Tropical Update: ITCZ, Tropical Wave 22 Nears T&T

Tropical Update Overview:
Tropical Storm Fay – Tropical Storm Fay has formed in the far West Atlantic, forecast to make landfall across the Northeastern United States. Tropical Storm Warnings in effect from New Jersey to Rhode Island, including New York City. No threat to T&T.
Tropical Wave 22 & The ITCZ – A large, tilted tropical wave is in the Central Atlantic, forecast to move across T&T on Saturday into Sunday. Ahead and behind the wave axis, the ITCZ is forecast to affect T&T, bringing periodic rainfall with isolated to scattered showers and isolated thunderstorms beginning Friday through Sunday.

Total Precipitable Water Imagery showing the Tropical Waves (analyzed by the National Hurricane Center, Weather Prediction Center, and TTWC) that exist east of Trinidad and Tobago.

Impacts to T&TThere are no direct tropical threats facing T&T over the next 5 days. The passage of Tropical Wave 22 and the ITCZ are forecast to bring isolated to scattered showers and isolated to scattered thunderstorms beginning Friday through Sunday, with peak inclement weather possible on Friday. The main hazards include heavy rainfall, reducing visibility, and gusty winds up to and in excess of 55 KM/H. Street flooding is likely, with flash flooding possible. In thunderstorm activity, frequent lightning is also possible. Gusty winds may cause power dips/outages, downed trees, and localized wind damage.

Before we dive into the Tropical Update, a few notes:

  • Tropical waves are a normal part of the rainy season.
  • Not every tropical wave will form into a tropical cyclone.
  • Weaker tropical waves produce more rainfall across Eastern parts of the islands with mostly cloudy conditions and a few showers across western parts of the islands.
  • Rainfall will be more isolated and intermittent with weaker tropical waves that do not have ITCZ or upper-level support.
  • Saharan Dust may weaken tropical waves.

You can read more about the weather associated with Tropical Waves, as well as what to expect as these waves move through the region below.

Tropical Storm Fay

Tropical Storm Fay forecast cone as of the 11:00 PM AST Thursday 9th July 2020 Tropical Update (NHC)
Tropical Storm Fay forecast cone as of the 11:00 PM AST Thursday 9th July 2020 Tropical Update (NHC)

Invest 98L strengthened into Tropical Storm Fay on Thursday evening, off the east coast of the United States. It is now the earliest 6th Atlantic named storm formation on record. The previous earliest 6th named storm formation record in the Atlantic was Franklin on July 22 in 2005. On average, the Atlantic Basin sees the 6th named storm form by September 8th.

At 11:00 PM AST Tropical Update, the center of Tropical Storm Fay was located near latitude 36.3 North, longitude 74.8 West. Fay is moving toward the north near 8 MPH (13 KM/H). A northward to north-northeastward motion at a faster forward speed is expected over the next couple of days. On the forecast track, the center of Fay is forecast to move near the mid-Atlantic coast on Friday or Friday night, and move inland over the northeast United States late Friday night or on Saturday.

Maximum sustained winds are near 45 MPH (75 KM/H) with higher gusts. Some slight strengthening is forecast tonight and Friday while the center remains over water. Weakening should begin after the center moves inland.

Tropical-storm-force winds extend outward up to 140 miles (220 KM) mainly to the east and southeast of the center. The estimated minimum central pressure is 1005 millibars (29.68 inches).

Tropical Wave 22 & The ITCZ

Tropical Wave 22 is analyzed from 20N and 40W, to 5N and 53W, with much of the activity located along the northern half of the wave axis, producing cloudiness and isolated to scattered showers, as well as isolated thunderstorms (Weathernerds)
Tropical Wave 22 is analyzed from 20N and 40W to 5N and 53W, with much of the activity located along the northern half of the wave axis, producing cloudiness and isolated to scattered showers, as well as isolated thunderstorms (Weathernerds)

As of the 11:00 PM Tropical Update, the 22nd tropical wave for the 2020 Atlantic Hurricane Season is tilted, located from 20N and 40W, to 5N and 53W based on our analysis. The wave axis is moving westward around 10 to 15 knots (18 to 27 KM/H).

