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The next Invest?
07-08-2017, 11:40 AM (This post was last modified: 07-08-2017 11:46 AM by Her-icane.)
Post: #1
The next Invest?
NWS San Juan PR


000
FXCA62 TJSJ 081449
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1049 AM AST Sat Jul 8 2017

.UPDATE...Doppler radar indicated isolated to scattered showers
mostly across the surrounding coastal waters...with few of them
affecting the U.S. Virgin Islands, Vieques, Culebra and eastern
sections of Puerto Rico from time to time during the morning hours.
Not significant precipitation was observed elsewhere across the
region.


PREV DISCUSSION... /issued 510 AM AST Sat Jul 8 2017/

SYNOPSIS...A tropical wave is passing through the Mona passage this morning and will continue to carry moisture with it today. There
will be a dry slot before moisture from the next tropical wave-- that was previously tropical depression number 4--moves through on
Sunday. Then an area of drier air loaded with Saharan dust will come in Monday and Tuesday. An easterly wave will move through on
Wednesday with drying Thursday night.

SHORT TERM...As the wave left the region overnight, the lingering moisture brought showers across the U.S. Virgin Islands and the east half
portion of Puerto Rico. These showers produced periods of moderate to heavy rainfall, which result in hazardous driving conditions as
well as ponding of water on roadways and in poor drainage areas. This morning, passing showers will continue across the windward
sections. However, the west half section of Puerto Rico should remain with little or no shower activity. Then, the combination of
the available moisture and local effects will enhance showers and thunderstorms development mainly across the interior and west
sections of Puerto Rico. At the same time, patches of moisture will bring showers across the Northern U.S. Virgin Islands, which in turn
will move westward into Culebra and the east municipalities of Puerto Rico.

By Sunday, a tropical wave is forecast to pass north of the local islands Sunday. Although the bulk of moisture will move across the
Atlantic waters, shower and thunderstorm activity is expected to increase through Sunday. This tropical wave is surrounded with
Saharan dust which could make it way through the islands. As the tropical wave moves into the Western Atlantic, a southerly wind flow
is expected to prevail Sunday and Monday. Under this southerly wind flow warm temperatures could lead to heat indices around the high
90s and low 100s each afternoon. Another air mass with Saharan dust particulate is forecast to reach us by Monday.

LONG TERM...Tuesday through Friday
The TUTT low to the northeast of the area will wander toward us for a few days but will begin to lose strength as it becomes
nearly north of the area at about 500 miles. This will leave high pressure over the area at upper levels. An approaching tropical
wave will shift the low level winds back to the northeast briefly later on Tuesday, but we will return to a more southeasterly flow
afterward with its passage on Wednesday. In the meantime moisture levels remain normal to slightly above normal until around midday
on Thursday to create scattered showers almost everywhere and afternoon thunderstorms in the western portions of Puerto Rico.
After a drier night, a larger envelope of good moisture enters the eastern Caribbean on Friday and will begin to increase
showers and thunderstorms.

Beyond Friday we are continuing to monitor model outputs that suggest a tropical system will move into the Caribbean Friday
night and affect most of the area over the weekend with winds and rain. Model outputs are still wavering on the track of this
system, but conditions appear favorable for development
.


AVIATION...SHRA expected to continue across TJSJ/TIST/TISX and TJPS at times during the morning hours. Expected to diminish around
08/12z. SHRA/TSRA are expected to develop across the west/interior PR btwn 08/17-22z. MVFR conds could be required at TJBQ/TJMZ and
possibly at TJSJ/TIST during the afternoon. Calm to light and vrb winds, increasing at 10 to 15 knots aft 08/13z with higher gusts in
sea breeze variations and showers.

MARINE...Seas in the northeast corner of the local outer Atlantic waters continue to run 5 to 6 feet and winds in the nearshore
Atlantic waters are occasionally reaching 18 knots. Condtions are expected to become more tranquil after Sunday. Small craft
advisories are not expected before Saturday of next week.

&&

[Image: D8PzomF.jpg]

.
Could well be a replay of 94L/TD 4
.
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07-09-2017, 09:51 AM
Post: #2
RE: The next Invest?
Area Forecast Discussion
Issued by NWS San Juan, PR



000 FXCA62 TJSJ 091001 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 601 AM AST Sun Jul 9 2017

SYNOPSIS...A tropical wave--that was previously tropical depression number 4--will move through the U.S. Virgin Islands this morning and Puerto Rico today. Then an area of drier air and increasing Saharan dust will come in Monday and Tuesday. An easterly wave will move through on Wednesday with drying Thursday night. An envelope of very moist air will move into the eastern Caribbean on Friday with the potential for showers, thunderstorms and gusty winds increasing over next weekend.

