 kt. This is also in agreement with the latest Dvorak satellite estimates from TAFB and SAB. Another Air Force Hurricane Hunter mission into Fiona is scheduled for 00Z to see if Fiona is strengthening again.

Vertical wind shear over Fiona, as diagnosed by the SHIPS model, is predicted to remain moderate for the next few days. However, the hurricane is likely to remain in a moist unstable air mass and over a warm ocean for the next couple of days which is likely to offset the influence of shear. In general, the intensity model guidance continues to show strengthening for about the next 48 hours, and so does the official forecast. Fiona is expected to become a category 4 hurricane in a day or so. By 96 hours, global model guidance indicates that the system will be transformed into a vigorous extratropical cyclone near Atlantic Canada.

The hurricane is still headed toward the north-northwest with an initial motion estimate of 330/7 kt. The track forecast scenario is generally unchanged from the previous advisory. Fiona should turn northward while moving along the western side of a mid-level anticyclone during the next day or so. In 2-3 days, an intense mid-tropospheric trough will be moving off the northeast United States coast. This feature should cause Fiona to accelerate toward the north-northeast and northeast during the latter part of the forecast period. The official forecast follows about the same trajectory as the previous one, but is just a tad slower. This is in good agreement with both the simple and corrected consensus predictions.

Key Messages:

  1. Heavy rains around the center of Fiona will continue to impact the Turks and Caicos through this evening with continued life-threatening flooding. Localized additional flash and urban flooding is possible in Puerto Rico and the Dominican Republic.
  2. Hurricane conditions are affecting portions of the Turks and Caicos islands, while tropical storm conditions should affect portions of the southeastern Bahamas during the next few hours.
  3. Tropical storm conditions are possible on Bermuda by late Thursday.
  4. Fiona is expected to affect portions of Atlantic Canada as a powerful hurricane-force cyclone late Friday and Saturday, and could produce significant impacts from high winds, storm surge, and heavy rainfall. Interests in these areas should closely monitor the progress of Fiona and updates to the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 20/2100Z 22.6N 71.8W 100 KT 115 MPH
12H 21/0600Z 23.6N 72.0W 110 KT 125 MPH
24H 21/1800Z 25.0N 71.9W 115 KT 130 MPH
36H 22/0600Z 26.9N 71.3W 115 KT 130 MPH
48H 22/1800Z 29.4N 70.1W 120 KT 140 MPH
60H 23/0600Z 32.4N 67.8W 115 KT 130 MPH
72H 23/1800Z 36.9N 63.5W 105 KT 120 MPH
96H 24/1800Z 46.5N 60.0W 85 KT 100 MPH…POST-TROP/EXTRATROP
120H 25/1800Z 55.0N 58.0W 55 KT 65 MPH…POST-TROP/EXTRATROP

Hurricane Fiona continues to increase strength as it heads north. (National Hurricane Center).

Tropical Storm Gaston Discussion Number 2 NWS National Hurricane Center Miami FL AL082022 Issued by the NWS Weather Prediction Center College Park MD 900 PM GMT Tue Sep 20 2022

Satellite images indicate that deep convection is persisting near and to the north of the center of the cyclone during the past several hours. Drifting buoy 44857 recently reported a minimum pressure of 1009 mb near the center of the low, which is a 8 mb decrease from earlier today. An ASCAT-C pass from several hours ago showed maximum winds of about 35 kt in the northeast and northwest quadrants. Based on that data, the initial intensity is increased to 35 kt, making the system Tropical Storm Gaston.

Gaston has turned north-northeastward and is moving a little faster than before. The initial motion estimate is 020/15 kt. A turn to the east is expected in a couple of days when the tropical storm moves along the northern periphery of a subtropical ridge. By the end of the week, however, Gaston is expected to stall to the west of the Azores in weak steering currents as high pressure builds near and to the north of the cyclone. After that time, a turn to the northwest or north is expected as Gaston moves in the flow between Hurricane Fiona and the ridge. The models have trended a little faster this cycle, and the NHC track forecast has been adjusted accordingly.

Gaston is currently moving over relatively warm water, in a region of upper-level diffluence within a somewhat favorable moist environment. These factors should allow the system to strengthen slowly during the next day or two. However, after that time, much cooler SSTs, drier air, and an increase in westerly shear should end the strengthening trend. The system is expected to become extratropical on Saturday when it moves over SSTs just above 20C and merges with a mid- to upper-level trough. The NHC intensity forecast is about the same as the previous one and near the middle of the guidance envelope.

TROPICAL WEATHER OUTLOOK TUESDAY AFTERNOON

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

Active Systems:
The National Hurricane Center is issuing advisories on Hurricane
Fiona, located near the Turks and Caicos islands, and on Tropical
Depression Eight, located over the north-central Atlantic Ocean.

  1. Central Tropical Atlantic:
    A tropical wave located a few hundred miles east of the Windward
    Islands continues to show signs of organization. Additional
    development is expected, and a tropical depression is likely to form
    within the next few days as the system moves westward to
    west-northwestward at 15 to 20 mph across the eastern and central
    Caribbean Sea. Interests in the Windward Islands should closely
    monitor the progress of this system as heavy rainfall and gusty
    winds could affect these islands beginning on Wednesday.
  • Formation chance through 48 hours…medium…60 percent.
  • Formation chance through 5 days…high…80 percent.
  1. Eastern Tropical Atlantic:
    A tropical wave is forecast to move off the west coast of Africa in
    a couple of days. Thereafter, environmental conditions appear
    marginally favorable for some development while the system moves
    northward between west Africa and the Cabo Verde Islands through the
    end of the week.
  • Formation chance through 48 hours…low…near 0 percent.
  • Formation chance through 5 days…low…20 percent.

LOCAL JOURNALISM SUPPORTER.

Paul Saperstein

 

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