Former TS Dorian

[srainhoutx]

12Z Tropical Guidance has updated and now has Tropical Storm Dorian. Waiting on the official update from the NHC.

[wxman57]

Latest model guidance initialized at 45 kts (50 mph). Looks like a good estimate to me. It's a small storm. Distance across the core is only 75 miles. Total width including that long spiral band to the south is 150 miles.

[srainhoutx]

TROPICAL STORM DORIAN DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
1100 AM EDT WED JUL 24 2013

VISIBLE SATELLITE IMAGERY AND RECENT ASCAT SCATTEROMETER WINDS
INDICATE THAT THE TROPICAL DEPRESSION HAS BECOME BETTER ORGANIZED
AND HAS STRENGTHENED INTO TROPICAL STORM DORIAN. THE INITIAL
INTENSITY OF 45 KT IS BASED ON A 38-KT ASCAT SURFACE WIND AT
1111Z... AND VARIOUS OBJECTIVE SATELLITE INTENSITY ESTIMATES OF
ABOUT 45 KT.

THE INITIAL MOTION ESTIMATE IS 285/18 KT. DORIAN IS EXPECTED TO BE
STEERED WEST-NORTHWESTWARD TO WESTWARD BY A STRONG DEEP-LAYER
SUBTROPICAL RIDGE OVER THE CENTRAL AND EASTERN ATLANTIC. THE NHC
MODEL GUIDANCE REMAINS TIGHTLY PACKED IN EXCELLENT AGREEMENT ON
THIS TRACK SCENARIO...WITH THE ONLY DIFFERENCES BEING SLIGHT
VARIATIONS IN THE FORWARD SPEED. THE NHC OFFICIAL FORECAST TRACK IS
SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE MULTI-MODEL
CONSENSUS TVCN.

FOR THE NEXT 24 HOURS OR SO...THE VERTICAL SHEAR IS FORECAST TO BE
VERY LOW WHILE DORIAN REMAINS OVER MARGINALLY WARM SSTS. HOWEVER...
DURING THE 24-48 HOUR TIME PERIOD...DORIAN WILL BE MOVING OVER 25C
SSTS...WHICH COULD INDUCE SOME SLIGHT WEAKENING. THE CYCLONE IS
EXPECTED TO MAINTAIN THE CURRENT FAVORABLE EQUATORIAL INFLOW OF
WARM UNSTABLE AIR THAT IS OFFSETTING THE COOLER MORE STABLE AIR
BEING INGESTED FROM THE NORTH...AND THAT COULD OFFSET THE EFFECTS
OF DORIAN PASSING OVER COOLER WATERS. FOR THAT REASON...THE
INTENSITY FORECAST ONLY SHOWS SLIGHT WEAKENING AT 36- AND 48-HOURS.
AFTER THAT...THE CYCLONE IS LIKELY TO ENCOUNTER BOTH WARMER WATER
AND INCREASING WESTERLY SHEAR...SO THE INTENSITY FORECAST IS HELD
STEADY. THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE
PREVIOUS ADVISORY THROUGH THE NEXT 24 HOURS DUE TO THE HIGHER
INITIAL INTENSITY...BUT THEN FOLLOWS THE TREND OF CONSENSUS MODELS.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 14.3N 29.9W 45 KT 50 MPH
12H 25/0000Z 15.0N 32.6W 50 KT 60 MPH
24H 25/1200Z 15.8N 36.1W 50 KT 60 MPH
36H 26/0000Z 16.4N 39.8W 45 KT 50 MPH
48H 26/1200Z 17.1N 43.4W 40 KT 45 MPH
72H 27/1200Z 18.3N 51.2W 40 KT 45 MPH
96H 28/1200Z 19.3N 58.2W 40 KT 45 MPH
120H 29/1200Z 20.1N 64.0W 40 KT 45 MPH

$$
FORECASTER STEWART

[srainhoutx]

TROPICAL STORM DORIAN DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
500 PM EDT WED JUL 24 2013

CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THAT THE
CONVECTIVE STRUCTURE OF DORIAN HAS CHANGED LITTLE SINCE THE
PREVIOUS ADVISORY. HOWEVER...UPPER-LEVEL ANTICYCLONIC OUTFLOW HAS
IMPROVED IN ALL QUADRANTS AS THE VERTICAL SHEAR HAS DIMINISHED
SIGNIFICANTLY. THE INITIAL INTENSITY OF 45 KT IS BASED ON A
SATELLITE INTENSITY ESTIMATE OF T3.0/45 KT FROM TAFB.

