Hurricane Cristobal: Near The Bahamas

[Katdaddy]

Invest 96L still looking disorganized this morning and expected to continue WNW into the Caribbean Sea over the next 5 days. As it approaches the NW Caribbean Sea conditions could be more favorable for development. Excerpt from this morning's New Orleans AFD:

AS FOR THE TROPICS...NHC CONTINUES TO MONITOR AN AREA OF LOW PRESSURE EAST OF THE WINDWARD ISLANDS WITH A 50 PERCENT CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE OVER THE NEXT 5 DAYS AS IT MOVES INTO THE CARIBBEAN. MDLS DIFFER SIGNIFICANTLY ON EVENTUAL TRACK OF THIS SYSTEM AND WITH NOTHING EVEN DEVELOPED YET IT IS FUTILE TO TRY TO FCST WHERE THIS POSSIBLE SYSTEM WILL GO. AS ALWAYS IN MID
AUG...ITS HURRICANE SEASON AND NO MATTER WHAT YOU SHOULD PAY ATTENTION TO THE TROPICS.

[wxman57]

I'm not seeing any threat for the upper Texas coast at this time. I think it could develop into a TS south of Cuba around Monday and enter the SE Gulf by Tuesday. Threat from mid LA coast east to Florida. Can't rule out a track east of Florida, but I think it has a better shot at entering the Gulf.

[Andrew]

Models are doing a poor job right now with initialization of the storm. Most models want to take a NW track over the next day or two instead of the current WNW movement. We will see if the convection that has picked up slightly will continue into the overnight hours. Also another thing to note is the stronger trough that is expected to cross the eastern part of the US next week. It's forecasted to be deeper than originally thought.

[srainhoutx]

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT WED AUG 20 2014

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

1. Shower and thunderstorm activity associated with an elongated area
of low pressure located several hundred miles east of the Windward
Islands has become a little better organized during the past few
hours. Additional slow development of this system is possible during
the next day or two, and a tropical depression could form as the
system moves west-northwestward at 10 to 15 mph across the Lesser
Antilles and into the Caribbean Sea. After that time, land
interaction could limit development potential over the weekend.
Regardless of tropical cyclone formation, gusty winds and heavy
rainfall are possible across portions of the Lesser Antilles, Puerto
Rico, and the Virgin Islands on Thursday night and Friday. Interests
in those islands should closely monitor the progress of this system.
An Air Force Reserve Hurricane Hunter aircraft is scheduled to
investigate this system tomorrow afternoon, if necessary.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...high...60 percent.

Forecaster Brennan

[srainhoutx]

Evening Update from Jeff:

Monsoonal trough east of the Windward Islands is becoming better organized.

 

Development trend continues with the area of disturbed weather east of the Windward Islands. The broad trough of low pressure appears to be consolidating into a board surface low pressure center as expected on the SW flank of the mid Atlantic monsoon trough. Deep convection, while limited, has expanded this evening in the area of the lowering pressures. Dry air is lurking off to the north of the system and fairly strong upper level winds are located near the Windward Islands in association with an upper level trough north of Puerto Rico.

 

Overall conditions are favorable for slow development and gradual consolidation of the system into e tropical cyclone over the next few days. NHC currently gives the system a 50% chance of development in 48 hours and 70% chance in 5 days.

 

Track:

There has been a fairly significant track guidance shift over the last 24 hours with the reasoning lying in the position and intensity of the trough over the W ATL this weekend into early next week. Model guidance yesterday had a fairly shallow trough and a system tracking far enough south in the Caribbean to not feel the pull of this trough. Guidance today suggest 96L tracking more NW through the extreme northern Caribbean Sea or even north of the Caribbean Sea and feeling a greater pull from a stronger trough. This results in several of the operational global models at least suggesting a NW track or recurve near/east of FL and near the SE US coast. Factors that will influence the downstream track forecast include:

 