Much of this wave is surrounded by Saharan Dust, limiting convection, with nearly all of its activity near the northern area of the wave axis. An active ITCZ follows.

Note that a low-level trough exists around 55W, forecast to move the ITCZ across our area, ahead of the tropical wave, on Friday.

Models continue to show that this wave, its associated moisture, and the ITCZ will move across Trinidad and Tobago Saturday into Sunday. See below for details.

What does all of this mean for Trinidad and Tobago?

Tropical Wave 22 and the ITCZ impacts to T&T as of Thursday night's Tropical Update
Tropical Wave 22 and the ITCZ impacts to T&T as of Thursday night’s Tropical Update

Remainder of Thursday: Mostly settled, barring the odd isolated shower across Eastern areas of Trinidad and Tobago. An increase in showers are forecast after midnight into Friday.

Seas to remain moderate, with waves near 2.0 meters in open waters, occasionally up to 2.5 meters. In sheltered areas, near 1.0 meter.

No adverse weather impacts forecast, though air quality will be at moderate, improving by nightfall into Friday.


Friday – The Intertropical Convergence Zone is forecast to drift across mainly Trinidad. Activity associated with the ITCZ tends to favor hours after midnight through the early morning, and again during the afternoon. Seas are forecast to be moderate, with waves up to 2.0 meters in open waters, near 1 meter in sheltered areas but locally choppy and rough during heavy showers or thunderstorms.

AM: After midnight, isolated showers are forecast to begin moving across both islands, generally remaining brisk. Heavier showers are forecast to favor Southern and Eastern Trinidad, with thunderstorms possible by the mid-morning.

PM: Activity forecast to gradually move across Trinidad, lesser so Tobago, moving from the southeast to the northwest through the afternoon, with isolated heavy showers and thunderstorms favoring Southern, Western and hilly areas of Trinidad.

A brief lull in activity is forecast by the late afternoon through the evening, with a resurgence of activity forecast after nightfall, with heavier showers continuing to favor Southern and Eastern Trinidad, gradually moving across the islands.

The main hazards would be locally heavy rainfall, reducing visibility, and localized wind damage from wind gusts associated with heavier showers or thunderstorms. Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding.



Saturday – The ITCZ will remain across T&T, with Tropical Wave 22 moving across the region late Saturday. Heavier activity to remain north of T&T. Seas are forecast to be moderate, with waves up to 2.0 meters in open waters, near 1 meter in sheltered areas but locally choppy and rough during heavy showers or thunderstorms.

AM: Isolated to scattered showers are forecast after midnight, favoring Eastern areas of both islands, gradually moving westward. Heavier activity forecast to remain generally offshore Eastern and Southern Trinidad through the first half of the day, mainly affecting coastal areas.

PM: By midday, through the latter half of Saturday, the axis of Tropical Wave 22 will move across T&T, with heavier showers and thunderstorms remaining north of our country.. Isolated showers and isolated thunderstorms remain possible across our country, favoring Western and hilly areas, though activity will remain brief. Conditions are forecast to settle by nightfall, with brisk, isolated showers moving across both islands, favoring Tobago.

The main hazards would be locally heavy rainfall, reducing visibility, and localized wind damage from wind gusts associated with heavier showers or thunderstorms. Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding.



Sunday: The axis of Tropical Wave 22 will move west of T&T, with the ITCZ slowly drifting south across T&T. A surge of Saharan Dust will arrive across the region, with higher concentrations north of T&T. Seas are forecast to be moderate, with waves up to 2.0 meters in open waters, near 1 meter in sheltered areas but locally choppy and rough during heavy showers or thunderstorms.

AM: Isolated to scattered showers are forecast to return, mainly favoring offshore areas and north of T&T after midnight but by sunrise, moving across Tobago. Isolated showers will favor Tobago and Northern Trinidad though the morning.