THE INITIAL MOTION ESTIMATE IS 285/17 KT. DORIAN IS EXPECTED TO
REMAIN SOUTH OF AND MOVE WEST-NORTHWESTWARD TO WESTWARD IN TANDEM
WITH A STRONG SUBTROPICAL RIDGE LOCATED WELL TO THE NORTH. THE NHC
MODEL GUIDANCE CONTINUES TO REMAIN TIGHTLY PACKED AND IN EXCELLENT
AGREEMENT ON THIS SCENARIO. THE ONLY DIFFERENCES IN THE MODELS ARE
THE FORWARD SPEED...WHICH IS DUE TO THE STRENGTH AND VERTICAL DEPTH
OF DORIAN. THE GFS...UKMET...AND CANADIAN MODELS MAINTAIN A ROBUST
AND MORE VERTICALLY DEEP CYCLONE...WHICH GETS STEERED MORE SLOWLY
BY THE DEEPER MEAN FLOW. IN CONTRAST...THE HWRF AND ECMWF MODELS
WEAKEN DORIAN SIGNIFICANTLY AS THE CYCLONE PASSES OVER COOLER WATER
DURING THE NEXT 48 HOURS...WHICH RESULTS IN A SHALLOWER AND WEAKER
VORTEX BEING STEERED MORE RAPIDLY WESTWARD BY THE STRONGER EASTERLY
TRADE WIND FLOW. GIVEN THAT DORIAN WILL BE MOVING OVER COOLER WATER
AT A BRISK 18 KT FOR THE NEXT 24-36 HOURS...MY FEELING IS THAT THE
CYCLONE WILL NOT WEAKEN AS MUCH AS THE SOME OF THE MODELS ARE
FORECASTING...AND AS A RESULT...THE OFFICIAL TRACK FORECAST LEANS
TOWARD THE SLOWER GFS...UKMET...AND CANADIAN MODEL SOLUTIONS.

DORIAN IS BEGINNING TO MOVE OVER SUB-26C SSTS...AND THE CYCLONE
SHOULD REMAIN OVER COOLER WATERS NEAR 25C FOR THE NEXT 12 HOURS
OR SO...WHICH COULD INDUCE SOME SLIGHT WEAKENING. HOWEVER...BY 36-48
HOURS...DORIAN WILL BE MOVING BACK OVER SSTS WARMER THAN 26C AND IN
A VERY LOW VERTICAL SHEAR ENVIRONMENT...WHICH SHOULD ALLOW FOR SOME
RE-STRENGTHENING TO OCCUR. THE LATEST RUNS OF THE GFS AND ECMWF
ARE SHOWING A LESS HOSTILE UPPER-AIR PATTERN NEAR THE END OF THE
FORECAST PERIOD...WITH MORE RIDGING AND LESS INFLUENCE FROM AN
UPPER-LEVEL TROUGH OVER THE BAHAMAS. IN CONSIDERATION OF THAT...
THE FORECAST INTENSITIES AT DAYS 4-5 HAVE BEEN INCREASED RELATIVE
TO THE PREVIOUS ADVISORY.

FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 14.6N 31.4W 45 KT 50 MPH
12H 25/0600Z 15.3N 34.0W 45 KT 50 MPH
24H 25/1800Z 16.1N 37.5W 40 KT 45 MPH
36H 26/0600Z 16.8N 41.0W 40 KT 45 MPH
48H 26/1800Z 17.5N 44.7W 45 KT 50 MPH
72H 27/1800Z 18.7N 51.8W 45 KT 50 MPH
96H 28/1800Z 19.6N 58.9W 50 KT 60 MPH
120H 29/1800Z 20.0N 64.0W 50 KT 60 MPH

$$
FORECASTER STEWART

[srainhoutx]

Sunset across the Atlantic on Dorian. I've also noticed a bit of a spin around 10N and 35W or SW of TS Dorian. This feature exited Africa a day or two before the main circulation that became Dorian and is near the ITCZ.

[srainhoutx]

Afternoon e-mail update from Jeff:

4th tropical storm of the Atlantic hurricane season forms over the far eastern Atlantic Ocean about 500 miles W of the Cape Verde Islands.

Discussion:
TD # 4 was upgraded to a tropical storm this morning at 1000am. Since then the system has maintained or increased its upper level outflow in all sections of the system and has exhibited a ball of deep convection near/over the center. Dorian is moving W to WNW at a fast rate of speed (20mph) and this motion should continue.

