2008 “PRE-Season” In Review: A Comparison of Tropical

Cyclones Fay, Hanna, and Ike with Regards to Predecessor

Rainfall Event (PRE) Development

Michael L. Jurewicz, Sr.NOAA/NWS, Binghamton, NY

Northeast Regional Operational WorkshopNovember 5-6, 2008

Fay

Fay Overview

Fay came ashore as a Tropical Storm over the FL Keys on Aug. 19, then slowly meandered across the FL Peninsula the next several days

Synoptic Back-drop: Cutoff low over the southern plains Large, building anticyclone over the eastern

U.S., to the north and northeast of Fay

700 mb Analysis, 1200 UTC, 19 Aug.

LFay

Ridge Axis

925 mb Analysis, 1200 UTC, 19 Aug.

LFay

Ridge Axis

300 mb Analysis, 1200 UTC, 19 Aug.

SR Null-Case Composites

700 mb heights (dam) and upward vertical motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds (shaded, m s-1)

Center of composite TC

24-Hour QPE Through 1200 UTC, 20 Aug.

Fay’s Direct Rainfall

Radar Mosaic, 2100 UTC, 20 Aug.

Parcel Trajectories

Red – About 925 mbBlue – About 700 mbGreen – About 500 mb

700 mb Analysis, 1200 UTC, 21 Aug.

LFay

Ridge Axes

24-Hour QPE Through 1200 UTC, 21 Aug.

Fay’s Direct Rainfall

Disorganized Convection

Radar Mosaic, 1800 UTC, 21 Aug.

Parcel Trajectories

Red – About 925 mbBlue – About 700 mbGreen – About 500 mb

700 mb Analysis, 1200 UTC, 22 Aug.

L

Fay

Ridge Axes

24-Hour QPE Through 1200 UTC, 22 Aug.

Still Disorganized Convection

Fay’s Rainfall

Radar Loop – 20 Aug. to 24 Aug.

A Classic Null-Case

Fay produced tremendous rainfall across parts of the Southeastern U.S. Several day totals of 20”+ in parts of FL Due to the direct impacts of Fay’s rainfall shield

and her slow movementPRE development not observed

Expansive mid-level ridge was in place; nearly enveloped Fay

Precipitation maxima stayed tightly clustered around the circulation center

Hanna

Hanna Overview

Hanna came ashore as a Category 1 Hurricane near the NC/SC border around 0600 UTC, 6 Sept.

Synoptic Back-drop: Large western Atlantic ridge and central U.S.

troughiness Deep southerly flow regime over the eastern states

700 mb Heights/Winds, 0000 UTC, 6 Sept.

925 mb Heights/Theta-E and 200 mb Winds, 0000 UTC, 6 Sept.

Theta-E Ridge Line

Hanna Falls Within the SR Category; SR TC Tracks and PRE Locations

All SR TC Tracks All SR PPTC Tracks; with PRE centroids (colored dots)

SR PPTC Composites (PRE - 12)SR PPTC Composites (PRE - 12)

Center of composite TC

Trough axis

Ridge axis

θe-Ridge axis

700 mb heights (dam) and upward vertical

motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds

(shaded, m s-1)

Mid-level Streamlines

Representative TC Tracks

TC Rainfall

PREs

LL θe-Ridge Axis

See inset

UL Jet

Conceptual Model: LOT PRE Ahead Of SR Or AR TCConceptual Model: LOT PRE Ahead Of SR Or AR TC

Revised and updated from Fig. 13 of Bosart and Carr (1978)

PRE Outlook

Synoptic setting seemed somewhat favorable for potential PRE development poleward of Hanna TC embedded within southerly 700 mb flow, with short

wave upstream However, trough was less amplified than the composites

Strengthening upper-level jet streak to the north Developing 925 mb theta-e ridge, although a little

broader and farther east than the composites Proximity of low-level boundary

850 mb Moisture Transport, 0000 UTC, 6 Sept.

850 mb Moisture Transport, 1200 UTC, 6 Sept.

Precipitable Water and Low-Level Winds, 0000 UTC, 6 Sept.

Precipitable Water and Low-Level Winds, 1200 UTC, 6 Sept.

Radar Loop, 0000 – 1500 UTC, 6 Sept.

QPE, 0600-1200 UTC, 6 Sept.

