Tropical Weather Analysis 7-31-13

Southeast Florida Weather

 

In today’s tropical weather analysis, the NHC (National Hurricane Center) is monitoring one tropical wave.

The tropical wave is located from just north of western Cuba southward into the northwest Caribbean.  It is moving westward at 10 knots.  There are some showers and thundershowers associated with the wave which is probably primarily due to north/northeast winds aloft providing a diffluent upper air environment.

There is a weak surface trough (remnants of Dorian) from about eastern Cuba northward into the central Bahamas. The combination of surface convergence plus diffluent flow aloft due to an upper level Low nearby is helping to generate showers and thundershowers in the area. The area is moving slowly west to west northwest.

 

An extensive and dense level of SAL (Saharan Air Layer) has been emanating from West Africa for the past few days.  SAL hinders thunderstorm development as the environment is dry and stable. Tropical activity over the Atlantic east of the Lesser Antilles will be limited for the next several days due to this.  It is possible that the SAL can traverse across the entire Atlantic basin from west to east. It brings a hazy appearance to the sky.  Below is a modeled animated depiction of the SAL for the next few days.

 

 

 

 

Below is the CIMSS Meteosat Saharan Air Layer Tracking Product illustrating the level of dry air over the tropical Atlantic.

 

 

Tropical Weather, SAL

Saharan Air Layer 7-31-13 (8:00 pm)

 

Below is the surface analysis of the tropical Atlantic for this afternoon.

 

Tropical Weather, Surface Analysis

Tropical Atlantic Surface Analysis 7-31-13 (2:00 pm)

 

 

Below is the satellite image of the tropical Atlantic for this afternoon.

 

 

Tropical Weather, Satellite Image

Satellite Image 7-31-13 (2:15 pm)

 

Note, the milky/hazy appearance over the central/eastern Atlantic.  That is the SAL.

 

Most of the reliable forecast models do not have any significant tropical feature developing for the next 7 – 10 days.

 

Click here for the latest information from the National Hurricane Center.

 

 

Stay updated. Visit the website to check for constant updates via twitter or follow on twitter @Theweathercentr.

 

Southeast Florida Weather 7-31-13

Southeast Florida Weather

 

Analysis:

For southeast Florida weather, during the overnight hours, it was generally clear to partly cloudy. Isolated to widely scattered showers came ashore from the Atlantic and affected portions of the area.  Lows were generally middle 70’s to low 80’s.  Winds were light mostly easterly.

During the day, it was partly sunny early.  Widely scattered showers moved ashore, again affecting portions of the area.  Drier air had moved in which helped to reduce shower/thundershower activity.

 

Southeast Florida Weather, Moisture Level

Average Humidity 850 mb to 650 mb 7-31-13 (9:15 am)

 

By late morning, showers and a few thundershowers were developing over the interior areas of south Florida and they were moving westward.

During the afternoon, showers and thundershowers continued developing over the interior and spreading westward toward the western portion of south Florida. There was very little in the way of shower activity over the Atlantic and this kept the eastern areas of south Florida under mostly sunny to partly cloudy skies. By middle to late afternoon, most of the showers and thundershowers were focused over the western portion of south Florida.

Highs were mostly in the upper 80’s to low 90’s with few areas reaching middle 90’s.  Heat indices were around upper 90’s to low single 100’s.  Winds were generally easterly around 15 mph with occasionally higher gusts.

 

Forecast:

For tonight, it will be partly cloudy.  There will be widely scattered showers and thundershowers.  Lows will be in the middle 70’s to low 80’s

Winds will be east southeast at 10 – 15 mph.  Seas will be 2 – 3 feet.  Intracoastal waters and Biscayne Bay will have a moderate chop.

 

Thursday will be similar day as today.  With a general easterly flow pattern, the afternoon showers and thundershowers will be most focused over the interior and western portion of south Florida.  Also, as a surface trough (remnants of Dorian) approaches, some drier air may move in as south Florida will be on the subsidence side of the trough.

Also on Thursday, upper level trough digs south.  There will be a weakness near Florida between two upper Level Highs.  One is located over Texas and one over the central Atlantic.

 

Southeast Florida Weather, GFS Model

GFS 500 mb Forecast Model 7-31-13(12z) at 033 Hours

 

This will weaken the wind flow over the area by Friday and Saturday.  It will also focus most of the afternoon showers and thundershowers over the interior and northern portions of the area. As usual, outflow boundaries may allow some of the activity to be closer to the metro areas.

Meanwhile, the remnants of Dorian will be moving into the northwestern Bahamas near this weakness, plus the digging upper level trough.   It appears that part of the system will be tugged northward along with most of the moisture.  Therefore, most of the moisture will stay to the east of Florida.  The other portion system (surface feature) will continue moving westward across south Florida around Friday/Saturday. This may help to enhance showers and thundershowers across the area, especially over the interior sections with the daytime heating.

By later Saturday and rest of the weekend, the Atlantic High looks to have more control over the area which will provide for a more south and southwest wind flow aloft. Also, the upper level High will be suppressed further south with time leading to more westerly winds aloft.

 

Southeast Florida Weather, GFS Model

GFS 500 mb Forecast Model 7-31-13(12z) at 105 Hours

 

This typically will focus more of the afternoon showers and thundershowers to the eastern portion of the area.

 

For Thursday, it will be partly cloudy.  There will be widely scattered to scattered showers and thundershowers.  Highs will be middle 80’s to low 90’s.  Lows Thursday night will be middle 70’s to near 80.

Winds will be east and east southeast at 5 – 15 mph.  Seas will be around 2 feet.  Intracoastal waters and Biscayne Bay will have a light chop.

