Tropical weather analysis - August 27, 2014

By: KoritheMan , 7:59 AM GMT on August 27, 2014

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Notice: All forecasts presented here are based upon my own knowledge of atmospheric dynamics. They are created using my knowledge of the various computer models, satellite interpretation, and other tools and parameters. These forecasts, while striving to be accurate, are not intended to supersede predictions by the National Hurricane Center. Always follow NWS protocol and forecasts.

Cristobal

Hurricane Cristobal continues to move northward across the western Atlantic to the west of Bermuda. As of the 0600Z NHC intermediate advisory, the following coordinates were posted on the storm:

Wind: 80 mph, with higher gusts
Location: 30.4°N 72.0°W
Movement: Stationary
Pressure: 983 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

Like its predecessor Bertha, Cristobal's appearance on satellite does not resemble a typical hurricane. The convection is limited to two adjoining bands in the northern semicircle, with the western band trying to wrap around the ragged eye. Having said all of that, Cristobal's structure appears to be on the rebound, and if the convection can wrap more fully around the center, some additional strengthening could occur. Upper-level outflow is restricted to the south, but this is surprisingly probably more creditable to abundant subsidence on the western side of a deep-layer ridge over the southern United States than strong southwesterly shear.



Figure 1. Latest infrared satellite image of Hurricane Cristobal. Image credit: NOAA's Satellite Services Division (SSD).

The GFS and ECMWF show the most favorable upper-level wind configuration developing in Cristobal's path during the next 24-36 hours, and any barotropic intensification that is going to occur will have to do so during that window. Beyond that time, Cristobal will cross a sharp sea surface temperature gradient, and southwesterly shear will be increasing ahead of a progressive but deep mid- to upper-level trough moving across Atlantic Canada. It is uncertain how strong Cristobal might remain subsequent to extratropical transition. Most of the global models do show some intensification as a baroclinic low, and if those forecasts are correct, Cristobal could carry hurricane-force winds even longer than I have indicated below. Beyond 72 hours, I am unable to give a forecast point due to the limitations of the map I use to create my track forecasts. Due to the uncertainty, I have indicated some slight weakening at 72 hours, but it is entirely possible that baroclinic processes could keep post-tropical Cristobal stronger.

Satellite data suggest that Cristobal has probably begun to move again, although the data indicates that the hurricane has moved to the left of the NHC forecast points from 3Z. Other than a small westward shift to accommodate for this turn, my forecast track remains pretty similar to the NHC forecast track up until I terminate it after 72 hours due to the limitation of the graph. Most of the global models show Cristobal moving near or over southern Iceland in five days as a strong extratropical cyclone.

The tropical storm watch for Bermuda is still up. Although it is likely that Cristobal will not produce sustained tropical storm force winds there, especially in light of the current westward short-term shift, the wind field is large enough -- partially enhanced by a steep pressure gradient with the subtropical ridge to the east -- that some gusts to 40 or 45 kt could be possible on some of the higher elevations there.

Intensity forecast

Initial 08/27 0600Z 30.4°N 72.0°W 70 kt 80 mph
12 hour 08/27 1800Z 32.5°N 71.5°W 70 kt 80 mph
24 hour 08/28 0600Z 35.0°N 69.0°W 75 kt 85 mph
36 hour 08/28 1800Z 38.2°N 63.2°W 75 kt 85 mph
48 hour 08/29 0600Z 42.3°N 54.8°W 70 kt 80 mph
72 hour 08/30 0600Z 47.3°N 45.1°W 65 kt 75 mph: extratropical

Track forecast



Figure 2. My forecast track for Cristobal.

NHC storm information

000
WTNT34 KNHC 270536
TCPAT4

BULLETIN
HURRICANE CRISTOBAL INTERMEDIATE ADVISORY NUMBER 14A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
200 AM EDT WED AUG 27 2014

...CRISTOBAL HESITATES BUT STILL EXPECTED TO PASS TO THE NORTHWEST
OF BERMUDA LATER TODAY...


SUMMARY OF 200 AM EDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...30.4N 72.0W
ABOUT 445 MI...715 KM WSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...STATIONARY
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


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

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BERMUDA

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE IN THE NEXT 24 HOURS.

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


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 AM EDT...0600 UTC...THE CENTER OF HURRICANE CRISTOBAL WAS
LOCATED NEAR BY AN AIR FORCE RECONNAISSANCE PLANE NEAR LATITUDE 30.4
NORTH...LONGITUDE 72.0 WEST. CRISTOBAL HAS BEEN MOVING LITTLE
DURING PAST COUPLE OF HOURS...BUT IS FORECAST TO RESUME A MOTION
TOWARD THE NORTH NEAR 15 MPH...24 KM/H LATER THIS MORNING. A TURN
TOWARD THE NORTH-NORTHEAST AND NORTHEAST WITH A GRADUAL INCREASE IN
FORWARD SPEED IS EXPECTED OVER THE NEXT 48 HOURS. ON THE FORECAST
TRACK...THE CENTER OF CRISTOBAL WILL PASS TO THE NORTHWEST OF
BERMUDA LATER TODAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 80 MPH...130 KM/H...WITH
HIGHER GUSTS. SOME STRENGTHENING IS POSSIBLE DURING THE NEXT DAY OR
SO.