“PRE-like” Rainfall

A Quick PRE

A band of heavy rainfall did develop north of Hanna from late Friday, 9/6 into Sat., 9/7 However, it was transient in nature; almost like

a progressive warm front feature Limited rainfall in most areas to 1” or less Parts of RI/southeast MA did get heavier amounts (2-

3” and locally higher, in just a 3-6 hour period)• Best combination of moisture inflow and jet dynamics

Hanna’s Direct Rainfall Shield

A narrow band of heavy rain accompanied Hanna up the Eastern Seaboard Maximum rainfall shifted increasingly just to the

left of track with poleward extent Typical of transitioning TC

Generally, 3-6” of rain fell within a 6-10 hour period

Dry antecedent conditions and the lack of a significant “Along-Track” PRE mitigated any serious flood problems

Radar Loop from 1200 UTC, 6 Sept. to 0600 UTC, 7 Sept.

QPE, 1200 UTC, 6 Sept. to 1200 UTC, 7 Sept.

Where heavier rains fell earlier

Ike

Ike Overview

Ike came ashore as a Category 2 Hurricane along the TX coast around 0600 UTC, 13 Sept.

Synoptic Back-drop: Large southeastern U.S. ridge and western

states troughiness Deep southerly flow regime over the southern Plains

and up the Mississippi Valley

700 mb Heights/Winds, 0600 UTC, 12 Sept.

925 mb Heights/Theta-E and 200 mb Winds, 0600 UTC, 12 Sept.

Theta-E Ridge Line

Ike Falls Within the CG Category; CG TC Tracks and PRE Locations

All CG Tracks All CG PPTC Tracks; with PRE centroids (colored dots)

PRE Outlook

Synoptic setting seemed favorable for potential PRE development poleward of Ike TC embedded within southerly 700 mb flow,

with trough upstream Strengthening upper-level jet streak to the

north/northeast Sharpening 925 mb theta-e ridge axis Nearly stationary low-level boundary

Derived Total Precipitable Water, 0600 UTC, 12 Sept.

Channel of Moisture Inflow

LIke

Precipitable Water, 0600 UTC, 12 Sept.

850 mb Moisture Transport, 0600 UTC, 12 Sept.

Radar Loop, 0000 – 1800 UTC, 12 Sept.

Parcel Trajectories

Red – About 850 mbBlue – About 700 mbGreen – About 500 mb

LIke

Total Rainfall for PRE in Southern KS

Flood Pictures (West Wichita, KS)

700 mb Analysis, 1200 UTC, 13 Sept.

L

Ike

300 mb Analysis, 1200 UTC, 13 Sept.

925 mb Analysis, 1200 UTC, 13 Sept.

L

Ike

850 mb Moisture Transport, 1200 UTC, 13 Sept.

Precipitable Water, 1200 UTC, 13 Sept.

Radar Loop, 0600-1800 UTC, 13 Sept.

Total Rainfall for PRE in Northern IL

Ike’s Significant PRE

Two well defined PRE First from central OK to southern KS late on

Thu., 9/11 and early Fri., 9/12 Widespread 6”+ rainfall, with an embedded

band of 10-15” (Wichita, KS set all-time 24-hour precipitation record (nearly 11”))

Second from northern MO/southeastern IA to northern IL/IN

Several bands of 5-10” rainfall (locally higher amounts)

Ike’s Direct Rainfall Shield

TC Ike picked up speed as it gained latitude A band of 3-6” rainfall spread from the southern

Plains, to the Mississippi Valley, to the Lower Great Lakes region

Fortunately for KS, most of this rainfall occurred east of the Wichita area

Parts of MO and IL not so lucky Exacerbated existing flood problems from the PRE

Radar Loop from 1800 UTC, 13 Sept. to 1200 UTC, 14 Sept.

QPE, from 0600-1200 UTC, 14 Sept.

Hardest hit areas from Ike’s first PRE

QPE, from 1200-1800 UTC, 14 Sept.

Hardest hit areas from Ike’s second PRE

Flood Pictures (Chicago area)

Summary

Fay produced very heavy rainfall; but no PRE Strong ridge to the north/northeast prevented significant moisture

advection outward from the TC’s circulation center Hanna produced a transient PRE-like feature to its north

Fast PRE movement kept rainfall amounts down Not much overlap between PRE and direct TC rainfall

Ike produced two substantial PRE Stationary forcing features (frontal boundary and back-building

upper-level jet) were better able to anchor/lift deep tropical moisture plume

PRE had considerably more impact than direct TC rainfall in KS

PRE + TC rainfall created major runoff problems in MO and IL

The End !!

Any Questions ??