1)      Where the low level center eventually forms

2)      The intensity of the system in the 24-72 hour period

3)      The depth of the W ATL trough

4)      Position and intensity of ridging over the mid-south

 

Each of those factors will ultimately help in determining the final track solution. I have a hard time placing much stock in any of the guidance…except for general steering…without a low level center fixed and ingested into the model guidance. Some of this can be seen in the GFS and ECMWF ensemble mean runs showing a fairly large spread at 120 hours from the central Gulf to the SW Atlantic. In that regard there really has not been much change since yesterday with the upper air pattern suggesting the Gulf of Mexico and SE US coasts a potential threat. One thing of interest is that the pattern of W ATL/US E coast troughing has been in place nearly all summer and the forecasted attempt this weekend into early next week to break down this pattern with SE US ridging may in the end up failing to materialize allowing a greater potential for the system to curve northward and out to sea.  

 

NOTE: USAF recon. aircraft is tasked to investigate the system tomorrow afternoon if needed.

 

NHC Tropical Weather Outlook: Highlighted region indicates development region over the next 5 days

 

[srainhoutx]

96L continues to have a broad elongated area of low pressure and some shear and dry air entrainment from the N continues to keep the convection from consolidating. While the track guidance has shifted E, the reliable 00Z European Ensemble Mean suggests that if this disturbance survives land interaction with Hispaniola and Cuba, anywhere from the Yucatan Peninsula across the Gulf of Mexico and Florida into the SE United States may feel the effects of the disturbance. Until an actual closed surface low develops, caution is advised on buying into one particular dynamical computer model over another. RECON is scheduled to investigate later today and the data gained by that mission should assist the various computer guidance regarding the development and future track of this tropical disturbance.

RECON schedule issued moments ago for tomorrow and Saturday...

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT THU 21 AUGUST 2014
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 22/1100Z TO 23/1100Z AUGUST 2014
TCPOD NUMBER.....14-082

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA
FLIGHT ONE -- TEAL 77
A. 22/1730Z, 2330Z
B. AFXXX 0304A CYCLONE
C. 22/1630Z
D. 19.5N 66.5W
E. 22/1715Z TO 22/2330Z
F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 75
A. 23/0530Z, 1130Z
B. AFXXX 0404A CYCLONE
C. 23/0400Z
D. 21.0N 70.0W
E. 23/0515Z TO 23/1130Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY.....CONTINUE 6-HRLY FIXES
IF SYSTEM DEVELOPS.

[prospects8903]

Looking at the visible loop it looks like it is taking a more westerly track this morning

[prospects8903]

Is there still a chance this is a western GOM threat?

[ticka1]

Wow a difference two days makes. The models are now trending this out to see and missing CONUS all together. Good - this country does not need a tropic system this year.

[wxman57]

No Gulf storm out of this. Next!...

[prospects8903]

I'm seeing talk that the CoC may be reforming more to west...If that's the case do you still believe it's not a GOM storm?

[wxman57]

Chances of 96L entering the Gulf are not zero, but they appear low.

[TexasBreeze]

18z GFS is no longer out to sea it rides up Fla then up the east coast. Just one model suggestion.

[cperk]

[quote="TexasBreeze"]18z GFS is no longer out to sea it rides up Fla then up the east coast. Just one model suggestion.[/quote


Nice shift to the west on that run.

[Ptarmigan]

Latest forecast on where 96L will go. Yesterday a fish storm, now a westward trend.




Most intensity forecast model have it as a tropical storm by tomorrow.

[skidog40]

well to me system is a little further south than forecasted

[srainhoutx]

As of 8:00AM EDT Saturday...(RECON is currently investigating and finding lower pressures near 1006 MB)

...SPECIAL FEATURES...