SHORT TERM...Today through Tuesday Rainy conditions prevailed overnight across the northern USVI and the east half portion of PR. Meanwhile, the west and south sections of Puerto Rico observed mostly clear to partly cloudy skies with little or no shower activity around midnight. However, the approaching tropical wave brought showers across the west half of the island early this Sunday morning. Preliminary rainfall totals were estimated between one and three inches across the east half of Puerto Rico and less than a quarter of an inch across the west half. On the other hand, the rainfall estimates across the northern USVI ranged between 0.5 inches and 1.5 inches of rain and less than a quarter of an inch in St Croix. The approaching tropical wave will continue to enhance shower and thunderstorm activity across the islands this morning. Soils are already saturated across the east and west portions of Puerto Rico. Therefore, additional persistent rainfall accumulations will result in urban flooding as well as rapid river rises across these sections during. The tropical wave is forecast to induce a southerly wind flow, which is expected to prevail today and Monday. A dry air mass is then expected to move in by late Sunday night and under this southerly wind flow warm temperatures could be expected by Monday afternoon. Another air mass with Saharan dust particulate is forecast to reach us by Monday and Tuesday.

LONG TERM...Wednesday through Sunday High pressure at upper levels remains the dominant feature this week. Moisture from a previous tropical wave wraps around and returns from the northeast to join in the passage of the third tropical wave this week early on Wednesday morning. Showers and thunderstorms are expected to return with some possibility of urban and small stream flooding Wednesday. Moisture will then decrease to around normal levels for July on Thursday as a low and mid-level ridge moves across the area, and while showers will diminish, they are still expected during the early mornings in the east and the afternoons in the west. On Friday the outer edges of an envelope of good moisture arriving from the southern tropical North Atlantic waters near the equator begins to invade the eastern Caribbean and the local islands. On Saturday moisture is expected to increase considerably.

The ECMWF and the GFS diverge in their solutions over the weekend, with the ECMWF forecasting typical tropical trade winds and good rains on Friday night or Saturday, and the GFS developing a tropical system on Wednesday in the southern tropical North Atlantic and bringing it south of the U.S. Virgin Islands on Saturday and Puerto Rico Saturday afternoon through Sunday morning. The GFS has not been perfectly consistent with its solution from run to run and the 08/18Z run had only a moderately strong low pressure moving through the area. Therefore still consider this a low-confidence scenario. Should it develop as the 09/00z model indicates. Puerto Rico and the U.S. Virgin Islands could expect as early as Saturday strong gusty winds, heavy rains with a high potential for the most widespread flooding of the season and agitated seas of over 8 feet, accompanied by a high risk of rip currents. The rains could last through Monday, 17 July.

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07-09-2017, 11:16 AM
Post: #3
RE: The next Invest?
[Image: gfs_mslpa_Norm_watl_22.png]
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07-09-2017, 08:34 PM (This post was last modified: 07-09-2017 08:38 PM by Her-icane.)
Post: #4
RE: The next Invest?
[Image: two_atl_5d0.png]



ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Sun Jul 9 2017

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

1. A tropical wave passing south of the Cabo Verde Islands is
producing disorganized showers and thunderstorms. Some gradual
development of this system is possible during the next several
days while it moves westward at 15 to 20 mph.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

Forecaster Brown
.


[Image: DzDjCrg.jpg]
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07-09-2017, 11:55 PM
Post: #5
RE: The next Invest?
Let's remember that this is but ONE model, not supported fully (or even at all) yet by others, and is LONG range...but here's the latest GFS...just says, bears watching.....






[Image: 3e467da302919cadd2d76f3c624eb3b7.png]
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07-10-2017, 11:50 AM
Post: #6
RE: The next Invest?
[Image: two_atl_5d0.png]

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Mon Jul 10 2017

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

1. Disorganized showers and thunderstorms located several hundred
miles southwest of the Cabo Verde Islands are associated with a
tropical wave. Some gradual development is possible through the
week while this system moves westward at about 20 mph across the
tropical Atlantic Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

Forecaster Stewart
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07-10-2017, 07:33 PM
Post: #7
RE: The next Invest?
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Mon Jul 10 2017

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

1. A tropical wave located several hundred miles west-southwest of the
Cabo Verde Islands is producing a few disorganized showers and
thunderstorms. Environmental conditions are expected to be
only marginally conducive and development, if any, of this system
should be slow to occur over the next several days as it moves
westward at about 20 mph.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...10 percent.

Forecaster Brown


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