PM: By the afternoon, isolated showers continue, with isolated thunderstorms developing across Trinidad by midday through the afternoon. Isolated activity is forecast to continue into the night, with isolated thunderstorms developing across Southeastern Trinidad by midnight into Monday.

The main hazards would be locally heavy rainfall, reducing visibility, and localized wind damage from wind gusts associated with heavier showers or thunderstorms. Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding.


Monday through the week: A typical wet season pattern begins on Monday through the week as winds gradually decrease across the area. After a mostly settled and sunny morning, clouds are forecast to build by the late morning, with showers developing, favoring Western, Southern and hilly areas of both islands. By the afternoon, thunderstorms are possible near western coastal Trinidad and hilly areas, settling by the late afternoon into the evening. Saharan Dust concentrations will peak on Monday through Tuesday, decreasing as the week progresses.

Seas are forecast to be moderate, with waves between 1.5 and 2.0 meters in open waters, less than 1 meter in sheltered areas but locally choppy and rough during heavy showers or thunderstorms. By the end of the week, winds are forecast to reduce so seas become slight in open waters with waves between 1.0 and 1.5 meters while in sheltered areas, near calm.

The main hazards would be locally heavy rainfall, reducing visibility, and localized wind damage from wind gusts associated with heavier showers or thunderstorms. Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding.

Possible Impacts Over Next 5-7 Days

There are no tropical systems that pose a direct threat to T&T over the next week, as of today’s tropical update.

Winds: Sustained surface winds between 25 KM/H and 40 KM/H are forecast particularly through Sunday, with gusts up to and in excess of 55 KM/H possible in heavy showers or thunderstorms across Trinidad and Tobago, particularly on Friday and Saturday.

With wind gusts in excess of 55 KM/H, whole trees are expected to be in motion, and there may be some inconvenience when walking against the wind gusts. Light outdoor objects may topple or become airborne such as garbage cans, potted plants, loose galvanize or construction material and other outdoor furniture. Tents may jump. Older/weaker trees may fall, bringing down utility poles and lines.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Friday: Generally 10-15 millimeters with isolated totals between 20-40 millimeters, favoring Southern and Eastern Trinidad, as well as areas along Western Coastal Trinidad that experience localized downpours and thunderstorms.

Saturday: Generally 5-10 millimeters with isolated totals between 15-30 millimeters, favoring Southern and Eastern Trinidad, Tobago as well as areas along Western Coastal Trinidad that experience localized downpours and thunderstorms.

Sunday: Generally 5-10 millimeters with isolated totals between 15-30 millimeters, favoring Northern and Eastern Trinidad, Tobago as well as areas along Western Coastal Trinidad that experience localized downpours and thunderstorms.

Monday through the week: Generally 5-10 millimeters with isolated totals up to 25 millimeters, favoring areas along Western Coastal Trinidad that experience localized downpours and thunderstorms.

Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding in areas where more prolonged heavy rainfall may occur.

Frequent Lightning: In addition, with forecast thunderstorms, frequent lightning is likely. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.

Why I May Not/Will Not See Constant Rainfall?

A frequent complaint is the forecast is wrong because I didn’t experience any rainfall. Scattered showers mean that you, individually, may experience some showers intermittently throughout the day and there is a higher chance for this activity than isolated activity. Widespread showers mean that nearly all persons and areas may experience rainfall.

Isolated to scattered activity is forecast Friday through Sunday, with isolated activity through next week.

Forecast - Isolated, Scattered, Widespread - What do they mean?

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the first and second weeks of July. Though much of the points of origin are west or north of T&T as we move through the second month of the Hurricane Season, we need to pay attention to some of these waves and the ITCZ, which have historically brought major flooding events to T&T, hence all low-pressure systems in the Atlantic should be closely monitored, as we do in the Tropical Update.

List of names for the 2020 Atlantic Hurricane Season, which will be updated each tropical update as new systems develop.
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