A 1008 MB LOW IS LOCATED 10 NM MILES N OF THE COAST OF
HISPANIOLA NEAR 20N70W...MOVING WNW AT 10-15 KT. A SURFACE
TROUGH EXTENDS N FROM THE LOW CENTER TO 26N70W. SCATTERED
MODERATE TO STRONG CONVECTION IS LOCATED OVER HISPANIOLA AND THE
S BAHAMAS FROM 16N-23N BETWEEN 65W-73W. THIS LOW HAS BEEN
GETTING BETTER ORGANIZED IN THE PAST 12 HOURS. GUSTY WINDS AND
HEAVY RAIN ARE EXPECTED ACROSS PUERTO RICO...HISPANIOLA...THE
BAHAMAS...AND THE OPEN WATERS BETWEEN THESE ISLANDS TODAY. HEAVY
RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUDSLIDES...
ESPECIALLY IN THE MOUNTAINOUS AREAS OF HISPANIOLA AND PUERTO
RICO. GRADUAL DEVELOPMENT OF THE LOW IS EXPECTED DURING THE NEXT
FEW DAYS AS IT MOVES ALONG OR NORTH OF THE GREATER ANTILLES.
INTERESTS DOWNSTREAM OF THE LOW SHOULD MONITOR CLOSELY THE
PROGRESS OF THIS SYSTEM. CHANCES FOR DEVELOPMENT INTO A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS IS HIGH.

[Rip76]

Looks like recon may have found a LLC south of Turks & Caicos.
21.51N 72.15W (or close)

[tireman4]

TD 4 now?
000
WTNT34 KNHC 232048
TCPAT4

BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 1...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM AST SAT AUG 23 2014

CORRECTED TYPO IN HEADLINE

...TROPICAL DEPRESSION FORMS OVER THE TURKS AND CAICOS...
...TROPICAL STORM WARNING ISSUED FOR THE TURKS AND CAICOS
AND PORTIONS OF THE BAHAMAS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...21.8N 72.3W
ABOUT 75 MI...120 KM NE OF GREAT INAGUA ISLAND
ABOUT 255 MI...410 KM ESE OF THE CENTRAL BAHAMAS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF THE BAHAMAS HAS ISSUED A TROPICAL STORM WARNING
FOR THE SOUTHEASTERN BAHAMAS...INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS...AS WELL AS FOR THE TURKS AND CAICOS ISLANDS...AND FOR THE
CENTRAL BAHAMAS...INCLUDING CAT ISLAND...THE EXUMAS...LONG
ISLAND...RUM CAY...AND SAN SALVADOR.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* SOUTHEASTERN BAHAMAS...INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS...AS WELL AS FOR THE TURKS AND CAICOS ISLANDS
* CENTRAL BAHAMAS...INCLUDING CAT ISLAND...THE EXUMAS...LONG
ISLAND...RUM CAY...AND SAN SALVADOR

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN
THE NEXT 24 HOURS.

INTERESTS IN THE NORTHWESTERN BAHAMAS SHOULD MONITOR THE PROGRESS
OF THIS SYSTEM.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION FOUR
WAS LOCATED NEAR LATITUDE 21.8 NORTH...LONGITUDE 72.3 WEST. THE
DEPRESSION IS MOVING TOWARD THE NORTHWEST NEAR 12 MPH...19 KM/H. A
NORTHWESTWARD MOTION IS EXPECTED TO CONTINUE TONIGHT AND SUNDAY...
FOLLOWED BY A TURN TOWARD THE NORTH-NORTHWEST AND A DECREASE IN
FORWARD SPEED SUNDAY NIGHT AND MONDAY. ON THE FORECAST TRACK...THE
CENTER OF THE DEPRESSION WILL CONTINUE MOVING NEAR OR OVER THE
TURKS AND CAICOS AND SOUTHEASTERN BAHAMAS TONIGHT AND PASS NEAR
OR OVER PORTIONS OF THE CENTRAL BAHAMAS ON SUNDAY AND MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND THE DEPRESSION IS FORECAST TO BECOME A TROPICAL STORM BY SUNDAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON SURFACE DATA FROM
PROVIDENCIALES IN THE TURKS AND CAICOS ISLANDS IS 1005 MB...29.68
INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE RAINFALL TOTALS OF
4 TO 8 INCHES OVER THE SOUTHEASTERN BAHAMAS...THE TURKS AND
CAICOS ISLANDS...AND THE CENTRAL BAHAMAS THROUGH TUESDAY...WITH
ISOLATED AMOUNTS AROUND 12 INCHES POSSIBLE. STORM TOTAL RAINFALL
AMOUNTS OF UP TO 12 INCHES ARE POSSIBLE IN PORTIONS OF HISPANIOLA...
WHERE THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND
MUDSLIDES...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO SPREAD NORTHWARD
ACROSS THE WARNING AREA THROUGH SUNDAY NIGHT.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...800 PM AST.
NEXT COMPLETE ADVISORY...1100 PM AST.