Track:
Dorian is located south of a powerful north Atlantic ridge of high pressure and this high pressure cell is forecast to move generally W in conjunction with the W to WNW movement of Dorian. Global model track guidance is very well clustered through the next 3 days on the system crossing the open Atlantic Ocean. The models begin to diverge toward the end of the 5-day forecast period in which their handling of troughing currently along the US east coast comes into question. For not the forecast track through day 5 is of fairly high confidence and supported by good model agreement.

Intensity:
Dorian is a small compact small currently which can respond quickly to environmental changes around the circulation (dry air or wind shear) and this response can be both on the sides of rapid weakening or rapid intensification. Ahead of the system is a large mass of dry air that moved off the African coast a few days ago and this dry air may at times become ingested into the circulation. However small systems tend to be able to “protect” themselves at times from such dry air intrusions and thus far Dorian is holding its own. Dorian will also be crossing water temperatures currently marginal for development, but I think this will have a lower impact compared to the dry air. Wind shear is light currently with favorable outflow so if a well-defined inner core can develop, Dorian will begin to intensify especially once west of the cooler waters. Nearly all of the intensity guidance keep Dorian as a tropical storm for the next 5 days and in fact the ECMWF model (a highly respected model) weakens the system into an open wave. Given the support by the other guidance and the robust circulation associated with the system I am leaning away from the ECMWF suggesting of an open wave in favor of a closed system. With that said if dry air does wrap into the inner core then there could be some issues for the system over the next 3-4 days.

NOTE: now is a good time to remind all that the error cone represented in the NHC forecast track below is just that (the average of the track error by time over the last 5 years). It in no way represents the potential impacts (rainfall, wind, storm surge) from a tropical cyclone.

NHC Forecast Track and Error Cone:

[Paul Robison]

Hmmm.....

[srainhoutx]

The 12Z Track and Intensity guidance suggest a general WNW motion and little in the way of strengthening as it nears the Turks & Caicos in the SE Bahamas.

[wxman57]

Assuming Dorian survives for a week, the most likely scenario remains a recurve near the Bahamas and no Gulf entry.

[wxman57]

Some climo fun from Coastal Services Center. I plotted all storms which passed within 150NM (about 180 miles) from Dorian's current point. 93 such storms were found. Of those, only 2 entered the Gulf - Ike (2008) and the 1915 Galveston hurricane. From this, we can conclude that:

There is about a 2.15% chance that Dorian will enter the Gulf. However, if it does enter the Gulf, there is a 100% chance it will hit Houston/Galveston!

[Paul Robison]

From SWFMD.GOV:

South Florida Water Management District

Tropical Conditions Report

12:06PM Thursday, July 25, 2013 (eps)



Current Conditions:



LOCAL STORM/HURRICANE WATCHES/WARNINGS: None
Tropical Storm Force or Greater Winds Within 48 Hours: No



DISCUSSION:



At 5am, TROPICAL STORM DORIAN was located near 15.6N 34.5W, or about 700 miles west of the Cape Verde Islands, moving west-northwest near 17 mph with sustained winds up to 60 mph. Some strengthening is expected as Dorian heads generally westward along the southern edge of a high pressure ridge over the next few days. In the extended outlook, a weakness in the high pressure ridge located east of Florida would tend to draw the system more northward. If Dorian were to become a threat to the District, any potential impact of the system would be still about a week away.


BTW: Who was it that posted a forecast model image depicting a TS/hurricane hitting Houston coming from the Central Atlantic. Anybody think that could be Dorian?

[Belmer]

GFS models initialized as of 2am raise an eyebrow.
I read where this may not be an Ike storm as far as intensity goes, but the track ever so slightly looks familiar.
I know it's WAY to early to make a call on what this storm will do, but I know some of the meteorologist on air, like Travis Herzog, Tim Heller, Anthony Yanez basically said this would NOT be a Gulf storm, and were pretty adamant about it. While that still may be the case, I believe whenever you have a storm out in the Atlantic, anything is and can be possible and just like Ike did, it can give us surprise after surprise after surprise.
With that said.. Frank, Brooks and David Paul have done a good job on not hyping this storm, but constantly letting folks be aware of this storm and to monitor it.

Nonetheless, the models look interesting...

[srainhoutx]

Morning e-mail from Jeff:

Poorly organized tropical storm moving westward over the open Atlantic Ocean.

Discussion:
As suspected a couple of days ago Dorian has ran into somewhat unfavorable conditions with dry air and upper level wind shear taking a toll on the system. After a review of the first few visible images of the day, I am hard pressed to find a low level circulation, but for the sake of continuity assume there is likely a small circulation that remains under the current moderate bursts of convection. The overall cloud and convective pattern has greatly decline from yesterday, although Dorian has never had overly strong sustained convection. It is very possible that Dorian will not survive the next 48-72 hours dealing with dry air and upper level wind shear.

