Tropical Storm Isaias Creeps Northward

000

WTNT44 KNHC 030243

TCDAT4

Tropical Storm Isaias Discussion Number  24

NWS National Hurricane Center Miami FL       AL092020

1100 PM EDT Sun Aug 02 2020

Isais has not become better organized on satellite and radar imagery 

at this time.  The cyclone continues to produce vigorous deep 

convection but this convection continues to be displaced to the 

northeast of the center, and convective banding features are 

ill-defined.  Air Force Hurricane Hunter observations show that the 

central pressure has not fallen since earlier today, and 

flight-level and SFMR-observed surface wind measurements from the 

aircraft indicate that the intensity remains near 60 kt.  Although 

Isais will be moving through an environment of fairly strong 

southwesterly shear during the next day or so, it will also be 

traversing the warm waters of the Gulf Stream with its high oceanic 

heat content.  The latter factor could result in the system becoming 

a hurricane near landfall.  The official forecast is close to the 

intensity consensus, which keeps Isaias just below hurricane 

strength.

It should be emphasized that there is little difference between a 

strong tropical storm or a category 1 hurricane, in terms of 

impacts.

After landfall, the interaction with land and strong shear should 

result in steady weakening.  Based on the global models, the 

cyclone is likely to become an extratropical cyclone after it moves 

into Canada and dissipate over the north Atlantic shortly 

thereafter. 

The motion continues to be slightly west of due north or 345/8 kt.

There has been no significant change to the track forecast

reasoning.  Over the next couple of days, Isaias is expected to

accelerate north-northeastward on the east side of a large 500 mb

trough over the eastern United States and then turn northeastward

in 3 to 4 days as it moves through the mid-latitude westerlies.

The official track forecast is very close to the previous one and

similar to the latest corrected dynamical model consensus.  This is

between the GFS, which shows a slightly faster motion and the ECMWF,

which is slightly slower.

Key Messages:

1. There is the danger of life-threatening storm surge inundation of

2 to 4 feet above ground level from Edisto Beach South Carolina to

Cape Fear North Carolina along the immediate coastline and adjacent

waterways.  Life-threatening storm surge is possible along the

North Carolina coast from Cape Fear to Duck.  Residents in these

areas should follow advice given by local emergency officials.

2. Tropical storm conditions will spread northward within the

Tropical Storm Warning area from Florida to Maryland through

early Tuesday. Isaias is expected to be near hurricane strength when

it reaches the coast of northern South Carolina and southern North

Carolina Monday night, and strong tropical storm force winds are

likely with hurricane conditions possible in the Hurricane Watch

area.

3. Heavy rainfall from Isaias will continue to result in potentially

life-threatening flash flooding in the Northwest Bahamas through

tonight. Flash and urban flooding, some of which may be significant

in the eastern Carolinas and the mid-Atlantic, is expected through

midweek along and near the path of Isaias across the East Coast of

the United States. Widespread minor to moderate river flooding is

possible across portions of the Carolinas and the mid-Atlantic.

4. Tropical storm conditions are forecast to spread northward 

across the remainder of the U.S east coast on Tuesday and early 

Wednesday. A tropical storm watch is in effect through Long Island 

Sound and additional watches and warnings will likely be issued on 

Monday.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 28.5N  79.8W   60 KT  70 MPH

 12H  03/1200Z 29.7N  80.0W   60 KT  70 MPH

 24H  04/0000Z 32.2N  79.3W   60 KT  70 MPH

 36H  04/1200Z 35.9N  77.3W   55 KT  65 MPH...INLAND

 48H  05/0000Z 40.5N  74.0W   40 KT  45 MPH...INLAND

 60H  05/1200Z 45.5N  70.0W   35 KT  40 MPH...INLAND

 72H  06/0000Z 50.0N  65.5W   30 KT  35 MPH...POST-TROP/EXTRATROP

 96H  07/0000Z 55.5N  56.5W   25 KT  30 MPH...POST-TROP/EXTRATROP

120H  08/0000Z...DISSIPATED

$$

Forecaster Pasch

000

FXUS61 KCAR 030114

AFDCAR

Area Forecast Discussion

National Weather Service Caribou ME

914 PM EDT Sun Aug 2 2020

.SYNOPSIS...

Low pressure will track northwest of the region through Monday.

A cold front will cross the area Monday night. Isaias will

track northeast across Maine Wednesday. An upper low will track

north of the region Thursday. High pressure will build across

the region Friday.

&&

.NEAR TERM /THROUGH MONDAY/...

9:14 pm update: Area radars show scattered showers across parts

of Aroostook County and into northern Piscataquis County.

Upstream there are showers and thunderstorms in Quebec to the

north of NY and VT. Some of this activity could work into

northern Maine after midnight, but it will likely weaken to just

scattered showers. There are plenty of mid level clouds across

the FA this evening, and still expect that low clouds will

develop in a mild and muggy air mass overnight along the coast

and work north overnight. Made some adjustments to the PoPs and

weather based on the latest radar trends. Otherwise, changes

were very minor and based on the latest observations and

expected forecast trends.