$$
FORECASTER BRENNAN

[srainhoutx]

Update from Jeff regarding TD 4...

Tropical Depression forms over the SE Bahamas.

Discussion:

The tropical wave which has been traveling across the Greater Antilles for the past few days has finally developed a closed low level circulation and enough organized convection to be declared a tropical cyclone. USAF aircraft was able to close off a surface circulation over the SE Bahamas with a surface pressure of 1005mb. The satellite presentation shows banding features and established upper level outflow on the eastern and northern side of the large circulation and some restriction and weak wind shear over the western side of the system. The weak SW wind shear is a result of an upper level low in the region of Cuba/S FL.

Track:

TD 4 is moving toward the NW toward a break in the sub-tropical ridge over the W ATL caused by a trough along the US east coast. Dynamic global models have been and continue to greatly struggle with the upper air pattern over the SE US and W ATL over the next several days which is resulting in large variations of forecast tracks and swings between each model and each model run. The forecast track confidence is below average for TD 4.

There appears to be 3 plausible scenarios for the eventual track:

1) The western ATL trough is deep and strong enough to capture TD 4 and pull it northward off the US east coast and eventually out to sea…possibly nearing NC at some point. This track is supported by the ECMWF, GFS, and CMC.

2) The western ATL trough begins to lift out after pulling the system NW to NNW in the short term only to have high pressure behind the trough build in over the top of the system and to the NE blocking a full recurve and directing the system back toward the NW or WNW toward the SE US/FL coast. This solution would also offer a slow period over motion in the 36-96 hour time period off the FL east coast in the northern Bahamas.

3) The trough is unable to pull the system northward and the building post trough ridging forces the system toward the W or WNW toward S FL or the FL Keys and into the eastern Gulf of Mexico.

Given the motion over the last 24 hours it would appear that the system is being influenced enough by the trough that solution #3 looks the least likely with about equal support for # 1 and # 2. There is quite considerable spread in the GFS and ECMWF ensemble means so the ultimate track of this system is fairly uncertain and the spread in those ensembles are a result of the uncertainty of the capture of the trough or trapping of a building ridge…which have two significantly varying end results.

The current NHC forecast follows closely the TVNC consensus track of the major global models which is the best course of action in such wide model spread and disagreement.

Intensity:

The intensity forecast is about as problematic as the track forecast. TD 4 is a very large and sprawling system which will take time (and has) to consolidate. The upper level low over the FL Straits will move westward and should help reduce upper level SW wind shear over the system in the next 24-36 hours and this is supported by nearly all global models and the hurricane forecast models (HWRF and GFDL) all showing gradual intensification. The system will be moving over very warm waters so if wind shear and dry air stay away then conditions will be overly favorable for intensification. The intensity guidance is spread anywhere from a 60kt tropical storm to a category 2 hurricane. Most guidance makes the system a hurricane by Days 4 and 5 and the official NHC forecast follows that line of thinking.

Tropical Model Guidance (18Z):