CRISTOBAL HAS A LARGE WIND FIELD. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 60 MILES...95 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 240 MILES...390 KM.

THE MINIMUM CENTRAL PRESSURE JUST REPORTED BY AN AIR FORCE
RECONNAISSANCE PLANE WAS 983 MB...29.03 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...CRISTOBAL IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
AMOUNTS OF 1 TO 2 INCHES OVER BERMUDA.

WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE ON BERMUDA WEDNESDAY
AND WEDNESDAY NIGHT.

SURF...SWELLS GENERATED BY CRISTOBAL ARE AFFECTING BERMUDA AND
PORTIONS OF THE U.S. EAST COAST FROM CENTRAL FLORIDA NORTHWARD TO
NORTH CAROLINA...AND WILL SPREAD NORTHWARD ALONG THE U.S. EAST COAST
OVER THE NEXT FEW DAYS. THESE SWELLS ARE LIKELY TO CAUSE
LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. FOR MORE
INFORMATION...PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER
OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM EDT.

$$
FORECASTER AVILA



Ex-97L

A tropical wave located several hundred miles east of the Lesser Antilles, previously designated "97L" before the NHC ceased running models on it, is moving westward. Satellite images show that this system is very disorganized. The GFS develops a tropical cyclone in the Bay of Campeche from the southern portion of this tropical wave in about a week, a solution that it has been consistent on for the last day or so. Even if that does happen, I suspect the northern portion will be too disorganized to take advantage of potentially more favorable environmental conditions farther west.

Probability of development in 48 hours: 0%

Probability of development in 120 hours: 10%



Gulf of Mexico disturbance

An area of disorganized cloudiness and a few showers south of the southwestern Louisiana coast is associated with a weak surface trough. The vorticity is weak, dry air is abundant, and there is southwesterly shear over a system that's moving west-southwest to southwest, a synoptic situation that is not conducive for development. The global models show this system moving into southern Texas or northern Mexico during the next day or so, and I do not anticipate tropical cyclone development in this area.

Probability of development in 48 hours: 0%

Probability of development in 120 hours: 0%



Marie

The once mighty Marie is now a shell of its former self. As of the 0300Z NHC advisory, the following information was posted on Marie:

Wind: 90 mph, with higher gusts
Location: 21.6°N 121.4°W
Movement: WNW at 14 mph
Pressure: 971 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

Satellite data show little change to Marie's cloud pattern. Deep convection remains fairly deep for a high latitude hurricane entering cold waters, although shower activity remains limited in the northern semicircle, likely because that portion of the cyclone circulation is already over 23 to 24C sea surface temperature. Upper-tropospheric outflow remains remarkably well-defined, suggesting that Marie remains embedded within an environment of weak vertical shear.



Figure 3. Latest infrared satellite image of Hurricane Marie. Image credit: NOAA's Satellite Services Division (SSD).

Although the shear is unlikely to increase much during the next few days, Marie will be moving over progressively cooler waters and into a dry airmass associated with those waters. A steady weakening is expected during the next five days, with Marie becoming a remnant low in about 48 hours; however, I note that it is possible this transition could conceivably occur sooner. Some of the guidance shows the circulation dissipating before day five, but I suspect the models that show this aren't giving quite enough credit to the large circulation of Marie; as seen with Lowell last week, such circulations can take an exceptionally long time to fully spin down, particularly in the absence of vertical shear.

Satellite fixes suggest that Marie is moving to the left of the 0300Z NHC forecast track, likely due to a westward extension of the Pacific subtropical ridge. The 6z TVCA model consensus has shifted westward to accommodate for short-term trends, and my forecast track follows suit. It remains well to the left of the GFS and ECMWF global models forecast since those models move Marie northward before turning it westward, a solution that seems unrealistic in light of the deep-layer ridge ahead of Marie, and also because the cyclone is going to spin down, making it less susceptible to abrupt poleward turns, especially at longer ranges.

Intensity forecast

Initial 08/27 0600Z 21.3°N 120.8°W 80 kt 90 mph
12 hour 08/27 1800Z 22.0°N 123.2°W 75 kt 85 mph
24 hour 08/28 0600Z 22.6°N 125.0°W 65 kt 75 mph
36 hour 08/28 1800Z 23.4°N 127.6°W 50 kt 60 mph
48 hour 08/29 0600Z 24.5°N 131.3°W 40 kt 45 mph: post-tropical/remnant low
72 hour 08/30 0600Z 28.2°N 134.6°W 30 kt 35 mph: post-tropical/remnant low
96 hour 08/31 0600Z 30.1°N 136.1°W 25 kt 30 mph: post-tropical/remnant low
120 hour 09/01 0600Z 30.2°N 137.1°W 20 kt 25 mph: post-tropical/remnant low

Track forecast



Figure 4. My forecast track for Marie.

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.