With an east and southeast wind flow, there will be the risk of rip currents along the southeast Florida Atlantic beaches.  There will be at least a slight risk of rip currents.  An update via twitter will be sent if there is a change to the rip current risk level.

For Friday, it will be partly cloudy.  There will be a good chance of showers and thundershowers.  Highs will be middle 80’s to low 90’s.  Lows Friday night will be middle 70’s to around 80.

Winds during the day will be easterly at 5 – 15 mph.  Winds will become briefly north/northeast Friday night over the southern areas becoming southwesterly late.  Winds over the northern portions (Palm Beach County) will be southeasterly.  The winds will around 10 – 15 mph for Friday night.  Seas will be 2 feet or less.  Intracoastal waters and Biscayne Bay will have a light chop.

With an onshore wind flow, there will be the risk of rip currents along the southeast Florida Atlantic beaches.  There will be at least a slight risk of rip currents.  An update via twitter will be sent if there is a change to the rip current risk level.

For Saturday, it will be partly sunny to partly cloudy.  There will be widely scattered to scattered showers and thundershowers.  Highs will be middle 80’s to low 90’s.  Lows Saturday night will be middle 70’s to around 80.

Winds will be southeasterly at 5 – 15 mph.  Seas will be around 2 feet.  Intracoastal waters and Biscayne Bay will have a light to moderate chop.

With a southeasterly wind flow, there will be the risk of rip currents along the southeast Florida Atlantic beaches.  There will be at least a slight risk of rip currents.  An update via twitter will be sent if there is a change to the rip current risk level.

 

By early to middle of next week, the upper level High will move northward and become better established.

 

Southeast Florida Weather, GFS Model

GFS 500 mb Forecast Model 7-31-13(12z) at 147 Hours

 

This will take the area back to a more pronounced easterly wind flow regime. This will favor the afternoon and evening showers and thundershowers back to the interior and western portion of south Florida.  The eastern section of the area will be more favored during the night and morning hours for showers and thundershowers.  This looks to continue for at least few days if not longer.  There may be some fluctuations to this regime due to position and strength of the High.

 

GFS 500 mb Forecast Model 7-31-13(12z) at 192 Hours

GFS 500 mb Forecast Model 7-31-13(12z) at 192 Hours

 

South Florida may be affected to what is known as SAL (Saharan Air Layer) early next week.  This is a layer of dust that comes off the western portions of Africa.  It may lead to hazy skies.  Read more about it in the Hurricane and Tropical Weather page for today.

 

Stay updated. Visit the website to check for constant updates via twitter or follow on twitter @Theweathercentr.

 

Tropical Weather Analysis 7-30-13

Southeast Florida Weather

 

In today’s tropical weather analysis, the NHC (National Hurricane Center) is monitoring a tropical wave and the remnants of Dorian.

The tropical wave is located in the central Atlantic approximately half way between the Lesser Antilles and the west coast of Africa.  The wave is moving west at 10 knots.  It appears on satellite animated imagery that it is moving quicker.  It also appears that it marks the leading edge of a surge in SAL (Saharan Air Layer) coming off of western Africa.  This SAL is hindering convection due to the dry and stable air of the SAL.

The remnants of Dorian located in the southeastern Bahamas have been struggling since late yesterday.  Although, there was a rather vigorous mid-level circulation, it could not sustain a low level center of circulation.  Below is the satellite animation of the remnants of Dorian appearing to progressively losing its convection and structure today.

 

Tropical Weather, Satellite Animation

Satellite Animation 7-30-13 (PM)

Tropical Weather, Satellite Animation

Satellite Animation – RGB 7-30-13 (PM)



The presence of 20 – 30 knots of wind shear due to the upper level Low did not allow for any further development and weakened it.  The upper level Low did weaken as much or back away as much as it was forecasted.

 

 

Tropical Weather, Wind Shear

Wind Shear 7-30-13 (8:00 PM)

 

Below is the animated water vapor animation.  It appears that the upper level Low is absorbing the mid-level circulation of Dorian’s remnants

 

Tropical Weather, Water Vapor

Water Vapor Animation 7-30-13 (PM)

 

The NHC is giving the system a low (0%) chance of developing into a tropical cyclone within the next 48 hours.  The system will be moving west northwest through the Bahamas.

 

Tropical Weather

Graphical Atlantic Tropical Weather Outlook 7-30-13 (8:00 pm) Click here for Text

 

Most of the reliable global forecast models do not show Dorian’s remnants to regenerate as the upper air environment is too hostile.  Forecast models are no longer are being run on the system as invest 91L was deactivated earlier today.

 

Tropical Weather

Invest 91L Status 7-30-13

 

 

Below is the CIMSS Meteosat Saharan Air Layer Tracking Product illustrating the level of dry air over the tropical Atlantic.

 

Tropical Weather, SAL

Saharan Air Layer 7-30-13 (8:00 pm)

 

There is an extensive surge of SAL emanating from western Africa.

Below is the surface analysis of the tropical Atlantic for this afternoon.

 

Tropical Weather, Surface Analysis

Tropical Atlantic Surface Analysis 7-30-13 (2:00 pm)

 

Below is the satellite image of the tropical Atlantic for this afternoon.

 

Tropical Weather, Satellite Image

Satellite Image 7-30-13 (2:15 pm)

 

Most of the reliable forecast models do not have any significant tropical feature developing for the next 7 – 10 days.

 

 

Click here for the latest information from the National Hurricane Center.

 

 

 

Stay updated. Visit the website to check for constant updates via twitter or follow on twitter @Theweathercentr.

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