Previous discussion:

High pressure will slide southeast of the region tonight as a low

lifting north of the eastern Great Lakes pulls a warm front across

the area. Some showers are possible with this front, mainly across

northern areas this evening. Otherwise, an increasing gradient

between high pressure to the southeast and the low lifting up to our

west will bring an increasing southerly breeze and increasing

humidity overnight. The humid air lifting north over the waters will

likely bring some fog along the coast. Low pressure will lift north

of the region Monday as a corridor of drier air lifts across our

area. A few showers and perhaps an isolated thunderstorm may be

across the north. Otherwise, Monday will turn out partly cloudy and

humid. A weak cold front will slide across the area late Monday into

Monday evening ushering in just slightly drier air. High

pressure will follow later Monday night bringing a tranquil

night. Moisture running north well ahead of tropical storm

Isaias will bring increasing clouds late at night. Showers will

likely increase on Tuesday along a corridor of lift supported by

divergence aloft between the subtropical high to the east and

an upper trough approaching from the west. The best chance for

showers will be central and western areas where bands of

steadier rain may develop late in the day as the low center of

tropical storm Isaias tracks into southern New England.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...

Isaias will approach Tuesday night then cross the region

Wednesday. Models are in better agreement tracking the storm

northeast across Maine Wednesday while starting to transition

from a tropical to an extratropical system. However, uncertainty

still exists regarding the exact timing of the storm across

Maine. Winds, along with rainfall, will be dependent on both the

eventual track and intensity of the storm. Current indications

are that Isaias will have an over land trajectory while

approaching southern Maine Tuesday night, then remain over land

while tracking northeast across Maine Wednesday. Expect rain,

along with a chance of thunderstorms, to expand across the

region Tuesday night then persist with the system Wednesday. The

rain could be heavy at times later Tuesday night through

Wednesday. An upper trof approaching from the west could help

enhance rainfall with the system. Rainfall totals will also be

enhanced across the favored upslope terrain areas. Windy/very

windy conditions are also expected Wednesday. Temperatures will

be at near normal levels Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...

The storm will exit across the Maritimes Wednesday night. Rainfall

will diminish later Wednesday into Wednesday night in the wake of

the storm. An upper low will track north of Maine Thursday,

while surface high pressure builds across the region. Could have

the slight chance of afternoon showers across mostly the north

and mountains Thursday. Otherwise, expect generally partly

cloudy skies Thursday. High pressure will cross the region

Friday, with mostly clear skies. An upper level trof will cross

the region Saturday with partly cloudy skies along with a

slight chance of showers across mostly the north and mountains.

An isolated shower is possible Sunday. Otherwise, expect mostly

clear/partly cloudy skies Sunday. Near normal level

temperatures are expected Thursday, with slightly above normal

level temperatures Friday through Sunday.

Hazardous Weather Outlook

National Weather Service Caribou ME

820 PM EDT Sun Aug 2 2020

MEZ001>006-010-011-015>017-031-032-040030-

Northwest Aroostook-Northeast Aroostook-Northern Somerset-

Northern Piscataquis-Northern Penobscot-Southeast Aroostook-

Central Piscataquis-Central Penobscot-Southern Penobscot-

Interior Hancock-Central Washington-Southern Piscataquis-

Northern Washington-

820 PM EDT Sun Aug 2 2020

This Hazardous Weather Outlook is for Central Highlands Maine, Far

Eastern Maine, Far Northern Maine, Interior DownEast Maine, North

Woods Maine and Penobscot Valley Maine.

.DAY ONE...Tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Isaias is forecast to track across Maine by mid-week. Confidence is

increasing on the track of Isaias but some uncertainties remain in

timing. The exact track will determine the impacts, but gusty winds

and heavy rain will be possible.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather

conditions according to Standard Operating Procedures.

$$

8:59 AM ADT Sunday 02 August 2020

Tropical cyclone information statement for:

New Brunswick

For Tropical Storm Isaias.

The next information statement will be issued by 09:00 a.m. ADT Monday.

Current indications show Tropical Storm Isaias will approach Eastern Canada around mid-week, and could bring locally heavy rainfall and gusty winds to parts of the region Wednesday or Thursday.

The Canadian Hurricane Centre is closely monitoring the progress of Tropical Storm Isaias (pronounced ees-ah-EE-ahs), which is currently located just off of the south Florida coast. Isaias is expected to approach Eastern Canada from the New England region later Wednesday or Thursday. The most likely impacts for Canada will be potential for heavy rainfall and gusty winds.

There is still a wide range of potential track and intensity scenarios that are possible over the next several days for Isaias, thus details on impacts are difficult to determine at this time. Interests in Eastern Canada should closely monitor forecasts for early to midweek as this situation continues to evolve.

The Canadian Hurricane Centre will begin issuing regular updates on Isaias beginning 09:00am Monday.

Forecaster(s): Borgel/CHC

Please continue to monitor alerts issued by the Canadian Hurricane Centre and forecasts issued by Environment Canada.