Track:
Dorian is moving generally W at near 20mph on the south side of a strong Atlantic high pressure ridge. The trade wind flow north of the system is clearly noted by the fast low cloud motions from ENE to WSW. The current ridge of high pressure helping to steer the system is forecasted to move generally westward in tandem with Dorian keeping the storm on a general westward track for the next 5 days. Model guidance is in good agreement with this westward track and this has been a southward adjustment over the past 24 hours. After 5 days what form Dorian is in begins to come into play as a trough of low pressure is expected to be in place along the mid-Atlantic coast into the NE US. Models have been generally backing down on the intensity and amplitude or depth of this trough and have been increasing more ridging over the SW Atlantic and FL north of Dorian. Many of the GFS ensembles which were showing a recurve of Dorian over the Bahamas are now more split between that pattern and some degree of entry into the Gulf of Mexico. For now expect to see Dorian in some form near eastern Cuba in about 5 days.

Intensity:
The bigger question marks comes on the intensity side of things. Dorian is struggling due to the dry air to its west and some upper level shear. As stated a few days ago, small systems such as Dorian tend to respond very rapidly to surrounding environmental changes and it is very easy to disrupt their small and fragile inner cores. It is likely that dry air has been getting entrained into the system which is keeping convection to a minimum. The recent increase in wind shear has resulted in the low level center becoming exposed on the western side of the thunderstorm activity at times and the system is not vertically aligned. The global forecast models have never been overly supportive of Dorian and it is very possible like with Chantal that Dorian degrades into an open wave at some point over the next few days. If Dorian does weaken more, it would be possible that it would be steered more westward and into some of the mountainous islands of the northern Caribbean Sea. The current NHC forecast is running on the higher side of the intensity guidance clustering especially in the 72-120 hour time period. Most of the models keep Dorian as a 50kt or weaker tropical storm and the ECMWF, GFS, and HWRF all show weakening to below a tropical storm…possibly an open wave.

[wxman57]

My vote is for dissipation within 12-24 hrs now. I think it's losing or has lost its LLC. Wave approaching the DR in 4-5 days. No redevelopment likely.

[srainhoutx]

My vote is for dissipation within 12-24 hrs now. I think it's losing or has lost its LLC. Wave approaching the DR in 4-5 days. No redevelopment likely.

I agree. August and September may be active enough...

TROPICAL STORM DORIAN DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
1100 AM AST FRI JUL 26 2013

VISIBLE SATELLITE IMAGES SHOW THAT THE CLOUD PATTERN OF DORIAN IS
RATHER DISORGANIZED...WITH LITTLE OR NO EVIDENCE OF BANDING
FEATURES. THE CURRENT INTENSITY ESTIMATE IS HELD AT 45 KT IN
AGREEMENT WITH A DVORAK ESTIMATE FROM TAFB AND A RECENT ASCAT
OVERPASS. WATER VAPOR IMAGERY AND TOTAL PRECIPITABLE WATER DATA
INDICATE THAT DORIAN WILL BE ENCOUNTERING DRY AIR OVER THE NEXT DAY
OR SO AND THIS...ALONG WITH MODERATE WEST-SOUTHWESTERLY
SHEAR...SHOULD CAUSE SOME WEAKENING OF THE TROPICAL CYCLONE. LATER
IN THE FORECAST PERIOD...THE DYNAMICAL GUIDANCE SHOW ONLY A SLIGHT
DECREASE IN SHEAR. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO
THE PREVIOUS ONE AND IS ONLY A LITTLE BELOW THE STATISTICAL-
DYNAMICAL GUIDANCE. AN ALTERNATIVE SCENARIO...WHICH IS CERTAINLY
POSSIBLE...IS THAT DORIAN COULD DEGENERATE INTO A TROPICAL WAVE
WITHIN THE NEXT COUPLE OF DAYS.

THE STORM CONTINUES TO MOVE RAPIDLY WEST-NORTHWESTWARD IN THE FLOW
SOUTH OF A STRONG MID- TO LOW-LEVEL HIGH PRESSURE AREA. THE GLOBAL
MODELS CONTINUE TO FORECAST THE RIDGE TO BUILD WESTWARD TO THE
NORTH OF DORIAN...WHICH SHOULD CAUSE THE TROPICAL CYCLONE TO MOVE
GENERALLY TOWARD THE WEST OR SLIGHTLY NORTH OF WEST THROUGH THE
FORECAST PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE
PREVIOUS NHC TRACK AND LEANS TOWARD THE GFS AND HWRF SOLUTIONS.
THIS IS ALSO CLOSE TO...BUT A LITTLE SLOWER THAN...THE FLORIDA
STATE UNIVERSITY SUPERENSEMBLE.

FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 17.7N 43.4W 45 KT 50 MPH
12H 27/0000Z 18.1N 46.4W 40 KT 45 MPH
24H 27/1200Z 18.7N 50.3W 40 KT 45 MPH
36H 28/0000Z 19.2N 54.2W 40 KT 45 MPH
48H 28/1200Z 19.7N 58.2W 40 KT 45 MPH
72H 29/1200Z 20.2N 64.4W 40 KT 45 MPH
96H 30/1200Z 20.5N 70.0W 45 KT 50 MPH
120H 31/1200Z 21.5N 75.0W 45 KT 50 MPH

$$
FORECASTER PASCH

[srainhoutx]

TS Dorian's center is completely exposed at this time and unless storms begin to fire again this evening, its life may be near the end. That said the latest track as switched to W from WNW and the 12Z GFS Ensembles are agreement that a more Westerly motion will remain in the days ahead if it is still an identifiable disturbance.

[tireman4]

Do we call Bones yet?

[srainhoutx]

TROPICAL STORM DORIAN DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
500 PM AST FRI JUL 26 2013

UNDER THE INFLUENCE OF WESTERLY SHEAR AND DRIER AIR...DORIAN HAS
BECOME EVEN LESS ORGANIZED THAN IT WAS EARLIER TODAY. VISIBLE
SATELLITE IMAGES INDICATE THAT THE LOW-LEVEL CENTER HAS BECOME
DISPLACED TO THE WEST OF AN AREA OF WEAKENING DEEP CONVECTION.
ALSO...ANIMATION OF THE IMAGERY SHOWS THAT CIRCULATION IS BARELY
CLOSED AT THIS TIME. USING A BLEND OF DVORAK ESTIMATES FROM SAB
AND TAFB...THE ADVISORY INTENSITY IS REDUCED TO 40 KT. THE
OFFICIAL WIND SPEED FORECAST NOW SHOWS GRADUAL WEAKENING WITH
DISSIPATION BY DAY 5...IN GENERAL AGREEMENT WITH THE GFDL AND HWRF
GUIDANCE. GIVEN THE CURRENT TRENDS...HOWEVER...THE SYSTEM COULD
DEGENERATE INTO AN OPEN WAVE MUCH SOONER THAN THAT.

THE LATEST CENTER FIXES INDICATE THAT DORIAN IS MOVING RAPIDLY
WESTWARD...SLIGHTLY TO THE SOUTH OF THE PREVIOUS TRACK. A STRONG
LOW- TO MID-LEVEL HIGH PRESSURE SYSTEM TO THE NORTH OF DORIAN IS
FORECAST TO BUILD WESTWARD WITH TIME BY THE GLOBAL MODELS. THIS
SHOULD MAINTAIN A GENERALLY WESTWARD MOTION FOR THE NEXT SEVERAL
DAYS. THE OFFICIAL TRACK FORECAST IS SHIFTED A BIT TO THE SOUTH OF
THE PREVIOUS ONE AND IS ABOUT IN THE MIDDLE OF THE GUIDANCE
ENVELOPE. THE LATEST ECMWF MODEL TRACK IS A LITTLE FARTHER NORTH
BUT THAT MODEL DOES NOT INITIALIZE NOR FORECAST A CLOSED SURFACE
CIRCULATION.



FORECAST POSITIONS AND MAX WINDS

INIT 26/2100Z 17.8N 45.8W 40 KT 45 MPH
12H 27/0600Z 18.2N 48.8W 40 KT 45 MPH
24H 27/1800Z 18.6N 52.8W 35 KT 40 MPH
36H 28/0600Z 19.0N 56.7W 35 KT 40 MPH
48H 28/1800Z 19.5N 60.5W 30 KT 35 MPH
72H 29/1800Z 20.0N 67.0W 30 KT 35 MPH
96H 30/1800Z 20.5N 74.0W 25 KT 30 MPH
120H 31/1800Z...DISSIPATED

$$
FORECASTER PASCH

[TexasBreeze]

TS Flossie in the East/Central Pac could become more interesting than Dorian in seeing if it strikes Hawaii as a classified ts or td. NHC says it will be close.

[srainhoutx]

It appears that Dorian was able to slip underneath a weak anti cyclonic upper ridge and maintained its self over night. The track guidance suggest westward bound for the duration and the statistical SHIP intensity guidance strengthens Dorian as it passes N of Puerto Rico and Hispaniola.